Infrared spectrum of mass-selected CH3S radicals investigated with infrared + vacuum ultraviolet photoionization

We present a detailed spectral study of the atmospherically important methylthio (CH3S) radical demonstrating the advantage of IR-VUV photoionization for vibrational spectroscopy of free radicals due to its mass selectivity. Photolysis of CH3SH produced CH3S radicals that were ionized with (1 + 1) IR-VUV photoionization and detected with the time-of-flight technique. The IR spectrum of CH3S was obtained in the range 2790–3270 cm−1. Absorptions features near 2819 and 2904 cm−1 are assigned to ν1 and ν4 modes of CH3S, respectively, and those near 2978 and 3241 cm−1 are tentatively assigned as combination transitions 315161(e) and 315161(a), respectively, from the ground vibrational state.