Perkins Bradford G, Nesbitt David J
JILA, University of Colorado and National Institute of Standards and Technology, Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0440, USA.
J Phys Chem B. 2006 Aug 31;110(34):17126-37. doi: 10.1021/jp060980v.
Quantum-state-resolved dynamics at the gas-liquid interface are probed by colliding supersonically cooled molecular beams of CO(2) with freshly formed liquid surfaces in a vacuum. Translational, rotational, and vibrational state distributions of both incident and scattered fluxes are measured by high-resolution direct infrared absorption spectroscopy and laser dopplerimetry in the 00(0)0 and 01(1)0 rovibrational manifolds of CO(2) in the asymmetric stretch manifold. The present studies investigate the role of incident molecular beam energy (E(inc) = 1.6(1), 4.7(2), 7.7(2), and 10.6(8) kcal/mol) on these distributions for a series of perfluorinated, hydrocarbon, and hydrogen-bonded liquids. Boltzmann analysis of the internal quantum-state populations provide evidence for nonthermal scattering dynamics, as confirmed by Dopplerimetry on the absorption profiles. The data provide quantum-state-resolved support for a dual channel picture of the scattering process, consisting of either prompt impulsive scattering (IS) or longer duration trapping-desorption (TD) events, with the fraction observed in each channel dependent on incident kinetic energy and the physical properties of the liquid surface. The clear evidence that internal CO(2) rotational populations arising from the IS channel can be adequately described by a Boltzmann temperature (albeit with E(IS) > RT(S)) is consistent with previous gas-solid scattering studies and suggests that even nominally "prompt" IS events reflect both single (i.e. direct) and multiple impulsive interactions with the liquid interface.
通过在真空中将超声冷却的二氧化碳分子束与新形成的液体表面碰撞，来探测气液界面处的量子态分辨动力学。通过高分辨率直接红外吸收光谱法和激光多普勒测速法，在非对称伸缩振动流形中二氧化碳的00(0)0和01(1)0振转流形中，测量入射通量和散射通量的平动、转动和振动状态分布。本研究考察了入射分子束能量（E(inc) = 1.6(1)、4.7(2)、7.7(2)和10.6(8)千卡/摩尔）对一系列全氟化物、碳氢化合物和氢键液体的这些分布的作用。对内部量子态布居的玻尔兹曼分析为非热散射动力学提供了证据，这在吸收谱的多普勒测速中得到了证实。这些数据为散射过程的双通道图景提供了量子态分辨支持，该图景由即时脉冲散射（IS）或持续时间更长的俘获-解吸（TD）事件组成，每个通道中观察到的比例取决于入射动能和液体表面的物理性质。来自IS通道的内部二氧化碳转动布居可以用玻尔兹曼温度充分描述（尽管E(IS) > RT(S)），这一明确证据与先前的气固散射研究一致，并表明即使是名义上“即时”的IS事件也反映了与液体界面的单次（即直接）和多次脉冲相互作用。
