ABSOLUTE INTENSITIES MEASUREMENTS IN THE $\nu_{4} + \nu_{5}$ BAND OF $^{12}C_{2}H_{2}$: ANALYSIS OF HERMANWALLIS EFFECTS AND FORBIDDEN TRANSITIONS
Loading...
Date
2000
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
We have measured absolute line intensities in two bands of $^{12}C_{2}H_{2}$ near $7.5\mu m$, namely the $\nu_{4} + \nu_{5} (\Sigma^{+}_{u}) - 0(\Sigma^{+}_{g})$ and $\nu_{4} + \nu_{5}(\Delta_{u}) - 0(\Sigma^{+}_{g})$ bands, using Fourier transform spectroscopy with an accuracy estimated to be better than 2%. Using theoretical predictions from $Watson ^{a}$, the observation of the forbidden $\nu_{4} + \nu_{5}(\Delta_{u}) - 0(\Sigma^{+}_{g})$ band and the Herman-Wallis behavior exhibited by its rotational lines were studied quantitatively in terms of two types of interactions affecting the levels involved by the band: $\ell$-type resonance and Coriolis interaction. In the case of the $\nu_{4} + \nu_{5} (\Sigma^{+}_{u}) - 0(\Sigma^{+}_{g})$ band, the influences of $\ell$-type resonance is also confirmed. We also attributed the intensity asymmetry observed between the R and P branches of that latter band to a Coriolis interaction with $\ell = 1$ levels. We did not observe the $\nu_{4} + \nu_{5}(\Sigma^{-}_{u})- 0(\Sigma^{+}_{g})$ band, consisting only of a Q branch, in agreement with Watson's prediction.
Description
$^{a}$ J.K.G. Watson, J. Mol. Spectrosc. 188, 78 (1998)
Author Institution: Laboratoire de Chimie Physique Mol\'eculaire C. P. 160/09, Universit\'e Libre de Bruxelles
Author Institution: Laboratoire de Chimie Physique Mol\'eculaire C. P. 160/09, Universit\'e Libre de Bruxelles