Thermochemistry of the plutonium fluorides from electron impact studies

Abstract

The ionization potentials of the molecules PuF5, PuF4, and PuF3 have been measured using electron impact ionization. The values are, respectively, 14.5±0.1, 11.8±0.4, and 8.6±0.5 eV. The parent ion PuF+6 was not detected. From the ionization potentials and the fragment ion appearance potentials the bond dissociation energies of the molecules F5Pu–F, F4Pu–F, F3Pu–F, and F2Pu–F have been calculated to be 53±2, 108±12, 113±5, and 141±16 kcal/mol, respectively. Upon comparison with data available on the plutonium fluorides the bond energies of F3Pu–F and F2Pu–F are accurate to within the stated uncertainty. The values of the bond energies of F5Pu–F and F4Pu–F disagree with the reported enthalpy of formation of PuF6(s). Analysis of available data indicates that the enthalpy of formation of PuF6(s) is most likely −484±10 kcal/mol.