Photodissociation spectra of transition metal sulfides: Spin-orbit structure in charge transfer bands of FeS⁺ and NiS⁺

Photofragment spectra of FeS⁺ and NiS⁺ are reported. Analysis of the FeS⁺ spectrum reveals it to arise from a ⁶Π←⁶Σ charge-transfer transition, and gives the vibrational frequency, ω_e^′=295cm^-1, and spin-orbit constant, |A|=125cm^-1, in the ⁶Π state. The onset of the NiS⁺ spectrum appears to occur in the middle of a vibrational progression, thus giving a precise measurement of the Ni⁺-S bond strength, D₀(Ni⁺-S)=238±4kJmol^-1. Analysis of the spectrum for vibrational and spin-orbit structure leads to a tentative assignment of a ⁴Δ ground state and suggests the spectrum is composed of overlapping transitions to two near-degenerate excited electronic states, most likely a ⁴Π and ⁴Φ pair.