Electronic emission spectra of ¹²C ¹⁶O, ¹³C ¹⁸O, ¹³C ¹⁸O⁺, and ¹⁵N₂⁺

Prasad, Chintalapati V.V. (1987) Electronic emission spectra of ¹²C ¹⁶O, ¹³C ¹⁸O, ¹³C ¹⁸O⁺, and ¹⁵N₂⁺. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

A hollow-cathode discharge tube of special design with physical separation of the anode and cathode columns was used to excite the neutral molecules ¹²C¹⁶O and ¹³C¹⁸O and the molecular ions ¹³C¹⁸O⁺ and ¹⁵N₂⁺. The initial experiments have demonstrated that the cathode glow is an excellent source of molecular ions as well as neutral molecules in their high-lying excited states while the anode glow contains almost exclusively the neutral molecules. The excited spectra were recorded on medium and high resolution optical spectrographs. -- Six bands of the Herzberg (C¹∑⁺ - A¹π) system of ¹³C¹⁸O in the spectral region 3660 - 4190 Å were observed for the first time and the rotational structure of five of them was analyzed. Perturbations observed in the v = 3 and 5 levels of state A were analyzed and information concerning the perturbing states was obtained. -- In a reinvestigation of the third positive (b³∑⁺ - a³πr) system and the three Kaplan bands (which have not been understood since their first observation in 1930) of ¹²C¹⁶O in the region 2500 - 3830 Å, five new bands of this molecule were observed in the present work. The Kaplan bands and the five new bands are now assigned to a v"- progression with v' = 2 of the third positive system. The new vibrational assignments are confirmed from the calculated Franck-Condon factors and from the experimental data of the corresponding bands of ¹³C¹⁸O, observed for the first time. With the identification of the v = 2 level in state b of CO, the controversy regarding the dissociation limit of CO existing in the literature is now satisfactorily resolved. -- Three bands of the Baldet-Johnson (B²∑⁺ - A²πi) system in the region 3700 - 4225 Å and seven bands of the comet-tail (A²πi - X²∑⁺) system in the region 3620 - 6165 Å, of ¹³C¹⁸O⁺, were rotationally analyzed for the first time. -- Of the fifteen bands observed in the first negative (B²∑u⁺ - X²∑g⁺), system of ¹⁵N₂⁺, in the region 3570-5170 Å, twelve bands were rotationally analyzed. Perturbations observed in the v = 0 level of state B were analyzed and was found to be perturbed by the v = 25 level of the A²πi,u state of ¹⁵N₂⁺. In all these investigations, with the exception of third positive system of CO (for which only the vibrational analysis was performed), final molecular constants of various electronic states involved were obtained by the method of "merging."

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