Vibrational relaxation of highly excited toluene
- The Department of Atmospheric, Oceanic, and Space Sciences, Space Physics Research Laboratory, The University of Michigan, Ann Arbor, Michigan 48109-2143 (USA)
The collisional loss of vibrational energy from gas-phase toluene, pumped by a pulsed KrF laser operating at 248 nm, has been observed by monitoring the time-resolved infrared fluorescence from the C--H stretch modes near 3.3 {mu}m. The fragmentation quantum yield of toluene pumped at 248 nm was determined experimentally to be {similar to}6%. Energy-transfer data were obtained for 20 collider gases, including unexcited toluene, and analyzed by an improved inversion technique that converts the fluorescence intensity to the bulk average energy, from which is extracted {l angle}{l angle}{Delta}{ital E}{r angle}{r angle}, the bulk average amount of energy transferred per collision. Comparisons are presented of these results with similar studies of benzene and azulene, and with the time-resolved ultraviolet absorption study of toluene carried out by Hippler {ital et} {ital al}. (J. Chem. Phys. {bold 78}, 6709 (1983)). The present results show {l angle}{l angle}{Delta}{ital E}{r angle}{r angle} to be nearly directly proportional to the vibrational energy of the excited toluene from 5000 to 25 000 cm{sup {minus}1}. For many of the colliders at higher energies, the energy dependence of {l angle}{l angle}{Delta}{ital E}{r angle}{r angle} is somewhat reduced. A simple method is described for obtaining good estimates of {l angle}{Delta}{ital E}{r angle}{sub {ital d}} (the energy transferred per collision in deactivating collisions) by carrying out an appropriate least-squares analysis of the {l angle}{l angle}{Delta}{ital E}{r angle}{r angle} data. The values of {l angle}{Delta}{ital E}{r angle}{sub {ital d}} are then used in master-equation calculations to investigate possible contributions from supercollisions'' (in which surprisingly large amounts of energy are transferred) in the deactivation of toluene.
- OSTI ID:
- 5486298
- Journal Information:
- Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 95:1; ISSN JCPSA; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ALKYLATED AROMATICS
AROMATICS
COLLISIONS
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
FLUIDS
FLUORESCENCE
GASES
HYDROCARBONS
LASER RADIATION
LUMINESCENCE
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
OPTICAL PUMPING
ORGANIC COMPOUNDS
PUMPING
RADIATIONS
RELAXATION
TOLUENE
VIBRATIONAL STATES