Bubas Amanda R, Zhang Wen-Jing, Armentrout P B
Department of Chemistry, University of Utah, 315 S 1400 E Rm 2020, Salt Lake City, Utah 84112-0850, USA.
J Chem Phys. 2023 Dec 28;159(24). doi: 10.1063/5.0183836.
A guided ion beam tandem mass spectrometer was employed to study the reactions of U+ + CO2, UO+ + O2, and the reverse of the former, UO+ + CO. Reaction cross sections as a function of kinetic energy over about a three order of magnitude range were studied for all systems. The reaction of U+ + CO2 proceeds to form UO+ + CO with an efficiency of 118% ± 24% as well as generating UO2+ + C and UCO+ + O. The reaction of UO+ + O2 forms UO2+ in an exothermic, barrierless process and also results in the collision-induced dissociation of UO+ to yield U+. In the UO+ + CO reaction, the formation of UO2+ in an endothermic process is the dominant reaction, but minor products of UCO+ + O and U+ + (O + CO) are also observed. Analysis of the kinetic energy dependences observed provides the bond energies, D0(U+-O) = 7.98 ± 0.22 and 8.05 ± 0.14 eV, D0(U+-CO) = 0.73 ± 0.13 eV, and D0(OU+-O) = 7.56 ± 0.12 eV. The values obtained for D0(U+-O) and D0(OU+-O) agree well with the previously reported literature values. To our knowledge, this is the first experimental measurement of D0(U+-CO). An analysis of the oxide bond energies shows that participation of 5f orbitals leads to a substantial increase in the thermodynamic stability of UO2+ relative to ThO2+ and especially transition metal dioxide cations.
使用导向离子束串联质谱仪研究了U⁺ + CO₂、UO⁺ + O₂以及前者的逆反应UO⁺ + CO的反应。研究了所有体系在约三个数量级动能范围内反应截面与动能的函数关系。U⁺ + CO₂反应生成UO⁺ + CO的效率为118% ± 24%，同时还生成UO₂⁺ + C和UCO⁺ + O。UO⁺ + O₂反应在一个放热、无势垒的过程中形成UO₂⁺，并且还导致UO⁺的碰撞诱导解离产生U⁺。在UO⁺ + CO反应中，吸热过程中UO₂⁺的形成是主要反应，但也观察到UCO⁺ + O和U⁺ + (O + CO)的少量产物。对观察到的动能依赖性的分析给出了键能，D₀(U⁺-O) = 7.98 ± 0.22和8.05 ± 0.14 eV，D₀(U⁺-CO) = 0.73 ± 0.13 eV，以及D₀(OU⁺-O) = 7.56 ± 0.12 eV。D₀(U⁺-O)和D₀(OU⁺-O)得到的值与先前报道的文献值吻合良好。据我们所知，这是D₀(U⁺-CO)的首次实验测量。对氧化物键能的分析表明，5f轨道的参与导致UO₂⁺相对于ThO₂⁺，特别是过渡金属二氧化物阳离子的热力学稳定性大幅增加。
