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Radiative decay lifetimes of CH<sup> - </sup><sub>2</sub>

Okumura, M. and Yeh, L. I. and Normand, D. and van den Biesen, J. J. H. and Bustamente, S. W. and Lee, Y. T. and Lee, Timothy J. and Handy, Nicholas C. and Schaefer, Henry F., III (1987) Radiative decay lifetimes of CH<sup> - </sup><sub>2</sub>. Journal of Chemical Physics, 86 (7). pp. 3807-3815. ISSN 0021-9606.

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Recently the presence and radiative decay of vibrationally excited CH<sup> - </sup><sub>2</sub>, generated in a hot cathode discharge of methane, was established by measuring the time dependent photodetachment from excited states of CH<sup> - </sup><sub>2</sub> as it radiatively relaxed in a high vacuum ion trap. The time dependence of the photodetachment was found to be consistent with an electron affinity of 5250 cm^−1 (0.65 eV) for ground state X-tilde 3B1 methylene. The radiative decay lifetimes of the first three excited bending vibrations of CH<sup> - </sup><sub>2</sub> were also tentatively assigned. Here, we report a more refined analysis of the experimental data along with theoretical ab initio determinations of the radiative decay lifetimes of the first four excited bending vibrational levels of CH<sup> - </sup><sub>2</sub>. There is some discrepancy between the ab initio values (431, 207, 118, and 68 ms for the v2=1, 2, 3, and 4 levels respectively) and the experimental values (525, 70, and 14 ms for v2=1, 2, and 3 respectively) for v2=2 and 3. Possible reasons for this discrepancy are discussed but none of the alternatives are entirely satisfactory.

Item Type:Article
Additional Information:Copyright © 1987 American Institute of Physics. Received 4 November 1986; accepted 16 December 1986. The authors thank Dr. P.R. Bunker for a copy of his SRB program and helpful correspondence. We also thank Professor C.W. Lineberger and Dr. D.G. Leopold for helpful discussions. This research was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.
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Deposited On:17 Apr 2008
Last Modified:26 Dec 2012 09:58

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