Photoionization spectrum and ionization energy of CH3SCl

Photoionization-efficiency (PIE) spectra in the wavelength range 108–144 nm were measured for CH₃SCl generated from the reaction system Cl/Cl₂ /CH₃SH(CH₃SSCH₃) in a discharge-flow reactor coupled to a photoionization mass spectrometer employing a synchrotron as the source of  radiation. According to the PIE spectrum of CH₃SCl thus obtained, the ionization energy (IE) is (9.147±0.007) eV. Based on GAUSSIAN-2 calculations, the observed ionization of CH₃SCl near the threshold region is likely to form from singlet CH₃SCl to doublet CH₃SCl⁺; the calculated IE 9.140 eV agrees well with the experimental value. Two vibrational frequencies of singlet CH₃SCl and one of doublet CH₃SCl⁺ were found to be (244±60) cm^-1, (513±60) cm^-1, and (631±60) cm^-1,  respectively.