Knowledge Bank

The electronic spectra of $HCl+$ and $DCl+$ have been obtained in emission from an electrodeless discharge excited by microwave radiation. Previous $observations1,2$ have been extended to include many additional bands involving higher vibrational levels in both the ground $(X2\Pi i)$ and excited $(A2\Sigma +)$ electronic states, leading to much improved values of equilibrium constants and dissociation energies. The work includes the first analysis of the system for the $Cl-37$ isotope. For each isotopic molecule, combination differences taken from at least seven bands were used to determine term values for the $v^\{\backslash prime\}^\{\backslash prime\}=O$ vibrational level. These were used along with observed transitions to obtain term values for all other observable energy levels in both electronic states. This procedure has provided the most efficient use of the more than 10 000 lines that have been assigned.