The reactions of atomic thorium cations with methane and other 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 thorium to H, O, N, C, CH, and CH3. In the reaction of Th+ with methane, which has previously been studied using ion cyclotron resonance mass spectrometry, it is shown that the dehydrogenation reaction forming ThCH2+ exhibits a small barrier, see Figure 1, in contrast to the conclusions of the ICR studies. However, the rate of reaction at thermal energies agrees with the ICR results, establishing the origins of the inefficiency of this reaction. Theoretical studies indicate that the barrier corresponds to the CH bond activation step, rather than the overall reaction enthalpy. It is hoped that the thermochemistry resulting from these studies will provide benchmark data useful in evaluating the actinides.

Thermochemistry of reactions of thorium cations with methane and other small molecules

247th National Meeting (2014)

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