Liu Jianbo, Uselman Brady W, Boyle Jason M, Anderson Scott L
Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850.
J Chem Phys. 2006 Oct 7;125(13):133115. doi: 10.1063/1.2229207.
A combined experimental and trajectory study of vibrationally state-selected NO2+ collisions with Ne, Ar, Kr, and Xe is presented. Ne, Ar, and Kr are similar in that only dissociation to the excited singlet oxygen channel is observed; however, the appearance energies vary by approximately 4 eV between the three rare gases, and the variation is nonmonotonic in rare gas mass. Xe behaves quite differently, allowing efficient access to the ground triplet state dissociation channel. For all four rare gases there are strong effects of NO2+ vibrational excitation that extend over the entire collision energy range, implying that vibration influences the efficiency of collision to internal energy conversion. Bending excitation is more efficient than stretching; however, bending angular momentum partially counters the enhancement. Direct dynamics trajectories for NO2+ + Kr reproduce both the collision energy and vibrational state effects observed experimentally and reveal that intracomplex charge transfer is critical for the efficient energy transfer needed to drive dissociation. The strong vibrational effects can be rationalized in terms of bending, and to a lesser extent, stretching distortion enhancing transition to the Kr+ -NO2 charge state.
本文介绍了对振动态选择的NO₂⁺与Ne、Ar、Kr和Xe碰撞的实验与轨迹相结合的研究。Ne、Ar和Kr具有相似之处，即仅观察到解离至激发单重态氧通道；然而，这三种稀有气体之间的出现能相差约4 eV，且这种变化在稀有气体质量方面是非单调的。Xe的行为则大不相同，它能有效地进入基态三重态解离通道。对于所有四种稀有气体，NO₂⁺振动激发都有很强的影响，这种影响延伸到整个碰撞能量范围，这意味着振动会影响碰撞到内能转换的效率。弯曲激发比拉伸激发更有效；然而，弯曲角动量会部分抵消这种增强作用。NO₂⁺ + Kr的直接动力学轨迹再现了实验观察到的碰撞能量和振动态效应，并揭示了复合物内电荷转移对于驱动解离所需的有效能量转移至关重要。强振动效应可以通过弯曲，以及在较小程度上通过拉伸畸变增强向Kr⁺ - NO₂电荷态的转变来解释。
