Valence and high electronic states of PN have been calculated with accurate quantum chemistry methods. The variety of theoretical methods used includes complete active space self-consistent field, multireference configuration interaction and the newly developed explicitly correlated coupled cluster methods. The large correlation-consistent atomic orbitals basis sets AVQZ, AV5Z and AV(5+d)Z are used for the potential energy curves calculations in the bonding and long-range regions. The spectroscopic constants (Re,Be,ωe,ωexe,αe,De,Te) and the vibrational levels of the bound valence states (X1Σ+, A1Π, a3Σ+, d3Δ, e3Σ−, C1Σ−, b3Π, D1Δ and E1Σ+and some higher bound states) are determined and compared with experimental findings when available. Significant spin–orbit interactions between triplet states and A1Π and E1Σ+excited states are found near the crossing points of the potential energy curves and could explain predissociation phenomena and the perturbations of the vibrational levels experimentally observed for PN in their A1Π and E1Σ+states. [ABSTRACT FROM PUBLISHER]