Vibrational relaxation of carbon dioxide (101) and carbon monoxide (v=2) during gas-surface collisions

Abstract

The probability for deactivation of CO(v=2) and CO2(101) on collision with polycrystalline silver surfaces has been measured. The deactivation probability for CO(v=2) was found to decrease from 0.33 at 300 K to 0.20 at 440 K, while the deactivation probability for CO2 (101) was found to decrease from 0.72 at 300 K to 0.37 at 440 K. Since no population was observed in the CO(v=1) and CO2 (001) intermediate levels, it appears that each deactivation proceeds completely to produce the vibrational ground level. The magnitudes for the deactivation probabilities and the temperature dependencies indicate that a dominant mechanism for relaxation involves trapping and subsequent deactivation by one or more of several mechanisms, including electron-hole pair formation, vibration-to-rotation energy transfer, or perhaps even transfer of energy to the surface phonons. The experiments were performed in a UHV chamber by using a tunable infrared laser source to excite gas-phase molecules vibrationally before their collision with the surface and by measuring the population of vibrationally excited molecules through their time-resolved infrared fluorescence. © 1985 American Institute of Physics.