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¹⁵Be has not been observed. The calculated mass excess is 51.18 MeV: see (81AJ01). ¹⁵Be is then unstable with respect to ¹⁴Be + n and ¹³Be + 2n by 3.4 and 0.04 MeV, respectively. (85PO10) calculate [in a (0 + 1)h-barω model space] that the first four states of ¹⁵Be at 0, 0.07, 2.32, 3.10 MeV have, respectively, J^π = 5/2⁺, 3/2⁺, 9/2⁺, 7/2⁺. See also (87SA15; theor.).