SYMMETRY AND SPECTROSCOPIC CONSTANTS OF THE UPPER STATE OF THE VACUUM UV EMISSION CONTINUUM OF $Ar_{2}$
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Date
1974
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Ohio State University
Abstract
The red-degraded first continuum of $Ar_{2}$, which begins at 1074 {\AA} $^{1}$ (the energy of the $^{3}P_{2}$ metastable) shows oscillatory structure out to 1500 {\AA}. A semiclassical $procedure^{2}$ has been used to derive the upper state potential curve between 2.0 and 3.2 {\AA} from the observed structure and different assumed lower (repulsive) potentials. Vibrational levels were found numerically, and a comparison of computed level spacings with those observed by Tanaka and $Yoshino^{3}$ for the $1_{u}$ state (dissociation limit $^{3}P_{2} + ^{1}S_{0}$) and the $0^{+}_{u}$ state (limit $^{3}P_{1} + ^{1}S_{0}$) show that the radiating state is a high vibrational level ($v^{\prime} = 22 \pm 2)$ of $O^{+}_{u}$ rather than a continuum level of $1_{u}$. Spectroscopic constants for $O^{+}_{u}$ depend somewhat on the assumed lower potential; we obtain $D^{\prime}_{e} = 6000 \pm 500$ $cm^{-1}$, $\omega^{\prime}_{e} = 310 \pm 30$ $cm^{-1}$, $\omega_{e}x^{\prime}_{e} = 2.5 \pm 0.5$ $cm^{-1}$, and $R^{\prime}_{e} = 2.32 \pm 0.1$ {\AA}. These constant agree well with those predicted by assuming that $O^{+}_{u}$ is a Rydberg state with configuration $Ar_{2}$ ($X ^{2}\Sigma^{+}_{u}$) $4s\sigma_{g}$. Calculations of bound-continuum emission from low vibrational levels of $O^{+}_{u}$ confirm that it is also the upper state of the second continuum of $Ar_{2}$ which peaks at $\sim$ 1270 {\AA}.
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$^{1}$R. C. Michaelson and A. L. Smith, Chem. Phys. Letters 6, 1 (1970). $^{2}$A. L. Smith, J. Chem, Phys. 49, 4813 (1968). $^{3}$Y. Tanaka and K. Yoshino, J. Chem, Phys. 53, 2012 (1970).
Author Institution: Department of Chemistry, Yale University
Author Institution: Department of Chemistry, Yale University