Collisional vibrational relaxation of a triplet state: Energy-dependent energy loss from [ital T][sub 1] pyrazine
- Department of Chemistry and Rice Quantum Institute, Rice University, Houston, Texas 77251 (United States)
The loss of vibrational energy from gas phase [ital T][sub 1] pyrazine molecules has been measured for thermal collisions with helium, argon, H[sub 2], SF[sub 6], and ground state pyrazine. Triplet pyrazine was prepared with a well defined vibrational energy of 5433 cm[sup [minus]1] through [ital S][sub 1][r arrow][ital T][sub 1] intersystem crossing following optical excitation to the 8[ital a][sup 1] level of [ital S][sub 1]. The time-dependent vibrational energy content of the excited pyrazine molecules was then deduced using a recently developed direct'' method involving the kinetics of subsequent [ital T][sub 1][r arrow][ital S][sub 0] intersystem crossing. For each of the collision partners studied, it was possible to find the average energy lost per gas kinetic collision for donor energies ranging from ca. 2000 to 5433 cm[sup [minus]1]. The magnitudes of these energy losses generally increased with the mass and vibrational complexity of the relaxing collision partner. For vibrational energy contents near 5000 cm[sup [minus]1], relaxation of the triplet pyrazine was enhanced by factors of as much as 24 relative to [ital S][sub 0] benzene at a similar vibrational energy. In addition, with all collision partners studied the average energy lost per collision showed appparent threshold behavior near 3000 cm[sup [minus]1], increasing by approximately an order of magnitude as the donor's energy increased from 2500 to 5000 cm[sup [minus]1]. The findings of this first quantitative study of triplet relaxation suggest that collisional vibrational energy transfer from organic triplet states may proceed by mechanisms different from those that dominate ground state relaxation.
- OSTI ID:
- 5406656
- Journal Information:
- Journal of Chemical Physics; (United States), Vol. 98:8; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARGON
ATOM-MOLECULE COLLISIONS
ENERGY TRANSFER
HELIUM
HYDROGEN
MOLECULE-MOLECULE COLLISIONS
PYRAZINES
SULFUR FLUORIDES
ELASTIC SCATTERING
ENERGY LOSSES
GASES
GROUND STATES
RELAXATION
TIME DEPENDENCE
TRIPLETS
VIBRATIONAL STATES
ATOM COLLISIONS
AZINES
COLLISIONS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
LOSSES
MOLECULE COLLISIONS
MULTIPLETS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RARE GASES
SCATTERING
SULFUR COMPOUNDS
664300* - Atomic & Molecular Physics- Collision Phenomena- (1992-)