Identification of singlet and triplet SCNO+ cations in the gas phase: theory and experiment

Experimental evidence, based on collisional activation (CA) mass spectrometry, is provided for the existence in the gas phase of SCNO+ singlet and triplet cations. The production of the triplet state is enhanced upon collisional activation with oxygen or nitric oxide as collision gas. The identification of the two spin states of SCNO+ is strongly supported by ab initio calculations of their unimolecular fragmentation energies. Theory predicts SCNO+ has a singlet ground state, with the triplet state lying close in energy (38 kJ mol−1). The singlet state is best described as an ion–neutral complex (SC··NO+) while the triplet state is a normal covalently bounded species (SCN+O). The CA mass spectrum of the isomeric SNCO+ ions is also discussed.