Approximate calculation of the Jahn–Teller energy and Ham reduction factor for CH3S

CAS Calculation of the Excited States of the Methylthio Neutral Radical and Its Ions

The complete active space (CASSCF) and the multiconfiguration second-order perturbation theory (CASPT2) calculations with 6-311++G(3df,3pd) gauss basis sets are performed for several electronic states of the methylthio neutral radical and its cation and anion. Twenty-two electronic states are optimized in the C _s point group. Through the vertical promotion calculations, the absorption spectral is simulated for the neutral radical. Furthermore, through the energy comparison between the neutral radical and relative ions, the ionization energy and the electronic absorption energy are understood adiabatically.

Two-color resonant four-wave mixing spectroscopy of highly predissociated levels in the ÃA12 state of CH3S

We report results of two-color resonant four-wave mixing experiments on highly predissociated levels of the methylthio (or thiomethoxy) radical CH3S in its first excited electronic state A 2A1. Following photolysis of jet-cooled dimethyl disulfide at 248 nm, the spectra were measured with a hole-burning scheme in which the probe laser excited specific rotational transitions in band 3(3). The spectral simplification afforded by the two-color method allows accurate determination of line positions and homogeneous linewidths, which are reported for the C-S stretching states 3v(v=3-7) and combination states 1(1)3v(v=0-2), 2(1)3v(v=3-6), and 1(1)2(1)3v(v=0,1) involving the symmetric CH3 stretching (nu1) mode and the CH3 umbrella (nu2) mode. The spectra show pronounced mode specificity, as the homogeneous linewidth of levels with similar energies varies up to two orders of magnitude; nu3 is clearly a promoting mode for dissociation. Derived vibrational wave numbers omega1', omega2', and omega3' of the A state agree satisfactorily with ab initio predictions.