Abstract: | Heats of formation for HCOS+ and HCS2+, obtained from high-quality ab initio calculations, have been used to determine the thermochemistry of several reactions which may form these ions in interstellar clouds or mass spectrometer experiments. Radiative association of HCO+ or HCS+ with either O or S may be important in interstellar clouds, whereas proton transfer from H3+ or HCO+ to CS2 or COS may be a means of synthesizing these ions by mass spectrometry. In the latter case, the relevant heats of formation are: HCS2+(1A1) 1042 kJ mol?1 and HCOS+ (1A′) 996 kJ mol?1. |