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Vibrational relaxation of carbon dioxide at LiF(100)

Journal Article · · Journal of Chemical Physics; (USA)
DOI:https://doi.org/10.1063/1.458498· OSTI ID:6826053
;  [1];  [2]
  1. Department of Chemistry, Cornell University, Ithaca, New York 14853-1301 (USA)
  2. School of Chemical Engineering, Cornell University, Ithaca, New York 14853 (USA)
The vibrational relaxation of CO{sub 2} at LiF(100) has been investigated by monitoring infrared fluorescence from vibrationally excited molecules under conditions where they are relaxed primarily by collisions with the solid surface. The relaxation probabilities are found to be 0.65{plus minus}0.10 at room temperature and 0.35{plus minus}0.10 at 450 K. In order to understand better the vibrational relaxation results, angular distributions of CO{sub 2} scattered from LiF(100) were measured with a molecular beam scattering apparatus. At slow incident beam velocities, the trapping probability of CO{sub 2} at LiF(100) is essentially unity. Thus, in the vibrational relaxation measurements, where the incident velocity is even slower than in the scattering experiments, vibrational relaxation is preceded by trapping. Possible mechanisms for relaxation are discussed. Excitation of phonons in the solid and transfer of energy to other degrees of freedom of the molecule (i.e., translation, rotation, and other vibrational modes) are both plausible relaxation channels.
OSTI ID:
6826053
Journal Information:
Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 92:9; ISSN JCPSA; ISSN 0021-9606
Country of Publication:
United States
Language:
English