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²⁰N has been observed. It is particle stable: see (72AJ02). Recent calculations of the atomic mass excess of ²⁰N are 21.67 MeV (TH74), 21.60 (JE75; transverse form of IMME), 21.88 (JA76M) and 22.2 MeV (WA77). Assuming that the atomic mass excess is 22.0 MeV, ²⁰N is then stable with respect to ¹⁹N + n by 1.9 MeV (see ¹⁹N). See also (TH72K, TO73G, VO75H, WA76L, AR77B, BH77) and (WI73J, BE75Q; theor.).