RYDBERG-RYDBERG EMISSION SPECTRUM OF CARBON MONOXIDE IN THE NEAR-INFRARED REGION: AN {AB INITIO} STUDY OF NEWLY OBSERVED $^{3}\Pi - ^{3}\Sigma^{+}$ TRANSITION
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Date
1994
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Publisher
Ohio State University
Abstract
Recently we have observed a new emission spectrum of carbon monoxide (CO) in the near-infrared region, $8240 cm^{-1}$, which can he ascribed to the transition between $^{3} \Pi$ and $^{3} \Sigma$ states. In order to identify the states, potential energy and transition dipole moment curves for the lowest four valence $(a ^{3} \Pi, a^{\prime}{^{3}\Sigma}^{+}, d^{3} \Delta, \ and \ e {^{3}\Sigma}^{-})$ and the lowest three Rydberg $(b {^{3}\Sigma}^{+}, j {^{3}\Sigma}^{+},\ and \ c ^{3}\Pi)$ triplet suites of CO were calculated theoretically by the highly correlated {ab initio} Multi-Configuration Self-Consistent Field and internally contracted Multi-Reference Configuration Interaction (MCSCF-MRCI) method with basis sets of double-zeta plus polarisation quality. Observed $^{3}\Pi-^{3}\Sigma$ spectra can be assigned to none of the transitions between valence $^{3}\Pi$ and $^{3}\Sigma$ styles nor to those- between valence and Rydberg states. Only possibility remained is the transition between the low-lying c $^{3}\Pi$ and \ $b ^{3}\Sigma$ Rydberg states. The potential curves for these Rydberg states are isolated clearly enough to give simple emission spectrum, and the transition dipole moment between these states is very large, 8 Debye. These indicate that the newly observed spectrum should be attributed to the transition between c $^{3}\Pi$ and $b^{3}\Sigma^{+} $states.
Description
Author Institution: Department of Chemistry, Faculty of Science, Ochanomizu University; Department of Industrial Chemistry, Faculty of Engineering, University of Tokyo; Department of Chemistry, Faculty of Science, Ochanomizu University; Department of Chemistry, Nobeyama Radio Observatory