INFRARED EMISSION SPECTRA OF HIGHLY VIBRATIONALLY EXCITED $NO_{2}$ PREPARED BY INTERNAL CONVERSION OF THE ELECTRONIC EXCITED STATE
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Date
1993
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Ohio State University
Abstract
Laser excitation of the $NO_{2} \bar{A}^{2}B_{2}/\bar{B}^{2}B_{1}$ states at $20,000-22,000 cm^{-1}$ yields highly vibrationally excited $X^{-2}A_{1} NO_{2}$ because of strong vibronic coupling between the $\bar{A}^{2}B_{2}/\bar{B}^{2}B_{1}$ and $\bar{X}^{2}A_{1}$ states. The highly vibrationally excited $\bar{X}^{-2}A_{1} NO_{2}$ is subsequently deactivated by collisions with the bath gas. The progress of vibrational relaxation was followed through the time (500 ns) and frequency ($\geq 1 cm^{-1}$) resolved NIR/IR emission recorded by time-resolved Fourier transform emission spectroscopy. In addition, IR emission was observed from excited vibrational levels of the bath gas which were populated by vibrational energy transfer from the hot $NO_{2}$ molecules. The nature of the high vibrational levels of $NO_{2}$ at $22,000-20,000 cm^{-1}$ and their relaxation will be discussed.
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Author Institution: Department of Chemistry, University of Pennsylvania