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

机译：与分子氢的单次碰撞事件中OH A〜2SIGMA〜+自由基的电子猝灭：OH X〜2PI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 ~2SIGMA~+by molecular hydrogen.The experiments utilize a pump-probe scheme to determine the OH X ~2PI population distribution following collisional quenching in a pulsed supersonic expansion.The pump laser excites OH A ~2SIGMA~+(v'=O,N'=0),which has a significantly reduced fluorescence lifetime due to quenching by H2.The probe laser monitors the OH X~2II (v",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 ~2II products observed in v"=1 and 2 as well as a pronounced propensity for quenching into the II(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 ~2SIGMA~+by H2 proceeds through conical intersections between two potentials of A' reflection symmetry (in planar geometry) that correlate with the electronically excited A ~2SIGMA~+and ground X ~2II states of OH.The conical intersections occur in high-symmetry geometries,in which the O side of OH points toward H2.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-H2 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~2PI products.
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的分子氢原子对OH A〜2SIGMA〜+的电子淬灭，该实验利用泵浦探针方案确定了在碰撞淬灭后OH X〜2PI的分布。泵浦激光器激发OH A〜2SIGMA〜+（v'= O，N'= 0），由于被H2猝灭，荧光寿命显着降低，探针激光器监测OH X〜2II（v在单个碰撞条件下，通过在各种AX跃迁上通过激光诱导的荧光“，N”）种群。实验揭示了在v''= 1和2时观察到的淬灭OH X〜2II产物的高度旋转激发（N“），这些实验还辅之以广泛的多参考，配置-相互作用计算，旨在探索相关势能的拓扑结构。 H2对OH A〜2SIGMA〜+的电子猝灭是通过A'反射对称性的两个电位（在平面几何形状）中的圆锥形相交进行的，该电位与电子激发的A〜2SIGMA〜+和OH的基态X〜2II相关。圆锥形相交出现在高对称几何中，其中OH的O侧指向H2。证实并扩展了Hoffman和Yarkony的早期工作[J.Chem.Phys.113,10091（2000）]，这些计算显示出陡峭的OH-H2圆锥形交点处的梯度随OH方向和片段间距离的变化而变化。对于淬灭的OH X〜2PI产物，前者会引起高度的OH旋转激发。

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