Molecular supercollisions: Evidence for large energy transfer in the collisional relaxation of highly vibrationally excited pyrazine by CO{sub 2}

Journal Article · Sat Apr 15 00:00:00 EDT 1995 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.469338· OSTI ID:26042

Mullin, A S; Michaels, C A; Flynn, G W ^[1]

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1. Department of Chemistry and Columbia Radiation Laboratory, Columbia University, New York, New York 10027 (United States)

The temperature dependence of the collisional quenching of highly vibrationally excited pyrazine by CO{sub 2} molecules has been investigated for the temperature range 243--364 K using high resolution time resolved diode laser spectroscopy. Particular emphasis is placed on vibration to rotation-translation ({ital V}{r_arrow}{ital R}/{ital T}) energy transfer which leaves the CO{sub 2} vibrations unexcited and occurs predominantly through short-range repulsive forces. Vibrationally hot pyrazine is prepared by 248 nm excimer laser pumping, followed by rapid radiationless transitions to the ground electronic state. For the range of experimental cell temperatures used here, the nascent rotational population distributions of the 00{sup 0}0 ground state of CO{sub 2} resulting from collisions with hot pyrazine were probed at short times following excitation of pyrazine by the excimer laser pulse. The CO{sub 2} translational recoil velocity was also measured for individual rotational levels of the 00{sup 0}0 state. In addition, temperature dependent rate constants and probabilities were determined for energy transfer from the vibrationally hot pyrazine into individual rotational levels of the 00{sup 0}0 state of CO{sub 2}. The rotational distributions, velocity recoils, and quenching rates exhibit a very weak temperature dependence for production of CO{sub 2} high {ital J} states, indicating that the CO{sub 2} molecules involved in these energy transfer events originate from rotational levels only slightly greater than the thermal mean {ital J} value. Based on these results, values for {Delta}{ital E}, the energy transfer from hot pyrazine to CO{sub 2} resulting in final CO{sub 2} 00{sup 0}0 states {ital J}=58 through {ital J}=82, are estimated to range from 2550 to 7090 cm{sup {minus}1} in a single collision.

• DOE Contract Number: FG02-88ER13937
• OSTI ID: 26042
• Journal Information: Journal of Chemical Physics, Vol. 102, Issue 15; Other Information: PBD: 15 Apr 1995
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
PYRAZINES
MOLECULE-MOLECULE COLLISIONS
CARBON DIOXIDE
ENERGY TRANSFER
TEMPERATURE DEPENDENCE
VIBRATIONAL STATES
EXCITED STATES
RELAXATION
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
RESOLUTION
TIME RESOLUTION
LASER SPECTROSCOPY
EXCIMER LASERS
ROTATIONAL STATES
VELOCITY
RECOILS