Experimental and Theoretical Study of Rotationally Inelastic Collisions of CN(A2Π) with N2

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• 作者：Ani Khachatrian ; Paul J. Dagdigian ; Doran I. G. Bennett ; Franois Lique ; Jacek Kł ; os ; Millard H. Alexander
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：April 23, 2009
• 年：2009
• 卷：113
• 期：16
• 页码：3922-3931
• 全文大小：389K
• 年卷期：v.113,no.16(April 23, 2009)
• ISSN：1520-5215

文摘

Optical−optical double resonance was employed to study rotational energy transfer in collisions of selected rotational/fine-structure levels of CN(<i>Ai>²Π, <i>vi> = 3) with N₂. The CN radical was generated by 193 nm photolysis of BrCN in a slow flow of N₂ at total pressures of 0.2−1.4 Torr. Specific fine-structure Λ-doublet levels of CN(<i>Ai>²Π, <i>vi> = 3) were prepared by pulsed dye laser excitation on isolated lines in the CN <i>Ai>−<i>Xi> (3,0) band, while the initially excited and collisionally populated levels were observed after a short delay by laser-induced fluorescence in the <i>Bi>−<i>Ai> (3,3) band. Total removal rate constants for specified rotational/fine-structure levels involving total angular momentum <i>Ji> from 4.5 to 12.5 were determined. These rate constants decrease with increasing <i>Ji>, with no obvious dependence on the fine-structure/Λ-doublet label. State-to-state relative rate constants were determined for several initial levels and show a strikingly strong collisional propensity to conserve the fine-structure/Λ-doublet label. Comparison is made with the results of quantum scattering calculations based on potential energy surfaces averaged over the orientation of the N₂ molecule. Reasonable agreement is found with experimentally determined total removal rate constants. However, the computed state-to-state rate constants show a stronger propensity for fine-structure and Λ-doublet changing transitions. These differences between experiment and theory could be due to the neglect of the N₂ orientation and the correlation of the CN and N₂ angular motions.