Quantum electronic control on chemical activation of methane by collision with spin–orbit state selected vanadium cation
Quantum electronic control on chemical activation of methane by collision with spin–orbit state selected vanadium cation
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量子电子控制通过与自旋轨道态选择的钒阳离子碰撞化学活化甲烷
DOI：
10.1039/d0cp04333h
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发表时间：
2021
影响因子：
3.3
通讯作者：
Armentrout, P. B.
中科院分区：
文献类型：
--
作者：
Ng, Cheuk-Yiu;Xu, Yuntao;Chang, Yih-Chung;Wannenmacher, Anna;Parziale, Matthew;Armentrout, P. B.
将一个新研制的量子电子态选择的超声冷却钒离子（V+）束源与双四极-双八极（DQDO）离子-分子反应装置耦合，研究了V+[α 5] DJ反应的绝对积分截面（σ s）（J = 0，2）、a5 FJ（J = 1，2）和a3 FJ（J = 2，3）] + CH 4，覆盖Ecm = 0.1-10.0 eV的质心碰撞能量范围。基于Ecm-阈值测量明确地鉴定了三个产物通道，VH+ + CH 3、VCH 2 + + H2和VCH 3 + + H。单个电子态的σ曲线（σ与Ecm图）没有J依赖性，这可能表明自旋-轨道耦合很弱，对化学反应性的影响很小。对于所有三个产物通道，三重态α_3FJ的最大σ值[σ（α_3FJ）]比五重态σ（α_5DJ）和σ（α_5FJ）的最大σ值大十倍以上，表明反应机理有利于总电子自旋守恒.在没有进行详细理论研究的情况下，我们初步解释了弱的五重态到三重态自旋交叉对活化反应是有效的。关于σ VH+、VCH 2+和VCH 3+产物离子通道的（a5 D 0、a5 F1和a3 F2）测量以及由于CH 4的热增宽效应而引起的动能分布的计算沿着允许确定0 K键解离能：D0（V+-H）= 2.02（0.05）eV，D0（V+-CH2）= 3.40（0.07）eV，和D0（V+-CH3）= 2.07（0.09）eV。详细的分支比的产物离子通道的标题反应也已报道。用相应的Boltzmann布居数加权σ（a5 DJ，a5 FJ，a3 FJ）曲线的线性组合，可以很好地模拟1800-2200 K下表面电离产生的V+的σ曲线。除了作为一个强有力的验证热灯丝电离源中的V+电子态的布居的热平衡假设，这些结果之间的一致性也证实了V+（a5 DJ，a5 FJ，和a3 FJ）在这个实验中制备的状态是在100%纯度的单自旋轨道状态。
By coupling a newly developed quantum-electronic-state-selected supersonically cooled vanadium cation (V+) beam source with a double quadrupole-double octopole (DQDO) ion–molecule reaction apparatus, we have investigated detailed absolute integral cross sections (σ's) for the reactions, V+[a5DJ (J = 0, 2), a5FJ (J = 1, 2), and a3FJ (J = 2, 3)] + CH4, covering the center-of-mass collision energy range of Ecm = 0.1–10.0 eV. Three product channels, VH+ + CH3, VCH2+ + H2, and VCH3+ + H, are unambiguously identified based on Ecm-threshold measurements. No J-dependences for the σ curves (σ versus Ecm plots) of individual electronic states are discernible, which may indicate that the spin–orbit coupling is weak and has little effect on chemical reactivity. For all three product channels, the maximum σ values for the triplet a3FJ state [σ(a3FJ)] are found to be more than ten times larger than those for the quintet σ(a5DJ) and σ(a5FJ) states, showing that a reaction mechanism favoring the conservation of total electron spin. Without performing a detailed theoretical study, we have tentatively interpreted that a weak quintet-to-triplet spin crossing is operative for the activation reaction. The σ(a5D0, a5F1, and a3F2) measurements for the VH+, VCH2+, and VCH3+ product ion channels along with accounting of the kinetic energy distribution due to the thermal broadening effect for CH4 have allowed the determination of the 0 K bond dissociation energies: D0(V+–H) = 2.02 (0.05) eV, D0(V+–CH2) = 3.40 (0.07) eV, and D0(V+–CH3) = 2.07 (0.09) eV. Detailed branching ratios of product ion channels for the titled reaction have also been reported. Excellent simulations of the σ curves obtained previously for V+ generated by surface ionization at 1800–2200 K can be achieved by the linear combination of the σ(a5DJ, a5FJ, and a3FJ) curves weighted by the corresponding Boltzmann populations of the electronic states. In addition to serving as a strong validation of the thermal equilibrium assumption for the populations of the V+ electronic states in the hot filament ionization source, the agreement between these results also confirmed that the V+(a5DJ, a5FJ, and a3FJ) states prepared in this experiment are in single spin–orbit states with 100% purity.