CN− bond length in e+CN−: contrast with H+CN−

The CN− bond length in e+CN− was determined by positron annihilation. The obtained value (0.192 nm) was compared with those of CN− in HCN (or H+CN−) (0.116 nm) and in MCN (M+=Na+, K+, Rb+, Cs+, Tl+) (ca. 0.190 nm). This finding supports the statement, already advanced, based on the rate constants of Ps (positronium) and Mu (muonium) spin exchange reactions, that positronium behaves more as an element different from hydrogen than as its super-light isotope.