Dissociative electron ionization (70 eV) of ethyl carbomylmethanedithioate generates m/z 77 ions of composition [H, C, S-2](+). The collision-induced dissociation (CID) mass spectrum of these ions is consistent with the mercaptothiocarbonyl connectivity HSCS+ (a(+)). Calculations predict that some of the a+ ions may equilibrate with HC(S)S+ (b)(+) ions prior to dissociation. Neutralization-reionization mass spectrum (NRMS) of these ions confirmed that neutral HSCS center dot is stable in the rarefied gas phase. The relative, dissociation, and isomerization energies for the ions and neutrals studied at B3LYP/6-311G(d,p) and G2/G2(MP2) levels, are used to support and interpret the experimental results. (C) 2007 Elsevier B.V. All rights reserved.