Long- and short-range interactions in the temperature dependent collisional excitation of the antisymmetric stretching CO{sub 2}(00{sup 0}1) level by highly vibrationally excited pyrazine
- Department of Chemistry and Columbia Radiation Laboratory, Columbia University, New York, New York 10027 (United States)
The relaxation of highly vibrationally excited pyrazine, C{sub 4}H{sub 4}N{sub 2}, by collisions with CO{sub 2} that produce molecules in the vibrationally excited antisymmetric stretch state (00{sup 0}1) has been investigated using high resolution infrared transient absorption spectroscopy at a series of ambient cell temperatures. The vibrationally hot ({ital E}{sub vib}{approx}5 eV) pyrazine molecules are formed by 248 nm excimer laser pumping, followed by rapid radiationless decay to the ground electronic state. The nascent rotational and translational product state distributions of the vibrationally excited CO{sub 2} molecules are probed at short times following the excitation of pyrazine. The temperature dependence of this process, along with the CO{sub 2} product state distributions, strongly suggest that the vibrational excitation of CO{sub 2} occurs via two mechanisms. The vibrational energy transfer is dominated by a long-range attractive force interaction, which is accompanied by almost no rotational and translational excitation. However, the CO{sub 2}(00{sup 0}1) product state distribution also reveals a smaller contribution from a short-range interaction that results in vibrational excitation accompanied by substantial rotational and translational excitation. The long-range interaction dominates scattering into low angular momentum ({ital J}) states while the short-range interaction is most important for molecules scattering into high {ital J} states. The implications of these results for our understanding of the relaxation of molecules with chemically significant amounts of vibrational energy are discussed.
- DOE Contract Number:
- FG02-88ER13937
- OSTI ID:
- 29274
- Journal Information:
- Journal of Chemical Physics, Vol. 102, Issue 17; Other Information: PBD: 1 May 1995
- Country of Publication:
- United States
- Language:
- English
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