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

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+, CH2S+, CH3S+ and CH3SCH3 +. Power dependence studies at 355 nm show a (2 + 1) REMPI process for the formation of parent ion. Peaks at m/e = 46, 47 and 61 show two-photon laser power dependence whereas m/e = 15 and 45 peaks show four-photon dependence. However, in 532 nm photoionisation, no parent ion signal is observed. A peak at m/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.