Chemical Dynamics Simulations of Intermolecular Energy Transfer: Azulene + N2 Collisions

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• 作者：Hyunsik Kim ; Amit K. Paul ; Subha Pratihar ; William L. Hase
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：120
• 期：27
• 页码：5187-5196
• 全文大小：632K
• 年卷期：0
• ISSN：1520-5215

文摘

Chemical dynamics simulations were performed to investigate collisional energy transfer from highly vibrationally excited azulene (Az*) in a N₂ bath. The intermolecular potential between Az and N₂, used for the simulations, was determined from MP2/6-31+G* ab initio calculations. Az* is prepared with an 87.5 kcal/mol excitation energy by using quantum microcanonical sampling, including its 95.7 kcal/mol zero-point energy. The average energy of Az* versus time, obtained from the simulations, shows different rates of Az* deactivation depending on the N₂ bath density. Using the N₂ bath density and Lennard-Jones collision number, the average energy transfer per collision ⟨ΔE_c⟩ was obtained for Az* as it is collisionally relaxed. By comparing ⟨ΔE_c⟩ versus the bath density, the single collision limiting density was found for energy transfer. The resulting ⟨ΔE_c⟩, for an 87.5 kcal/mol excitation energy, is 0.30 ± 0.01 and 0.32 ± 0.01 kcal/mol for harmonic and anharmonic Az potentials, respectively. For comparison, the experimental value is 0.57 ± 0.11 kcal/mol. During Az* relaxation there is no appreciable energy transfer to Az translation and rotation, and the energy transfer is to the N₂ bath.