ON THE INTERPRETATION OF THE PREDISSOCIATION IN THE $C ^{2}\Sigma^{+}$ STATE OF CH AND CD. SOME ASTROPHYSICAL CONSEQUENCES.
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Date
1969
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Ohio State University
Abstract
Decay rates determined from absolute phase-shift vs. frequency data for the $C ^{2}\Sigma^{+}$ state of CH and of CD have been interpreted as quantitative measures of forbidden predissociation $probabilities.^{1}$ High resolution spectrograms enable us to specify a simple and plausible model for the observed phase-shifts in which the $F_{1}$ spin components predissociate about three times faster than the $F_{2}$ components. The predissociation in CH is also determined to be about five times stronger than in CD for both spin components. Qualitative arguments indicate that the most probable state causing the predissociation is $B ^{2}\Sigma^{-}$. This predissociation is found to be more efficient for destroying interstellar CH than the usual photo-dissociation mechanism of Bates and Spitzer.$^{2}$ As a result, to account for the observed interstellar densities, either the formation rates must be significantly increased or large regions of space are substantially shielded from the dissociating radiation.
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$^{1}$ J.E. Hesser and B.L. Lutz, Phys. Rev. Letters 20, 363 (1968). $^{2}$ D.R. Bates and L. Spitzer, Astrophys. J. 113, 441 (1951).
Author Institution: Division of Pure Physics, National Research Council of Canada; Observatorio Interamericano de Cerro Tololo La Serena, Chile.
Author Institution: Division of Pure Physics, National Research Council of Canada; Observatorio Interamericano de Cerro Tololo La Serena, Chile.