Observation of the D 1Δ→X 1Σ+ Transition of CO in the Vacuum-Ultraviolet Region

Abstract
Weak new bands in the vacuum‐ultraviolet absorption spectrum of CO have been observed and analyzed as the D 1Δ←X 1Σ+ (1–0) bands for both 12C16O and 13C16O. The observed rotational intensity distribution indicates this transition arises through mixing of the D 1Δ state with neighboring states, principally the A 1II state of the strong electric‐dipole‐allowed fourth‐positive system. A brief correlation of observed electronic states with those arising from various electronic configurations is given.
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