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14Be (1991AJ01)

(See the Isobar Diagram for 14Be)

14Be has been observed in the 14C(π-, π+)14B reaction (1984GI09), in the interaction of 30 MeV/A 18O ions with 181Ta (1986CU01) and in the spallation of thorium by 800 MeV protons (1988WO09). See also (1986AJ01). The atomic mass excess reported by (1984GI09) is 40.10 ± 0.13 MeV but it is not clear that the ground state was observed. (1988WO09) report an atomic mass excess of 39.74 ± 0.14 MeV which we adopt. 14Be is then bound by 3.0 and 1.12 MeV, respectively, with respect to decay into 13Be + n and 12Be + 2n [see, however, 13Be].

14Be decays by β- emission to states in 14B. Its half-life is 4.2 ± 0.7 ms (1986CU01), 4.35 ± 0.17 ms (1988DU09). We adopt the latter value. The branching ratios for 0n, 1n and 2n emission are 0.14 ± 0.03, 0.81 ± 0.04 and 0.05 ± 0.02 (1988DU09). We remind the reader that the two bound states of 14B are the ground state [Jπ = 2-] and an excited state with Jπ = (1-). The binding energies of 1n and 2n in 14B are, respectively, 0.97 and 5.85 MeV: see Fig. 5.

The interaction cross section at 790 MeV/A for 14Be ions on C is reported by (1988TA10) who also derive the interaction and the r.m.s. radii for the nucleon distribution in 14Be. See also (1989BE03; theor.) and (1989SA10). A calculation in a (0 + 1)ℏω model space suggests that the first four states of 14Be calculated to be at 0, 1.95, 3.67 and 5.30 MeV have Jπ = 0+, 2+, 4+, 2+, respectively (1985PO10). See also (1986AN07, 1986WI04, 1987AJ1A, 1988MI1G, 1988TA1N, 1989AJ1A, 1989DE52, 1989TA1K, 1989TA2S, 1989VOZM) and (1987BL18, 1987SA15, 1987YA16, 1989PO1K, 1990BR1S, 1990LO10; theor.).