The electronic spectrum of NS2 : Low-lying quartet states

Abstract

An investigation concerning nine electronically low-lying doublet states of the SNS molecule appeared recently. The present paper represents the conclusion of studies on the NS2 molecule, focusing on the low-lying SNS quartet states. Nine quartet states, including six bent structures (4A2, 4B2, two 4A1, and two 4B1 ) and three linear structures (4Πg and two 4Πu ), have been investigated at the self-consistent field (SCF), single and double excitation configuration interaction (CISD), and complete active space (CAS) SCF levels of theory with five basis sets, double zeta (DZ) through triple zeta plus double polarization (TZ+2P). Four of these quartet states lie within 1.8 eV (42.0 kcal mol−1 ) of the 2A1 ground state of NS2. Thus one or more of these quartet states (which lie much lower than for the valence isoelectronic NO2 molecule) should be observable. At the SCF level of theory the stability of the wave functions and the relative energies of the nine quartet states are discussed in conjunction with the molecular orbital (MO) Hessian.