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GENERAL: See also (66LA04) and Table 6.7 [Table of Energy Levels] (in PDF or PS).

Model calculations: (BA66T, BA68GG, FA68C, VA68P, TH69B, LA70C).

Other topics: (GO65I, GO66J, FO70J, AN72B, CA72P, GH72, JA72H, WE73R).

1. (a) 3He(3He, γ)6Be	Qm = 11.488	Eb = 11.488
(b) 3He(3He, p)5Li	Qm = 10.89
(c) 3He(3He, 2p)4He	Qm = 12.8601
(d) 3He(3He, 3p)3H	Qm = -6.9546
(e) 3He(3He, 3He)3He
(f) 3He(3He, d)4Li	Qm = -8.4

The yield of γ-rays to ⁶Be*(1.7) (reaction (a)) increases smoothly from 0.4 to 9.3 μb (assuming isotropy) for 0.86 < E(³He) < 11.8 MeV (90°). No transitions were observed to ⁶Be(0) [σ < 0.01 μb at E(³He) = 1.4 MeV]. This is understood in terms of a direct capture of ³He by ³He in the singlet spin state and with zero angular momentum: the 0⁺ --> 0⁺ γ transition is forbidden. Reaction (a) is thus of negligible astrophysical importance compared to reaction (c) (HA67M) [see below]. The capture cross section from E(³He) = 11 to 27 MeV continues to increase smoothly with energy at first and then shows a broad structure centered at E(³He) = 23 ± 1 MeV [E_x = 23.0 ± 0.5 MeV], Γ_c.m. ~ 5 MeV (VE72D, VE73A, VE73F) this appears to be a ³³F cluster resonance which decays by an E1 transition to ⁶Be*(1.7). The γ-ray angular distributions are consistent with J^π = 3^- (VE73F).

Measurements of the total cross section for reaction (c) have been carried out for E(³He) = 60 to 300 keV (DW73B) and 0.16 to 2.2 MeV (DW69, DW71). The measurements of (DW73B), down to E_c.m. = 30 keV, eliminate the possibility of a resonance [which might help explain the observed absence of solar neutrinos], unless it is extremely narrow (Γ < / ~ 100 eV): θ²_p ~ 3 x 10^-6 (DW73B). (BA72JJ) has commented that such a high ³He + ³He cluster purity, a ⁶Be state at ~ 11.5 MeV is not expected. The cross section factor S(E_c.m.) = [5.5 - 3.1 E_c.m. + 1.4 E²_c.m.] MeV · b [error in S is ± 20% for E_c.m. > 40 keV] (DW73B). Cross sections are also reported for E(³He) = 0.5 to 1.7 MeV by (NE66B). See (66LA04) for a discussion of earlier work and (BA66AE, SH67I, TO67G, BA68D, MA68O, BA69AC, MA70M, BA72JJ, BA72PP, FE72, FO72I, KO72G, TO72C, BA73O, FO73H, PA73M, TR73) for a discussion of the astrophysical implications of reaction (c). From a kinematically complete study of reaction (c) (KU72C, KU72N) find a_pp = -7.6 ± 0.6 fm. (GR70E) report a_pp = -7.52 ± 0.22 fm. A study of the proton spectrum at E(³He) = 6.9, 7.9 and 9.1 MeV indicates that reaction (c) proceeds mainly via a direct mechanism (SL72A). See also (BO70H, RO73) and ⁵Li.

The elastic scattering (reaction (e)) has been studied for E(³He) = 3 to 12 MeV (TO63B), 9.1 and 11.1 MeV (IV68), 11.9 to 18.9 MeV (BA68T), 17.9 to 32.0 MeV (JE70) and 18 to 80 MeV (BA68CC). The excitation function shows a smooth monotonic behavior except for an anomaly at E(³He) = 25 MeV in the l = 3 partial wave corresponding to a broad state in ⁶Be at E_x ~ 24 MeV (BA68CC, JE70). Polarization measurements have been reported at E(³He) = 4.33 to 9.83 MeV (BO72U) and 9.3 to 17.5 MeV (HA72GG): the polarization is consistent with zero at θ ~ 63°, consistent with a description of the scattering which leaves the P- and F-wave phase shifts unsplit (BO72U, HA72GG).

For reaction (f) see (ME68A). See also (TO68A) and (TH67A, SU68C, TH68C, KR69K, MA70M, NE70F, BR71Q, BR72Q, GR73G, TH73C; theor.).

2. 4He(3He, n)6Be

Qm = -9.090

Neutron groups have been observed to ⁶Be*(0, 1.7) at E(³He) = 19.4 MeV (AD67E), 26 MeV (EC66) and 29.8 MeV (GU66A): see Table 6.8 (in PDF or PS). There is no evidence for other states of ⁶Be with E_x < / ~ 5 MeV (EC66). See also (BA70B).

3. 6Li(p, n)6Be

Qm = -5.070

Neutron groups have been observed to ⁶Be*(0, 1.7) as has the ground state threshold. The width of the ground state is 95 ± 28 keV (HO67A). The parameters of ⁶Be*(1.7) are displayed in Table 6.8 (in PDF or PS) (BA65V, EC66, BA68PP, WA68I, AR72P). Higher excited states have been reported by (BA65V, BA68PP, WA68I): there is very strong evidence that states analog to these do not exist in ⁶He. At E_p = 24.9 MeV no evidence is found for a ⁶Be state near E_x = 11.5 MeV (WO73A). See also reaction 4.

Angular distributions have been obtained at E_p = 8.3 to 18.0 MeV (WA68I; n₀), 15 MeV (WA68I; n₁) and 30.2 and 49.4 MeV (BA68PP, CL69C; n₀). See also (JU69) and (66LA04).

4. 6Li(3He, t)6Be

Qm = -4.306

Triton groups have been observed to ⁶Be*(0, 1.7). The width of the ground state is 89 ± 6 keV (WH66). The parameters of the excited state are displayed in Table 6.8 (in PDF or PS) (MA66H, RO66D). No other excited states have been seen with E_x < 13 MeV (MA66H: E(³He) = 40 MeV), < 10 MeV (RO66D: E(³He) = 31 MeV). An attempt has been made at E(³He) = 25.5 MeV (PA73E) and at 46.3 MeV (HA73CC) to observe a possible ⁶Be state at E_x = 11.5 MeV, of astrophysical interest: dσ/dΩ < / ~ 0.19 μb/sr at θ_c.m. = 45° at the lower energy; dσ/dΩ < / = 1.6 μb/sr at 8.4° and at 46.3 MeV. Upper limits for the spectroscopic factor are S < / = 0.006 (PA73E) and < / = 0.001 (HA73CC). The ground-state angular distribution shows a pronounced oscillatory character, consistent with l = 0; that for the 1.7 MeV state is relatively structureless (RO66D). Angular distributions are also reported by (NU69C; n₀: 14, 18 MeV) and by (GI71E, GI72D; n₀: 27.0 MeV). The α-decay spectra of ⁶Be*(0, 1.7) have been studied by (GE73).

5. 6Li(6Li, 6He)6Be

Qm = -7.797

See (WH73B), and reaction 9 in ⁶He and reaction 16 in ⁶Li. See also (WH73C).

6. 9Be(3He, 6He)6Be

Qm = -9.692

This reaction has been observed at E(³He) = 37 MeV [dσ/dΩ(13°) = 9 μb/sr] (GO67O) and at 70 MeV (BE73Y). No new states were observed with E_x < 15 MeV (BE73Y).