Properties and reactions of uranium(IV) tetrahydroborate by ion cyclotron mass spectrometry

Abstract

The gas-phase ion chemistry of U(BH/sub 4/)/sub 4/ is studied with the techniques of ion cyclotron resonance spectrometry. An electron impact ionization energy of 9.0 +- 0.5 eV is determined, and appearance energies for several positive fragment ions are reported. These data are analyzed to give ..delta..H/sub f/(U(BH/sub 4/)/sub 4/) = -7 +- 14 kcal/mol as well as several bond dissociation energies for the parent neutral and its fragment ions. U(BH/sub 4/)/sub 4/ attaches thermal electrons to form the molecular anion. Fragment negative ions are observed with higher energy electrons. The reactions of both positive and negative ions in U(BH/sub 4/)/sub 4/ alone and with other gases are reported. The trapped-electron spectrum is obtained and compared with previous optical spectroscopic studies of U(BH/sub 4/)/sub 4/. Irradiation of major positive ions by a low-power CW CO/sub 2/ laser produced no evidence of photochemistry.