2014ApJ...782...73M

The main focus of this paper is to explore the possibility of finding two deuterated isotopomers of H₂Cl⁺ (chloronium) in and around the interstellar medium. The presence of a chloronium ion has recently been confirmed by the Herschel Space Observatory's Heterodyne Instrument for the far-infrared. It observed para-chloronium toward six sources in the Galaxy. To date the existence of its deuterated isotopomers (HDCl⁺ and D₂Cl⁺) have not been discussed in the literature. We find that these deuterated gas phase ions could be destroyed by various ion-molecular reactions, dissociative recombination (DR), and cosmic rays (CRs). We compute all of the ion-molecular (polar) reaction rates by using the parameterized trajectory theory and the ion-molecular (non-polar) reaction rates by using the Langevin theory. For DR- and CR-induced reactions, we adopt two well-behaved rate formulas. We also include these rate coefficients in our large gas-grain chemical network to study the chemical evolution of these species around the outer edge of the cold, dense cloud. In order to study spectral properties of the chloronium ion and its two deuterated isotopomers, we have carried out quantum chemical simulations. We calculated ground-state properties of these species by employing second-order Moller-Plesset perturbation theory (MP2) along with quadruple-zeta correlation consistent (aug-cc-pVQZ) basis set. Infrared and electronic absorption spectra of these species are calculated by using the same level of theory. The MP2/aug-cc-pVQZ level of theory is used to report the different spectroscopic constants of these gas phase species. These spectroscopic constants are essential to predict the rotational transitions of these species. Our predicted column densities of D₂Cl⁺, HDCl⁺, along with spectral information may enable their future identification around outer edges of cold, dark clouds.