(See Energy Level Diagrams for 16O)
GENERAL: See 2 [Electromagnetic Transitions in A = 16-17] (in PDF or PS), 16.12 [General Table] (in PDF or PS), 16.13 [Table of Energy Levels] (in PDF or PS) and 16.14 [Radiative decays in
Abundance = (99.762 ± 0.015)% (1984DE53)
|g| = 0.556 ± 0.004 (1984AS03)
Total reaction cross sections and characteristic γ-ray cross sections for 9Be + 9Be were measured for Ec.m. = 1.4 - 3.4 MeV (1988LA25). Gamma rays were observed from levels at 6.13 (3-), 6.917 (2+), and 7.1117 (1-) MeV populated by the 9Be(9Be, 2n)16O reaction. Cross sections calculated with optical models agreed with elastic scattering data, but the total reaction cross section was underpredicted by a factor of 2 to 3.
Energy spectra of the 16O nuclei were measured (1986BE35) for incident 11B energies of 88 MeV to obtain information on the 4He system.
This reaction was studied by (1988BEYJ).
At E(6Li) = 4.9 MeV, the cross sections for reactions (b) to (f) leading to low-lying states in the residual nuclei are proportional to 2Jf + 1: this is interpreted as indicating that the reactions proceed via a statistical compound nucleus mechanism. For highly excited states, the cross section is higher than would be predicted by a 2Jf + 1 dependence: see (1982AJ01, 1986AJ04).
States of 16O observed at E(10B) = 20 MeV are displayed in 16.10 (in PDF or PS) of (1977AJ02). At the higher excitation energies, states are reported at Ex = 17.200 ± 0.020, 17.825 ± 0.025, 18.531 ± 0.025, 18.69 ± 0.03, 18.90 ± 0.035, 19.55 ± 0.035, 19.91 ± 0.02, 20.538 ± 0.015, 21.175 ± 0.015, 21.84 ± 0.025, 22.65 ± 0.03 and 23.51 ± 0.03 MeV. The reaction excites known T = 0 states: σt follows 2Jf + 1 for 11 of 12 groups leading to states of known J. The angular distributions show little structure: see (1977AJ02).
Cross section measurements at Ec.m. = 1.46 - 6.10 MeV were reported in (1990DA03).
The yield of capture γ-rays has been studied for Eα up to 42 MeV [see 16.11 (in PDF or PS) in (1977AJ02) and (1982AJ01)]. See also (1986AJ04). Observed resonances are displayed in 16.15 (in PDF or PS) here.
This reaction plays an important role in astrophysical processes. The cross sections at astrophysical energies have been obtained by fitting measured cross sections and extrapolating them to low energies utilizing standard R-matrix, Hybrid R-matrix and K-matrix procedures. A list of recent values of the E2 and E1 astrophysical factors for E0 = 300 keV obtained from fits to the data is given in 16.16 (in PDF or PS).
The influence of vacuum polarization effects on subbarrier fusion is evaluated in (1988AS03), and the relevance of Coulomb dissociation of 16O into 12C + α is studied in (1986BA50, 1989BA64, 1992SH11). Calculations to test the sensitivity of stellar nucleosynthesis to the level in 12C at 7.74 MeV are described in (1989LI29). For other astrophysical studies see (1982AJ01, 1986AJ04) and (1985TA1A, 1986FI15, 1986MA1E, 1986WO1A, 1987AR1C, 1987BO1B, 1987DE32, 1987RO25, 1988CA26, 1988PA1H, 1988TRZZ, 1990BL1K, 1990BR1Q, 1990JI02).
At higher energies the E2 cross section shows resonances at Ex = 13.2, 15.9, 16.5, 18.3, 20.0, and 26.5 MeV [see 16.16 (in PDF or PS)]. Some E2 strength is also observed for Ex = 14 to 15.5 and 20.5 to 23 MeV. In the range Eα = 7 to 27.5 MeV the T = 0 E2 strength is ≈ 17% of the sum-rule value. It appears from this and other experiments that the E2 centroid is at Ex ≈ 15 MeV, with a 15 MeV spread. Structures are observed in the yield of γ-rays from the decay to 16O*(14.8 ± 0.1) for Ex = 34 - 39 MeV. It is suggested that these correspond to a giant quadrupole excitation with Jπ = 8+ built on the 6+1 state at Ex = 14.815 MeV: see (1982AJ01, 1986AJ04).
For reaction (a) cross section measurements from threshold to Eα = 24.7 MeV [see (1986AJ04)], and at Eα = 10.5 to 20 MeV (see 16.16 (in PDF or PS) here). For excitation functions from Eα = 21.8 to 27.2 MeV, see (1986AJ04). Thick-target neutron yields have been measured for Eα = 1.0 to 9.8 MeV (1989HE04) and for 4 - 7 MeV (1982WE16). For reaction (b) cross section measurements from threshold to 33 MeV, see (1986AJ04). The excitation curve for p3 (to 15N*(6.32), measured for Eα = 24 to 33 MeV, shows a large peak at Ex ≈ 29 MeV, Γ ≈ 4 MeV. It is suggested that it is related to the GQR in 16O: see (1982AJ01). For reaction (c) deuteron spectra have been measured for Eα = 200, 400, 600, 800 MeV/nucleon (1991MO1B). For the observed resonances see 16.16 (in PDF or PS) here.
The yield of α-particles leading to 12C*(0, 4.4, 7.7) and 4.4, 12.7 and 15.1 MeV γ-rays has been studied at many energies in the range Eα = 2.5 to 42 MeV [see (1986AJ04)], and at Eα = 0.4 - 1.8 MeV (1990TO09). Observed resonances are displayed in 16.15 (in PDF or PS). Attempts have been made to observe narrow states near 16O*(8.87, 9.85). No evidence has been found for a narrow (100 eV) 0+ state in the vicinity of the 2- state at 8.87 MeV [see (1982AJ01)] nor for a 3- state near the 2+ state at 9.84 MeV (1986AJ04).
For total cross section measurements see (1986AJ04) and for Eα = 100 MeV (1986DU15). For integral cross sections for inelastic scattering at 50.5 MeV, see (1987BU27). For elastic scattering differential cross sections at Eα = 96.6 MeV see (1990KO2C), at 90 MeV (1990GL02), at 90 and 98 MeV (1991GO25). For diffraction scattering at momentum 17.9 GeV/c, see (1991AB1F). For inelastic scattering and polarization of 12C (9.64 MeV, 3-) see (1989KO55, 1991KO40), who report that the reaction at Eα = 27.2 MeV proceeds mostly via an 8+ state in the compound system. For pion production at momenta 4.5 GeV/c per nucleon see (1990AB1D), at 4.2 GeV/c per nucleon (1987AG1A), at energies of 3.6 GeV per nucleon (1987AN20), and at 200 to 800 MeV per nucleon (1987LH01), at Eα = 0.8, 1.6 GeV (1991LE06). Differential cross sections at Eα = 1 - 6.6 MeV measured to obtain information on 12C(α, γ) stellar reaction rates are reported by (1987PL03).
Calculations of total cross sections for Eα = 96.6 - 172.5 MeV are presented in (1989KU30) and distributions of α-particle strengths in (1988LE05). Energy dependence at high energies (≈ 1 GeV/nucleon) is studied in (1988MO18). The iterative-perturbative method for S-matrix to potential inversion was applied to α + 12C phase shifts at Elab = 1.0 - 6.6 MeV in (1990CO29). See also (1991LI25). Nucleus-nucleus scattering and interaction radii were studied in (1986SA30). Core-plus alpha particle states in 16O populated in α + 12C scattering are studied in terms of vibron models in (1988CS01). See also (1991AB10, 1991DE15, 1991ES1B, 1991RU1B, 1992SA26). The effects of electron screening on low energy fusion reactions of astrophysical interest are explored in (1987AS05, 1990TO09). The nature of the α + 12C potential at low energy is explored in (1990AL05). For other theoretical work see (1986MI24, 1986SU06, 1987BA83, 1989BA92, 1990DA1Q).
The yield of 8Be from reaction (a) shows a number of resonances: see 16.16 (in PDF or PS). There is no evidence below Ex ≈ 24 MeV for Jπ = 8+ states although the existence of such states below this energy cannot be ruled out since it is possible that the L of the entrance channel inhibits the formation of such states. Above 26 MeV L = 8 becomes dominant: see (1982AJ01, 1986AJ04). See also the angular distribution measurements of (1991GL03) at Eα = 90 MeV. For differential cross sections for reaction (b) at Eα = 27.2 MeV see (1987KO1E). See also (1977AJ02).
This reaction has been studied at many energies: see (1977AJ02) and 16.17 (in PDF or PS) here. At higher energies the spectra are dominated by states with J ≥ 4 and natural parity (1986AJ04). A kinematic coincidence technique was applied in (1986CA19) to study the unresolved doublet at Ex = 11.09 MeV enabling clear observation of the γ-decaying 3+ member at 11.080 MeV although it contributes only ≈ 15% of the singles yield of the doublet which is dominated by the 4+ member at 11.096 MeV. Angular correlation measurements (1980CU08) suggested that the 11.096 4+ state is populated via a two-step process, and this interpretation was confirmed in calculations by (1988SE07). See also (1986AJ04). An interference effect was observed in the angular correlation function for the 7- level at Ex = 20.9 MeV in measurements by (1987AR28). See also (1986AR1A, 1987BE1C, 1987GO1C, 1988ARZU).
A numerical method for evaluation of (6Li, d) stripping into the 5- (15.6 MeV) and 6+ (16.3 MeV) states is presented in (1989SE06). See also (1991SE12). An extensive discussion of alpha clustering in nuclei is presented in (1990HO1Q). Cluster stripping and heavy-group substitution in the reaction is discussed in (1988BE49), and the effect of including Coulomb forces in the Faddeev formalism is studied in (1988OS05).
This reaction has been studied extensively: see (1977AJ02, 1982AJ01) and 16.17 (in PDF or PS) here. Measurements of α-t angular correlations for the process 12C(7Li, t)16O(α)12C are reported in (1988AR22) for the 7- (20.9 MeV), 6+ (16.3 MeV), and 5- (14.6 MeV) levels in 16O. Analyses of the (7Li, t) reaction for cluster states in 16O are reported in (1986CO15, 1988BE49). See also (1987BE1C, 1988BE1D, 1988BEYB, 1989AL1D, 1990HO1Q) and the sections on 19F in (1983AJ01, 1987AJ02).
Angular distributions at E(10B) = 18 and 45 MeV have been studied involving 16O*(0, 6.1, 7.1, 8.9, 9.9, 10.4). At E(10B) = 68 MeV angular distributions to 16O*(0, 6.1, 6.9, 10.4, 11.1, 14.7, 16.2, 20.9) are forward peaked and fairly structureless. 16O*(0, 6.9, 11.1) are weakly excited: see (1982AJ01, 1986AJ04, 1990HO1Q).
Angular distributions have been reported at E(12C) to 63 MeV [see (1977AJ02)] and at 4.9 to 10.5 MeV, and 11.2 to 12.6 MeV [see (1986AJ04)]. Angular correlations at E(12C) = 78 MeV confirm Jπ = 4+, 5-, 6+ and 7- for 16O*(10.36, 14.59, 16.3, 20.9). Γγ0/Γ = 0.90 ± 0.10, 0.75 ± 0.15 and 0.90 ± 0.10, respectively, for the first three of these states. In addition a state is reported at Ex = 22.5 ± 0.5 MeV which may be the 8+ member of the Kπ = 0+, 4p-4h rotational band (1979SA29). For further work at E(12C) = 90, 110 and 140 MeV see (1986SH10). At E(12C) = 120 MeV α0 decays of 16O*(16.3, 20.9) [Jπ = 6+, 7-] and α1 decays of 16O*(19.1, 22.1, 23.5) are observed as is a broad structure in both channels corresponding to 16O*(30.0) with Jπ = 9- + 8+. A gross structure 12C - 12C resonance at Ec.m. = 25 MeV in the reaction leading to the 16O 11.09 MeV 4+ state is reported in (1987RA22). For other work on alpha cluster resonances see (1986ALZN, 1986RAZI, 1987RA02, 1990HO1Q). Measurements of differential cross sections at sub-barrier energies 2.43 ≤ Ec.m. ≤ 5.24 MeV are reported in (1989CU03) and a statistical model calculation is discussed in (1990KH05). See also (1991CE09). For the decay of 20Ne states see (1983AJ01, 1986AJ04, 1987AJ02), and for excitation functions see (1986AJ04).
Angular distributions are reported at E(14N) = 53 MeV involving 16O*(0, 6.05, 6.13, 6.92) and various states of 10B, and at 78.8 MeV involving 16Og.s.: see (1982AJ01). Angular distributions have been measured for the g.s. in reaction (b) for E(17O) = 40 to 70 MeV (1986AJ04). See also (1986AR04, 1989WUZZ, 1990HO1Q), the two-center shell model basis calculations of (1991TH04) and the review of Landau-Zener effect investigations in (1990TH1D).
Angular distributions have been measured to E(20Ne) = 147 MeV: see (1977AJ02). For yield measurements see (1986AJ04). Studies of projectile-breakup and transfer re-emission in the 12C + 20Ne system at an incident 20Ne energy of 157 MeV are described in (1987SI06). See also (1990HO1Q).
The yield of capture γ-rays (reaction (a)) has been studied for E(3He) up to 16 MeV [see (1977AJ02)], as have angular distributions. Observed resonances are displayed in 16.18 (in PDF or PS). It is suggested that the structures at Ex ≈ 26 - 29 MeV are related to the giant resonances built on the first few excited states of 16O (1979VE02). See also (1986AJ04).
The excitation functions (reaction (b)) up to E(3He) = 11 MeV are marked at low energies by complex structures and possibly by two resonances at E(3He) = 1.55 and 2.0 MeV: see 16.18 (in PDF or PS). See also (1977AJ02) for polarization measurements. Excitation functions (reaction (c)) for E(3He) = 3.6 to 6.6 MeV have been measured for p0, p1+2, p3: a resonance is reported at E(3He) = 4.6 MeV. A resonance at 6 MeV has also been observed: see 16.18 (in PDF or PS). A comparison of polarization measured in this reaction and of analyzing powers measured in 15N(p, 3He) has been made [see (1986AJ04)]. Analyzing powers have been measured at E(3He) = 33 MeV for the elastic scattering (reaction (d)) and the deuteron groups to 14N*(0, 2.31, 3.95, 9.51) (1986DR03).
Yields of α0, α1, α2, and γ-rays from the decay of 12C*(12.71, 15.11) (reaction (f)) have been studied up to E(3He) = 12 MeV. Observed resonances are displayed in 16.18 (in PDF or PS). Those seen in the yield of γ15.1 are assumed to correspond to 16O states which have primarily a T = 1 character. Analyzing power measurements are reported at E(3He) = 33 MeV to 12C*(4.4). Excitation functions for α0 and α1 are also reported for E(3He) = 16 to 23 MeV (1986AJ04). DWBA analyses for data at E(3He) = 50, 60 MeV are described in (1990ADZU). See also (1986ZE1B). The excitation function for 8Beg.s. (reaction (g)) has been studied for E(3He) = 2 to 6 MeV. It shows a strong resonance at E(3He) = 5.6 MeV corresponding to a state in 16O at Ex = 27.3 MeV. Jπ appears to be 2+ from angular distribution measurements. A search for anomalous deuterons at 10.8 GeV has been reported (1986AJ04).
Angular distributions for the n0 group have been measured for Eα = 12.8 to 22.5 MeV: see (1971AJ02). Polarization measurements for n0 at θ = 0 - 70° at Eα = 2.406 and 3.308 MeV are reported in (1990WE10). The energy of the γ-ray from the decay of 16O*(6.13) is 6129.266 ± 0.054 keV (1986AJ04) [based on the 198Au standard Eγ = 411804.4 ± 1.1eV]. See also (1982AJ01). Analytical expressions for reaction rates for 13C(α, n)16O and other astrophysically important low-mass reactions are given in (1988CA26). See also the related work of (1986SM1A, 1987HA1E, 1989KA24, 1990HO1I).
At E(13C) = 105 MeV, 16O*(6.05, 6.13, 10.35, 16.3, 20.7) are strongly populated: see (1977AJ02, 1982AJ01, 1986AJ04). Excitation functions (Ec.m. = 13.4 - 16.8 MeV) and angular distributions (Ec.m. = 13.4, 16.38 MeV) have been measured (1988JA1B).
At E(3He) = 11 to 16 MeV, neutron groups are observed to T = 2 states at Ex = 22.717 ± 0.008 and 24.522 ± 0.011 MeV (Γ < 30 keV and < 50 keV, respectively). These two states are presumably the first two T = 2 states in 16O, the analog states to 16C*(0, 1.75). Jπ for 16O*(24.52) is found to be 2+ from angular distribution measurements (1970AD01). At E(3He) = 25.4 MeV forward angle differential cross sections have been determined to the 0+ states of 16O*(0, 6.05, 12.05) (1986AJ04).
The γ0 yield has been studied for Ed = 0.5 to 5.5 MeV. Observed resonances are displayed in 16.20 (in PDF or PS). Radiative capture in the region of the GDR [Ed = 1.5 to 4.8 MeV] has been measured with polarized deuterons. See (1986AJ04).
For Ed = 0.66 to 5.62 MeV, there is a great deal of resonance structure in the excitation curves with the anomalies appearing at different energies at different angles: the more prominent structures in the yield curves are displayed in 16.20 (in PDF or PS). For polarization measurements see (1977AJ02) and (1981LI23) in 15O (1986AJ01).
The yield of various proton groups for Ed < 5.0 MeV shows some fluctuations and two resonances: see 16.20 (in PDF or PS) and (1982AJ01). For polarization measurements see (1982AJ01, 1986AJ04). Analyzing power measurements at Ed = 70 MeV are reported in (1986MO27).
The yield of elastically scattered deuterons has been studied for Ed = 0.65 to 5.5 MeV and for 14.0 to 15.5 MeV: see (1971AJ02, 1977AJ02). There is indication of broad structure at Ed = 5.9 MeV and of sharp structure at Ed = 7.7 MeV in the total cross section of the d1 group to the T = 1 (isospin-forbidden), Jπ = 0+ state at Ed = 2.31 MeV in 14N. The yield of deuterons (d2) to 14N*(3.95) [Jπ = 1+, T = 0] shows gross structures at Ed = 7.4 and 10.2 MeV (1970DU04): see 16.20 (in PDF or PS). The yield of d1 has also been studied for Ed = 10.0 to 17.9 MeV: see (1982AJ01). For polarization measurements see (1982AJ01, 1986AJ04).
There is a great deal of structure in the yields of various α-particle groups for Ed = 0.5 to 12 MeV. Broad oscillations (Γ ≈ 0.5 MeV) are reported in the α0 and α1 yields for Ed = 2.0 to 5.0 MeV. In addition, 16O*(23.54) is reflected in the α3 yield (see 16.20 (in PDF or PS)). The yield of 15.11 MeV γ-rays, [from the decay of 12C*(15.11), Jπ = 1+, T = 1] which is isospin-forbidden, has been studied for Ed = 2.8 to 12 MeV. Pronounced resonances are observed at Ed = 4.2, 4.58 and 5.95 MeV and broader peaks occur at Ed = 7.1 and, possibly, at 8.5 MeV: see (1982AJ01). For polarization measurements see (1982AJ01, 1986AJ04).
Observed proton groups are displayed in 16.21 (in PDF or PS). Angular distributions have been measured at E(3He) = 2.5 to 24.7 MeV: see (1982AJ01). Branching ratios and τm measurements are shown in 16.13 (in PDF or PS) and 16.14 (in PDF or PS).
Angular distributions to states of 16O have been reported at many energies to Eα = 48 MeV: see (1971AJ02, 1977AJ02). Among the states which have been reported [see 16.7 (in PDF or PS) in (1977AJ02)] are 16O*(11.094 ± 3, 13.98 ± 50, 14.32 ± 20, 14.400 ± 3, 14.815 ± 2, 15.17 ± 50, 15.44 ± 50, 15.78 ± 50, 16.214 ± 15, 17.18 ± 50) [MeV ± keV]: the results are consistent with Jπ = 5+, 6+, 4+ for 16O*(14.40, 14.82, 16.29) [2p-2h] and with 6+ for 16O*(16.30) [4p-4h]. [See refs. in (1977AJ02).] Work reported in (1979CL10) and reviewed in (1982AJ01) determined Γc.m. = 34 ± 12, 27 ± 5 and 70 ± 8 keV, respectively for 16O*(14.31 ± 10, 14.40 ± 10, 14.81).
The yield of γ-rays has been measured for Ep = 0.15 to 27.4 MeV [see (1986AJ04)] and for Ep = 6.25 - 13.75 MeV (1988WI16), 20 - 100 MeV (1988HA04), 20 - 90 MeV (1989KA02), and 10 - 17 MeV (1987BA71): observed resonances are displayed in 16.22 (in PDF or PS). The γ0 cross section shows a great deal of structure up to Ep = 17 MeV. Above that energy the γ0 yield decreases monotonically. Besides the GDR which peaks at 16O*(22.15) there is evidence for the emergence of a giant structure (E2) with Ex = 24 - 29 MeV in the γ1 + 2 + 3 + 4 yield (1978OC01). Measurements for (p, γ0) cross sections and analyzing powers for Ep = 6.25 - 13.75 MeV indicated a clear enhancement of the E2 cross section above Ex = 22 MeV. Differential cross sections for γ0 and several other (unresolved) γ-rays at Ep ≈ 28 to 48 MeV generally show a broad bump at Ex ≈ 34 ± 2 MeV. The angular distributions show a dominant E1 character (1986AJ04). See also (1988HA04, 1988KI1C, 1989BOYV) and the review of (1988HA12). For comparisons with measurements of the inverse reaction see (1991FI08).
Measurements of (p, γ1) yields (1987BA71) indicated a pronounced concentration of dipole strength which was interpreted as an E1 giant resonance built on the 16O first excited state. Other measurements of proton capture to excited states for Ep = 20 - 90 MeV are reported in (1989KA02).
Cross sections and analyzing powers for capture into the 3- state at Ex = 6.13 MeV were studied by (1988RA15). Studies of quadrupole and octupole radiation from 16O at Ex = 39 MeV determine σE2/σE1 = 0.124 ± 0.015, and σE3/σE1 = 0.0051 ± 0.0026 (1989KO29).
A study of the M1 decays of 16O*(16.21, 17.14) [both Jπ; T = 1+; 1] to 16O*(6.05) finds B(M1, 1+ → 0+2)/B(M1, 1+ → 0+1) = 0.48 ± 0.03 and 0.55 ± 0.04, respectively. 16O*(18.03) is a 3-; 1 state with a strength ΓpΓγ2/Γ = 1.96 ± 0.27 eV and 16O*(18.98) is the 4-; 1 stretched particle-hole state with a strength of (0.85 ± 0.10) eV (1983SN03). See also (1983SN03) for the identification of analog states in 16N and in 16O, and for a discussion of Gamow-Teller matrix elements in A = 14 - 18 nuclei. See also the review of (1987BE1G). A study of the strong M2 transitions Ex = 12.53 → 0 MeV and Ex = 12.97 → 0 MeV is reported in (1986ZI08).
For astrophysical considerations see (1986AJ04) and (1985CA41, 1988CA26, 1989BA2P). See also 16.14 (in PDF or PS) here. An application of this reaction for thin film analysis is described in (1992EN02).
Calculations of the decay of the GDR and GQR by (1990BU27) have included 1p-1h and 2p-2h configurations, but the fine structure of the GDR remains unexplained. RPA calculations overestimate p0 decay but the use of a non-local mean field partially corrects this. The ISGQR is misplaced by RPA calculations, but is lowered by coupling to α - 12C channels. Data from (e, e'α) experiments are needed. RPA spectra have been examined (1988BL10) using a relativistic Hartree-Fock model for the ground state. Hartree-Fock based calculations appear to be insensitive to short-range repulsion. 1- and T = 1 strength distributions for 16O have been calculated using Hartree and Hartree-Fock methods. Shell-model plus R-matrix and continuum shell-model results for 1p shell nuclei have been considered (1987KI1C), but underestimate ground state (γ, N0) decay branches. Ground state shell-model plus R-matrix calculations describe the GDR region reasonably well.
Excitation functions and cross sections have been measured for Ep = 3.8 to 19.0 MeV: see (1982AJ01). For a listing of observed resonances see 16.23 (in PDF or PS). (1983BY03) have measured the polarization and analyzing power for the n0 group for Ep = 4.5 to 11.3 MeV and have deduced integrated cross sections. Differential cross sections and analyzing powers at Ep = 200 and 494 MeV have been measured (1988CIZZ). See also (1986AJ04).
The theoretical work of (1987BE1D) has shown the sensitivity of the (p, n) reaction to spin dynamics and pionic fields for Ep = 150 - 500 MeV and isovector density below 50 MeV. The importance of configuration mixing in Gamow-Teller quenching is also considered. The authors of (1989RA15) discuss the failure of the DWIA to explain the analyzing power for (p, n) at 500 MeV, focusing on transverse and longitudinal spin-flip cross sections and projectile no-spin-flip cross sections as the sensitive terms primarily responsible for the inadequacies of this method.
Elastic scattering studies have been reported for Ep = 0.6 to 15 MeV and angular distributions and excitation functions have been measured for Ep = 2.5 to 9.5 MeV for the (p1+2γ) and (p3γ) transitions [see (1986AJ04)]. Measurements of the depolarization parameter Kyy' at Ep = 65 MeV are reported in (1990NA15). Excitation functions for α0 and α1 particles [corresponding to 12C*(0, 4.43)] and of 4.43 MeV γ-rays have been measured for Ep = 93 keV to 45 MeV [see (1982AJ01)] and at Ep = 77.6 keV to 9.5 MeV (1986AJ04). The yield of 15.1 MeV γ-rays has been measured for Ep = 12.5 to 17.7 MeV (1978OC01). Measurements of the 430 keV resonance in 15N(p, αγ)12C were carried out by (1987OS01, 1987EV01). Observed anomalies and resonances are displayed in 16.22 (in PDF or PS). The resonance at E(15N) = 6.4 MeV observed in the reaction 1H(15N, αγ)12C has been used extensively to determine hydrogen concentration in thin films. See (1987EV01, 1987OS01, 1990FU06, 1990HJ02, 1992FA04).
A phase shift analysis of angular distributions of cross section and analyzing power for elastic scattering has yielded information on many 16O states in the range Ex = 14.8 to 18.6 MeV. In particular a broad Jπ = 2-, T = 1 state at 17.8 MeV appears to be the analog of the 1p-1h (d3/2, p-11/2) 16N state at Ex ≈ 5.0 MeV (1986AJ04). The isospin mixing of the 2- states 16O*(12.53, 12.97) has been studied by (1983LE25): the charge-dependent matrix element responsible for the mixing is deduced to be 181 ± 10 keV. The α0 yield and angular distribution study by (1982RE06) leads to a zero-energy intercept of the astrophysical S(E) factor, S(0) = 65 ± 4 MeV · b. See (1982AJ01, 1986AJ04) for the earlier work. See also (1987RO25), and see the tables of thermonuclear reaction rates in (1985CA41).
Among recent theoretical developments related to these reactions, electron screening effects for 15N(p, α)12C at very low energies (< 50 keV) have been evaluated (1987AS05). Expressions for longitudinal and irregular transverse PNC analyzing powers in cases of parity-mixed resonances such as 15N(pol. p, p)15N and 15N(pol. p, α)12C are derived in (1989CA1L). Recent theoretical studies of the parity- and isospin-forbidden α-decay of the 12.97 MeV state to the 12C ground state are reported in (1991DU04, 1991KN03). See also the theoretical study of single particle resonances in (1991TE03).
An investigation into the separation of the strength of the giant resonance for underlying levels neglecting statistical assumptions (1986KL06) has shown deviations from statistical behavior at the tops of resonances, leading to missing spectroscopic strength. A calibration method for heavy-ion accelerators has been described by (1987EV01), who have also determined the energy of the Ep = 430 keV resonance in the 15N(p, αγ)12C reaction. Quantum fluctuations are shown to cause structures having collective properties (1986RO26). These new collective states are dissipative. 15N(p, p)15N is considered for 25 < Ep < 40 MeV. (1988RO09) consider the transition from resonance to direct reactions as well as the significance of quantum fluctuations.
The ground state of 16N decays to seven states of 16O: reported branching ratios are listed in 16.25 (in PDF or PS). The ground state transition has the unique first-forbidden shape corresponding to Δ J = 2, fixing Jπ of 16N as 2-: see (1959AJ76). The unique first-forbidden decay rates to the 0+ ground state and 6.06-MeV level are well reproduced by a large-basis (0 + 2 + 4)ℏω shell-model calculation (1992WA25). The decays to odd-parity states (see 16.25 (in PDF or PS)) are well reproduced by recent calculations of Gamow-Teller matrix elements (1993CH06). For the β-decay of 16N*(0.12), see reaction 1 in 16N.
The β-delayed α-decays of 16O*(8.87, 9.59, 9.84) have been observed: see (1971AJ02). The parity-forbidden α-decay from the 2- state 16O*(8.87) has been reported: Γα = (1.03 ± 0.28) × 10-10 eV [Eα = 1282 ± 5 keV]: see (1977AJ02).
Transition energies derived from γ-ray measurements are: Ex = 6130.40 ± 0.04keV [Eγ = 6129.142 ± 0.032 keV (1982SH23)], Ex = 6130.379 ± 0.04 [Eγ = 6129.119 ± 0.04 keV (1986KE15)] and Ex = 7116.85 ± 0.14 keV [Eγ = 7115.15 ± 0.14 keV]. See (1977AJ02). See also p.16 in (1982OL01).
The absorption cross section and the (γ, n) cross section are marked by a number of resonances. On the basis of monoenergetic photon data, excited states of 16O are observed at Ex = 17.3 [u], 19.3 [u] and 21.0 MeV [u = unresolved], followed by the giant resonance with its principal structures at 22.1 and 24.1 MeV, and with additional structures at 23 and 25 MeV: see (1986AJ04, 1988DI02). The integrated nuclear absorption cross section for Eγ = 10 to 30 MeV is 182 ± 16 MeV · mb (1986AJ04). See also reaction 42. The (γ, n) cross section has been measured for Eγ = 17 to 33 MeV: in that energy interval the (γ, 2n) cross section is negligible. The cross section for formation of the GDR at 22.1 MeV is 10.0 ± 0.4mb and the integrated cross section to 30 MeV is 54.8 ± 5 MeV · mb. There is apparently significant single particle-hole excitation of 16O near 28 MeV and significant collectivity of the GDR. A sharp rise is observed in the average En above 26 MeV. The cross section for (γ, n0) decreases monotonically for Ex = 25.5 to 43.8 MeV. In the range 30 - 35 MeV the E2 cross section exhausts about 4% of the isovector E2 EWSR. Over the range 25.5 to 43.8 MeV it exhausts ≈ 68% of the isovector E2 EWSR [see (1986AJ04) and references cited there]. M1, E1, and E2 strengths were studied by recent polarization and cross section measurements for Eγ = 17 to 25 MeV (1991FI08). An atlas of photoneutron cross sections obtained with monoenergetic photons is presented in (1988DI02).
The absorption cross section has been measured with bremsstrahlung photons of energies from Ebs = 10 MeV to above the meson threshold: see (1982AJ01). The (γ, n), (γ, 2n) and (γ, Tn) cross sections have been studied with monoenergetic photons for Eγ = 24 to 133 MeV. Above 60 MeV, the main reaction mechanisms appear to be absorption of the photons by a correlated n-p pair in the nucleus: the integrated cross section from threshold to 140 MeV is 161 ± 16 MeV · mb (1986AJ04). Differential cross sections for (γ, n0) have been measured at Eγ = 150, 200, and 250 MeV at θlab = 49°, 59°, and 88° (1988BE20, 1989BE14). See also 15O in (1991AJ01). For reaction (b) and pion production see (1986AJ04). For reaction (c) measurements have been carried out with bremsstrahlung photons with Eγ ≤ 150 MeV (1989VO19), and with tagged photons in the Δ(1232) resonance region (1987KA13). See also (1991VA1F). Measurements of reactions (d) and (e) were made with tagged photons of energies 80 - 131 MeV (1991MA39). Measurements of the total cross section at Eγ = 90 - 400 MeV are described in (1988AH04). Calculations which indicate that molecular effects are important in screening corrections to the cross section in the Δ resonance region are discussed. The hadron production cross section has been studied over the range 0.25 to 2.7 GeV see (1986AJ04).
Sum rules and transition densities for isoscalar dipole resonances are discussed in (1990AM06). For a calculation of monopole giant resonances see (1990AS06). Calculations relating to polarization effects are discussed in (1990BO31, 1990LO20). The contribution of six-quark configurations to the E1 sum rule has been considered (1989AR02), and upper bounds for the production probabilities of 6q-clusters have been derived. The continuum self-consistent RPA-SK3 theory predicts charge transition densities in 16O for excitation of GDR (1988CA07). Neutron and proton decay is also indicated. See also (1991LI28, 1991LI29). A contiuum shell model description of (γ,n) and (γ,p) data at medium energies is reported in (1990BRZY). Radial dependence of charge densities depends on whether r-values correspond to the interior of the nucleus or to the surface (1988CA07). In (1985GO1A) (γ, n) and (γ, p) experimental results are compared with those of large-basis shell model calculations. Good results were obtained, but a new source of spreading is warranted. Ratios of (γ, n)-to-(γ, p) cross sections have been computed using R-matrix theory including configuration splitting, isospin splitting, and kinematics effects (1986IS09). Computations of the partial photonuclear cross sections have been performed (1987KI1C) using the continuum shell model. GDR and other giant multipole resonances are also considered. The authors of (1988RO1R) use the continuum shell model as a basis for their study of "self-organization". The role of the velocity-dependent part of the N-N interaction is also examined. A method for solving the RPA equations, and an examination of the long-wavelength approximation is discussed in (1988RY03). Levinger's modified quasi-deuteron model is applied for 7 ≤ A ≤ 238 and Eγ = 35 - 140 MeV (1989TE06). The quantities L = 6.1 ± 2.2 and D = 0.72/A are also deduced. The role of distortion in (γ, np) reactions is explored in (1991BO29).
The (γ, p0) cross section derived from the inverse capture reaction (reaction 34) confirms the giant resonance structure indicated above in reaction 40, as do the direct (γ, p0) measurements. For the earlier work see (1982AJ01). For results of measurements with linear polarized photons at Ebs = 22 and 30 MeV and for differential cross sections at Eγ = 101.5 - 382 MeV and proton spectra at Eγ ≈ 360 MeV, see (1986AJ04). See also the reviews (1987BE1G, 1988KO1S), and see (1987MA1K). Angular distributions for (γ, p) reactions populating low-lying states of 15N were measured (1988AD07) with bremsstrahlung photons with Eγ = 196 - 361 MeV. Differential cross sections measurements with Eγ ≈ 300 MeV tagged photons (1990VA07) were used to study the interaction mechanism. Proton spectra measured at 90° (1990VA07) showed evidence for an absorption process in which the photon interacts with a T = 1 np pair. See also the comment (1992SI01) and reply on the interpretation of these data. A related calculation concerning quasideuteron behavior of np pairs is described in (1992RY02). See also (1987OL1A).
For reaction (b) see (1982AJ01). A study of the 16O(γ, α0) reaction (c) at θ = 45° and 90° shows a 2+ resonance at Ex = 18.2 MeV with an E2 strength which is spread out over a wide energy interval. A strong resonance corresponding to an isospin-forbidden 1- state at Ex ≈ 21.1 MeV is also observed (1986AJ04). The systematics of cross sections for reaction (d) are discussed in (1991BO26). For pion production reaction (e), pion angular distributions were measured for a mixed flux of real and virtual photons at Eγ = 320 MeV (1987YA02). Double differential cross sections with tagged photons with Eγ = 220 - 450 MeV are reported in (1991AR06). See also 16N and (1986AJ04). Exclusive cross sections for reaction (g) in the Δ resonance region are reported by (1992PH01).
Recent theoretical work includes calculations of sum rules and transition densities (1990AM06), monopole giant resonances (1990AS06), and polarization effects (1990BO31, 1990LO20). A scheme using fractional-parentage coefficients to separate the wavefunction into three fragments in arbitrary internal states has been proposed, and examples include 7Li(γ, t)4He, 16O(γ, dd)12C and 12C(γ, pd)9Be (1988BU06). A formula for cross sections for A(γ, dγ')A - 2 reactions with Eγ = 2.23 MeV has been derived (1988DU04). In a study of Dirac negative energy bound states, a relativistic shell model predicts γ + 16O → 15p-bar N + p has a threshold at 1.2 GeV and rises to about 5 μb by 1.6 GeV (1988YA08). (1988LO07) calculate 16O(γ, p)15N using Dirac phenomenology. Dirac spinors are used to describe the proton dynamics in a DWBA calculation, and results are compared to data. 16O(γ, p)15N for Eγ = 50 - 400 MeV has been calculated (1986LU1A) using a coupled-channels continuum shell-model technique. A single particle direct knock-out model is used by (1987RY03) to calculate (γ, π) cross sections for Eγ = 40 - 400 MeV. See also (1990BRZY, 1991IS1D). 16O(γ, p) at intermediate energies has been calculated using both a single particle and a pion-exchange-current mechanism in a relativistic form of the nucleon current operator and four-component nucleon wave functions (1988MC03). See also the study of the effects of current conservation in these reactions (1991MA39) and of scaling (1991OW01). An expression for the (γ, N) cross section with incident circularly polarized photons and outgoing nucleon polarization being detected is given in (1986PO14). A direct-semidirect model calculation for 16O(γ, N0) at 60 MeV is given as an example. A model, based on basic interactions between photons, pions, nucleons and isobars, providing an adequate description of the γN → πN reaction is described in (1992CA04).
Resonances have been reported (1970AH02) at Eγ = 22.5 ± 0.3, 25.2 ± 0.3, 31.8 ± 0.6 and 50 ± 3 MeV: the dipole sum up to 80 MeV exceeds the classical value by a factor 1.4. Elastic photon scattering cross sections for Eγ = 25 to 39 MeV have been measured. The E2 strength is 1.25+1.3-0.9 times the total EWSR strength over that interval. The widths of 16O*(6.92, 7.12) are, respectively, 94 ± 4 and 54 ± 4 MeV (1985MO10, 1986AJ04). Differential cross sections at angles of 135° and 45° for elastic scattering of tagged photons between 21.7 and 27.5 MeV in the giant dipole resonance region have been measured by (1987LE12). Differential cross sections for tagged photons with Eγ = 27 - 68 MeV have been reported by (1990MEZV). Polarizabilities of nucleons imbedded in 16O were measured via Compton scattering of 61 and 77 MeV photons by (1992LU01). See also 16.14 (in PDF or PS).
A non-perturbative study of damping of dipole and quadrupole motion in 16O is discussed in (1992DE06). (1987VE03) have used an extended isobar doorway model including open-shell configurations in both ground and excited states to calculate elastic and inelastic photon scattering in the Δ-region, and for linearly polarized photons.
The 16O charge radius = 2.710 ± 0.015 fm (1978KI01). Form factors for transitions to the ground and to excited states of 16O have been reported in many earlier studies [see (1982AJ01, 1986AJ04)], and by (1987HY01); see 16.26 (in PDF or PS). 16.26 (in PDF or PS) lists the excited states observed from (e, e'). The form factor for 16O*(9.84) indicates a transition density peaked in the interior (1986BU02). The energy-weighted M2 strength is nearly exhausted by the M2 states which have been observed. The isospin-forbidden (E1) excitation of 16O*(7.12) is reported: the isovector contribution interferes destructively with the isoscalar part and has a strength ≈ 1% of the T = 0 amplitude. The 0+ states of 16O*(6.05, 12.05, 14.00) saturate ≈ 19% of an isoscalar monopole sum rule. In a recent measurement, the magnetic monopole 0+ → 0- transition to 16O*(10.957) was observed (1991VO02). The E2 strength is distributed over a wide energy region: see 16.26 (in PDF or PS), and (1982AJ01, 1986AJ04) for references. See also the compilation of nuclear charge density distribution parameters (1987DEZV), and the reviews of (1989DR1C, 1987HO1F).
A study of reaction (b) at 500 MeV shows separation energies of 12.2 and 18.5 MeV, corresponding to 15N*(0, 6.32). The momentum distribution of the recoiling nucleus has been measured. High precision data with ≈ 100 keV resolution in the missing mass are reviewed in (1990DE16). The excitation of 16O*(11.52, 12.05, 22.3) and some other states is reported at Ee = 112 - 130 MeV in (e, e'). The (e, e'p) and (e, eα) processes lead to the excitation of 15N*(0, 6.32) and of 12C*(0, 4.44). (See (1982AJ01, 1986AJ04) for the references). In a recent measurement the nuclear response function RLT for 15N*(0, 6.32) was determined in (e, e'p) by (1991CH39). See also (1990MO1K). Coincidence experiments at Ee = 130 MeV are reported by (1987DM01). See also (1987RI1A). Non-spherical components in the 16O ground state are indicated by the (e, e'p) data of (1988LEZW). The inelastic cross section for 537 and 730 MeV electrons has been measured by (1987OC01), and the electromagnetic excitation of the Δ resonance was studied.
Angular correlation measurements for reaction (c) to determine isoscalar E2 strengths in 16O are reported in (1992FR05).
Inelastic electron-nucleus interactions for 16O at 5 GeV are reported in (1990DE1M).
In theoretical work on reactions (a) and (b), models for relativistic Coulomb sum rules are developed in (1989DO05). See also (1991LE14). A shell-model study of giant resonances and spectroscopic factors in 16O is described in (1988HO10). See also (1990BO31). (1988AM03) studied an isoscalar dipole excitation in 16O (7.12 MeV state). Core polarization was used in their limited shell model treatment. Exchange amplitudes proved crucial in fitting (p, p') data. A relativistic Dirac-Hartree-Fock approach is shown to give a reasonably good account of binding energies, single-particle energies and charge, as well as proton and neutron densities of 16O and other closed shell nuclei (1988BL1I). The application of Monte Carlo methods in light nuclei including 16O is reviewed in (1991CA35). Non-locality of the nucleon-nucleus optical potential has been used (1987BO54) to evaluate the missing single particle strength observed in (e, e'p) data. (1988BO40) have studied the charge form factor by taking the one- and two-body isoscalar charge operands into account in the topological soliton model. Nuclear responses were calculated (1987CA16) using self-consistent HF and RPA theory with a SK3 interaction. Decay properties in (e, e'p) and (e, e'n) for semidirect and knockout processes are also discussed. A self-consistent RPA with the SK3 interaction has been used by (1988CA10) to calculate (pol. e, e'x) reactions. Polarization structure functions are also discussed. (1989CA13) use self-consistent RPA with SK3 interactions to calculate monopole excitations in (e, e') and (pol. e, e'x) reactions. Evidence has been presented by (1989FR02) for a violation of Siegert's theorem, based on cross section measurements of the electro-excitation of the first 1- level in 16O. Previous Hartree-Fock calculations were used by (1990CA34) to study Siegert's Theorem in E1 decay in 16O. Their results show that the previously claimed violation cannot be definitely asserted. A pole graph method is used by (1987CH10) to calculate production of hypernuclei in the continuum. Radial wave functions obtained from realistic nuclear potentials have been used to calculate electron scattering form factors for stretched configurations, which are compared to data (1988CL03). (1987CO24) exhibit and discuss DWBA structure functions for (pol. e, e'x) cross sections. A numerical study of the decay of giant resonances of 16O was also conducted. The ratio of transverse-to-longitudinal electromagnetic response in (e, e'p) reactions has been examined in terms of relativistic dynamics and medium modifications (1987CO26). Electron scattering form factors have been calculated (1990DA14) using relativistic self-consistent RPA descriptions of discrete excitations. (1986GU05) derived an expression for the transition charge density in the Helm model, and (1988GU03) calculated charge density distributions using harmonic oscillator wave functions. Experimental values have been compared with calculated transition charge densities from various models in (1988GU14). (1988KU18) calculated binding energy, excitation spectra to ≈ 12 MeV, and e-scattering form factors using the mean-field approximation and the BZM boson image of the shell model Hamiltonian. Results appear superior to the standard shell model. The two-body pion exchange current contributions to the form factor of inelastic electron scattering has been calculated by (1986LA15) using the effective pion propagator approximation. Effects due to meson exchange currents and unbound wavefunctions for the valence nucleon were included in calculations of electron scattering form factors (1987LI30). Special attention was paid to 1ℏω stretched states. A Sum Rule formalism was used by (1989LI1G) to investigate giant resonances. Surface effects, non-Hermitian operators, and magnetic excitations were considered.
Normalized correlated wavefunctions were used by (1988MA29) to simplify a previously derived expression for the charge form factor in the non-unitary model operator approach, and compared to data. (1989MA06, 1990MA63) derived an approximate formula for the two-body term in the cluster expansion of the charge form factor, and discussed the correlation parameter. (1989MC05) used the Gelerkin approach to calculate a finite nucleus Dirac mean field spectrum, and then applied it to Dirac RPA response and the present results for 1- and 3- longitudinal form factors. A comprehensive study of a full set of 18 response functions relevant to the (pol. e, e'p) reaction is presented by (1989PI07). (1988PR05) have studied the linear response of 16O to external electroweak current in a relativistic model. Hartree-Fock-RPA quasi-elastic cross sections for 16O(e, e'p) are calculated by (1989RY01), who also discuss final state interactions. Electromagnetic quasi-free proton knockout in a one-photon exchange approximation is studied in (1991BO10, 1991PA06). (1989RY06) performed self-consistent HF-RPA model calculations for (e, e'p) and (e, e'n) using Skyrme interactions in parallel and perpendicular kinematics. A consistent extension of the QHD1 mean-field RPA theory including correlations induced by isoscalar σ and ω mesons of QHD1 is used by (1989SH27) to calculate (e, τ') form factors and transition charge and current densities. See also (1991ZH17). (1986TK01) calculated M1 resonances taking 1p-1h × phonon excitations into account. Comparisons were made with data. (1987YO04) studied 1ℏω stretched excitations in configuration mixing calculations based on first-order perturbation theory.
Angular distributions of elastically scattered pions have been studied at Eπ- = 20 to 240 MeV and at 1 GeV/c as well as at Eπ± = 20 to 315 MeV [see (1982AJ01, 1986AJ04)] and recently at Eπ± = 100 - 250 MeV at 175° (lab) (1987DH01), and at Eπ- = 30, 50 MeV (1990SE04). At Eπ± = 164 MeV, 16O*(0, 6.1, 6.9, 7.1, 11.5, 17.8, 19.0, 19.8) are relatively strongly populated. The π+ and π- cross sections to 16O*(17.8, 19.8) [Jπ = 4-; T = 0] are substantially different while those to 16O*(19.0)[4-; 1] are equal. Isospin mixing is suggested with off-diagonal charge-dependent mixing matrix elements of -147 ± 25 and -99 ± 17 keV (1980HO13). [See also reaction 67, 17O(d, t)]. The inelastic pion scattering is dominated by a single quasi-free pion-nucleon interaction mechanism at Eπ+ = 240 MeV (1983IN02): this is not the case at energies below the Δ-resonance (114 and 163 MeV). For recent inelastic measurements see (1987BLZZ).
For a study of (π+, 2p) and (π±, pn) at Tπ+ = 165 MeV see (1986AL22), at Tπ+ = 115 MeV see (1992MA09). See also (1986KY1A, 1986KY1B). Pion absorption at Tπ+ = 65 MeV followed by multinucleon emission is reported by (1992BA31). For (π+, π0p) at Tπ+ = 165 and 245 MeV see (1986GI15, 1988HO1L, 1991HO03). For (π+, π-) and (π-, π+) at Tπ+ = 180, 240 MeV see (1989GR06). For (π+, π+π-) at Tπ+ = 280 MeV see (1989GR05). See also (1987ME12, 1989ME10, 1990KO36).
A calculation of differential elastic cross sections in a local approximation to the delta-hole model is described in (1991GA07).
Angular distributions have been measured at En to 24 MeV [see (1982AJ01, 1986AJ04)] and recently at En = 18 to 26 MeV (1987IS04, 1988MEZX); n's were observed leading to 16O*(6.05, 6.13, 6.92, 7.12, 9.85, 10.35, 11.0, 11.52). For small-angle measurements at En = 14.8 MeV, see (1992QI02). Differential cross sections for (n, n) and (n, n') at En = 21.6 MeV are reported by (1990OL01). Polarization of gamma rays from (n, n') with polarized neutrons to 16O*(6.05, 6.13) was studied by (1988LI34) [see also (1987PO11)]. See also the evaluation of En = 10-5 eV - 20 MeV neutron data for 16O in (1990SH1D).
The folding model has been used to calculate the nucleon - 16O interaction potential, and the effect of different nucleon-nucleon forces has been discussed (1989HA24). See also the analysis with nonlocal potentials based on RGM formulations by (1992KA21) and the optical model study of (1992BO04). See also (1991KA19, 1991KA22, 1991SH08).
Angular distributions of elastically and inelastically scattered protons have been measured at many energies up to Ep = 1000 MeV [see (1982AJ01, 1986AJ04)] and recently at Ep = 7.58 MeV (1987KR19; p to 16O*(6.05)), 8.9 - 50 MeV, (1988LE08; p to 16O*(6.129)), 35 MeV, (1990OH04); p to 16O*(Ex ≤ 12.97)), 40 - 85 MeV, (1987LA11; p to 16O*(6.1299, 8.8719)), 22, 35, 42 MeV, (1988SA1B; p to 16O*(6.129)), 135 MeV, (1986GA31; p to 16O*(6.044, 7.117, 12.043)), (1989KE03; p to 16O*(6.049, 6.130, 6.917, 7.117, 9.847, 10.353, 11.09)), 180 MeV, (1990KE03; p to 16O*(Ex ≤ 12.1)), 200 MeV, (1986KIZW; p to 16O*(10.957)), (1989SAZZ; p to 16O*(10.957, 12.797)), 201 MeV. (1987DJ01; p to many states [see 16.27 (in PDF or PS)]), 320 - 800 MeV (1988BL07), 318 and 500 MeV, (1988FEZX, 1989FEZV, 1991FL01, 1991KE02), 100 and 200 MeV (1988SEZU, 1990GL09), 200, 318 MeV, (1990FEZY), 400 MeV (1991KI08), and 1000 MeV (1988BE2B). Parameters of the observed groups are displayed in 16.27 (in PDF or PS). See also (1990OP01) and the analysis of (1990ER09).
For reaction (b) see (1991CO13; 151 MeV), (1986MC10; 505 MeV) and the review of (1987VD1A). For reaction (c) see (1986BO1A; 50 MeV), (1986SA24; 76.1, 101.3 MeV). For reaction (p, pα) see (1986VD04; 50 MeV). See also the study with antiproton beams of (1986KO22).
(1987CO25) have performed calculations using the Dirac equation for p and n distortions for the 16O(pol. p, nπ+)16O reaction. A coupled-channels calculation using Dirac phenomenology for inelastic scattering of 800 MeV protons from 16O is presented in (1988DE35). (1988DE31) have studied the importance of a deformed spin-orbit potential in the calculations of (1988DE35). Approximate treatment of the nucleon-nucleus interaction in the resonating group method is discussed in (1991KA19). First order Kerman-McManus-Thaler optical potentials have been constructed from realistic meson-exchange models of N-N interaction including off-shell effects, and are found to be important for spin observables at 200 - 500 MeV (1989EL02). Optical phase shifts have been calculated to fifth order by (1988FR06), taking into account cm correlations. The significance of higher-order corrections is assessed. (1989GU06) consider breakup reactions in high temperature plasmas, including production of 6.129 MeV γ's from 16O: mainly from p + 16O → p' + 16O*, γ + 16O → γ' + 16O*, and p + 20Ne → X + 16O*. (1988HA08) found Dirac optical potentials constrained by relativistic Hartree theory to give good agreement with elastic scattering data. See also (1990TJ01, 1991SH08). Spin observables have been calculated by (1988HO1K) for proton quasi-elastic scattering in the relativistic plane wave-impulse approximation, and compared to (p, p') data at 490 MeV. Isoscalar spin response functions are studied in (1990SH10). (1987KE1A) constructed a parametrization of medium modifications of the 2N effective interaction to reproduce nuclear matter theory, and adjusted it to reproduce proton inelastic scattering data. They obtained good fits to cross section and analyzing power for nine states simultaneously. (1989KE05) performed similar calculations, and fitted 135 MeV proton cross section and analyzing power data with the effective interactions. (1986KU15) performed a DWIA calculation of σ(θ) and Ay(θ) for 16O(pol. p, 2p) at 200 MeV including spin-orbit and off-shell effects. (1987LU02) performed a semi-relativistic multiple scattering model calculation of intermediate energy proton elastic scattering, and investigated target nucleon correletion contributions. Multiple diffraction scattering theory was used to calculate cross sections and polarization observables in (1988BE57, 1991BE1E, 1991BE45, 1992BE03). See also (1991CH28, 1991CR04 1992CR05). A Skyrme force approach was explored in (1988CH08). A scalar-vector form of a second-order relativistic impulse approximation optical model including dispersion effects was used by (1988LU03) to calculate elastic proton scattering at 500 and 800 MeV. Evidence for a small imaginary potential or actual flux emission was presented (1988MA05) for nucleon scattering from 16O at 30 MeV. As an alternate explanation of the (1988MA05) findings, (1988MA31) discuss the "ψ-potential", related to projectile current. (1988MA1X) contains a review of relativistic theory of nuclear matter and finite nuclei. A relativistic microscopic optical potential derived from the relativistic Brueckner-Bethe-Goldstone equation is discussed in (1992CH1E). Polarization transfer measurements in (p, p') reactions have been examined by (1986OR03) with regard to correlations of tensor character. (1986OS08) used the T-matrix approximation with distorted waves to analyze knock-off nucleon (p, pN) and cluster (p, pX) proton induced reactions from 30 to 100 MeV. The scattering of 500 MeV protons has been calculated by (1987OT02) using the Dirac equation with and without recoil corrections. Both cross section and spin observables are examined and compared to data. See also (1991KA22). (1988OT04) present systematics of Dirac impulse approximation for cross sections and spin observables in elastic p scattering at 200, 500, and 800 MeV. Results are compared to data. A mixed-density expansion of the off-diagonal density matrix is used by (1988PE09) to study the non-local knockout exchange amplitude for nucleon-nucleus scattering. (1987PI02) studied 0+ → 0- transitions by medium energy protons using the relativistic impulse approximation. (1989PI01) considered corrections arising from the energy dependence of the NN interaction, especially for 0+ (pol. p, pol. p')0- reactions. Relativistic and non-relativistic dynamical scattering models have been used by (1988RA02) to predict elastic scattering observables in the forward angle for p + 16O at 500 and 800 MeV. See also (1990CO19, 1990RA12). (1989RA02) have obtained the leading three-body anti-symmetrization correction to nucleon-nucleus elastic scattering calculations using multiple scattering theory. Small effects are found at intermediate energies. Folding model potentials are used by (1986YA16) to perform a systematic analysis of proton elastic scattering from 65 - 200 MeV. See also (1990AR11, 1990CR02, 1990EL01, 1991AR11, 1991AR1K). Effects of short-range correlations on the self energy in the optical model of 16O are studied in (1992BO04). See also (1992LI1D).
Angular distribution studies have been carried out for Ed up to 700 MeV [see (1986AJ04)] and recently angular distributions and analyzing powers with polarized deuterons were measured at 19 - 24 MeV (1991ER03) and at 200, 400, 700 MeV (1987NG01). Observed deuteron groups are displayed in 16.27 (in PDF or PS). See also 18F in (1987AJ02), and see the analysis of (1990ER09).
Reaction (b) has been used for analysis of oxygen in Fluoride glasses (1990BA1M).
Coupled-channels variational formalism is discussed and applied to 16O(d, d)16O (1986KA1A). Coupling to the proton channel is significant at 11 MeV, but can be ignored at ≥ 40 MeV. Coupling to d-breakup channels decreases as E increases, but is still significant at 60 MeV. (1988IS02) use folding interactions to investigate polarized d-scattering at Ed = 56 MeV. Breakup channels are important, as is the D-state admixture in the deuteron ground state - especially for tensor analyzing powers. (1988IS02) employed the continuum-discretized coupled-channels (CDCC) method, and obtained good agreement with data. (1987GR16) studied d-scattering at 400 MeV using the folding model, but failed to describe Ayy at relatively low momentum transfers. They attribute this failure to inadequacies in off-shell properties of N-N potentials. (1986MA32) analyzed elastic data at 56 MeV using an optical model potential containing a complex tensor term. The OM potential was compared with folding-model results. (1987MA09) evaluate the Pauli-blocking correction of the three-body Schrödinger equation for d-nucleus reactions.
(1989WA26) studied the spin-orbit potential for triton scattering to explain previous discrepancies with folding model predictions.
Angular distributions have been measured to E(3He) = 132 MeV [see (1982AJ01, 1986AJ04)] and at E(3He) = 60 MeV (1990ADZU). The matter radius < r2 > 1/2 = 2.46 ± 0.12 fm (1982VE13). Inelastic groups are shown in 16.27 (in PDF or PS). See also the analysis of (1990ER09). Differential cross sections for reaction (b) have been measured at E(3He) = 60 MeV (1990ADZT). The reaction has also been used in thin film analysis (1990AB1G).
(1986WA1U) studied the spin-orbit potential for 3He scattering to explain previous discrepancies with folding model predictions. The M3Y double folding model is used (1987CO07) to fit data at 33 MeV. No change in the spin-orbit strength is necessary. The three-parameter strong absorption model of Trahn and Venter is applied to data at 25 and 41 MeV. (1987RA36) obtain radii, diffusivities and quadrupole deformation parameters. (1987TR01) perform a simple optical model analysis of elastic 3He scattering from 10 to 220 MeV.
Angular distributions and/or differential cross sections of α-particles have been measured up to Eα = 146 MeV [see (1982AJ01, 1986AJ04)] and recently at Eα = 48.7, 54.1 MeV (1987AB03; α0): see 20Ne in (1983AJ01, 1987AJ02). See also the work on (α, α0) resonances at Eα = 2.0 - 3.6 MeV (1985JA17, 1988BL1H). A search at Eα = 10.2 - 18 MeV for continuum levels in 20Ne with a large [16O*(0+2) + α] parentage is described in (1992LA01). Reaction (a) has also been observed in astrophysical measurements (1989LA1G). Observed excited states are displayed in 16.27 (in PDF or PS). See also the analysis of (1990ER09), and see (1990DA1Q, 1990IR01).
Reaction (b) has been studied at Eα = 13.92 MeV in a quasifree geometry (1987SA01). Angular correlations (reaction (c)) have been studied to 12Cg.s. at Eα = 23.0 to 27.5 MeV to try to determine if a 3- state exists near the 2+ state 16O*(9.84): the evidence is strong that this is not the case (1986AJ04). The isoscalar (E2, T = 0) giant resonance decays predominantly via the α1 channel which contains ≈ 40% of the E2 EWSR, rather than via the α0 and p0 channels. For the (α, αd), (α, αt) and (α, α3He) reactions see references in (1986AJ04).
In a theoretical study of nucleus-nucleus potentials, (1987BA35) determine shallow potentials that are phase equivalent to deep ones. This method eliminates non-physical bound states encountered in some microscopically founded potentials. (1987BU06) calculate the probability of direct alpha-decay of the giant quadrupole resonance in 16O. They find direct and statistical mechanisms to be commensurate, and obtain good agreement with the data. The construction of a cranked cluster wave function for molecular-like states is discussed by (1986HO33). (1986MA35) study the radial shape and the energy dependence of the dispersive contribution to the real potential and apply it to alpha-particle scattering from 16O. (1989MI06) show that alpha-particle scattering from 16O near the Coulomb barrier can be described if the interaction is angular momentum dependent and has a less diffuse surface than that used to describe scattering at higher energies. The potential separable expansion method based on Coulomb-Sturmian functions is presented (1988PA21) and the l = 3 phase shift is calculated for α + 16O at E = 12 MeV. (1987SA55) show the one-channel orthogonality condition model provides results which agree with experiment for Eα ≤ 7.5 MeV. (1987WA1B) compare a microscopic potential obtained from RGM calculations with the optical model potential. They conclude that internucleus antisymmetrization is responsible for a large part of the energy dependence of the real part of OM potential. (1989YA15, 1991YA08) use the many body theory which takes the Pauli principle into account to calculate the α - 16O complex potential from a realistic effective two-nucleon interaction. The role of the Pauli principle is also examined in (1991OM03). Internucleus potentials in α + 16O systems are calculated with Skyrme-type forces in (1990WA01). Nuclear molecular resonances are discussed in the analyses of (1990AB10, 1992SA26). See also (1990KR16). A peripheral 3-body coupling model is applied to reaction (c) in (1992JA04).
Elastic angular distributions for reaction (a) have been measured at E(6Li) = 4.5 to 75.4 MeV and E(16O) = 36 to 94.2 MeV [see (1986AJ04) and 16.25 (in PDF or PS) in (1977AJ02) and 16.23 (in PDF or PS) in (1982AJ01)] and recently at E(6Li) = 50 MeV (1988TRZY). See also (1987GO1C). Vector analyzing power has been measured with polarized 6Li beams at E(6Li) = 25.7 MeV (1987VAZY, 1989VA04). See also 6Li in (1988AJ01). For studies of d - α angular correlations see 20Ne in (1983AJ01, 1987AJ02). For a fusion cross section study see (1986MA19). Inelastic scattering to states in 16O are reported at E(6Li) = 50 MeV by (1990TR02).
Elastic distributions for reaction (b) have been studied at E(7Li) = 9.0 to 68 MeV [see (1986AJ04) and 16.25 (in PDF or PS) in (1977AJ02) and 16.23 (in PDF or PS) in (1982AJ01)] as well as at E(7Li) = 10.3 - 22.40 MeV (1988MA07). For fusion cross section studies see (1988SC14) and references in (1986AJ04). See also (1988KE07).
A generalized optical model within the method of orthogonal conditions (MOC) has been formulated by (1988GR32). Taking account of antisymmetrization improves the description of angular distribution data. See also (1990SA1O).
Elastic angular distributions have been reported at E(9Be) = 20 to 43 MeV and E(16O) = 15 to 29.5 MeV [see (1986AJ04) and 16.23 (in PDF or PS) in (1982AJ01)] and recently at Ec.m. = 7.2, 8.4, 9.0, 9.6, 10.2 MeV (1989WE1I). Projectile decomposition measurements were reported at E(16O) = 32 MeV/nucleon. For fusion cross sections see (1982AJ01, 1986AJ04, 1988HAZS). See also (1985BE1A).
Angular distributions have been reported at E(10B) = 33.7 to 100 MeV and at E(11B) = 41.6, 49.5 and 115 MeV [see (1986AJ04) and 16.23 (in PDF or PS) in (1982AJ01)] and recently at Ec.m. = 14.17, 16.15, and 18.65 MeV (1989KO10). See also (1989KO2A). For fusion cross section measurements (reaction (a)) see (1982AJ01, 1986AJ04).
Angular distributions have been reported at many energies to E(16O) = 1503 MeV [see (1982AJ01, 1986AJ04)] and recently at E(16O) = 49.14, 48.14, 48.06 MeV (1986BA80). A peak in the excitation function at Ec.m. = 33.5 MeV was observed by (1990KO1X). See also the review of (1986BA1D) and analyses of (1988BR04, 1988RO01, 1989VI09). Many of the studies of this reaction have involved yield and cross section measurements, as they apply to compound structures in 28Si, fusion cross sections and evaporation residues. See (1990SN1A). Some involve multinucleon transfer. Others involve fragmentation of the incident particle. See (1982AJ01, 1986AJ04) and (1986GA13, 1986IK03, 1986SU1G, 1987SU03, 1988KO17, 1988SZ02, 1990BO1X). See also (1986CH41, 1986DE40, 1986SN1B, 1986WU03, 1987HO1C, 1987NA1C, 1987YO1A, 1988BR1N, 1988CAZV, 1988KR11, 1988ME1H, 1989BEZC, 1989KRZX, 1989SU1I, 1989WE1E, 1990BA1Z).
At E(16O) = 100 MeV members of the Kπ = 0+ [16O*(6.05, 6.92, 10.35, 16.3)] and Kπ = 0- bands [16O*(9.63, 11.60, 14.67)] are reported to be preferentially populated. In reaction (b), as well as in the scattering of 140 MeV 16O on 13C and 28Si, 16O* states (9.83, 10.33, 11.04, 11.47, 11.98, 12.38, 13.81, 14.75, 15.33, 17.76), with Jπ = 2+, 4+, 4+, 2+, 0+, 1-, 2+, 4+, 6+, 3-, respectively, for the first ten states, are populated: the state at 11.5 MeV is preferentially populated [see references in (1982AJ01, 1986AJ04)]. For pion emission see (1986AJ04, 1988SA31, 1989LE12).
(1987BA50) have investigated the two-proton correlation function using the BUU (semiclassical transport equations) model with conserved total momentum. Experimental features of the correlation function are reproduced. (1988BA43) study the energy dependence of the real part of the nucleus-nucleus potential using a modified Seyler-Blanchard two-body effective interaction containing density and momentum dependence. (1987BRZW) perform an optical model analysis of 12C - 12C and 16O - 12C elastic scattering from 10 - 94 MeV; real part: double folding of a density dependent M3Y interaction - imaginary part: phenomenological.
(1988BR20) examine dips in the far-side cross sections which reduce or eliminate potential ambiguities from analyses as in (1987BRZW). (1988BR29) analyzed elastic data at 9 to 120 MeV per nucleon using a folded potential based on the density and energy-dependent DDM3Y interaction. (1987DA02) present a solution to the inversion problem (i.e., obtaining potentials from data) and apply it to 16O + 12C at 1503 MeV with good results. A microscopic calculation of pion-production in heavy-ion collisions is applied (1986DE15) to coherent pion-production in 16O + 12C collisions. Effects of Pauli blocking and a surface contribution to the optical potential are investigated by (1989EL01). Data require that a collective surface contribution be added to the volume part.
(1988FR14) resolve optical potential model ambiguities by using dips in far side cross section data along with other special features of the angular distributions of elastic scattering data. (1986HA13) performed a barrier penetration calculation of heavy-ion fusion cross sections, valid both above and below the Coulomb barrier. (1986KA1B) survey projectile breakup processes using the method of coupled discretized continuum channels. An optical model potential containing a parity dependence which accounts for elastic α-particle transfer can explain the oscillations seen in the total fusion excitation function of 16O on 12C (1988KA13). (1988KO27) perform an optical model analysis of 16O scattering data at E/A = 94 MeV. They explored potential shapes more general than folded or Woods-Saxon; no improvement in agreement with data. (1989LE23) analyzed reaction data using an eikonal approach. They input only the densities and transition densities of the nuclei and elementary nucleon-nucleon scattering amplitudes. Good agreement with data was obtained. The 12C + 16O internucleus potential is calculated with the use of Skyrme type forces by (1990WA01).
(1989MI1K) calculate zero-degree and transverse energy for relativistic collisions. Results fit data very well. Low energy optical potentials are derived (1987PA24) from effective interactions using double-folding. Only the effective interaction of Satchler and Love give good results over a wide energy range. (1988RA1G) explores the relationship between clustering and shell effects, and find that this relationship is a close one. (1986SA1D) perform a microscopic coupled-channels calculation. Breakup and virtual breakup effects are found to be important. (1987SC34) present an expression for the real part of the nucleus-nucleus potential (energy dependent) which arises in the framework of the elastic model for heavy-ion fusion. This model is applied to sub-barrier fusion. (1988WU1A) propose a non-compact group model to describe quasi-molecular nuclei.
For elastic scattering studies see 16.23 (in PDF or PS) in (1982AJ01), and see the more recent work at Ec.m. = 48.06, 48.48, 49.14 MeV (1986BA80), and Ec.m. = 19 - 30 MeV (1989FR04). For fusion cross sections see (1986AJ04) and recent work at Ec.m. = 7.8 - 14.6 MeV (1986PA10). See also the review of (1986ST1A). For the excitation of a number of states in 16O in reaction (a) see (1986AJ04). Cross sections for different exit channels of 16O + 13C at Ec.m. = 4.8 - 9.8 MeV were measured by (1991DA05). Emission ratios for pn to d and αpn to αd were studied in (1986GA13). Competition between p2n, dn, and t emission was studied at Ec.m. = 10 - 16 MeV (1990XE01). For reaction (b) a search for resonances in elastic scattering at Elab = 38 - 54 MeV is reported in (1990AB07).
(1987DA34) performed a six-parameter optical model analysis of 13C(16O, 16O)13C. A two-center shell model is applied (1987NU02) to the 13C + 16O system. Parity dependence of collisions between p- and sd-shell nuclei is studied (1986BA69) microscopically in the two-center harmonic oscillator model.
For elastic scattering studies see (1986AJ04) and 16.23 (in PDF or PS) in (1982AJ01) and (1977AJ02). Recent measurements on reaction (b) at Elab = 30 - 70 MeV were reported in (1986HA1F). For yield and total fusion cross-section measurements see (1982AJ01, 1986AJ04). See also (1986BA69).
The angular distributions for elastic scattering have been measured with E(16O) up to 140.4 MeV [see (1982AJ01, 1986AJ04)] and recently at Ec.m. = 17 MeV (1987TI01), E(16O) = 350 MeV (1989ST08) and E(16O) = 38 MeV/nucleon (1986BR25). Inelastic scattering studies involving 16O*(6.05) [Jπ = 0+] (1989ZUZZ) are reported at E(16O) = 51.0 to 76.0 MeV, and similar studies involving 16O*(6.13) [Jπ = 3-] (1988PAZZ) are reported at Ec.m. = 26.5 - 43.0 MeV. Coupled channels effects are important at energies a few times the Coulomb barrier (1977AJ02, 1986AJ04). Intermediate and compound structure studies are described in (1986GA10, 1986GA24).
For yield and fusion cross sections see (1982AJ01, 1986AJ04) and more recent work (1986IK03, 1986TH1A, 1987GO30, 1987KU02, 1988AU03). At E(16O) = 72 MeV, (1988AU1A) see no evidence for a low-l fusion window. At E(16O) = 70 - 130 MeV measurements of evaporation residues by (1986IK03) find no evidence for a low-l cutoff. For a study of α-transfer at near-barrier energies see (1986CA24). Light-particle emission at E(16O) = 25 MeV/nucleon was studied by (1986CH27). Related work includes an investigation of the role of isospin in the statistical decay of the GDR by (1986HA30) and the review of hot nuclear matter (1989SU1I). See also (1989FE1F, 1989SC1I).
(1988AS03) evaluate the influence of the Uehling potential on subbarrier fusion. (1987GO19) report a calculation of the fusion cross section using a classical microscopic equations of motion approach. (1987LO01) study the effect of elastic transfer process on sub-barrier fusion reactions between similar nuclei. (1987OH08) show that internal and barrier waves based on a semiclassical picture can account for the oscillations seen in fusion excitation functions. (1987RA28) use statistical theory to study the behavior of high spin states formed in fusion reactions. (1987SP11) calculate the fusion excitation function using the one-body wall friction.
(1987TO10) investigate the influence of nucleon-nucleon collisions in the low angular momentum limit for fusion predicted by TDHF. A relativistic mean-field model consisting of nucleons coupled to scalar and vector mesons is used to solve the time-dependent mean-field equations. A relativistic Vlasov equation derived from mean field theory is applied in (1990JI1C). An extended TDHF theory has been used (1989GO1F) to study mass fluctuations in deep-inelastic collisions. Results show differences from conventional TDHF calculations (1987BA10). (1988RE1A) performed TDHF calculations of 16O + 16O using various Skyrme forces. (1986TO14) calculate subthreshold pion-production using the TDHF formalism, and compare their findings with data. (1986UM02) study fusion of 16O + 16O using TDHF and Skyrme forces. See also the study of (1990SL01).
(1986CH44) perform an optical model analysis of elastic scattering data using a calculated real part of the potential. The potentials are constructed in the energy density formalism with nuclear density distributions obtained in the framework of the method of hyperspherical functions. (1989DA1C) develop a simple theory of a heavy-ion optical model potential. Colliding ions are described as two slabs of nuclear matter, with energy densities from properties of nuclear matter. (1986FA1A) extend and refine the calculation of the real and imaginary parts of the optical model potential in the 20 - 100 MeV/nucleon range. Techniques for choosing a unique potential are discussed in (1990KO18). See also (1990RE1E). (1988NA10) calculate microscopic nucleus-nucleus potentials using the energy-density formalism. See also (1991MA29). (1987PA24) derive real parts of the low-energy optical potential using the double-folding model. Pauli exchange effects within this model are studied in (1991KH08). A semiclassical method for calculating elastic scattering cross sections was used in (1991SA20).
(1989HU1C) combine the concepts from a partition temperature model and the wounded nucleon model to describe high-energy nucleus-nucleus collisions. (1988IT03) have applied coupled equations which treat the relative motion and internal excitation simultaneously to the case of 16O + 16O at intermediate energies. (1987KA04) study subthreshold pion production mechanisms for 16O + 16O at 40 and 80 MeV/nucleon. A quantum transport equation with two-body collisions included via a relaxation-time method is applied to 16O - 16O collisions between 40 and 200 MeV/nucleon (1988KO02). (1988KO09) compare predictions of momentum dependence of nucleus-nucleus interactions deduced from various models. (1989KO23) describe resonant phenomena in 16O + 16O in terms of an ion-ion potential. (1988MA1O) solve the inverse scattering problem for fixed angular momentum using E-dependent phases and a Povzner-Levian representation of the wave function. Adiabatic bound and Gamow states have been calculated (1986MI22) in a realistic two-center potential. Specific results for a neutron in a 16O + 16O potential are presented. (1985SH1A) develop a microscopic approach to describe elastic and inelastic cross sections. They employ the quasiparticle phonon model for heavy ions and resolve the "fusion-window-anomaly". The resonating group method is used by (1988WA31) to investigate constituent components of the 16O - 16O exchange potential. A two-center shell model description is discussed in (1990KH04).
Angular distributions of elastically scattered ions have been studied at E(16O) = 24, 28 and 32 MeV and E(17O) = 53.0 to 66 MeV, E(17O) = 22 MeV (reaction (a)) and at E(16O) = 24 to 54.8 MeV and E(18O) = 35 to 89.3 MeV (reaction (b)) [see (1982AJ01, 1986AJ04)]. Yields and fusion cross sections are reported in (1982AJ01, 1986AJ04). See also the studies on light-particle emission ratios in these reactions (1986GA13, 1990XE01).
(1987IMZZ) have studied the effects of rotational couplings by using the rotating molecular orbitals model. (1987IM1C) develop and use a formalism for dynamical treatment of the molecular orbitals of valence nucleons in nucleus-nucleus collisions. (1988IM02) consider the role of rotational coupling interactions in the transition between nucleon molecular orbitals. (1987MA22) use the semiclassical approach including both one- and two-step contributions to calculate the two-particle elastic transfer reaction, while (1988KA39) calculate differential cross sections for transfer of two neutrons taking Coulomb effects into account in a four-body model. (1986MI22) use a realistic two-center potential to show that a substantial fraction of the particle emission comes from sequential decay of the excited fragments after separation, and (1986VI08) consider two-particle exchange reactions using a parity-dependent optical potential.
Elastic scattering angular distributions have been studied at E(16O) = 21.4 and 25.8 MeV and at E(19F) = 33 and 36 MeV: see (1977AJ02). Angular distributions in reaction (b) have been measured at E(16O) = 40.7 to 94.8 MeV, 25.6 to 44.5 MeV, 44.1 to 63.9 MeV [see (1986AJ04)], 60 - 80 MeV (1986FUZV), and at E(20Ne) = 50 MeV (1986AJ04). Recent excitation functions were measured for reaction (b) at Ec.m. = 21.5 - 31.2 MeV (1988HE06). See also (1989SA14). For yield and fusion cross section measurements see (1986AJ04). Projectile breakup studies are reported at 3.6 GeV/nucleon. See also (1987AN1C). Hyperon production is investigated in (1986FUZV, 1988BO46). See also (1986HE1A, 1988BE2A).
Elastic angular distributions are reported at E(16O) = 35 to 60.7 MeV (reaction (b)) and 27.4 to 50 MeV (reaction (d)) [see (1982AJ01)] and E(16O) = 150 MeV (1986AJ04; reaction (b); elastic). More recent work on reaction (b) includes elastic scattering excitation function measurements at Ec.m. = 31.6 - 45.2 MeV (1986DR11, 1986DR1B) and inelastic measurements at Ec.m. = 33.6 - 49.2 MeV (1986NU01, 1986NU1A) and at Ec.m. = 64 - 88 MeV (1986PE1G). Orbiting cross sections for reaction (b) are reported in (1989BLZZ). For yield, evaporation residue and fusion measurements, see references in (1982AJ01, 1986AJ04).
(1988AL06) show that algebraic scattering theory provides a simple yet detailed description of the complex coupled channels problem (16O + 24Mg). (1989FI03) calculate the effect of the dynamic α-transfer potential on several channels of the 24Mg + 16O systems. (1987NA13) obtain an energy and angular momentum-dependent polarization potential from a compound nucleus level density dependent imaginary potential. They find that the elastic and fusion cross sections of 16O + 24Mg are hardly affected by this potential.
An elastic angular distribution has been measured at E(16O) = 46.5 MeV: see (1982AJ01). For yield, fusion and evaporation residue studies see (1982AJ01, 1986AJ04) and (1987IK01, 1988KO01, 1989CA14, 1989DE02, 1990KR1D). See also (1986BR26, 1987DEZV). For fragmentation studies see (1986AJ04) and (1986SH1F, 1987SH1C, 1987SH23, 1988AI1C, 1988BR1N, 1988SH1H, 1989CA14, 1989YI1A, 1990PAZW). For work on deeply inelastic collisions see (1986AJ04) and (1987SH21). For pion production see (1986AJ04) and (1987HU1C, 1988BA21, 1988JU02, 1989FO07). For total reaction cross sections see (1987KO12). Angular correlations have been studied at E(16O) = 65 - 65.6 MeV (1986AJ04) and at E(16O) = 82.7 MeV (1988SH1H), at 215 MeV (1990KR14), at Ec.m. = 80 - 250 MeV (1988DE1A, 1989DE02), and at E(16O) = 4 - 5 MeV/nucleon (1987CA1E). The sequential decay of 16O*(10, 11.6, 13.2, 15.2, 16.2, 21) is reported via α0 [see (1986AJ04)].
(1987BA01) evaluate the energy dependence of the real part of the nucleus-nucleus potential using two-body effective interactions, calculate 16O + 27Al, and compare to data. (1989CA11) introduce "pre-equilibrium" temperature to describe the thermodynamics of nuclear systems prior to equilibrium. (1988DA11) modify the coalescence model for complex-particle emission by correcting for the Coulomb barrier and the ejectile's binding energy.
Angular distributions for reaction (a) have been reported at E(16O) = 29.3 to 215.2 MeV [see (1982AJ01, 1986AJ04)], and recently at E(16O) = 94 MeV/nucleon (1987RO04). Elastic angular distributions for reactions (b) and (c) are reported at E(16O) = 60 MeV (1986AJ04). For yield, fusion cross section and evaporation residue measurements see (1982AJ01, 1986AJ04). See also (1986BL08). For a crystal-blocking measurement of time delays in reaction (a) see (1989MA23). For pion production see (1986AJ04).
(1988AL08) obtain expressions for the elastic S-matrix which include effects of the coupling to α-transfer channels to all orders. They study 16O + 28Si at 180°. (1988AS03) evaluate the influences of the Uehling potential on sub-barrier fusion and obtain noticeable modifications of the barrier penetrability. (1986BR11) study the E-dependence of an optical potential which fits all 16O + 28Si elastic data for E = 54.7 - 215.2 MeV. (1986HO18) employ a fixed energy potential inversion method to generate an optical model potential which fits 16O + 28Si elastic scattering data at 34.8 MeV. (1986BR19) create a deformed optical potential consistent with calculations based on nuclear structure information which fits 16O + 28Si scattering and fusion data. (1986BR23) use an optical model with repulsive core and coupled channels method to describe 16O + 28Si scattering data at large angles for E = 29 - 35 MeV. (1988CH28) use a Monte Carlo simulation to calculate the nucleon transfer part of the imaginary optical-model potential. (1987HU11) find good agreement with back angle elastic data in 16O + 28Si by including a derived α-transfer polarization potential. (1990DE35) employ a multistep α-transfer treatment to study back angle scattering of 16O + 28Si. (1985KH10) use a conventional optical model potential for Elab = 33.16 - 55 MeV. They parameterize the S-matrix in terms of Regge poles and look at semiclassical features. (1985KR1A) show that existing data do not allow one to draw conclusions about the relevance of Regge poles in 16O + 28Si. (1989MA08) use elastic phase shifts obtained by the algebraic approach to scattering theory in a fixed energy inversion procedure. Results point to an underlying nonlocal interaction. (1987NA13) show that the elastic and fusion cross sections are hardly affected by a strongly attractive real-polarization-potential. (1987VA03) have applied a fast algorithm-based method for performing unconstrained phase-shift analyses to 16O + 28Si at 21.1 MeV (Ec.m.). (1987XI01) formulate a molecular orbit theory for the 3α-transfer process and apply it to 16O + 28Si for E = 18.67 - 34.80 MeV, and compare it to data.
Elastic angular distributions are reported on 40Ca at E(16O) = 50 to 214.1 MeV [see (1982AJ01, 1986AJ04) and recently at E(16O) = 94 MeV/nucleon (1988RO01). Elastic angular distributions were reported at E(16O) = 60 MeV (42,44Ca; also inelastic distributions) and 150 MeV [see (1986AJ04)]. Similar measurements have been reported for 48Ca at E(16O) = 60 MeV [see (1982AJ01)] and at 56 MeV (1986AJ04; also 48Ca*) and 158.2 MeV (1986AJ04; also 48Ca*). Yield, fusion cross section and evaporation residue measurements are reported in (1982AJ01, 1986AJ04) and by (1986SA25, 1987BEZY, 1987BR20, 1987HI10, 1988KO1U, 1989BE17). See also (1986GU1C). For a measurement of the total non-fusion reaction cross section at E(16O) = 158.2 MeV (reaction (d)) see (1986AJ04). For a study of deep inelastic collisions at 142 MeV (reaction (d)) and for reaction (e) see (1986AJ04).
A microscopic study of the 16O + 40Ca potential is discussed in (1986WAZM). (1986AN18) calculate angular distributions for elastic scattering using a simple prescription for the part of the imaginary potential arising from inelastic processes and a folding expression for the real part of the potential, and fit it to the data. (1986CH20) perform a microscopic optical model analysis using folding and realistic NN interactions (direct and exchange terms). They compare their results to data. (1986CH38) calculate the real part of the optical model potential in a folding approximation using the density dependent M3Y interaction in factorized form. They also compare their results to data. (1989DA1C) describe colliding nuclei as two slabs of nuclear matter. Energy density is derived from properties of nuclear matter. (1989ES07) obtain good agreement with elastic and inelastic data using a coupled-channels treatment. (1987GR04) study peripheral reactions. Neutrons and protons behave separately in an effective mean field. They find a transition between incomplete deep inelastic processes and fragmentation reactions near 35 MeV/nucleon. (1986HA13) calculate barrier penetrations with Coulomb included. They obtain good agreement with data in the above and sub-barrier fusion regions. (1989HO10) calculated heavy-ion fusion reactions with a macroscopic model proposed by Bertsch. They give a good account of the fusion cross section up to very high energies. (1987DA23) develop a semi-microscopic model of elastic and inelastic scattering with a full finite range NN interaction. They also study the role of NN exchange correlations. The real and imaginary potentials have been derived (1987VI04) in a model which includes a large set of non-elastic channels. (1988PA20) calculate the particle transfer flux between two scattering nuclei from the time-dependent single-particle wave functions in the field of two moving potential pockets. They deduce the absorptive potentials which compare well with phenomenological ones. (1989SU05) study the excitation of the GDR within the framework of the Landau-Vlasov equation. They analyze the GDR excited in peripheral 16O + 40Ca reactions at E = 5 MeV/nucleon.
Angular distributions for the ground state deuteron group have been studied at Ep = 8.62 to 11.44 MeV. At Ep = 31 MeV, angular distributions are reported for the deuterons corresponding to 16O*(0, 6.05 + 6.13, 7.12, 8.87, 10.36, 12.97, 13.26). States at Ex = 15.22 and 15.42 MeV were also observed. Spectroscopic factors were obtained from a DWBA analysis: see (1977AJ02, 1986AJ04). See also (1989DE1P, 1989OB1B).
Differential cross sections and analyzing powers for the reaction were measured at Ed = 89 MeV by (1990SA27) and summarized in 16.28 (in PDF or PS). Earlier information obtained at Ed = 52 MeV is displayed in 16.20 (in PDF or PS) of (1986AJ04). As discussed there, comparison of the (d, t) and (d, 3He) reactions leads to assignments of analog states in 16N and in 16O [see 16.10 (in PDF or PS) in (1982AJ01)]. A study of this reaction, the (d, 3He) reaction, and reaction 68 [17O(3He, α)16O] below, suggests that there is more than 17% isospin mixing of the 2- states in 16O*(12.97, 12.53): the corresponding mixing matrix element is ≥ 155 ± 30 keV. An isospin mixing matrix element of 110 ± 10 keV for the 4- states of 16O*(17.79, 18.98, 19.80) is compatible with the results from this reaction and with pion scattering (1986AJ04). See also reaction 44 [16O(π±, π±)16O].
Angular distributions have been reported at E(3He) = 11 MeV [see (1977AJ02)], at E(3He) = 14 MeV (α0) and at E(3He) = 33 MeV (to many states of 16O) [see (1986AJ04)]. 16.28 (in PDF or PS) displays some of the information derived from this reaction. For polarization measurements see (1986AJ04) and 20Ne in (1983AJ01, 1987AJ02). See also (1982AJ01).
Angular distributions of tritons have been measured for Ep = 43.7 MeV [see (1982AJ01)] and at Ep = 90 MeV (1986VO10) (to 16O*(6.1, 6.92, 7.12, 9.84, 13.26, 16.35)): see also (1985BLZY). It is noted in (1986VO10) that the 16.35 MeV state may be the (0+, 1-, 2+) multiplet at Ex = 16.35 and 16.144 MeV (1982AJ01). The population of 16O*(22.7, 24.5) is consistent with L = 0 and 2, respectively, and with assignments of T = 2, Jπ = 0+ and 2+. The decay of 16O*(22.7), Jπ; T = 0+; 2, is via α0, α1 and α2 [12C*(0, 4.4, 7.7)] with (1.6 ± 0.7), (1.9 ± 0.7) and (14 ± 2)% branches and Γi(eV) = 190 ± 100, 230 ± 110 and 1680 ± 550 eV, respectively; via p0, p1+2, p3 with (7 ± 2), (11 ± 2) and (5 ± 2)% branches and Γi(eV) = 840 ± 343, 1320 ± 454 and 600 ± 300 eV; and via n1+2 with a (23 ± 15)% branch [Γn=2760 ± 1970eV] (the n0 branch is < 15%) [Γi are based on a total width of 12 ± 3.5 keV]. See (1986AJ04). See also (1982AJ01) and 19F in (1987AJ02).
Angular distributions have been measured at many energies up to Ep = 44.5 MeV [see (1982AJ01)] and Ep = 1.55 to 2.03 MeV (α0, α1), 1.66 to 1.86 MeV (α0), 10.0 to 11.4 MeV (16O*(0, 6.05, 6.13, 6.92, 7.13, 8.87, 9.84, 10.36, 10.96, 11.08 + 11.10)) [see (1986AJ04)]. See also 16.31 (in PDF or PS) in (1971AJ02). For a DWBA analysis of data for incident energies below the Coulomb barrier see (1991HE16). A recent measurement of the absolute differential cross section at Ep = 2 - 3.4 MeV is reported in (1986OU01). Measurements at Ep = 1.55 - 1.64 MeV by (1990AZZY) were used to study resonances corresponding to states in 20Ne. Absolute yields, angular distributions and resonance widths of the 6.13, 6.92, and 7.12 MeV photons from the 340.5 keV resonance are reported in (1991CR06). See also (1991MC08) for a study of resonance-yield deconvolution techniques.
The internal conversion to pair production ratio of the E0 transition 16O*(6.05 → g.s.) [0+ → 0+] is (4.00 ± 0.46) × 10-5. The ratio of double γ-emission to pair production ΓE1E1/ΓE0(π) = (2.5 ± 1.1) × 10-4. τm for 16O*(6.05, 6.13) are 96 ± 7 psec and 26.6 ± 0.7 psec, respectively. See (1982AJ01) for references. |g| for 16O*(6.13) = 0.556 ± 0.004 (1984AS03, 1986AJ04). For γ-ray branching ratios and mixing ratios see 16.14 (in PDF or PS) and (1986AJ04).
Differential cross section measurements at Et = 38 MeV are reported in (1992CL04).
See (1988SH05) for a DWBA analysis of differential cross section data at Eα = 140 MeV.
The angular distribution to 16Og.s. has been measured at Ed = 13.6 MeV (1986AJ04).
Angular distributions have been reported at Eα = 22.8 to 25.4 MeV and at 90.3 MeV, the latter to 16O*(0, 6.1, 7.0, 8.8, 9.8, 10.3) [see (1982AJ01)] and at Eα = 25.1 to 27.8 MeV (1986AJ04). Excitation functions measured for Eα = 26 - 37 MeV at θlab = 30°, 40°, 60° have been reported (1986ESZV, 1989ES06). See also (1987SH1B, 1988SH1F).
The ground state angular distribution has been studied at E(12C) = 40 MeV [see (1986AJ04)]. 16O + 8Be breakup of 24Mg following inelastic scattering of 24Mg projectiles on 12C has been reported (1989FU10).
Forward-angle yields of 16O measured at E(28Si) = 100 - 170 MeV have been reported (1986SH25).
Forward-angle yields of 16O measured at E(28Si) = 100 - 170 MeV have been reported (1986SH25).