A TIME-RESOLVED FOURIER TRANSFORM EMISSION STUDY OF ROTATIONAL ENERGY TRANSFER AND REACTION OF EXCITED RO-VIBRONIC LEVELS OF $CH_{2}$,
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Date
1993
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Ohio State University
Abstract
Time-resolved Fourier transform emission spectroscopy spectra of the $CH_{2} b^{-1}B_{1} \to \bar{a}^{1}A_{1}$ band were recorded after pulsed excitation of a single rotational level of the $b^{-1}B_{1} (0.16^{0},0)$ state. The temporal behavior of emission from the initially excited level and from levels populated by rotational energy changing collisions with the bath gas (ketene) was used to deduce the state-to-state cross-sections for rotational energy transfer and the state-resolved cross-sections for reactive collisions between $b^{-1}B_{1} CH_{2}$ and ketene. The observed propensity rules for rotational energy transfer $\Delta J = \pm 2. \Delta K_{4} =0$. and $\Delta K_{e} = \pm 2$ indicate a quadrupole-dipole interaction between $b^{-1}B_{1} (0,16^{0},0) CH_{2}$ and ketene. The bent $CH_{2}$ excited above the bending barrier behaves like a linear molecule. The reactive cross-sections for the $CH_{2} b^{-1}B_{2}$ state, which is shown to be more reactive than the $\bar{a}^{1}A_{1}$ state, increase with rotational energy.
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Author Institution: Department of Chemistry, University of Pennsylvania, Philadelphia, PA