Knowledge Bank

The emission spectra of the comet-tail $(A2\Pi i-X2\Sigma +)$ and the Baldet-Johnson $(B2\Sigma +-A2\Pi +)$ bands of the molecular ion $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C18O+$, excited in the cathode glow of a hollow-cathode discharge tube of special design, and occurring in the spectral regions 3700 - 4225 {\AA} and 1620 - 6165 {\AA}, respectively, were observed for the first time. The rotational structure of seven bands of the A-X system involving $v\prime =0$ to 5 and $v\prime \prime =0$ to 2 and that of three (1-0, 0-0, and 1-0) bands of the B-X system were photographed in the 2nd and/or 3rd orders of 2 m and 3.4 m grating spectrographs. All the twelve branches of each of the bands of both systems (except only six branches for the 0-1 and 0-2 bands of the A-X system arising from $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2-X2\sigma +$) were rotationally analyzed. The molecular constants obtained from the analysis of the wavenumber data of the individual bands of both systems were merged together and a unique set of constants for the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +-A2\Pi i$ and $B2\Sigma +$ states of 13C18O+ was obtained.