Electronic structure, stability and spectroscopy of low-lying states of NO−, HNO− and HON− molecular anions

Abstract

Accurate post Hartree-Fock methods have been used to investigate electronic structure, spectroscopy, stability and metastability of low-lying electronic states of HNO, HON, NO, NO−, HNO− and HON−. Accurate vertical transition energies between lowest electronic states of HNO and HON isomers have been determined. The HNO vertical transition energy of the X∼1A′-ã3A″ transition is shown to be 0.87eV. Core-valence correlations and relativistic corrections have been taken into account to determine accurately spectroscopic constants of electronic states of NO− and NO. Adiabatic excitation energies and dipole moments of low-lying electronic states of NO− have also been calculated. The adiabatic electron affinity of NO has been deduced to be 0.0289eV, which is in excellent agreement with the experimental value of 0.026±0.05eV. The comparison of potential energy curves of low-lying states of NO/NO−, HNO/HNO− and HON/HON− reveals short-lived excited electronic states. The HON− anion appears as an unbound anion unlike to HNO− which is a bound anion. Three-dimensional potential energy surfaces (3D-PESs) for both HNO (X∼1A′) and HNO−(X2A″) ground states, have been generated and fitted by second order perturbation theory to produce accurate spectroscopic constants. Spectroscopic data of HNO−(X2A″) deduced from this work is computed for the first time.