The low-lying electronic states X3Σ-, a1Δ and b1Σ+of PO-, NS-and PS-according to MRD-CI calculations

Large-scale MRD-CI computations have been carried out on the pi 4 pi * 2 states X 3 Sigma - , a 1 Delta and b 1 1 Sigma + of PO - , NS - and PS - , using extended AO basis sets. The a 1 Delta state of NS - is found to be stable upon electron attachment, as experimentally known for the similar state of PO - . For both NS - and PO - , the zero vibrational level of the b 1 Sigma + state is predicted to be slightly more stable than the ground state of the corresponding neutral molecule, while both singlet states of PS - are placed well below X 2 Pi of neutral PS. The electron affinity of PS is estimated to be 1.60+or-0.10 eV. Spectroscopic parameters and Franck-Condon factors for electron detachment are given for NS - and PS - . The dipole moments for the ground state of the neutral molecules and all negative-ion states, are reported.