Temperature-dependent relaxation of CO(v=1) by HD, D/sub 2/, and He and of D/sub 2/(v=1) by D/sub 2/
Rate constants for the vibrational deactivation of CO in collisions with HD, D/sub 2/, and He have been measured as a function of temperature using the laser excited vibrational fluorescence technique. Throughout the 109--630 degreeK range, CO--He and CO--HD samples exhibit a single exponential decay, dominated by V--T,R transfer, with rates increasing rapidly with temperature. Typical collision deactivation rate constants at 630 degreeK are 22.7 sec/sup -1/ torr/sup -1/ for He and 82.5 sec/sup -1/ torr/sup -1/ for HD, and, at 109 degreeK, 0.067 sec/sup -1/ torr/sup -1/ for He and 0.27 sec/sup -1/ torr/sup -1/ for HD. At low temperatures, diffusion and radiative decay become important contributions to the observed rates. In CO--D/sub 2/ mixtures, double exponential decay of CO fluorescence at large D/sub 2/ mole fractions is obtained, corresponding to rapid V--V transfer between the (v=1) vibrational levels of CO and D/sub 2/, followed by coupled V--T,R deactivation. The V--V transfer rate (..delta..E=-850 cm/sup -1/) increases from 0.26 sec/sup -1/ torr/sup -1/ at 202 degreeK to 69.4 sec/sup -1/ torr/sup -1/ at 633 degreeK. The V--T,R deactivation rate constant for excited CO by D/sub 2/ is significantly slower than that by HD and H/sub 2/, going from 0.089 sec/sup -1/ torr/sup -1/ at 156 degreeK to 3.7 sec/sup -1/ torr/sup -1/ at 450 degreeK, indicating the decreased importance of the rotational states of D/sub 2/ in the deactivation of CO than hypothesized for H/sub 2/ and HD. The deactivation of excited D/sub 2/ by collisions with D/sub 2/ also increases with temperature, ranging from 0.080 sec/sup -1/ torr/sup -1/ at 202 degreeK to 6.9 sec/sup -1/ torr/sup -1/ at 450 degreeK. (AIP)
- Research Organization:
- Department of Chemistry, Georgetown University, Washington, D.C. 20057
- OSTI ID:
- 7175531
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 65:4
- Country of Publication:
- United States
- Language:
- English
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CARBON MONOXIDE
ATOM-MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
DEUTERIUM
HELIUM
HYDROGEN DEUTERIDE
ENERGY TRANSFER
RELAXATION
VIBRATIONAL STATES
ATOM COLLISIONS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
COLLISIONS
CRYOGENIC FLUIDS
DEUTERIDES
DEUTERIUM COMPOUNDS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
MOLECULE COLLISIONS
NONMETALS
NUCLEI
ODD-ODD NUCLEI
OXIDES
OXYGEN COMPOUNDS
RARE GASES
STABLE ISOTOPES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena