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USNDP

7B (1984AJ01)


(See the Isobar Diagram for 7B)

GENERAL: (See also (1979AJ01).)

See (1979BE1H, 1982NG01).

Mass of 7B:This nucleus has been studied in the 7Li(π+, π-)7B and 10B(3He, 6He)7B reactions. In the (π+, π-) work (1981SE1B; preliminary) find the mass excess to be 27.80 ± 0.10 MeV and Γ for the ground state is 1.2 ± 0.2 MeV. In the earlier (3He, 6He) work [see (1974AJ01)] M-A was reported to be 27.94 ± 0.10 MeV, Γ=1.4 ± 0.2 MeV. We adopt 27.87 ± 0.10 MeV, Γ = 1.3 ± 0.2 MeV. The isobaric quartet mass law would predict M-A = 27.76 ± 0.17 MeV. 7B is unbound with respect to 6Be + p (Q = 2.21), 5Li + 2p (Q = 1.61), 4He + 3p (Q = 3.58). The expected single-particle width is Γ = 0.64 MeV: it is suggested that the two-proton and three-proton decays make an appreciable contribution to the width: see (1974AJ01).