Selective formation and spectroscopic characterization of the H2CCS•+ radical cation via dissociative ionization of thiophene

The chemistry of sulfur-containing molecules is of significant interest to fields ranging from the combustion of petrochemicals to astrochemistry (with multiple S-containing species unambiguously detected in the interstellar medium or circumstellar shells). Here, infrared predissociation action spectroscopy and mass-analyzed ion kinetic energy spectroscopy measurements of the m/z 58 fragment from the dissociative ionization of thiophene are presented. Comparison is made between these experimental results and ab initio calculations (of both the spectral features and the fragmentation potential energy surface), which allows the fragment to be identified as the H2CCS•+ radical cation. This conclusive identification addresses long-standing questions about the dissociative ionization of thiophene. The findings will enable further spectroscopic measurements and reactivity studies to be conducted, allowing H2CCS•+ to be incorporated into models of astrochemical environments.