Theoretical and experimental studies of unimolecular dissociation of phosphorus tribromide ions

The heat of formation of PBr2+, 842.9±1.5 kJ/mol at 0 K, has been determined by the dissociative photoionization of the phosphorus tribromide by threshold photoelectron photoion coincidence spectroscopy (TPEPICO) technique. Also measured was the adiabatic ionization energy of the phosphorus tribromide, 9.35±0.02 eV, and the new value of the 0 K heat of formation of PBr3·+ ion was determined, 787±2 kJ/mol. The performance of G2 and density functional theory calculations with four functionals, B3PW91, B3P86, B3LYP, and BLYP in characterizing the ionization energy of PBr3 and the appearance energy of the fragment PBr2+ ion was examined.