Laser-induced fluorescence studies of the CH3S radical

Abstract

Methylthio radicals (CH₃S) have been generated by the 248 nm photodissociation of dimethyl disulphide [(CH₃S)₂] and 193 nm photodissociation of methylmercaptan [CH₃SH]. Fluorescence has been excited on the òA₁â†�X²E transition. The transitions excited were 3²₀ at 366.0 nm, 3¹₀ at 371.3 nm and 0⁰₀ at 377.0 nm. Vibrational relaxation and electronic quenching of the upper state have been studied with a number of gases. By varying the delay between the excimer and dye laser pulses, it has also been possible to study vibrational relaxation in the ground state in the presence of the same gases. No reaction of the CH₃S radical could be found with either O₂ or O₃(k_O3⩽ 8 × 10^–14 cm³ molecule^–1 s^–1), although the fast reaction with NO₂ was confirmed.