The heat of formation of CISO+

The heat of formation of CISO+, 802 ± 1 kJ mol−1 at 0 K, has been obtained by the dissociative photoionization of supersonically cooled thionyl chloride, Cl2SO. Threshold photoelectron photoion coincidence spectroscopy was used to obtain the appearance energy from the cross-over point in the breakdown diagram for the dissociation. Also measured was the adiabatic ionization energy of thionyl chloride, 10.85 ± 0.05 eV. The experimentally measured kinetic energy release was found to agree with that calculated by statistical theory confirming that there is no reverse energy barrier to the Cl loss reaction. The interpretation was aided by ab initio MO calculations.