The electronic structure of CaO is complex due to the large number of low-lying energy states and a multitude of rovibronic interactions among them. Several vibrionic bands of the A 1 Π − X 1 Σ + CaO have been identified in the visible region using laser induced fluorescence. Analysis of these rotationally resolved data provides more accurate band origins and rotational constants for levels that were previously determined indirectly using perturbation data. Fluorescence decay lifetime measurements were used to determine the radiative decay rate for the A state. A previously noted homogeneous perturbation of the C 1 Σ + state was examined to determine the identity of the perturbing state. Dispersed fluorescence spectra and fluorescence decay rate measurements were used to show that the perturbation results from the interaction with a state of 3 Π(0+) symmetry.

The associative ionization reaction Sm + O → SmO+ + e – is being investigated as an electron source that could transiently modify high-altitude electron densities via Sm vapor release. Electronic spectra have been obtained from tests where sounding rockets released Sm vapor, but the interpretation of these results has been hampered by the limited laboratory spectral data available for both SmO and SmO+. The present study extends the spectroscopic characterization of SmO in the 645–670 nm range, where the field data show the most prominent molecular emission features. Rotationally resolved excitation spectra, dispersed laser-induced fluorescence spectra, and fluorescence decay lifetimes are reported. The results are consistent with the assignment of a subset of the red-region bands to configurational transitions of the form Sm2+(4f 5 6s)­O2– ↔ Sm2+(4f55d)­O2–. Analysis of the excited state hyperfine structure supports this configurational description.

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