Theoretical investigation of rare gas hydride cations: HRgN2+ (Rg=He, Ar, Kr, and Xe)

Rare gas containing protonated nitrogen cations, HRgN₂⁺ (Rg=He, Ar, Kr, and Xe), have been predicted using quantum computational methods. HRgN₂⁺ ions exhibit linear structure (C_∞v symmetry) at the minima and show planar structure (C_s symmetry) at the transition state. The stability is determined by computing the energy differences between the predicted ions and its various unimolecular dissociation products. Analysis of energy diagram indicates that HXeN₂⁺ is thermodynamically stable with respect to dissociated products while HHeN₂⁺, HArN₂⁺, and HKrN₂⁺ ions are metastable with small barrier heights. Moreover, the computed intrinsic reaction coordinate analysis also confirms that the minima and the 2-body global dissociation products are connected through transition states for the metastable ions. The coupled-cluster theory computed dissociation energies corresponding to the 2-body dissociation (HN₂⁺ + Rg) is -288.4, -98.3, -21.5, and 41.4 kJ mol^-1 for HHeN₂⁺, HArN₂⁺, HKrN₂⁺, and HXeN₂⁺ ions, respectively. The dissociation energies are positive for all the other channels implying that the predicted ions are stable with respect to other 2- and 3-body dissociation channels. Atoms-in-molecules analysis indicates that predicted ions may be best described as HRg⁺N₂. It should be noted that the energetic of HXeN₂⁺ ion is comparable to that of the experimentally observed stable mixed cations, viz. (RgHRg^')⁺. Therefore, it may be possible to prepare and characterize HXeN₂⁺ ions in an electron bombardment matrix isolation technique.