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¹²Li is not observed in the 4.8 GeV proton bombardment of a uranium target: it is particle unstable. Its atomic mass excess would then be > 49.0 MeV. (TH74) calculate the mass excess of ¹²Li to be 52.92 MeV, while (JE75) calculate 52.94 MeV. Taking the average of these two values, ¹²Li would then be unstable with respect to ¹¹Li + n, ¹⁰Li + 2n and ⁹Li + 3n by 3.92, 2.96 and 3.76 MeV, respectively. See also (75AJ02) and (BE75Q, IR76C; theor.).