The chemistry of samarium is of interest to the U. S. Air Force because the chemi-ionization reaction, Sm + O -> SmO+ + e�, was believed to be exothermic. The chemistry of actinide metals is of interest to establish whether f orbitals participate in bonding. In our laboratory, the reactions of atomic samarium and thorium cations with small molecules has been studied using a guided ion beam tandem mass spectrometer. The kinetic energy dependence of the reactions is analyzed to determine the binding energies of Sm+ and Th+ to ligands such as H, O, N, C, CH, and CH3. Recent studies of several oxygen donors in our laboratory demonstrate that the ionization energy of SmO is larger than listed in the literature, which has implications for the Air Force project. The dehydrogenation of methane by Th+ has previously been studied using ion cyclotron resonance mass spectrometry and thought to be exothermic. Our kinetic energy dependent studies show clearly that the reaction forming ThCH2+ exhibits a small barrier. Theoretical studies indicate that the barrier corresponds to the CH bond activation step, rather than the overall reaction enthalpy.

Thermochemistry of reactions of lanthanide and actinide cations

248th National Meeting (2014)

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