Perkins Bradford G, Nesbitt David J
JILA, University of Colorado and National Institute of Standards and Technology, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0440, USA.
J Phys Chem A. 2007 Aug 9;111(31):7420-30. doi: 10.1021/jp0709048. Epub 2007 Jun 20.
Energy transfer dynamics at the gas-liquid interface have been probed with a supersonic molecular beam of CO2 and a clean perfluorinated-liquid surface in vacuum. High-resolution infrared spectroscopy measures both the rovibrational state populations and the translational distributions for the scattered CO2 flux. The present study investigates collision dynamics as a function of incident angle (thetainc = 0 degrees, 30 degrees, 45 degrees, and 60 degrees), where column-integrated quantum state populations are detected along the specular-scattering direction (i.e., thetascat approximately thetainc). Internal state rovibrational and Doppler translational distributions in the scattered CO2 yield clear evidence for nonstatistical behavior, providing quantum-state-resolved support for microscopic branching of the gas-liquid collision dynamics into multiple channels. Specifically, the data are remarkably well described by a two-temperature model, which can be associated with both a trapping desorption (TD) component emerging at the surface temperature (Trot approximately TS) and an impulsive scattering (IS) component appearing at hyperthermal energies (Trot > TS). The branching ratio between the TD and IS channels is found to depend strongly on thetainc, with the IS component growing dramatically with increasingly steeper angle of incidence.
利用二氧化碳的超音速分子束和真空中清洁的全氟液体表面，对气液界面处的能量转移动力学进行了探测。高分辨率红外光谱法测量了散射二氧化碳通量的振转态布居和转动分布。本研究考察了作为入射角（入射角θinc = 0°、30°、45°和60°）函数的碰撞动力学，其中沿镜面散射方向（即散射角θscat约等于入射角θinc）检测柱积分量子态布居。散射二氧化碳中的内态振转和多普勒转动分布为非统计行为提供了明确证据，为气液碰撞动力学微观分支进入多个通道提供了量子态分辨支持。具体而言，数据能用双温度模型很好地描述，该模型可与在表面温度（转动温度Trot约等于表面温度TS）出现的俘获解吸（TD）成分以及在超热能量（转动温度Trot > TS）出现的脉冲散射（IS）成分相关联。发现TD和IS通道之间的分支比强烈依赖于入射角θinc，随着入射角越来越陡，IS成分急剧增加。
