PHOTODISSOCIATION SPECTROSCOPY OF $Ca^{+}$ -RARE GAS COMPLEXES
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Date
1996
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Ohio State University
Abstract
Weakly bound complexes of the form $Ca^{+}$ -RG (RG = Ar, Kr, Xe) are prepared in a pulsed nozzle/laser vaporization cluster source and studied with mass-selected resonance enhanced photodissociation spectroscopy. The $Ca^{+}$ ($^{2}P\leftarrow ^{2}S$) atomic resonance line is the chromophore giving rise to the molecular spectra in these complexes. Vibrationally resolved spectra are measured for these complexes in the corresponding $^{2}\Pi\leftarrow X^{2}\Sigma^{+}$ molecular electronic transition. These spectra are red-shifted from the atomic resonance line, indicating that each complex is more strongly bound in its excited $^{2}\Pi$ state than it is in the ground state. Vibronic progressions allow determination of the excited state vibrational constants: $Ca^{+}$ -Ar, $\omega_{e}^{\prime} = 165$ $cm^{-1}$; $Ca^{+}$ -Kr, $\omega_{e} = 149$ $cm^{-1}$; $Ca^{+}$ -Xe, $\omega_{e}=142$ $cm^{-1}$. Extrapolation of the excited state vibrational progressions, and combination with the known atomic asymptotes and spectral shifts, leads to determination of the ground state dissociation energies; $Ca^{+}$ -Ar, $D_{0}^{\prime\prime} = 700\pm 100$ $cm^{-1}$ (0.09eV); $Ca^{+}$ -Kr, $D_{0}^{\prime\prime} = 1400\pm 150$ $cm^{-1}$ (0.17eV); $Ca^{+}$ -Xe, $D_{0}^{\prime\prime} = 2300\pm 150$ $cm^{-1}$ (0.29 eV). The spin-orbit splitting in the $^{2}\Pi_{1/2,3/2}$ state for these complexes is larger than expected by comparison to the $Ca^{+}$ atomic value.
Description
Author Institution: Department of Chemistry, University of Georgia