Accurate ab initio study of low-lying electronic states of phosphorus nitride radical

This paper employs the highly accurate valence internally contracted multireference configuration interaction method to investigate the potential energy curves (PECs) for the ground state (X¹\varSigma⁺) and two low-lying excited states (A¹\varPi and D¹\varDelta of phosphorus nitride (PN) radical with the correlation-consistent basis set, aug-cc-pV6Z, in the valence range. Relativistic effects are considered in these calculations. The spectroscopic constants of the X¹\varSigma⁺ and A¹\varPi states are calculated based on the PECs, and the results are in good accord with the available experimental data. The first 30 vibrational states for the A¹\varPi state and the first 40 vibrational states for the A¹\varPi state are determined when J =0. For each vibrational state, molecular constants G(v), B(v) and D(v) are also attained.