Theoretical and experimental studies of the doubly charged ionHCl2+

Energies of excited states of ${\mathrm{HCl}}^{2+}$ have been determined experimentally by the technique of double charge transfer and are compared with present results of a multireference single- and double-excitation configuration-interaction calculation. The calculation shows the existence of four bound states. The good agreement obtained permits a direct assignment of the four lowest-energy excited states with singlet symmetry. Comparison of our work with previous information obtained from photoion-photoion coincidence, electron impact, charge stripping, and also from HCl xuv Auger analysis is given. We report the double-ionization energies of stable states ${}_{}{}^3{}_{}{}^{}\mathrm{\Sigma }_{}^{\mathrm{-}}{}_{}{}^{}$, ${}_{}{}^1{}_{}{}^{}\mathrm{\Delta }$, and ${\Sigma }^{+}$ ${\mathrm{HCl}}^{2+}$ as 35.9±0.2, 37.4±0.15, and 38.6±0.3 eV, respectively, while dissociative states ${}_{}{}^1{}_{}{}^{}\mathrm{\Pi }$ and 2 ${}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ are at 40.9±0.3 and 45.6±0.3 eV.