(See Energy Level Diagrams for 8B)
Nuclear models: (1975KH1A).
The β+ decay leads mainly to 8Be*(2.9). The mean of half-lives listed in (1974AJ01) is 770 ± 3 msec; log ft = 5.64 (1966BA1A). There is also a branch to a 8Be state at ≈ 16.6 MeV; log ft = 2.9 (1964MA35), 3.33 (1969BA43). See reaction 29 in 8Be. See (1973TR1B, 1974BA1Q, 1974CL1E, 1974UL1B, 1974VA1C, 1975UL1A, 1977HA1M) for astrophysical considerations.
Angular distributions for the n0 group have been reported at E(3He) = 4.8 to 5.7 MeV. The appearance of a forward peak indicates an L = 0 transfer and hence a knockout mechanism (L = 0 is forbidden for simple diproton stripping) (1967VA24). The first excited state is at 767 ± 12 (1965FA03), 783 ± 10 keV (1965MC06: Γ = 40 ± 10 keV). See also (1966LA04) and 9B.
Absolute cross sections have been measured for Ep = 0.165 to 10.0 MeV [see (1974AJ01)] and at Ep = 0.36 MeV (1977WI05). A resonance at Ep = 724 keV [9B*(0.77)] with Γlab ≈ 46 keV [σpeak = 2.20 ± 0.22 μb, Γγ = 50 ± 25 meV] is reported by (1966PA16, 1972KA1B).
The zero-energy cross-section factor S(0) = 0.032 ± 0.003 keV · b, dS/dE = -3 × 10-5 b ((1972KA1B) and P.D. Parker, private communication). The change in the S-value is due to a remeasurement of the 7Li(d, p) cross section: see 9Be. See also (1974AJ01, 1977WI05). The relevance of this reaction to astrophysics is discussed by (1971BA1A, 1973BA1H, 1974VA1C, 1974HO11). See also (1974AJ01, 1974LO1B).
The ground state tranisition has been studied at Eπ+ = 50 MeV (1977AM1B).
At Ep = 49.5 MeV angular distributions have been measured for the tritons to 8B*(0, 2.32) (1970SQ01): L = 2 and L = 0 + 2, leading to Jπ = 2+ and 3+, respectively. See also 10B(p, 3He)8Be. The energy of the excited state is 2.29 ± 0.05 MeV (1970SQ01), 2.34 ± 0.04 MeV (1968BR23): Γlab = 390 ± 40 keV (1967MC14). 8B*(0.78) is also observed.
At E(3He) = 50 MeV, 6He groups are observed to the first three states of 8B (1976MC14). At E(3He) = 72 MeV the first T = 2 state is observed at Ex = 10.619 ± 0.009 MeV, Γ < 60 keV: dσ/dΩ(lab) = 190 nb/sr at θlab = 9°. No other states are observed within 2.4 MeV of this state (1975RO01).