First observation of the Comet-Tail (A₂?_i ? X²?⁺) system in the ¹²C¹⁷O⁺ cation

In the emission spectrum of the (CO+)-C-12-O-17 isotopologue the Comet-Tail (A(2)Pi(i) -> X-2 sigma(+)) system has been observed and analysed for the first time. 1215 spectral transitions in the 16 950 to 22 0 0 0 cm(-1) re-gion, belonging to three A - X ( 1 - 0,1 - 1 and 1 - 2 ) bands, were recorded with the Fourier-transform spectrometer and measured with an accuracy of 0.01 cm(-1). As a result of analysis, 15 molecular pa-rameters of the A(2)Pi(i) (v = 1) and X-2 sigma(+)(v = 0,1, 2) levels were obtained. The ro-vibronic term values of the A2 & UPi;i (v = 1) level were also determined. Moreover, a very weak A(2)Pi(i) (v = 1) similar to X-2 sigma(+)(v = 11) perturbation of a complex, spin-orbit, spin-electronic and L-uncoupling character was identified and worked out. A percentage (2)Pi character of the A(2)Pi(i) (v = 1) and X-2 sigma(+)(v = 11) levels was considered in detail.(C) 2022 The Author(s). Published by Elsevier Ltd.