Perturbations in the A1[pi] state of the isotopomers of the CO and the comet-tail system of the 13C16O+

Haridass, Chandran (1996) Perturbations in the A1[pi] state of the isotopomers of the CO and the comet-tail system of the 13C16O+. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The electronic band spectra of the neutral molecule 12C16O, its isotopomers 13C16O, 12C18O, and 13C18O, and the molecular ion 12C16O+ are of considerable importance in astrophysics and atmospheric physics. The rotational emission spectra of these molecules are routinely used in millimeter radio astronomy to map the molecular densities in the interstellar medium. These molecules are present in circumstellar envelopes, and cometary and planetary atmospheres. The molecular ion CO+ has applications in the study of radiative heating of hypersonic space craft at escape velocity and in the atmospheric fringe of Venus. – The vacuum ultraviolet spectra of the fourth positive (A 1Π – X 1Σ+) system of carbon monoxide isotopomers 12C18O and 13C18O excited in the anode column of a hollow-cathode discharge tube, and of the isotopomers 13C16O and 13C18O generated in emission in a jet discharge apparatus were photographed in the spectral region 1370 – 1935 Å on a 10.6 m vacuum grating spectrograph. Detailed rotational analysis for thirty nine bands of the three isotopomers of the A-X system has been carried out. Several perturbations occurring in the A 1Π state due to its neighbouring states e 3Σ-, a´ 3Σ+, d 3Δi, I 1Σ-, and D 1Δ were observed. From a deperturbation analysis, the deperturbed molecular constants, were obtained for the A 1Π state as well as for the perturbing states of the three isotopomers. Perturbing parameters and mixing coefficients which characterize perturbations were also derived. – Using the experimental data of the fourth positive system of the three isotopomers, the term values of the A 1Π, v=0 to 9 levels of 13C16O, v=1 and 2 levels of 12C18O, and v=1 level of 13C18O were determined. The term values of the Rydberg states B 1Σ+, v=0 and 1, C 1Σ+, and E 1Π, v=0 were calculated for the isotopomers 12C18O and 13C18O, by combining the present data and those of the B 1Σ+ - A 1Π, C 1Σ+ - A 1Π, and E 1Π – A 1Π systems taken from the literature. The molecular constants of Rydberg states B, C, and E were determined from the calculated term values. – The comet-tail (A 2Πi – X 2Σ+) system of 12C16O+ occurring in the cathode glow of a hollow cathode discharge tube and photographed in the spectral range 3345 – 8500 Å at high resolution was reinvestigated. Spin-splitting of the rotational levels of all the analyzed ten bands was observed. The observed intensity distribution of the branches is in good agreement with theoretical calculations. Rotational constants were obtained for the A 2Πi and X 2Σ+ states from a global fit of the present data of the comet-tail system and the infrared and microwave data available from the literature.

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