(See Energy Level Diagrams for 15O)
Collective and deformed nuclei: (1974PU02).
Giant resonance: (1973DE1V).
Muon and neutrino capture and reactions: (1972BL01).
Other topics: (1970RY04, 1970SI1C, 1970SU1B, 1971BE59, 1971ER1C, 1971LA1D, 1971RY1A, 1972AN05, 1972CA37, 1972LE1L, 1972SH32, 1973BA2J, 1973DE13, 1973RE17, 1973RO1R, 1973RO1P, 1973SP1A, 1973WA35, 1974SA05, 1974SL1C, 1974VA24, 1975BE48, 1975MI02, 1975SH20, 1975SH1H).
Mass of 15O: A re-determination of the mass of 15O has resulted from studies of the 14N(p, γ)15O (1972NE05) and 15N(p, n)15O (1972JE02, 1972SH08) reactions. Based on the (1971WA1E) masses for n, p, 14N and 15N, the mass excesses are 2854.2 ± 1.1 keV (1972JE02), 2856.4 ± 0.9 keV (1972SH08) and 2855.9 ± 1.0 keV (1972NE05): the weighted mean of these three values is 2855.6 ± 0.6 keV (1972SH08) and we adopt it for 15O. The mass of 15O is then 15.0030656 (7) a.m.u., based on the conversion factor 931.502 (3) MeV/a.m.u.
Reported half-lives are listed in Table 15.19 (in PDF or PS) of (1970AJ04): the weighted mean is 122.24 ± 0.16 sec. See also (1972LE33). Using this value of τ1/2 and Qm, log f0t = 3.636 [see (1972JE02)]. The K/β+ ratio is (10.7 ± 0.6) × 10-4 (1972LE33). See also (1970DA21, 1970KO41, 1970ST04, 1972KO1A (also astrophys.), (1973MU1D, 1973WI04, 1973WI11, 1974LE1G, 1974WI1M, 1975BA59, 1975BL1G, 1975KR14; theor.).
Excitation functions for these reactions have been measured over a wide range of energies: see Table 15.20 (in PDF or PS) in (1970AJ04) and Table 15.20 (in PDF or PS) here. Observed resonances are displayed in Table 15.21 (in PDF or PS). For angular distributions see the writeups of the residual nuclei in (1974AJ01, 1975AJ02) and in 13N, 14N and 14O.
The yield of n0 (reaction (a)) shows a resonance for E(3He) < 10 MeV [see, e.g., (1964OS01)] and little structure above, to 30.6 MeV (1970SI15). The yield of protons (to many final states in 14N) (reaction (b)) shows some clear resonances below E(3He) = 4.5 MeV and some uncorrelated structures [see Fig. 3 in (1973SO04) for a summary of the (1969HA49, 1973SO04) work for E(3He) = 4 to 12 MeV] at higher energies, with the possible exception of states at Eres = 7.8, 9.2 - 9.6 and (10.5) MeV (1973SO04). The reaction proceeds predominantly via the compound nucleus up to E(3He) = 12 MeV. The p0, p1 and p2 yields show no appreciable structure for E(3He) = 16 to 30.6 MeV (1970SI15). See also (1973HE09), (1970VY1A; theor.) and the earlier references in (1970AJ04).
The activation cross section for 13N (reaction (c)) shows no structure for E(3He) = 6.5 to 30.6 MeV (1970SI15). A structure at E(3He) = 29.5 MeV is reported by (1970SI16: E(3He) = 22.3 to 30.6 MeV) in reaction (d). The elastic scattereing (reaction (e)) shows some resonant structure near 3, 5 and 6 MeV (see Table 15.21 (in PDF or PS)) and some largely uncorrelated structures in the range E(3He) = 16.5 to 24 MeV (1972MC01). There is some suggestion, however, of two resonances at E(3He) = 17 and 20 MeV (1972MC01). The 90° yield of reaction (d) to 12C*(15.1) [Jπ = 1+; T = 1] shows a strong peak at 21.5 MeV, Γ ≈ 2.5 MeV (1970SI16). See also (1975WA1N; theor.).
The yield of α-particles has been measured at many energies to E(3He) = 18.6 MeV. Below E(3He) = 8 MeV resonances are observed†: see Table 15.21 (in PDF or PS). Broad fluctuations are observed in the excitation functions for α0, α1 and α3 for E(3He) = 12 to 18.6 MeV (1970GR08). For reaction (g) see (1971DE37: 37.7 to 41 MeV). For spallation reactions see (1975FU01, 1976WA1P).
† I am indebted to Prof. H.R. Weller for pointing out errors in Table 15.21 (in PDF or PS) in (1970AJ04).
Angular distributions of the n0 group have been measured at Eα = 18.4 to 23.1 MeV (1973CO04) and at 21.9 MeV (1975SK1B: also to some (unlisted) excited states). See also (1972DA32, 1974SH06) and (1970AJ04).
States observed in this reaction are displayed in Table 15.22 (in PDF or PS) (1975BI06: E(6Li) = 59.8 MeV). Comparisons of angular distributions of the triton groups in this reaction and of the 3He groups to analog states in 15N have been made: analog correspondence is established for (10.48 - 10.80), (12.84 - 13.15 [u]) and (15.05 - 15.49 [u]) [Ex in 15O - Ex in 15N; u = unresolved]. Previous suggestions of analog pairs in 12C(10B, 7Li) and 12C(10B, 7Be) seem doubtful in view of this high resolution study which shows that some of the states involved in the previous comparisons were unresolved doublets (1975BI06). See also the work of (1970JO09, 1970JO1D: 12, 13, 14 MeV; t0) and of (1971CH1R: 30.8 MeV; many states, comparisons with analogs). See also (1971LA1B, 1971BA2Q, 1972BA2B, 1974HO1P) and (1971BA2V, 1973OG1A).
At E(10B) = 100 MeV angular distributions have been measured for groups to 15O*(5.24, 7.28, 9.64, 10.47, 12.89, 15.36, 15.88, 17.13) and comparisons have been attempted with those for the reaction (10B, 7Be) to analog states in 15N [but see reaction above]. 15O*(12.89, 15.36) are very strongly populated (1973NA09). See also (1973BR1C, 1973SC1B).
At E(12C) = 187 MeV, θlab = 8° the spectrum is dominated by 15O*(12.84, 15.05) [assumed Jπ = 1/2-, 13/2+, respectively]. 15O*(7.28) [Jπ = 7/2+] is populated but 15O*(0, 6.79) are not observed (1974AN36, 1974SC1M). The situation is similar at E(12C) = 114 MeV but at E(12C) = 72 MeV (θlab = 11°) 15O*(0, 5.2, 7.28) are populated with comparable intensities (1974AN36). See also (1971SC1F, 1972SC21, 1973SC1J, 1973SC1B, 1973VO1E, 1975HA1P, 1975VO1H) and (1972BR21, 1975KU1L; theor.).
Angular distributions of the n0 group have previously been measured at E(3He) = 1.70 to 10.1 MeV: see (1970AJ04). Recent measurements of the distributions to most states of 15O with Ex < 10.5 MeV are displayed in Table 15.23 (in PDF or PS) (1971HI04, 1972ET01, 1972GE02: E(3He) = 5.5 - 6.2 MeV). At these energies it is necessary to combine direct interaction and compound nuclear calculations: these suggest that 15O*(5.18, 5.24, 7.28, 8.28(?)) have large 3p-4h strengths (1972GE02). See also (1973RH1A).
Observed resonances and states observed in the γ-decay are listed in Tables 15.24 (in PDF or PS) and 15.25 (in PDF or PS). Branching ratios are displayed in Table 15.19 (in PDF or PS): see (1970AJ04) and (1972KR14, 1972PH02, 1974KE02). See also (1971SH1D, 1972KU1J).
The cross section increases from (8.5 ± 3.7) × 10-12 b at 100 keV to (140 ± 30) × 10-12 b at 135 keV (1957LA13). Extrapolation from the Ep = 0.28 MeV resonance gives S(0) = 2.75 ± 0.50 keV · b, with zero slope to Ep = 0.05 MeV (1963HE11). For astrophysical implications see (1970AJ04, 1971BA1A, 1972CA1N, 1973CL1E, 1973TR1E).
(1972NE05) has measured accurately both the energy of the second resonance [1058.0 ± 0.5 keV] and the excitation energy of the corresponding state in 15O (Ex = 8284.1 ± 0.8 keV): this leads to a mass excess for 15O of 2855.9 ± 1.0 keV. For a comparison of this value and of two others which have led to a new mass of 15O see the "GENERAL" section here.
The 90° yield curve has been measured for Ep = 2.2 to 19.0 MeV: resonances are observed over most of the range in the γ0 yield. The (γ1 + γ2) yield is relatively weak (1970KU09). For Ep = 18 to 28 MeV the excitation function for γ0 decreases smoothly with energy: there is no evidence for structures (1975HA39). The (p, γ0) reaction populates the T = 1/2 component of the giant dipole resonance: in 15N, 14C(p, γ0) can populate both the T = 1/2 and the T = 3/2 components (1973PA1P). See also (1972SN1A, 1974MA1U), (1973HA1X, 1973SU1E) and (1970FR11; theor.).
The scattering anomalies are superposed on a background which decreases less rapidly than the Rutherford cross section; for Ep < 2.3 MeV, the background is largely s-wave with some p-wave contribution above Ep = 1.5 MeV.
Observed resonances are displayed in Table 15.25 (in PDF or PS). The Jπ assignments shown arise from considerations of branching ratios (see Table 15.19 (in PDF or PS)), measurements of angular distributions of γ-rays in the (p, γ) reaction, angular correlation studies and the work discussed in this section. See (1970AJ04) for the earlier references.
The recent work of (1969WE02, 1971LA23, 1972CH28, 1972PH02) has given us a much clearer picture of the resonances in this reaction below Ep = 6.2 MeV. These results, together with those obtained in the (p, γ) reaction, lead to a good understanding of the correspondence of the analog states in 15N and 15O below Ex ≈ 13 MeV: see (1972PH02) and Fig. 13 (Isobar Diagram).
Excitation functions have also been measured for the p0, p1 and p2 groups for Ep = 17 to 26.5 MeV: there is no evidence for resonant behavior but the p1 yield shows a large increase between Ep = 20 and 23 MeV (1972LU10). Total cross sections for the p0 → p9 groups have been measured at Ep = 8.6, 10.6, 12.6 and 14.6 MeV by (1973HA54). See also (1971ES1A, 1971OD01).
The polarization of the p0 group has been measured at Ep = 49.4 MeV (1970CL10). The depolarization parameter, D, has been determined for the elastic transition at Ep = 16.15 MeV (1974CL1H). For other polarization measurements [Ep = 3.0 to 155 MeV] see Table 15.25 (in PDF or PS) in (1970AJ04). See also (1971ES1A).
The excitation function has been measured for Ep = 6.3 to 12 MeV. Broad resonances are observed for Ep = 7.5 to 9.85 MeV: see Table 15.25 (in PDF or PS) (1964KU06). See also (1970AJ04), (1973CL1E; astrophys. questions) and (1970AL1J; theor.).
See 12N in (1975AJ02).
Excitation functions for the ground state group have been measured at Ep = 7 to 11 MeV: some resonant structure is indicated (see Table 15.25 (in PDF or PS)) (1970ME30). Total cross section for the transitions to 12C*(0, 4.4) have been measured in the range Ep = 20.5 to 44.6 MeV (1974PI05). See also (1970AJ04) and 12C in (1975AJ02).
Excitation functions and total cross section measurements have been carried out for the α0 group for Ep = 3.78 to 6.38 MeV (1976IN01), 5 to 22 MeV (1974JA11), 6 to 10.5 MeV (1968SH11; also α1 in the range 8.2 - 10.5 MeV), 7 to 11 MeV (1970ME30; also α1), 9 to 12 MeV (1974HU02) and 20 to 45 MeV (1974PI05; also α1, α2+3, α4+5+6). Fairly sharp structures persist until Ep = 15 MeV (1974JA11): see Table 15.25 (in PDF or PS) for the parameters of observed resonances, and in particular footnote g. Reaction (b) whose cross section has been measured for Ep = 14 to 24 MeV displays a broad peak at ≈ 20 MeV (1974JA11). For astrophysical questions see (1974JA11, 1976IN01). See also (1975AJ02).
Angular distribution studies have been carried out at many energies in the range Ed = 0.9 to 11.8 MeV: see Table 15.27 (in PDF or PS) in (1970AJ04) and (1970RI01: Ed = 2.80 - 5.35 MeV; Ex < 7.6 MeV), (1970BU15: 4.35, 5.5 MeV; n0), (1972FO07: 5.2 MeV; pol. n to Ex < 7.6 MeV), (1971BO35: 5.6 and 6 MeV; Ex < 8.3 MeV) and (1971HI09: Ed-bar = 10.0, 11.8 MeV; n0). See also (1970ME25, 1975HS01; theor.). The latter experiment shows that jp in the ground state transition is predominantly 1/2. Information derived from DWBA analysis of the angular distributions, and from the very accurate γ-ray measurements of (1965WA16, 1966AL18, 1967CH19) are shown in Table 15.26 (in PDF or PS). See also (1973HI1C).
Neutron thresholds have been observed at Ed = 0.143 ± 0.004, 0.206 ± 0.005 (1963CS02), 1.24 ± 0.02, 1.967 ± 0.004 and 2.044 ± 0.004 MeV (1955MA85), corresponding to 15O*(5.198, 5.253, 6.16, 6.792, 6.859).
Gamma ray branching ratios are shown in Table 15.19 (in PDF or PS) (1965WA16, 1968GI11); lifetime measurements are listed in Table 15.18 (in PDF or PS). For polarization measurements see 16O in (1971AJ02) and (1977AJ02).
Angular distributions have been measured for the n0 group at Ep = 3.95 to 18.5 MeV [and for the n2 group at Ep = 5.5 MeV]: see (1970AJ04) for a listing of the references. See also (1971TH1D) and (1969HA1J, 1969SC1H; theor.). The threshold measurements listed above have led to a redetermination of the mass of 15O: see the "GENERAL" section here. See also 16O in (1977AJ02).
Angular distributions for the t0, t1+2, t3, t4+5, t6 and t7 groups have been studied in great detail for E(3He) = 16.5 to 37.7 MeV by (1975PI01) and 39.8 and 44.6 MeV (1969BA06: see Table 15.27 (in PDF or PS)). (1975PI01) report evidence that a tensor term is needed in the effective interaction and that all transitions show a similar decreasing trend with energy, while the cross sections for populating the analog states in 15N (in 15N(3He, 3He)) is increasing: this is consistent with DWBA with an energy-independent interaction (1975PI01). For other states of 15O observed in this reaction see Table 15.27 (in PDF or PS).
The spectrum of photoneutrons has been investigated at many energies. Meaurements over the giant dipole resonance region show the predominant strength is to the Jπ = 1/2- and 3/2- states at Ex = 0 and 6.18 MeV, consistent with the basic validity of the single-particle, single-hole theory of photoexcitation in 16O. However, the positive parity states at Ex = 5.18, 5.24, 6.86 MeV are also populated suggesting some more complicated excitations in 16O: see (1970HO21) and the earlier references in (1970AJ04). The angular distributions of the ground state neutrons have been measured from threshold to Eγ = 28 MeV (1970JU02). See also (1969NA1D, 1970CO1G, 1971AD05, 1974SC23), (1970FI1D), (1969VA1A, 1970MU1D, 1973BA2H, 1973SP03, 1973WA1H; theor.) and 16O in (1977AJ02). For τm measurements see Table 15.18 (in PDF or PS) (1969MU07).
Reaction (a) goes primarily to 15O*(0, 6.18). Angular distributions have been reported at many energies for Ep = 18.5 to 155.6 MeV: see Table 15.30 (in PDF or PS) in (1970AJ04) and (1975RO27: Ep = 65 MeV; d0, d3). See (1975RO27) for a review of spectroscopic factors. See also (1969SN1B, 1972KA1A, 1973FA10, 1975KA1A), (1972PA1A) and (1970DE38, 1970PR1A, 1971JO22, 1971MC15, 1972PR01, 1973BL04, 1973SA1A, 1973TA27; theor.). For reaction (b) see (1973GO27) and (1970AJ04).
Angular distributions have been reported at Ed = 20 MeV (1969PU04; t0 → t3; ln = 1, 0, 2, 1) and 28 MeV [(1968GA13; t0), (1970IN1A, 1971IN1C; unpublished; t0, t1+2, t3; also t0 at Ed = 20 and 24 MeV)]. See (1970AJ04) for earlier references. At Ed = 28 MeV detailed comparison is made with the results from the mirror reaction 16O(d, 3He)15N (1968GA13). At Ed = 52 MeV the spectrum at θlab = 11° is dominated by 15O*(0, 6.18); 15O*(9.61, 10.48) are also populated (1973MA21). See also (1972PA1A), (1971BO50, 1974DA1D; theor.) and 18F in (1978AJ03).
The p1/2 and p3/2 hole states at Ex = 0 and 6.18 MeV are strongly populated in this reaction. Information on these and other states of 15O observed in this reaction is shown in Table 15.28 (in PDF or PS). Angular distributions have been measured at E(3He) = 5.2 to 36.6 MeV [see Table 15.32 (in PDF or PS) of (1970AJ04)], and more recently at E(3He) = 15 MeV (1974EL09), 16 MeV (1969DE06), 24 and 28 MeV (1973FU02) [see Table 15.28 (in PDF or PS)] and at 216 MeV (1974GE09; α0, α3). Branching ratios and multipole mixing ratios are displayed in Table 15.19 (in PDF or PS) (1965WA16, 1969KU01, 1971AV04). For lifetime measurements see Table 15.18 (in PDF or PS) (1965AL19).
15O*(7.28) has an excitation energy of 7274.2 ± 1.4 keV (1967HE1A) (which is 23.2 keV below the Eb of 14N + p) and Jπ = 7/2+: thus it plays no significant role in determining that rate of the 14N(p, γ)15O reaction (1967HE1A). See also (1971BA1A). See also (1970CA28) and (1970LI1K, 1971MC15; theor.).
At E(6Li) = 36 MeV angular distributions have been measured for the transitions 15Og.s. + 7Lig.s.,0.48 (1973SC26).
Angular distributions involving 15O(0) have been investigated at E(10B) = 100 MeV (1975NA15).
Angular distributions are reported at E(3He) = 40.7 MeV invloving (15Og.s. + 7Li*g.s.,0.48), (15O*5.19+5.24 + 7Li*g.s.,0.48) and (15O*6.18 + 7Lig.s.) (1971DE04, 1971DE37): see also the analog reaction 19F(3He, 7Be)15N [reaction 88 in 15N].