An investigation into low-lying electronic states of HCS₂ via threshold photoelectron imaging.

Low-energy photoelectron imaging spectra of HCS2(-) are reported for the first time. Vibrationally resolved photodetachment transitions from the ground state of HCS2(-) to the ground state and low-lying excited states of HCS2 are observed. Combined with the ab intio calculations and Franck-Condon simulations, well-resolved vibrational spectra demonstrate definitive evidence for the resolution of the ground-state and excited states of HCS2 radical in the gaseous phase. The ground state and two low-lying excited states of HCS2 radical are assigned as (2)B2, (2)A2, and (2)A1 states, respectively. The adiabatic electron affinity is determined to be 2.910 ± 0.007 eV. And the term energies of the excited states, T0 = 0.451 ± 0.009 eV and 0.553 ± 0.009 eV, are directly measured from the experimental data, respectively. Angular filtering photoelectron spectra are carried out to assist in the spectral band assignment.