RADIATILVE AND NONRADIATIVE DECAY OF ELECTRONICALLY EXCITED NCO
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Date
1996
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Ohio State University
Abstract
Electronically excited levels in the NCO free radical have been probed using laser fluorescence excitation, in order to observe higher vibronic levels of the $\tilde{A}^{2}\Sigma^{+}$ state and to locate the onset of predissociation. Spectra have been recorded over the wave number range 27 400 - $32 900 cm^{-1}$, from the $\tilde{A}(0, 0, 2)^{2}\Sigma^{+}\leftarrow \tilde{X}(0, 0, 0)^{2}\Pi$ band up through the $\tilde{B}(1,0,0)^{2}\Pi\leftarrow \tilde{X}(0, 0, 0)^{2}\Pi$ band. Vibrational assignments have been made for a number of newly observed $\tilde{A}(0, 0, 2)^{2}\Sigma^{+}\leftarrow \tilde{X}(0, 0, 0)^{2}\Pi$ bands, and the band origin wave numbers and upper level rotational constants have been derived by comparison of spectra with simulations. Decay lifetime have been measured for a large number of both assigned and unassigned excited vibronic levels. The onset of predissociation appears to occur at energies slightly below that of the $\tilde{B}(0,0,0)$ level, at $31 750 cm^{-1}$. These data also suggest that predissociation occurs at lower energies in bent geometries that in a linear configuration.
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Author Institution: Department of Chemistry, The Johns Hopkins University