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首页> 外文期刊>The Journal of Chemical Physics >Electronic quenching of OH A (2)Sigma(+) radicals in single collision events with molecular hydrogen: Quantum state distribution of the OH X (2)Pi products
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Electronic quenching of OH A (2)Sigma(+) radicals in single collision events with molecular hydrogen: Quantum state distribution of the OH X (2)Pi products

机译：在与分子氢的单次碰撞事件中，OH A（2）Sigma（+）自由基的电子猝灭：OH X（2）Pi产物的量子态分布

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摘要

We report a combined experimental and theoretical investigation of the nonreactive quenching channel resulting from electronic quenching of OH A (2)Sigma(+) by molecular hydrogen. The experiments utilize a pump-probe scheme to determine the OH X (2)Pi population distribution following collisional quenching in a pulsed supersonic expansion. The pump laser excites OH A (2)Sigma(+) (nu(')=0, N-'=0), which has a significantly reduced fluorescence lifetime due to quenching by H-2. The probe laser monitors the OH X (2)Pi (nu '', N '') population via laser-induced fluorescence on various A-X transitions under single collision conditions. The experiments reveal a high degree of rotational excitation (N '') of the quenched OH X (2)Pi products observed in nu ''=1 and 2 as well as a pronounced propensity for quenching into the Pi(A(')) Lambda-doublet level. These experiments have been supplemented by extensive multireference, configuration-interaction calculations aimed at exploring the topology of the relevant potential energy surfaces. Electronic quenching of OH A (2)Sigma(+) by H-2 proceeds through conical intersections between two potentials of A(') reflection symmetry (in planar geometry) that correlate with the electronically excited A (2)Sigma(+) and ground X (2)Pi states of OH. The conical intersections occur in high-symmetry geometries, in which the O side of OH points toward H-2. Corroborating and extending earlier work of Hoffman and Yarkony [J. Chem. Phys. 113, 10091 (2000)], these calculations reveal a steep gradient away from the OH-H-2 conical intersection as a function of both the OH orientation and interfragment distance. The former will give rise to a high degree of OH rotational excitation, as observed for the quenched OH X (2)Pi products. (C) 2007 American Institute of Physics.
机译：我们报告了结合的实验和理论研究的非反应性淬灭通道，由分子氢对OH A（2）Sigma（+）进行电子淬灭。实验利用泵浦探针方案在脉冲超音速膨胀中发生碰撞猝灭后确定OH X（2）Pi的分布。泵浦激光器激发OH A（2）Sigma（+）（nu（'）= 0，N-'= 0），由于被H-2淬灭，其荧光寿命显着降低。探测激光器通过激光诱导的荧光在单个碰撞条件下的各种A-X跃迁上监测OH X（2）Pi（nu``，N''）的数量。实验揭示了在nu''= 1和2中观察到的高淬灭OH X（2）Pi产物的高度旋转激发（N''）以及淬灭到Pi（A（'））的明显倾向拉姆达双峰水平。这些实验还辅之以旨在探索相关势能面拓扑的广泛的多参考，配置-相互作用计算。 H-2对OH A（2）Sigma（+）的电子猝灭通过与电激发的A（2）Sigma（+）相关的​​A（'）反射对称性的两个电势（在平面几何形状中）的圆锥形相交进行。 OH的X（2）Pi基态。圆锥形相交出现在高对称几何形状中，其中OH的O侧指向H-2。佐证并扩展了霍夫曼和雅各尼的早期工作[J.化学物理113，10091（2000）]，这些计算揭示了一个与OH-H-2圆锥形相交点相距较远的陡峭梯度，它是OH方向和片段间距离的函数。如对淬灭的OH X（2）Pi产物所观察到的，前者将引起高度的OH旋转激发。 （C）2007美国物理研究所。

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