Franck–Condon analysis of the photoelectron spectra of S2O−: Including Duschinsky effects

A program developed to calculate multidimensional Franck–Condon factors including Duschinsky effects is described and used to simulate the vibrationally resolved photoelectron spectra of S2O− combining with ab initio molecular orbital calculations. Geometry optimizations and harmonic vibrational frequency calculations have been performed on the X ˜ 1 A ′ state of S2O and X ˜ 2 A ″ state of S2O−. Franck–Condon analysis and spectral simulations were carried out on the first photoelectron band of S2O−. The simulated spectra obtained by using B3LYP/6-311+G(3df) are in excellent agreement with the experiment. In addition, the accurate equilibrium geometric parameters, r(ss) = 0.1996 ± 0.0005 nm and r(so) = 0.1514 ± 0.0005 nm, of the X ˜ 2 A ″ state of S2O−, are deduced by employing an iterative Franck–Condon analysis procedure in the spectral simulation. Furthermore, the well-resolved theoretical spectrum is derived by improving the resolution of photoelectron spectra in simulations.