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12Be (1968AJ02)

(See the Isobar Diagram for 12Be)

An activity of τ1/2 = 11.4 ± 0.5 msec, ascribed to 12Be, is observed in the GeV proton irradiation of 15N, 16O, 18O, 19F, 23Na and 27Al targets (1965PO03). A peak in the particle-identifier spectrum from 5.3 GeV protons on U confirms the existence of 12Be, but the assignment of the 11.4 msec half-life is rendered uncertain by the discovery of 11Li (1966PO09). A calculation by Kurath (see ref 8 in (1965PO03)) suggests log ft = 3.5 for the ground state; Eβ-(max) is then ≈ 11.7 MeV for the above τ1/2. (M - A) for 12Be is then ≈ 25.1 MeV, which would mean that 12Be is bound with respect to 11Be + n by ≈ 3.2 MeV. See also (1960GO1B, 1960ZE03, 1961BA1C, 1967AU1B).