Quantum-State-Resolved CO_2 Scattering Dynamics at the Gas-Liquid Interface:Dependence on Incident Angle

摘要

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(theta_(inc)= 0°,30°,45°,and 60°),where column-integrated quantum state populations are detected along the specular-scattering direction(i.e.,theta_(scat)≈theta_(inc)).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(T_(rot)≈T_S)and an impulsive scattering(IS)component appearing at hyperthermal energies(T_(rot)≈T_S).The branching ratio between the TD and IS channels is found to depend strongly on theta_(inc)with the IS component growing dramatically with increasingly steeper angle of incidence.