Theoretical adiabatic electron affinities are often considered inaccurate because they are referenced to only a single value. Ground state electron affinities for all the main group elements and homonuclear diatomics were identified recently using the normalized binding energy of the hydrogen atom: [0.75420375(3)/2 = 0.37710187(1) eV]. Here we revisit experimental values and extend the identifications to diatomics in the G2-1 set. We assign new ground state electron affinities: (eV) Cl 2 , 3.2(2); Br 2 , 2.87(14); CH, 2.1(2); H 2 , 0.6 ; NH, 1.1, SiH, 1.90. Anion Morse potentials are calculated for H 2 and N 2 from positive electron affinities and for hyperfine superoxide states for the first time.

Hund's state conservation rule predicts (1 × 6) [N ( 4 S) + O(-)( 2 P)] plus 9 × 9 [( 3 P) N(-) + O( 3 P)] = 87 spin states for NO(-). The experimental E a (NO) , 0.92(2)-0.16(2) eV are assigned to the (3 + 27) bonding states with anion bond orders, 0.80-1.15. The E a (NO) 0.026(5)-0.14(2) eV are assigned to seven of the 27 nonbonding states with anion bond orders about one. The negative E a (NO) for the 20 other nonbonding and 30 antibonding states are estimated. Ionic Morse potentials are calculated for 87 predicted states for NO(-) and the 54 bonding and antibonding states of superoxide.