Electronic States of CH and NH

Abstract

Ab initio calculations (LCAO–MO–SCF) are performed on a series of valence levels of the molecules CH and NH+. Correlation energies are estimated semiempirically from corresponding atomic data. Close agreement with experiment is found for known states for a series of molecular properties such as equilibrium internuclear distances, vibration frequencies, term values, and dissociation energies. A low-lying Σ4− state in CH is calculated to lie 7500 cm−1 above the X 2Π state. No observable quartet transition could be found for CH, while for NH+ a Π4−Σ4− transition should occur in the region of 1000 Å. Other qualitative differences in the observed spectra of the two molecules are discussed. Finally a value of D00(NH+) = 3.4 eV is calculated.