The Dissociation Energy of Acetylene
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Date
1990
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Ohio State University
Abstract
Recently we reported [J. Chem. Phys. 91, 5160(1989)] an upper bound measurement of $D_{0}^{0} (HCC-H) \le 126.65 kcal/mol$, based on observations of Stark-induced increases in radiative decay rates of securely assigned rovibronic levels of the $HCCH \widetilde{A}^{1}Au$ state. The lowest level to show a significant zero-pressure-extrapolated lifetime decrease (from 667(5)ns at $\varepsilon=0 volts/cm to 514(4)ns$ at $\varepsilon=113kV/cm$) is $v_{3}=2, K_{a}=1, J=1$ at $44295.65(10) cm^{-1}$ above $v^{\prime\prime}=0, J^{\prime\prime}=0$ of the $\bar{X}$-state. Our interpretation of this Stark-induced lifetime decrease as predissociation has been the subject of considerable controversy, owing to the importance of $D_{0}^{0}(HCC-H)$ and $\Delta H_{1}^{0}(HCC)$ in models of combustion kinetics and to recent reports of experimental and ab initio values 5-7 kcal/mol larger than our upper bound value. Alternative interpretations of our Stark effect result and other conflicting experimental results will be discussed.
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Author Institution: Division of Geology and Planetary Sciences; Wiess School of Natural Sciences, Rice University; Department of Chemistry, Massachusetts Institute of Technology