DEPERTURBATION OF THE BeS $A^{1}\pi -X^{1}\Sigma^{+}$ TRANSITION. THE $a^{3}\pi$ STATE
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Date
1980
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Ohio State University
Abstract
The perturbations observed by Cheetham, Gissane, and $Barrow^{1}$ in the BeS $A^{1}\pi-X^{1}\Sigma^{+}$ transition have been analyzed. A coherent picture of these perturbations could be drawn only by combining fragmentary spectroscopic data with ab initio calculations of spin-orbit and rotation-electronic perturbation parameters, spin-orbit splittings, and energy seperations of isoconfigurational $^{1}\pi$ and $^{3}\pi$ states. Once the perturbations analysis was complete, the original experimental observations alone were sufficient to confirm most aspects of the analysis and to serve as verification of theoretical predictions. Perturbations of $A^{1}\pi$ previously suggested as being due to a $^{1}\Delta$ $state^{1}$ were shown to be due to $^{3}\pi_{2}$ and $^{3}\pi_{1}$ components, where the relative vibrational numbering is $A^{1}\pi (v) \sim a^{3} \pi (v+2)$. $A^{1}\pi \sim X^{1}\Sigma^{+}$ perturbations are also analyzed. Molecular constants for the newly identified lowest excited $a^{3}\pi$ state of BeS as well as electronic parameters for the $A \sim X, A \sim $a, and $a \sim X$ interactions have been determined.
Description
$^{1}$C. J. Chetham, W.J.M. Gissane, and R. F. Barrow, Trans. Faraday Soc. 61, 1308 (1965).
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