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

► We applied the (1 + 1) IR-VUV photoionization method to obtain the IR spectrum of the CH3S radical in the range 2780-3270 cm−1. ► With the advantage of the mass-selective detection, the IR spectrum of CH3S shows absorption bands with no interference from the precursor. ► Our results provide direct evidence for the assignments of ν1 and ν4 modes of gaseous CH3S.