Multiphoton dissociation/ionisation of dimethyl sulphide (CH₃SCH₃) at 355 and 532 nm

Abstract

Multiphoton dissociation/ionization has been studied for CH₃SCH₃ at 355 and 532 nm using a time-of-flight mass spectrometer. The major ion signals observed at 355 nm are C⁺, CH₃ ⁺, HCS⁺, CH₂⁺, CH3S⁺ and CH₃SCH₃ ⁺. Power dependence studies at 355 nm show a (2+1) REMPI process for the formation of parent ion. Peaks atm/e = 46, 47 and 61 show two-photon laser power dependence whereasm/e = 15 and 45 peaks show four-photon dependence. However, in 532 nm photo-ionisation, no parent ion signal is observed. A peak atm/e = 35 corresponding to SH₃ ⁺ has been observed. SH₃ ⁺ has been suggested to originate from CH₃SCH₂ ⁺ via a cyclic transition state. Photoionisation results of CH₃SCH₃ have been compared with those of CH₃SSCH₃, at these two wavelengths.