The ground and first few excited electronic states of HCN and its deprotonated anion CN− are investigated by ab initio calculations including electron correlation. The excited states of HCN are bent with their bonds stretched in comparison to the linear ground state. The 3A′ state is lowest for HCN, lying about 110 kcal/mol above the1Σ+ ground state, followed by 3A″ and then by 1A′. The deprotonation energies of these excited states are between 10 and 20 kcal/mol greater than that of the ground state. The electronic excitation shifts density toward the C atom.
Available at: http://works.bepress.com/steve_scheiner/313/