Experimental and Theoretical Investigations of Rotational Energy Transfer in HBr + He Collisions

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• 作者：Md. Humayun Kabir ; Ivan O. Antonov ; Jeremy M. Merritt ; Michael C. Heaven
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：October 28, 2010
• 年：2010
• 卷：114
• 期：42
• 页码：11109-11116
• 全文大小：259K
• 年卷期：v.114,no.42(October 28, 2010)
• ISSN：1520-5215

文摘

Rotational relaxation rates for HBr(v = 1) colliding with helium atoms at room temperature have been measured using a time-resolved optical−optical double resonance technique. Rotational state selective excitation of v = 1 for rotational levels in the range J = 1−9 was achieved by stimulated Raman pumping. The population decay in the prepared states and the transfer of population to nearby rotational states was monitored via 2 + 1 resonance-enhanced multiphoton ionization (REMPI) spectroscopy using the g³Σ⁻−X¹Σ⁺ (0−1) band. Collision-induced population evolution for transfer events with |ΔJ| ≤ 8 was observed at pressures near 0.7 Torr. The experimental data were analyzed using fitting and scaling functions to generate state-to-state rotational energy transfer rate constant matrices. Total depopulation rate constants were found to be in the range (1.3 to 2.0) × 10⁻¹⁰ cm³ s⁻¹. As a test of current computational methods, state-to-state rotational energy transfer rate constants were calculated using ab initio theory. The total removal rate constants were in good agreement with the measured values, but the transfer probabilities for events with |ΔJ| ≥ 3 were underestimated. Inspection of the anisotropic characteristics of the potential energy surface did not yield an obvious explanation for the discrepancies, but it is most likely that the problem stems from inaccuracies in the potential surface.