Structure and fragmentation of doubly ionized HNCS

Double ionization spectra of isothiocyanic acid (HNCS) have been measured using multi-electron and multi-ion coincidence techniques combined with high-level theoretical calculations. The adiabatic double ionization energy of HNCS is found at 27.1 ± 0.1 eV and is associated with the formation of the X 3A″ ground state of HNCS2+. The characteristics of different dissociation channels are examined and compared to the results of electronic structure calculations obtained by systematically elongating the three bonds H-NCS, HN-CS, and HNC-S. For instance, the adiabatic double ionization energy of the NCS fragment is deduced to be 30.95 ± 0.5 eV. In addition, the C+ and NS+ dissociation channels are of particular interest, possibly indicating the involvement of a structural rearrangement process upon doubly ionizing HNCS.