Radiative decay lifetimes of CH−2

Recently the presence and radiative decay of vibrationally excited CH−2, generated in a hot cathode discharge of methane, was established by measuring the time dependent photodetachment from excited states of CH−2 as it radiatively relaxed in a high vacuum ion trap. The time dependence of the photod...

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Veröffentlicht in:The Journal of chemical physics 1987-04, Vol.86 (7), p.3807-3815
Hauptverfasser: Okumura, M., Yeh, L. I., Normand, D., van den Biesen, J. J. H., Bustamente, S. W., Lee, Y. T., Lee, Timothy J., Handy, Nicholas C., Schaefer, Henry F.
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Sprache:eng
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Zusammenfassung:Recently the presence and radiative decay of vibrationally excited CH−2, generated in a hot cathode discharge of methane, was established by measuring the time dependent photodetachment from excited states of CH−2 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 X̃ 3B1 methylene. The radiative decay lifetimes of the first three excited bending vibrations of CH−2 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−2. 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.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.451939