Predissociation mechanism of acetylene A1AU state1.2

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1990

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Ohio State University

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The fluorescence excitation spectrum, the MPI spectrum and the absorption spectrum of acetylene were observed for the $\bar{A}^{1}A_{u}\leftarrow \bar{X} ^{1}\Sigma^{+}_{g}$ band system in a static gas cell and in a supersonic jet. A sudden and drastic decrease in fluorescence quantum yield, $\Phi_{r}$ was found between the $V_{4}K_{2} (46339cm^{-1})$ and $2^{1}V^{3}K^{0} (46673cm^{-1})$ sublevels. The decrease in $\Phi_{f}$ is concluded to be due to the predissociation into $C_{2}H+H$. J dependence of $\Phi_{f}$ was found for the V4K1 vibronic sublevel, while it is absent for the level lying above $V_{4}K_{1}$. From the observed J. dependence, the predissociation mechanism was concluded to be vibrational predissociation by tunneling through a potential barrier. Deuterium effect on the predissociation of acetylene is also discussed.

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[1] Chem. Phys. Lett., 150, 380 (1988) pbaOs6d@JPNTOHOK [2] J. Chem. Phys., 92, 959 (1990)
Author Institution: Department of Chemistry Faculty of Science, Tohoku University

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