Fragmentation of the valence electronic states of SeF6+ and TeF6+ studied by threshold photoelectron–photoion coincidence spectroscopy

Threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has been performed on SeF6 and TeF6 and breakdown diagrams constructed. The ground electronic states of XF6+ (X=Se, Te) are repulsive in the Franck–Condon region, meaning that the first ion signal only gives an upper limit to the energy of the first dissociative ionisation pathway (XF5++F+e−). Using TPEPICO time-of-flight spectra to determine the kinetic energy (KE) released in fragmentation over a range of energies, however, we have extrapolated to zero KE to calculate values of 14.1±0.5 and 14.5±0.6 eV for the first dissociative ionisation energy for SeF6 and TeF6, respectively. Upper limits for the enthalpies of formation of SeF4+, SeF3+, TeF4+ and TeF3+ at 0 K are determined to be 426±36, 368±28, 428±36 and 380±28 kJ mol−1, respectively.