Experimental and quantum-chemical studies on dissociative photoionization of c-C2H4S

The dissociative photoionization of thiirane (c-C2H4S) in a region ∼9-20 eV was investigated with photoionization mass spectroscopy and calculations of molecular energies with the Gaussian-3 method. An adiabatic ionization energy of 9.051 eV for c-C2H4S agrees with a prediction of 9.07 eV for formation of c-C2H4S+; predictions of energies of formation of ring-opened isomers CH3CHS+, CH2CHSH+ and CH2SCH2+ are 8.85, 8.91 and 9.37 eV, respectively. Major fragment ions C2H3S+, C2H2S+, HCS+, H2S+ and C2H3+ were observed with their respective appearance energies at 10.71, 13.07, 11.13, 11.96 and 12.58 eV. Based on comparison of determined appearance energies and predicted reaction energies, we established six dissociation channels c-C2H4S+ → CH3CS+ + H, HCS+ + CH3, H2S+ + C2H2, C2H3+ + HS, CH2CS+ + H2 and CHCSH+ + H2. Ring-opening and H migration are involved in these processes.