(See Energy Level Diagrams for 6Li)
GENERAL: References to articles on general properties of 6He published since the previous review (1988AJ01) are grouped into categories and isted, along with brief descriptions of each item, in the General Tables for 6Li located on our website at (www.tunl.duke.edu/NuclData/General_Tables/6li.shtml).
Ground State Properties:
Q = -0.818(17) mb (1998CE04).
The interaction nuclear radius of 6Li is 2.09 ± 0.02 fm (1985TA18). These authors have also derived nuclear matter, charge and neutron r.m.s. radii.
Quadrupole moment: The tiny quadrupole moment of 6Li poses a difficult task for theoretical calculations. Except for a phenomenological (1985ME02), a microscopic cluster (1986ME13), and a Greens-Function Monte-Carlo (1997PU03) calculation, the models fail even to predict the sign. See the discussion of three-body models in (1993SC30). In (1991UN02), this failure of the three-body models is blamed on the missing antisymmetrization of the valence nucleons with the nucleons in the alpha-core. Another microscopic cluster calculation (1992CS04) considers the findings of (1986ME13) to be due to a fortuitous choice of the model space.
Asymptotic D/S ratio1: The ratio of the D- and S-state asymptotic normalization constants, referred to in the literature as η, has been used widely to quantify the properties of the D-state wave function. There is general agreement in the A = 2 - 4 systems between theoretical calculations and empirical determinations of the normalization constants. See (1988WE20, 1990EI01, 1990LE24). The S-state α + d normalization constant for 6Li appears to be well determined (1993BL09, 1999GE02), but both the magnitude and sign of η are uncertain.
1 We are very grateful to K.D. Veal and C.R. Brune for providing these comments on the asymptotic D/S ratio for 6Li.
In a two-body α + d model it was found (1984NI01) that in order to reproduce the experimental quadrupole moment Q, the wave functions must have η < 0. However, three-body (α + n + p) models consistently result in predictions of η > 0 (1990LE24, 1995KU08). Recent microscopic six-body calculations using realistic NN potentials predict η = -0.07 (1996FO04).
The asymptotic D/S ratio has been probed empirically by studying scattering processes, transfer reactions, and 6Li breakup. These determinations usually rely on an underlying assumption as to the scattering or reaction mechanism. The S- and D-state asymptotic normalization constants were determined in a study of d-α scattering (1978BO43) from which η was found to be +0.005 ± 0.014. Several pol. 6Li + 58Ni elastic scattering studies (1984NI01, 1995DE06, 1995RU14) have described polarization observables with η ≈ -0.01, while an investigation of the breakup of pol. 6Li on 1H suggests η > 0 (1992PU03). A study of the 6Li(d, α)4He reaction (1990SA47) found that η should lie in the range -0.010 to -0.015. Recently, a phase-shift analysis of pol. 6Li + 4He scattering determined η = -0.025 ± 0.006 ± 0.010 (1999GE02) while an analysis of (pol. 6Li, d) transfer reactions resulted in a near zero value of η = +0.0003 ± 0.0009 (1998VE03).
In the previous review (1988AJ01), information on radiative capture of 3H on 3He was summarized as follows: "Capture γ-rays (reaction (a)) to the first three states of 6Li [γ0, γ1, γ2] have been observed for E(3He) = 0.5 to 25.8 MeV, while the yields of γ3 and γ4 have been measured for E(3He) = 12.6 to 25.8 MeV. The γ2 excitation function does not show resonance structure. However, the γ0, γ1, γ3 and γ4 yields do show broad maxima at E(3He) = 5.0 ± 0.4 [γ0, γ1], 20.6 ± 0.4 [γ1], ≈ 21 [γ3] and 21.8 ± 0.8 [γ4] MeV. The magnitude of the ground-state-capture cross section is well accounted for by a direct-capture model; that for the γ1 capture indicates a non-direct contribution above E(3He) = 10 MeV, interpreted as a resonance due to a state with Ex = 25 ± 1 MeV, Γcm = 4 MeV, T = 1 (because the transition is E1, to a T = 0 final state) [the E1 radiative width |M|2 ≥ 5.2/(2J + 1) W.u.], Jπ = (2, 3, 4)-, α + p + n parentage. The γ4 resonance is interpreted as being due to a broad state at Ex = 26.6 MeV with T = 0. Jπ = 3- is consistent with the measured angular distribution. The ground and first excited state reduced widths for 3He + t parentage, θ02 = 0.8 ± 0.2 and θ12 = 0.6 ± 0.3: see (1974AJ01). See also (1985MOZZ, 1986MOZQ, 1987MO1I)."
Since the previous review (1988AJ01), a new resonance analysis (1988MO1I, 1990HE20, 1990MO10, 1992HE1E) has been applied to the 3He + 3H elastic scattering in odd parity states and to the 3He(3H, γ) data. This analysis explains the shape of the capture cross sections and angular distributions in terms of very wide overlapping resonances. See 6.5 (in PDF or PS). These correspond to 6Li states at Ex = 17.985 ± 0.025 MeV, Γcm = 3.012 ± 0.007 MeV, Jπ = 2-; Ex = 24.779 ± 0.054 MeV, Γcm = 6.754 ± 0.110 MeV, Jπ = 3-; Ex = 24.890 ± 0.055 MeV, Γcm = 5.316 ± 0.112 MeV, Jπ = 4-; Ex = 26.590 ± 0.065 MeV, Γcm = 8.684 ± 0.125 MeV, Jπ = 2- (all with S = 1, T = 1). The analysis is compatible with an almost pure 3He - 3H cluster structure of the negative parity unbound 6Li states with S = 1, T = 1. These results are supported by calculations described in (1995OH03) which utilize a complex-scaled 3He + t resonating group method to calculate the energies and widths of the 6Li 3He + t states. Note, however, that the calculated scattering phase shifts rise only gradually with energy and stay well below 90°. Consequently the stated precision on the extracted level parameters is a point of controversy between the authors of (1990MO10, 1990HE20) and one of the authors [H.M.H.] of this review. The radiative capture reaction as a source of 6Li production in Big Bang nucleosynthesis is discussed in (1990FU1H, 1990MA1O, 1997NO04). See also (1995DU12).
The angular distribution and polarization of the neutrons in reaction (b) have been measured at E(3He) = 2.70 and 3.55 MeV. The excitation function for E(3He) = 0.7 to 3.8 MeV decreases monotonically with energy. The excitation function for n0 has been measured for E(3He) = 2 to 6 MeV and for E(3He) = 14 to 26 MeV; evidence for a broad structure at E(3He) = 20.5 ± 0.8 MeV is reported [6Li*(26.1)]: see (1979AJ01).
Angular distributions of deuterons (reaction (c)) have been measured for Et = 1.04 to 3.27 MeV and at E(3He) = 0.29 to 32 MeV. Polarization measurements are reported for Et = 9.02 to 17.27 MeV [see (1979AJ01)], as well as at E(pol. 3He) = 18.0 and 33.0 MeV (1986RA1C). See also (1986KO1K) and (1985CA41). A microscopic calculation for reaction (c) and its inverse with special emphasis on isospin breaking in the analyzing power is described in (1990BR09). See also the calculations of (1990BLZW, 1993DU02, 1993FI06).
Elastic scattering (reaction (d)) angular distributions were measured at E(3He) = 5.00 to 32.3 MeV and excitation functions were reported for E(3He) = 4.3 to 33.4 MeV see (1979AJ01). At the lower energies the elastic yield is structureless and decreases monotonically with energy. Polarization measurements were reported for Et = 9.02 to 33.3 MeV. A strong change occurs in the analyzing power angular distributions at Et = 15 MeV. See (1988AJ01) for a description of earlier analyses of these data. More recently a new resonance analysis (1990HE20, 1990MO10) of these same data along with 3He(3H, γ) data led to the 6Li S = 1, T = 1 states discussed above under reaction 3(a). See 6.5 (in PDF or PS). A coupled-channels variational model calculation of the 3He(total) cross section for Et = 9 MeV has been reported by (2001TH12). For other channels see (1984AJ01). See also (1984KR1B). For thermonuclear reaction rates see (1988CA26).
6Li*(0, 2.19) have been populated with reaction (a): see (1974AJ01). See also 7Li (1983CO1E) and (1983FU11). Cross sections for Eα < 20 MeV were calculated with a resonating group method by (1991FU02). A kinematically complete experiment on reaction (b) at Eα = 67.2 MeV is described in (2000GO35). 6Li excited states at Ex = 14.5 and 16.0 MeV with widths ≈ 1 MeV are reported. In a similar experiment (1999GO36) at Eα = 67.2 MeV on reaction (c) a 6Li level at Ex ≈ 20 - 21 MeV was reported based on the energy of the final state between 3H and 3He.
Differential cross sections were measured for the transitions to 6Li*(0, 2.19) for E(3He) = 350, 420, 500 and 600 MeV (1983LE26). See also (1984AJ01), (1983BR31, 1983JA13) and (1984GE05). Analyses of data for E(3He) = 295 - 810 MeV and microscopic reaction model calculations are reported by (1991HA22). See also the calculations of (1999VO01).
The previous review (1988AJ01) summarized the information on this reaction as follows: "No resonance has been observed corresponding to formation of 6Li*(3.56) [0+; T = 1]: the parity-forbidden Γα ≤ 6 × 10-7 eV (1984RO04)". See also (1984BU01, 1986BU07).
"The cross section for the capture cross section has been measured for Eα = 3 to 25 MeV by detecting the recoiling 6Li ions: the direct capture is overwhelmingly E2 with a small E1 contribution. The spectroscopic overlap between the 6Lig.s. and α + d is 0.85 ± 0.04: see (1984AJ01). See also (1982KI11), (1985CA41, 1986LA22, 1986LA27) and theoretical work presented in (1984AK01, 1985AK1B, 1986AK1C, 1986BA1R)." Since the previous review (1988AJ01), measurements of the cross section at energies Eα ≈ 2 MeV corresponding to the 3+ resonance at Ex = 2.186 MeV in 6Li have been reported (1994MO17). Values extracted for the total width Γ and the radiative width Γγ confirm the adopted value (1988AJ01). An experimental search for the reaction at Ecm ≈ 53 keV (1996CE02) gave an upper limit for the S factor of 2 × 20-7 MeV · b at the 90% confidence level. Implications for Big Bang nucleosynthesis of 6Li are discussed. Thermonuclear reaction rates for this reaction calculated from evaluated data are presented in the compilation (1999AN35).
A considerable amount of theoretical work has been devoted to this reaction - much of it related to its importance in astrophysics. A list of references with brief descriptions is provided in 6.6 (in PDF or PS).
Reaction (a) has been studied to Eα = 165 MeV and to Ed = 21.0 MeV: see (1979AJ01, 1984AJ01). Measurements are also reported at Ed = 5.4, 6.0 and 6.8 MeV (1985LU08), 6 to 11 MeV (1985OS02), 10.05 MeV (1983BR23) and 12.0 and 21.0 MeV (1983IS10) and at Eα = 11.3 MeV (1987BR07). See also (1986DO1K).
More recently, measurements of the cross section and transverse tensor analyzing power at Ed = 7 MeV were made (1988GA14) with kinematic conditions chosen to correspond to production of the singlet deuteron. Coulomb and nuclear field effects in these reactions are discussed in (1987KO1X, 1988KA38). Cross sections and polarization observables from data at Ed < 12, 17 MeV are compared with three-body model predictions in (1988SU12).
For reaction (b), measurements of vector and tensor analyzing power at Ed = 35, 45 MeV have been reported (1986BR1N, 1986VA23, 1986VUZZ, 1987VU1A). Cross sections and polarization observables were measured at Ed = 32.1, 35.15, 39.6, 49.7 MeV to investigate 3H and 3He asymptotic normalization constants (1987VU1B) and charge symmetry breaking (1988VU01). Cross sections and polarization observables measured at Ecm = 14 - 33 MeV (1989BR23) were compared with microscopic-model predictions in a study of isospin violation. See also (1990BR09). The role of tensor force was explored in (1988BR18).
For earlier work and other breakup channels, see (1988AJ01).
Elastic differential cross-section and polarization measurements have been carried out up to Eα = 166 MeV and Ed = 45 MeV: see (1974AJ01, 1979AJ01, 1984AJ01). Measurements were also reported at Ed = 0.87 to 1.43 MeV (1984BA19, 1985BAYZ), at Ed = 11.9 MeV (1988EL01), 21 MeV (1986MI1E), 24.0 and 38.2 MeV (1986GR1D), 31.8 to 39.0 MeV (1986KO1M), 40 MeV (1989DE1A), 56 MeV (1985NI01) and at Eα = 7.0 GeV/c (1984SA39). A compilation of data for energies Ed = 1 - 56 MeV is presented in (1987GR08). For a study of the inclusive inelastic scattering at Eα = 7.0 GeV/c see (1987BA13).
Phase-shift analyses, particularly that by (1983JE03) which uses all available differential cross section, vector and tensor analyzing power measurements and L ≤ 5, in the range Ed = 3 to 43 MeV lead to the results displayed in 6.7 (in PDF or PS). It is found that the d-wave shifts are split and exhibit resonances at Ex = 2.19 (3D3), 4.7 (3D2) and 5.65 MeV (3D1). (1983JE03) suggest very broad G3 and G4 resonances at Ed = (19.3) and 33 MeV, a D3 resonance at 22 MeV and F3 and F2 resonances at ≈ 34 and ≈ 39 MeV, corresponding to states which are primarily of (d + α) parentage.
(1985JE04) have investigated the points where Ayy = 1 and report four such points at Ed = 4.30 [θcm = 120.7°], 4.57 (58.0°), 11.88 (55.1°) and 36.0 ± 1.0 MeV (150.1 ± 0.3°). [For the latter see also (1986KO1M)]. The correspondence of these polarization maxima to 6Li states is discussed by (1985JE04). For a discussion of the M-matrix see (1988EL01). For work on (α + d) correlations involving 6Li*(0, 2.19, 4.31 + 5.65) see (1987CH08, 1987CH33, 1987PO03) and (1987FO08).
For additional references to early work see references cited in (1988AJ01).
Angular distributions have been measured at E(3He) = 8 to 18 MeV and Eα = 42, 71.7 and 81.4 MeV: see (1974AJ01). More recently, proton polarization was measured as a function of angle at Ecm = 12.6 MeV (1989GR02). At Eα = 28, 63.7, 71.7 and 81.4 MeV the α-spectra show that the sequential decay (reaction (b)) involves 6Li*(2.19) and possibly 5Li: see (1979AJ01). See also the recent theoretical work of (1993GO16) and the multiconfiguration RGM calculations of (1995FU16).
Reactions (a) and (b) have been studied to Eα = 158.2 MeV [see (1979AJ01, 1984AJ01)] and at 198.4 MeV (1985WO11). The dependence of the cross section on energy shows that the α + α process does not contribute significantly to 6Li (and 7Li) synthesis above Eα = 250 MeV (1985WO11) [and see for additional comments on astrophysical problems]. A more recent measurement of the cross section for reaction (b) (2001AU06, 2001ME13) at Eα = 159.3, 279.6 and 619.8 MeV found cross sections which differ significantly from tabulated values commonly used in cosmic-ray production calculations and lead to lower predicted production of 6Li. For reaction (c) [and excited states of 4He] see (1984AJ01): 6Li*(2.19) is involved in the process.
See 6He, reaction 1.
The (p, n) reaction has been studied in inverse kinematics by 1H(6He, 6Li)n experiments with secondary 6He beams. An experiment utilizing a secondary 6He beam with E(6He) = 42 MeV/A was reported by (1995CO05, 1998CO1M, 1998CO19, 1998CO28). The 6Li ground state and Ex = 3.56 MeV state were observed. Angular distributions were reported and the ratio of the cross section for the Gamow-Teller transition to the ground state and the Fermi transition to the isobaric analog state was measured. The reaction was also studied at E/A = 93 MeV (1996BR30). The 0° ground state cross section was measured to be dσ/dΩ = 43 ± 16 mb/sr. The ratio of Gamow-Teller to Fermi strength was found to be (87 ± 6)% of that expected from p, n systematics and beta decay. Differential cross sections at E/A = 41.6 - 68 MeV were measured by (1997CO04) to study the effects of halo structure. Measurements on reactions (a) and (b) utilizing a secondary 6He beam at 36 MeV/A are reported by (2001DE19).
The status of theoretical and experimental research on nuclei featuring a two-particle halo was reviewed in (1996DA31).
A theoretical study in a microscopic three-cluster model of the parity-violating α + d decay of the lowest 0+ state in 6Li (Ex = 3.5629 MeV) is described in (1996CS03). A phase shift analysis of 4He + d was used in a determination of the vertex constant for the 6Li(1+; 0)g.s. → α + d virtual decay by (1992BLZX, 1993BL09, 1997KU14). See also (1990RY07, 1991KR02, 1993BO38).
The previous review (1988AJ01) summarizes the information on these reactions as follows: "The (γ, n) and (γ, Xn) cross sections increase from threshold to a maximum at Eγ ≈ 12 MeV then decrease to Eγ = 32 MeV: see (1984AJ01) and (1988DI02). (1984DY01) also report a broad peak at 16 MeV. The cross section for photoproton production (reaction (b)) is generally flat up to 90 MeV. [The previously reported hump at Eγ ≈ 16 MeV is almost certainly due to oxygen contamination: see (1984AJ01).] See also (1988CA11) and 5He. The cross section for reaction (c) is ≤ q5 μb in the range Eγ = 2.6 to 17 MeV consistent with the expected inhibition of dipole absorption by isospin selection rules: see (1966LA04). The onset of quasideuteron photodisintegration between 25 and 65 MeV is suggested by the study of (1984WA18; Eγ(bremsstrahlung) = 67 MeV). The 90° differential cross section for reaction (e) decreases monotonically for Eγ = 18 to 70 MeV: reaction (e) contributes ≈ 1/3 of the total cross section for 6Li + γ, consistent with a 3H + 3He cluster description of 6Lig.s. with θ2 ≈ 0.68. The agreement with the inverse reaction, 3H(3He, γ) [see reaction 3] is good: see (1984AJ01). See also (1986LI1F)."
"The absorption cross section has been studied in the range Eγ ≈ 100 to 340 MeV; it shows a broad bump centered at ≈ 125 MeV and a fairly smooth increase to a maximum at ≈ 320 MeV: see (1984AJ01). For spallation studies see (1974AJ01, 1984AJ01). For pion production see (1986GL07, 1987GL01) and (1984AJ01)."
Since the previous review (1988AJ01) tagged photons were used to study 6Li(γ, p) at θp = 0° for Eγ ≈ 59 and 75 MeV. Strong evidence for the photo-deuteron mechanism was found. Measurements made for angles between 30° and 150° (1995DI01) showed most of the strength occurring in three-body breakup channels. Studies at these same energies of the (γ, d) and (γ, t) reaction were reported in (1997DI01). See also (1994RY01). Measurements of 6Li(γ, d) at Eγ ≈ 60 MeV indicated strict non-violation of the isospin selection rule for E1 absorption.
The (γ, pn) reaction was also studied at Eγ = 55 - 100 MeV with bremsstrahlung photons and with linearly polarized tagged photons for Eγ = 0.3 - 0.9 GeV. See also (1990RIZX).
Linearly polarized photons were used to measure the cross section asymmetry in 6Li(γ, t)3He up to Eγ ≈ 70 MeV (1989BU10) and differential cross sections up to Eγ ≈ 90 MeV (1993DE07, 1995BU08). Results of a measurement of the absolute total photoabsorption cross section for Eγ = 300 - 1200 MeV are presented in (1994BI06).
The width, Γγ, of 6Li*(3.56) = 8.1 ± 0.5 eV: see (1974AJ01) and 6.4 (in PDF or PS) in (79AJ01); Ex = 3562.88 ± 0.10 keV: see (1984AJ01). See also (1987PI06). The results of an absolute measurement of the total photoabsorption cross section are described in (1994BI06). Photon absorption and photon scattering for light elements is discussed in terms of a collective resonance phenomenon in (1990ZI03).
Measurements of neutral-pion photoproduction yield (reaction (a)) for E < 10 MeV above threshold were reported in (1989NA23). The total cross section was measured in the energy region from the reaction threshold to Eγ ≈ 146.5 MeV (1989GL07) and analyzed in the impulse approximation. The cross section increases monotonically to σ = 6.50 ± 0.96 μb at Eγ = 146.5 MeV. See also (1986GL07, 1987GL01) and (1984AJ01). An analysis (1991TR1C) of early measurements suggests that anomalously large measured values of the cross section are due to target impurities. The differential cross section at small angles at energies E ≈ 300 - 450 MeV has been measured by (1991BE16). Total and differential cross sections were measured within 23 MeV of threshold with tagged photons by (1999BE14). Differential cross sections for reaction (b) leading to the 6He ground state have been measured at Eγ = 200 MeV (1991SH02) and analyzed by DWBA. See also the measurements of (1991GA26). The energy distributions of electroproduced π+ at Ee ≈ 200 MeV were measured and (γ, π+) cross sections were deduced (1994SH38). For reaction (c) see (1988KA41, 1991GA26).
Theoretical studies of pion photoproduction include: an impulse-approximation calculation for (γ, π0) at Eγ = 300 MeV (1989TR09); an impulse approximation and shell model study of inelastic photoproduction of pions (1991TR02); a DWIA Feynman-diagram production-operator-based calculation of (γ, π+) at Eγ = 200 MeV (1990BE49); and multicluster dynamic-model calculation of π+ photoproduction off 6Li (1995ER1B); and an exclusive (γ, π+) production calculation for Eγ = 200 MeV (1995DO24).
The previous review (1988AJ01) summarized the information then available on electron scattering as follows: "The elastic scattering has been studied for Ee = 85 to 600 MeV: see (1974AJ01, 1979AJ01, 1984AJ01). The results appear to require that the ground state be viewed as an α-d cluster in which the deuteron cluster is deformed and aligned. The ground-state M1 current density has also been calculated (1982BE11). A model-independent analysis of the elastic scattering yields rr.m.s. = 2.51 ± 0.10 fm. See also the discussion in (1984DO20)."
6.10 (in PDF or PS) summarizes the results obtained in the inelastic scattering of electrons. Form factors have been measured for 6Li*(2.19, 3.56, 5.37) as well as for the t + 3He continuum up to 4 MeV above threshold [no narrow structures corresponding to 6Li states are observed]: see (1984AJ01)". In more recent work, nucleon spin structure functions were extracted from measurements of deep inelastic scattering on polarized targets by (1999RO13).
For reaction (b) see 5He and (1987VA08) and (1987VA1N). Angular distributions for the d0 group in the (e, d0) reaction have been measured for Ex = 10 to 28 MeV. The deduced E1 and E2 components of the (γ, d0) cross section show no structure. The E1 strength implies non-negligible isospin mixing in this energy region (1986TA06). Triple differential cross sections were measured for Ex = 27 - 49 MeV in a search for GDR evidence (1999HO02). At Ee = 480 MeV (reaction (c)) the α-d momentum distribution in the ground state of 6Li has been studied. The results are well accounted for by an αNN model. The α-d probability in the ground state of 6Li is 0.73 [estimated ± 0.1]. The data are consistent with the expected 2S character of the α-d relative wave function (1986EN05). See also (1986EV1A). π0 production involving 6Li*(2.19, 3.56, 5.37) is reported at Ee = 500 MeV (1987NA1I).
Since the previous review (1988AJ01), experimental results on quasielastic response have been reviewed (1988LO1E). Measurements of the quasielastic scattering cross section for electrons on 6Li are reported at momentum transfer 0.85 - 2.3 fm-1 (1988BU25). See also the measurements at Ee = 80 - 680 MeV by (1989LI09). Cross sections for 6Li(e, ep) were measured in the missing energy region 0 ≤ Em ≤ 30 MeV and in the range -100 ≤ pm ≤ 200 MeV/c of missing momentum (1989LA22). The 6Li → p + (nα) spectral function was measured (1989LA13). The ratio of transverse and longitudinal response function was investigated in (1990LA06). See also the review (1990DE16) of proton spectral functions and momentum distributions in (e, e'p) experiments and see the report (1990GH1E) on nuclear density dependence of electron proton coupling in 6Li(e, e'p).
Reaction (c) was used (1990JO1D) in a study of correlation functions in 6Li. A measurement in parallel kinematics to study the mechanism of the 6Li(e, e'α)2H reaction is reported in (1991MI19, 1994EN04). Cross sections for 6Li(e, e't)3He (reaction (d)) at Ee = 523 MeV and the momentum-transfer dependence of the 3H and 3He knockout reaction was measured by (1998CO06).
Elastic angular distributions have been measured at Eπ+ ≈ 50 MeV [see (1984AJ01)] and at Eπ± = 100, 180 and 240 MeV (1986AN04; also to 6Li*(2.19)). Differential cross sections are also reported for Eπ+ = 100 to 260 MeV to 6Li*(0, 2.19, 3.56, 4.25). The excitation function for the unnatural-parity transition to 6Li*(3.56) has an anomalous energy dependence (1984KI16).
A number of experimental studies with polarized targets have been reported for elastic and inelastic (Ex(6Li) = 2.19 MeV, Jπ = 3+) scattering. Measurements of polarization observables are reported at Eπ+ = 134, 164 MeV (1989TA21, 1990TA1L, 1991BO1R), Eπ+ = 160 - 219 MeV (1991RI01, 1994RI06). Comparison of these data with a coupled channels model is discussed in (1995BO1H). See also the Δ-hole model analysis of (1992JU1B) and the multicluster dynamic model analysis by (1995RY1C). Calculations of cross sections and polarization observables at Eπ+ = 80 - 260 MeV are presented in (1988ER06, 1988NA06). A theoretical study in terms of a strong absorption model is described in (1998AH06). Quantum Monte-Carlo calculations of cross sections for Eπ = 100 - 240 MeV are reported in (2001LE01). Transition densities and B(E2) transition strengths were also calculated.
Measurements of pion double-charge exchange cross section (reactions (b) and (c)) at incident pion energies Eπ = 180, 240 MeV are reported in (1989GR06, 1995FO1J). In (1991SE06) it is shown that continuum missing mass spectra from reaction (c) can be explained in terms of the presence of dineutrons in the products of the breakup.
Pion absorption followed by nucleon emission (reactions (e), (f), (g), (h), (j), (k), (l)) has been studied in a number of experiments. For reaction (k) see (1983BA26, 1983LO10, 1985MC05, 1986MC11). Measurements have been reported for cross sections for reaction (g) at Eπ+ = 30, 50, 80, 115 MeV (1989ROZY); reactions (g) and (h) angular distributions at Eπ = 70, 130, 165 MeV (1989YO05); reactions (g) and (h) angular correlations at Eπ = 165 MeV (1989YO07); cross sections for reaction (g) at Eπ+ = 115, 140, 165, 190, 220 MeV (1989ZHZZ); angular distributions for reaction (h) at Eπ = 70, 130, 165 MeV (1989YO03); two-particle coincidences for reactions (g) and (h) at low energies (1991YO1C); cross sections at Eπ = 50, 100, 150, 200 MeV (1990RA05, 1990RA20, 1992RA01, 1992RA11); differential and total cross sections for reaction (g) at Eπ+ = 100, 165 MeV (1995PA22, 1996LO04); inclusive spectra of 3He produced in reaction (l) (1992AM1H, 1993AM09); total reaction cross sections for (π+, X), (π-, X) at Eπ = 42 - 65 MeV (1996SA08). See also the earlier work on reaction (g) at Eπ+ = 59.4 MeV (1986RI01), and see the compilation and review of (1992BA57, 1993IN01).
Analysis of particle emission following π+ absorption on 6Li (1990RA20) has produced evidence for a three-nucleon absorption model. Distorted-wave impulse approximation calculations of cross sections and analyzing powers have been made (1992KH04) for two-nucleon pion absorption on polarized 6Li targets. A model based solely on isospin was used (1993MA14) in a calculation of ratios of pion absorption on three nucleons and agreement with experiment suggest a one-step process.
Angular distributions involving the groups to 6Li*(0, 2.19) have been reported at En = 1.0 to 14.6 MeV [see (1984AJ01)], 4.2, 5.4 and 14.2 MeV (1985CH37; n0, n1), 7.5 to 14 MeV (1983DA22; n0), 8.9 MeV (1984FE1A; n0), 8.0 and 24 MeV (1986HAZR; n0, n1), En = 5 to 17 MeV (1986PF1A; n0), 11.5, 14.1 and 18 MeV (1998CH33; n0, n1), and at 11.5 and 18.0 MeV (1998IB02; n0, n1).
An analysis (1988HA25) of (n, n) and (n, n') data at En = 24 MeV indicated that neutron and proton transition densities were approximately equal (ρn ≈ ρp) in 6Li. Cross sections and analyzing powers for En = 8 - 40 MeV were analyzed (1989HAZV) with microscopic optical model potentials. Secondary neutron spectra induced by 14.2 MeV neutrons on 6Li were measured by (1993XI04).
An analysis of (n, n') data at En = 7.45 - 14 MeV is discussed in (1990BE54). See also the calculation for elastic coherent and incoherent scattering of thermal neutrons on 6Li (1990GO26) and the multi-cluster dynamic model calculation for 6Li(n, n) at En = 12 MeV (1992KA06).
Theoretical studies of 6Li(n, n) include multiconfiguration resonating group calculations (1988FU09, 1991FU02), folding model descriptions for En = 25 - 50 MeV (1993PE13), study of antisymmetry in NN potentials (1995CO18), study of optical model potentials for intermediate energies (1996CH33).
A number of experiments on the (n, p) charge exchange (reaction (c)) have been reported. They include: measurements of σ(Ep) and σ(θ) at En ≈ 198 MeV (1987HE22); σ(θ, Ep) at En ≈ 118 MeV (1987PO18, 1988HA12, 1998HA24); σ(θ) at En = 198 MeV (1988JA01); σ(θ) to explore the Gamow-Teller sum rule (1988WA24); σ(θ), σ(Ep) at En = 280 MeV for an isospin symmetry test (1990MI10); σ(θ, E) at En = 60 - 260 MeV (1992SO02); and polarization observables at En = 0.88 GeV (1996BB23).
For reaction (e), measurements were reported at thermal neutron energies (1994IT04) and at En < 10 MeV (1994DR11). For reaction (f), measurements of parity violation with cold polarized neutrons are described in (1990VE16, 1993VE1A, 1996VE02). A discussion of nuclear reaction rates and primordial 6Li is presented in (1997NO04). See also the application-related calculation of (1993FA01).
Theoretical work related to reactions (b), (c), (d), (e), (f) includes: dynamical cluster-model calculation (1991DA08); microscopic calculation in a 3-particle α + 2N model (1993SH1G); supermultiplet-symmetry-approximation calculation at En = 6.77 MeV (1993DU09); multiconfiguration RGM calculation (1995FU16); and three-body cluster model calculations of 6Li(n, p) at En = 50 MeV (1997DA01, 1997ER05).
Double-differential cross sections for the continuum yield [Ex = 1.5 - 3.5 MeV] are reported at Ep = 65 MeV (1987TO06). See also (1983GLZZ, 1983PO1B, 1983POZX). More recently differential cross sections and/or polarization observables have been measured at Ep = 6 - 10 MeV (1989HA17) [optical model analysis]; Ep = 1.6 - 10 MeV (1989HA18) [phase shift analysis]; Ep = 65, 80 MeV (1989TO04) [DWIA analysis]; Ep = 200 MeV (1990GL04); Ep = 65 MeV (1992NA02) [microscopic DWBA analysis]; Ep = 72 MeV (1994HE11) [depolarization parameters]; Ep < 2.2 MeV (1995SK01) [deduced resonance parameters]; Ep = 0.88 GeV (1996BB23) [polarized target]; Ep = 250 - 460 keV (1997BR37), Ep = 280 MeV (1990MI10) [deduced isospin symmetry test]; Ep = 14 MeV [optical model, coupled channels]; E(6Li) = 62, 72, 75 MeV/A, 1H(6Li, p) [neutron halo states] (1996KUZU); Ep = 1.6 - 2.4 GeV (1999BB21, 1999DE47). For a summary of the results on excited states see 6.12 (in PDF or PS).
Reaction (b) was studied at 70 MeV (1983GO06), at 50 - 100 MeV (1984PA1B, 1985PA1B) and 1 GeV (1985BE30, 1988BE2B, 2000MI17): see 5He and (1984AJ01) for the earlier work. Reaction (c) has been studied at Ep = 9 MeV to 1 GeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at 20 and 42 MeV (1983CA13) [report involvement of 6Li*(4.31, 5.65)], at 70 MeV (1983GO06, 1985PAZL, 1985PA04) and at 119.6 and 200.2 MeV (1984WA09, 1985WA25). In the latter experiments the spectroscopic factors for 6Lig.s. are deduced to be 0.76 [at 119.6 MeV] and 0.84 [at 200.2 MeV] using DWIA and a bound-state Woods-Saxon 2S wave function (1984WA09, 1985WA25).
Work on reaction (d) has suggested that the 3He + t parentage of 6Li is comparable with the α + d parentage: see (1984AJ01). See also (1985PAZL). Reaction (e) was studied at Ep = 70 MeV (1988PA27). See also 5Li, 6Be and (1985BE30, 1993ST06). The (p, 3p) reaction has been studied by (1984NA17). The spectral function for pn pairs in 6Li was obtained in a study of the 6Li(p, pα)pn reaction at Ep = 200 MeV (1990WA17). A measurement of tensor analyzing powers in 1H(6Li, d or α or t)X with 4.5 GeV polarized 6Li deuterons provided information on the 6Li D state (1992PU03). Systematic studies of electron screening effects on low energy reactions including 6Li + p are reported in (1992EN01, 1992EN04, 1995RO37). For antiproton studies see (1987AS06). See also (1984AJ01, 1988AJ01) for the earlier work.
Angular distributions of deuterons have been measured at Ed = 4.5 to 19.6 MeV [see (1979AJ01)] and at 50 MeV (1988KO1C, 1996RU10). The 0+, T = 1 state, 6Li*(3.56) is not appreciably populated. For a summary of the results on excited states see 6.12 (in PDF or PS). Gaussian potentials were derived for the description of 6Li + d elastic scattering by (1992DU07).
At Ed = 21 MeV reaction (b) shows spectral peaking (characteristic of 1S0 for the pn system [T = 1]) when 6Li*(3.56) is formed, in contrast with the much broader shape (characteristic of 3S1) seen when 6Li*(0, 2.19) are populated. A study of reaction (c) at Ed = 52 MeV shows that the α-clustering probability, Neff = 0.12+0.12-0.06 if a Hankel function is used. The α-particle and the deuteron clusters in 6Li have essentially a relative orbital momentum of l = 0. The D-state probability of the ground state of 6Li is ≈ 5% of the S-state. Quasi-free scattering is an important process even for Ed = 6 to 11 MeV. Interference effects are evident in reaction (c) proceeding through 6Li*(2.19, 4.31): this is due to the experiment being unable to determine whether the detected particle was emitted first or second in the sequential decay. Reactions (c) and (d) studied at Ed = 7.5 to 10.5 MeV indicate that the three-body breakup of 6Li at these low energies is dominated by sequential decay processes (1979AJ01, 1990YA11). Differential cross sections for cluster pickup by 20 MeV/A deuterons on 6Li were measured by (1995MA57).
At Et = 17 MeV angular distributions have been measured for the tritons to 6Li*(0, 3.56): see (1979AJ01).
More recently, differential cross sections were measured for elastic scattering at E(3He) = 93 MeV (1994DO32), and at E(3He) = 60 MeV (1995MA57), and for inelastic scattering to 6Li*(Ex = 2.185 MeV, Jπ = 3+) at E(3He) = 50, 60, 72 MeV (1995BU20). A microscopic-potential analysis of data at E(3He) = 34, 50, 60, 72 MeV is described in (1993SI06). Differential cross section and energy spectra were compiled and analyzed by (1995MI16). For reaction (b), cross sections have been measured at E(3He) = 11, 13, 14 MeV (1989ARZR, 1989AR08); E(3He) = 2.5 MeV (1989AR20); E(3He) = 1.6 MeV (1991AR25); E(3He) = 1.6 - 9 MeV (1992AR20); E(3He) = 8 - 14 MeV (1995KO51); E(3He) = 2.0, 22 MeV (1992DA1K); E(3He) = 7, 9 MeV (1993AR12). A calculation of near-threshold two-fragment resonance amplitudes and widths for this reaction at E(3He) = 8 - 14 MeV was reported in (1995KO51). See also 5Li, (1984AR17, 1987ZA07), and 9B in (1988AJ01).
Angular distributions (reaction (a)) have been measured at Eα = 1.39 to 166 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at Eα = 36.6 and 50.5 MeV (1986BR31). See also (1986ROZK, 1987BU27). See also 10B in (1988AJ01).
More recent measurements at Eα = 50.5 MeV of elastic and inelastic 6Li*(Ex = 2.185 MeV, Jπ = 3+) were reported by (1994BUZY, 1996BU06). Tensor polarization for inelastic scattering to 6Li*(2.185, 3+) has been measured at Eα = 80 MeV (1992KO19, 1993KO33). Angular distributions for (α, α') in the continuum region were studied at Eα = 50 MeV (1992SA01) and at Eα = 40 MeV (1994SA32), at Eα = 10 MeV/A (1996SI13) and at Eα = 119 MeV (1993OK1A). Cross sections and analyzing powers for elastic scattering of polarized 6Li by 4He are reported for E(6Li) = 50 MeV (1995KE10) and Ecm = 11.1 MeV (1996GR08).
Studies of continuum coupling effects in inelastic scattering are described in (1995KA1Y, 1995KA43, 1997RU06, 2000RU03). Folding-model potential analyses of elastic scattering are reported in (1993SI09, 1995SA12). Multiconfiguration resonating group methods applied to the 6Li + α system are discussed in (1994FU17, 1995FU11). Other recent theoretical studies include: a potential model description (1999MA02); analysis of density distribution influence (1998GO1J); a phase-shift-analysis determination of the asymptotic D- to S-state ratio (1999GE02); a calculation for Eα = 16.3 and 48 MeV with a modified Volkov-potential (2000KO52); and a calculation of the nuclear potential and polarization tensor for Eα = 27.2 MeV (2000KO67). See also (1988KO32, 1989LE07, 1999OG09).
Reaction (b) has been studied at Eα = 6.6 to 700 MeV: see (1974AJ01, 1979AJ01, 1984AJ01). At the latter energy and using a width parameter of 60.6 MeV/c the effective number of α + d clusters for 6Lig.s., neff = 0.98 ± 0.05. The results are very model dependent: see (1984AJ01). At Eα = 27.2 MeV 6Li*(2.19) is very strongly populated (1985KO29). See also references cited in (1988AJ01).
In more recent work, two dimensional coincidence spectra of charged particles were measured at Eα ≈ 100 MeV (1992GA18). Quasi-free scattering processes were studied at Eα = 77 - 119 MeV (1992OK01), Eα = 118 MeV (1993OK1B), and Eα = 118.4 MeV (1997OK01). The four-body 6Li(α, 2α)pn breakup reaction was measured at Eα = 77 - 119 MeV (1992WA18, breakup cross sections); Eα = 118 MeV (1988WA29, 1989WA26; spectral functions of pn pair).
Angular distributions of 6Li ions have been studied for E(6Li) = 3.2 to 36 MeV [see (1974AJ01, 1979AJ01, 1984AJ01)] and at E(6Li) = 2.0 to 5.5 MeV (1983NO08) and 156 MeV (1985SA36; 6Li*(0, 2.19)), (1985MI05; elastic; 6Li*(2.19, 3.56) are also populated), (1987EY01; several states in 12C). Reaction (b) has been studied for E(6Li) = 36 to 47 MeV: enhancements in yield, due to double spectator poles, have been observed in d-d and α-α but not in α-d double coincidence spectra. The widths of the peaks are smaller than those predicted from the momentum distribution of α + d clusters in 6Li. 6Li*(2.19) was also populated. See references in (1984AJ01). Other work on reaction (b) is reported by (1984LA19: 2.4 and 4.2 MeV) and by (1985NO1A).
For reaction (c), the energy dependence of quasi-free effects were investigated in the range E(6Li) = 2.4 - 6.7 MeV (1987LA25, 1988LA11). An analysis (1996CH1C) used quasi-free data from reaction (c) to extract the 6Li(d, α)4He excitation function at astrophysical energies. See also 12C in (1985AJ01) and references cited in (1988AJ01).
More recently, elastic scattering angular distributions were measured for E(6Li) = 5 - 40 MeV (1997PO03; optical model analysis). Eikonal-approximation calculations of differential cross sections and phase shifts for E(6Li) = 156 MeV were reported in (1992EL1A).
The elastic scattering has been studied in inverse kinematics at E(6Li) = 4.0, 6.0 and 24 MeV [see (1979AJ01)], at 32 MeV (1985CO09) and at 50 MeV (1988TRZY; also inelastic). Recently angular distributions for elastic and inelastic scattering to 6Li*(2.186, 3+) were measured (1995MU01) at Ecm = 7, 10, 12 MeV. Excitation functions for Ecm ≈ 4 - 12 were also reported. See also 9Be in (1988AJ01). For the interaction cross section at E(6Li) = 790 MeV/A see (1985TA18).
The elastic scattering has been studied at E(6Li) = 5.8 and 30 MeV: see (1979AJ01).
The elastic and inelastic scattering (reaction (a)) has been studied at E(6Li) = 4.5 to 156 MeV [see (1984AJ01)] and at E(6Li) = 19.2 MeV (1983RU09), 36 and 45 MeV [and E(12C) = 72 and 90 MeV] (1984VI02, 1985VI03; also to 6Li*(2.19, 4.31) and to various states of 12C), at E(12C) = 58.4 MeV (1987PA12), 90 MeV (1987DE02; also to various states of 12C), 123.5 and 168.6 MeV (1988KA09; and to various states of 12C), 150 MeV (1987TA21, 1988TA08), 156 MeV (1987EY01; and to various states in 12C) and at 210 MeV (1988NA02). See also (1986SHZP, 1987PA12). More recently, measurements of cross sections and/or analyzing power observables have been reported at E(6Li) = 93 MeV (1989DE34); at Ecm = 13.3 MeV ((1989HN1A, 1995CA26) and to 6Li*(3+, 2.186) and 12C*(2+, 4.44)); at E(6Li) = 210 MeV (1989NA11, to 12C*(2+, 4.44)); at E(6Li) = 30 MeV (1989VA04, to 12C*(2+, 4.44)); at 50 MeV (1990TR02, to 12C*(2+, 4.44; 0+, 7.65; 3-, 9.64)); at E(6Li) = 30 MeV (1994RE01); at E(6Li) = 30, 60 MeV (1996KE09, to 12C*(2+, 4.44; 0+, 7.65; 3-, 9.64)); at Ecm = 20 MeV (1996GA29, to 6Li*(3+, 2.18) and 12C*(2+, 4.44)); at E(6Li) = 318 MeV (1993NA01); at E(6Li) = 30 MeV (1994RE15, to 12C*(2+, 4.44; 3-, 9.64)); and at E(6Li) = 50 MeV (1995KE10). At E(6Li) = 34 MeV the d-α angular correlations involve 6Li*(0, 2.19) (1985CU04). See also (1988SE07), and see 12C in (1985AJ01, 1990AJ01). An experimental study of the α + d breakup in 6Li + 12C collision at E(6Li) = 156 MeV is reported in (1989JE01). For pion production see (1984CH16). For the interaction cross section at E(6Li) = 790 MeV/A see (1985TA18). For VAP measurements at E(6Li) = 30 MeV see (1988VAZY). Fusion cross sections for E(6Li) = 3.11 - 12.07 MeV are reported by (1998MU12).
The elastic scattering (reaction (b)) has been studied for E(6Li) = 5.8 to 40 MeV: see (1984AJ01). Measurements of differential cross sections for Ecm = 26 MeV and observations of a nuclear quasi rainbow were reported by (1994DE43). See also (1987CA30, 1988WO10). The elastic scattering (reaction (c)) has been measured for E(6Li) = 93 MeV (1987DE02). See also 18F and 19F in (1987AJ02) and references cited in (1988AJ01).
Several theoretical studies relating to 6Li + 12C have been reported. The role of the Pauli Principle in heavy ion scattering has been studied (1988GR32). The dispersive contribution to the 6Li + 12C real potential was estimated (1990KA14). Elastic cross sections for E(6Li) = 30 MeV were analyzed (1990SA05). A semimicroscopic analysis of inelastic scattering at E(6Li) = 156 MeV is described in (1992GA17). Folding model analysis of 6Li + 12C scattering is discussed in (1994NA03, 1994SA10, 1995KH03). Differential cross sections were analyzed with an S-matrix approach by (1998PI02).
Elastic angular distributions have been reported at E(6Li) = 4.5 to 50.6 MeV [see (1984AJ01)], at E(6Li) = 35.3 and E(16O) = 94.2 MeV (1984VI02) and at 50 MeV (1988TRZY; also inelastic). At E(6Li) = 25.7 and E(16O) = 68.6 MeV (1984VI01, 1985VI03) report some σ(θ) to 6Li*(2.19) [and to 16O*(6.13)]. See also (1987PA12). See (1985VI03, 1986SC28) for studies of the breakup. Polarization observables have has been measured at E(6Li) = 25.7 MeV, and also using 16O ions (1987VAZY, 1989VA04). Measurements of E(6Li) = 50 MeV for elastic scattering and inelastic scattering to 16O*(2+, 6.05; 3-, 6.13; 2+, 6.92; 1-, 7.12) were reported (1990TR02). For fusion cross sections see (1986MA19). See also 16O in (1986AJ04), (1986MO1E, 1987PA12) and references cited in (1988AJ01). Theoretical work on this scattering reaction includes: E(6Li) = 29.8 MeV, optical model description (1990SA05); E(6Li) = 29.8 - 30.6 MeV, Pauli Principle rule (1988GR32); E(6Li) = 30.6, optical model analysis (1990SA05); projectile effects (1991BO48); E(6Li) = 154 MeV, 3-body cluster model (1991HI07); E(6Li) = 22.8 MeV, nonresonant breakup states (1991HI11); and E(6Li) = 30 MeV, double-folding model, role of Pauli Principle (1991SA26).
Elastic scattering for reaction (a) was studied at E(6Li) = 156 MeV (1995DE53). Reaction (c) has been studied at E(6Li) = 88 MeV and 36 MeV (1984AJ01) and at 44 MeV (1989RU05; polarization observables), and E(6Li) = 60 MeV (1994WA20; polarization observables). Reaction (d) was studied at E(6Li) = 156 MeV by (1987NI04; particles and gammas from inelastic scattering). See also the measurements at E(6Li) = 790 MeV/A (1985TA18).
Theoretical studies for these reactions include: analyzed non-Rutherford cross sections (1991BO48); effects of nonresonant breakup states (1991HI11); strong absorption model analysis (1994SA33); cluster folding interaction (1991HI07); coupled channels study (1992HI02); and cluster-folding analysis (1994RU11).
The elastic scattering has been studied at E(6Li) = 13 to 154 MeV [see (1984AJ01)], at 27 and 34 MeV (1983VI03) and at 210 MeV (1988NAZX). For a study of the decay see (1987NI04). See also references cited in (1988AJ01).
More recent measurements have been reported at E(6Li) = 210 MeV (inelastic σ(θ) to 28Si*(first 2+ state) (1989NA11); elastic σ(θ), optical parameters (1989NA02); and E(6Li) = 318 MeV (σ(θ), folding model potentials (1990NAZZ, 1993NA01)). Related analyses and other theoretical studies include: Pauli Principle role (1988GR32, 1991SA26); scattering matrix approach (1990KU23); deduced model parameters (1990SA05); non-Rutherford cross section thresholds (1991BO48); cluster-folding interactions (1991HI07); energy dependence, dispersion relation (1991TI04); strong absorption model (1994SA33); E(6Li) = 210, 318 MeV, energy approximation (1995EM03); microscopic description (1996CA01); microscopic potentials, density matrix formalism (1996KN02); E(6Li) = 35, 53 MeV/A, breakup effect (1997SA57); and E(6Li) = 210, 315 MeV, S-matrix approach (1998PI02).
For reaction (b) see (1987AR13).
Elastic scattering has been studied for E(6Li) = 26 to 99 MeV: see (1984AJ01, 1988AJ01), and at E(6Li) = 34 MeV (reaction (b)) by (1987VA31) and at 210 MeV (1988NAZX, 1989NA02; reaction (b)). 6Li*(2.19) has been studied at E(40Ca) = 227 MeV (1987VA31). Reaction (d) was studied at E(6Li) = 150 MeV (1990KAZH). For fusion measurements (reaction (b)) see (1984BR04). For breakup measurements (reaction (b)) see (1984GR20, 1990YA09, 1992YAZW, 1993GU10, 1995AR15, 1996YA01).
For theoretical studies related to these reactions see: energy and target dependence of projectile breakup (1987SA21); sequential breakup cross sections (1987VA31); role of Pauli Principle (1988GR32); exchange effects (1988KH08, 1990DA23); imaginary part of channel-coupling potentials (1990TA1I); E(6Li) = 30 MeV, deduced optical model parameters (1990SA05); cluster folding interactions (1991HI07); strong absorption model (1994SA33); S-matrix approach (1995BE60, 1998PI02); and microscopic potentials (1996KN02). For earlier work see references cited in (1988AJ01).
Transitions to 6Li*(0, 2.19, 3.56) have been observed in reaction (a): see (1979AJ01, 1984AJ01). Differential cross sections are reported for Ebrem = 60 to 120 MeV for the n0 + n2 groups (1985SE17). Bremsstrahlung yield for (γ, n0) was measured for Eγ = 7 - 9 MeV (1989KA30). Reaction (b) at 0.9 GeV involves 6Li*(2.19) (1985RE1A). See also the measurements of Eγ = 350 MeV reported by (1991GA26), and see 7Li, (1985ST1A, 1986BA2G, 1986GO1M).
An analysis of 7Li(γ, n) data in the giant resonance energy region is described in (1987VA05). Cluster effects were explored in (1992VA12). Calculation with a potential two cluster model are reported in (1997DU02).
Quasielastic pion-proton backward scattering was measured at Eπ = 0.7, 0.9, 1.25 GeV (2000AB25). Fermi momentum distributions for 6Li were deduced.
Differential cross sections have been measured at Eπ+ = 75 and 175 MeV for the transitions to 6Li*(0, 2.19): see (1984AJ01). Proton spectra measured at momentum exchange 660 MeV/c (1989LIZO) provided evidence for an η-meson nuclear bound state.
Angular distributions of deuterons (reaction (a)) have been studied for Ep = 167 to 800 MeV [see (1979AJ01, 1984AJ01)] and at 18.6 MeV (1986GO23, 1987GO27; d0, d1, d2; see for spectroscopic factors), 200 and 400 MeV (1985KR13; d0, d1; d2 is weakly populated at 200 MeV) and at 800 MeV (1984SM04; d0, d1). The ratio of the intensities of the groups to 6Li*(2.19) and 6Lig.s. increases with energy. It is suggested that this can be understood in terms of a small admixture of 1f orbital in these states (1985KR13). A DWBA analysis of Ep = 185 MeV data leads to C2S = 0.87, 0.67, 0.24, (0.05), 0.14, respectively for 6Li*(0, 2.19, 3.56, 4.31, 5.37). No other states were seen below Ex ≈ 20 MeV: see (1979AJ01). The tensor analyzing power T20 was measured for the 1H(7Li, d)6Li reaction at E(7Li) = 70 MeV to 6Li*(0, 2.186) (1991DA07). Data at Ep = 33.6 MeV were analyzed by (1991AB04) in a test for Cohen-Kurath wave functions. See also the analysis of data at Ep = 698 MeV by (1993AL05; η production). In reaction (b) at Ep = 1 GeV the separation energy between ≈ 6.5 MeV broad 1p3/2 and 1s1/2 groups is reported to be 18.0 ± 0.8 MeV (1985BE30, 1985DO16). See also (1983LY04, 1988BE1I, 1988GUZW). Differential cross sections were measured at Ep = 70 MeV (1988PA26) and at Ep = 2.7 - 3.8 MeV (1988BO37; application). See also the measurements for nuclear microprobe utilization (1995RI14).
A study at Ed = 23.6 MeV of the relative cross sections of the analog reactions 7Li(d, t)6Li (to the first two T = 1 states at 3.56 and 5.37 MeV) and 7Li(d, 3He)6He (to the ground and 1.80 MeV excited states) shows that 6Li*(3.56, 5.37) have high isospin purity (α2 < 0.008): this is explained in terms of antisymmetrization effects which prevent mixing with nearby T = 0 states: see (1979AJ01). (1987BO39) [Ed = 30.7 MeV] deduce that the branching ratio of 6Li*(4.31) [2+] into a dinucleon [T = 1, S = 0] is (85 ± 10)%: see also reactions 21 in 6He and 4 in 6Be. See also (1987GUZZ; Ed = 18 MeV; angular distributions to 6Li*(0, 2.19, 3.56)) and (1984BL21, 1986AV01, 1988GUZW). See also the analysis method discussed in (1995GU22; DWBA and dispersive theory).
Angular distributions have been reported at E(3He) = 5.1 to 33.3 MeV [see (1974AJ01, 1984AJ01): the lower energy work has not been published] and more recently at E(3He) = 60 MeV (1994BUZX). Excited states observed in this reaction are displayed in 6.12 (in PDF or PS). See also (1968CO07) which reported observation of 6Li states at 0.0, 2.17 ± 0.02, 3.55 ± 0.02 and 5.34 ± 0.02 MeV. (1986AN04) have analyzed unpublished data which suggest the involvement of several broad highly excited states of 6Li. See also (1987AL23).
Several attempts have been made to observe the isospin-forbidden decay of 6Li*(5.37) [2+; 1] via 7Li(3He, α)6Li* → d + α: the branching is < 1%. Γp/Γ = 0.35 ± 0.10 and Γp + n/Γ = 0.65 ± 0.10 for 6Li*(5.37): see (1979AJ01). 4He + d spectra suggest the excitation of 6Li*(4.3) [Ex = 4.3 ± 0.2 MeV, Γ = 1.6 ± 0.3 MeV] and 6Li*(5.7) [Ex = 5.65 ± 0.2 MeV, Γ = 1.65 ± 0.3 MeV]: see (1984AJ01). See also (1985DA29, 1988BO1Y). A more recent measurement at E(3He) = 4, 5, 6 MeV (1995AR14) gave values for the width of of 6Li*(4.31) in agreement with the adopted value Γ = 1700 ± 200 keV and found no dependence on incident energy. Measurements of d-α coincidence spectra at E(3He) = 11.5 MeV (1988AR20) and 5.0 MeV (1991AR19) gave spectroscopic parameters for 6Li*(5.65) in agreement with adopted values (1988AJ01). At E(3He) = 120 MeV the missing mass spectra for (3He, 2d) and (3He, pt) reflect the population of 6Li*(0, 2.19) and suggest broad structures at Ex = 28.5 and 32.9 MeV (1985FR01). See also 10B in (1988AJ01) and (1983KU17, 1988BO1J).
At E(6Li) = 93 MeV a broad group (Γ ≈ 11 MeV) centered at Ex = 20 MeV is reported in addition to other peaks at Ex = 17.1 ± 0.3, 18.9 ± 0.3 and 21.2 ± 0.3 MeV (1987GLZW). See (1984KO25) for reaction (b).
Cross section measurements were made with virtual photons using electrons at 21.0 - 39.0 MeV (1999SH05). A compilation and evaluation of cross section data for Eγ < 30 MeV has been done by (1999ZHZN).
Angular distributions of α-particles (reaction (a)) have been measured at Ep = 0.11 to 45 MeV. [see (1974AJ01, 1979AJ01)] and at Ep = 22.5, 31 and 41 MeV (1986HA27; α0, α1, α2; see for spectroscopic factors). See also 6.12 (in PDF or PS) and (1984AJ01). Recent measurements of angular distributions and analyzing power at Ep = 77 - 321 keV are reported by (1998BR10). Measurements at Ex = 1 GeV are reported in (2000ANZX). Calculations of the cross section and polarization observables for Ep = 40 MeV are reported in (2000GA49, 2000GA59). A study of possible reasons for non-observation of certain 6Li excited states in the reaction is discussed in (1999TI07). 6Li*(3.56) decays by γ-emission consistent with M1; Γα/Γ < 0.025 [forbidden by spin and parity conservation]: see (1984AJ01). An analysis of the 9Be(p, α) cross section at Ep = 16 - 700 keV is described in (2001BA47). Astrophysical S-factor, analyzing powers and R-matrix parameters were deduced. At Ep = 9 MeV the yield of reaction (b) is dominated by FSI through 8Be*(0, 2.9) and 6Li*(2.19) with little or no yield from direct three-body decay: see (1979AJ01). More recent measurements of cross sections and/or polarization observables have been reported at Ep = 50 MeV (1989GU05), Ep = 25, 30 MeV (1992PE12; determined spectroscopic strengths), Ep = 40 MeV (1997FA17) [see also (1989FA1B)], Ep = 2 - 5 MeV (1988ABZW), Ep = 16 - 390 keV [deduced S(E)] (1997ZA06), Ep = 77 - 321 keV [deduced stellar reaction rates] (1998BR10), Ep = 30 - 300 keV (2000ISZZ). See also application-related experiments (1990RE09, 1995RI14). Analyses of data for this reaction have been reported for Ep = 45 - 50 MeV [DWBA] (1996YA09, 1997YAZV) and Ep < 2 MeV [analyzed reaction rates, primordial 6Li] (1997NO04). Reactions (b) and (c) at Ep = 58 MeV involve 6Li*(0, 2.19) (1985DE17). See also 10B in (1988AJ01) and (1985MAZG, 1986AN26, 1986KA26).
Angular distributions of 6Heg.s. + 6Lig.s. and 6Heg.s. + 6Li*(3.56) [both ions listed were detected] have been measured at Et = 21.5 and 23.5 MeV. In the latter case the final state is composed of two isobaric analog states: angular distributions are symmetric about 90° cm, within the overall experimental errors. In the reaction leading to the ground states of 6He and 6Li differences from symmetry of as much as 40% are observed at forward angles. Angular distributions involving 6Heg.s. + 6Li*(2.19) and 6Lig.s. + 6He*(1.8) have also been measured. This reaction appears to proceed predominantly by means of the direct pickup of a triton or 3He from 9Be. Differential cross sections are also reported at Et = 17 MeV: see (1984AJ01) for references.
Angular distributions of 6Li ions have been obtained at E(3He) = 6 to 10 MeV: see (1974AJ01). A study of the continuum suggests the population of 6Li states at Ex = 8 - 12, ≈ 21 and 21.5 MeV: see (1984AJ01). More recently, measurements at E(3He) = 60 MeV of differential cross sections have been reported (1990MA1O, 1990MAZG, 1995MA57). Spectroscopic factors were deduced. Angular distributions at E(3He) = 60 MeV for transition to the 6Li ground state and to 6Li*(3+, 2.185; 2+, 5.37; 1+, 5.65) were measured (1996RU13) and analyzed by coupled-channels methods.
Differential cross sections are reported at En = 14.4 MeV involving 6Li*(2.19) and 5Heg.s. (1984TU02).
Angular distributions involving 6Li*(0, 2.19) have been measured at E(3He) = 30 MeV: see (1974AJ01).
At Eα = 72.5 MeV only 6Li*(0, 2.19) are observed: the latter is excited much more strongly than is the ground state [Sα for the ground state is 0.4 that for 6Li*(2.19)]. The angular distributions for both transitions are flat: see (1979AJ01). See also (1984AJ01). A more recent measurement of differential cross sections at Eα = 27.2 MeV is reported in (1995FA21). Spectroscopic factors were deduced.
Angular distributions involving 7Be*(0, 0.43) have been measured at Ep = 40.3 MeV (1985DE05). For the earlier work at Ep = 30.6 to 56.8 MeV see (1974AJ01, 1979AJ01). See also references cited in (1988AJ01).
Angular distributions involving states in 8Be have been studied at Ed = 19.5 and 51.8 MeV [see (1974AJ01)] and at 50 MeV (1985GO1G, 1989GO07, 1989GO26), 54.2 MeV (1984UM04) and 78 MeV (1986JA14), as well as at Ed = 18 and 22 MeV (1987TA07) and 51.7 MeV (1986YA12). See also (1984NE1A, 1987GO1S) and the DWBA calculations at Ed = 50 MeV (1988KA46) and Ed = 15 MeV (1988RA27).
Angular distributions have been obtained at E(3He) = 28 to 40.7 MeV [see (1974AJ01)] and at E(3He) = 33 MeV (1989SI02), E(3He) = 33.4 MeV (1986CL1B; also Ay), E(3He) = 60 MeV (1990MAZG, 1993MA48), E(3He) = 30 - 60 MeV (1995MA57). See also (1989GL1D) and see 9B in (1988AJ01).
Angular distributions (reaction (a)) at Eα = 42 MeV involve 6Li*(0, 2.19): see (1974AJ01). Differential cross sections were measured at Eα = 90 MeV and cluster spectroscopic amplitudes were deduced (1991GL03). At Eα = 65 MeV reaction (b) goes via 6Li*(2.19, 4.31): see (1984AJ01). See also 10B in (1988AJ01) and (1987GA20).
An analysis involving excited states of 6Li and 14N was applied to cross section and analyzing power data at E(6Li) = 33 MeV by (2000MA43).
Measurements of triple differential cross sections for elastic breakup of 156 MeV 6Li (reaction (b)) were reported in (1989HE28, 1989HE17, 1989RE1G). A diffraction dissociation model analysis was used. See also reaction 70. Partial cross sections for the 6Li + 12C reaction were measured for E(6Li) = 3.11 - 12.07 MeV by (1998MU12).
See 16O in (1986AJ04).
Measurements of angular distributions at E(11B) = 25, 35, 40 MeV have been reported by (1996JA12). Transfer mechanisms were studied.
The fragmentation of 12C into two 6Li ions has been observed at E(12C) = 2.1 GeV/A (1986LIZP).
Angular distributions of reaction products were measured for E(14N) = 50 MeV, and multinucleon transfer mechanisms were studied (1992ARZX). See also the analysis for E(14N) = 54 MeV (1987GO12), and see 20Ne in (1987AJ02, 1998TI06).
Measurements of differential cross sections and analyzing powers were reported by (1989SI02). Spectroscopic factors were extracted.
Angular distributions and polarization observables involving 6Li ions and several 12C states are reported at Ed = 22 MeV (1987TA07) and 51.7 MeV (1986YA12) and at Ed = 54.2 MeV (1984UM04). See also (1984NE1A), and 12C in (1990AJ01) for polarization studies.
Measurements and analyses of differential cross sections at E(3He) = 30 - 60 MeV have been reported (1995MA57).
Differential cross sections at Ed = 50 MeV were reported (1990GO14).
Angular distributions have been measured at E(3He) = 11 to 40.7 MeV involving 6Li*(0, 3.56) and various states of 16O: see (1974AJ01, 1977AJ02). Differential cross sections have been reported for E(3He) = 66 MeV (1991MA56).
Measurement of the tensor analyzing power made at E(6Li) = 34 MeV (1978VE03) were analyzed to obtain the D- and S-state ratio for the dα|6Li| bound state overlap.
Angular distributions measured for E(6Li) = 21 - 32 MeV are reported by (1999MA16).
For reaction (b) measurements of triple differential cross sections for elastic breakup of 156 MeV 6Li were reported in (1989HE28, 1989HE17, 1989RE1G). Data were analyzed on the basis of a diffractive disintegration approach. Breakup measurements at E(6Li) = 60 MeV were reported in (1988HE16). See also reaction 56, and see the theoretical study of angular correlation of breakup fragments in (1989BA25).