10.1021/jp806452w.s001 Vincent Brites Vincent Brites Otto Dopfer Otto Dopfer Majdi Hochlaf Majdi Hochlaf Theoretical Spectroscopy of the N<sub>2</sub>HAr<sup>+</sup> Complex American Chemical Society 2008 CCSD N 2HAr order perturbation theory ab initio computations Strong anharmonic resonances rovibrational energy surface 2008-11-06 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Theoretical_Spectroscopy_of_the_N_sub_2_sub_HAr_sup_sup_Complex/2902366 The six-dimensional potential energy surface of the electronic ground state of N<sub>2</sub>HAr<sup>+</sup> is determined by<i></i> ab initio computations at the CCSD(T) level of theory. The potential energy surface is used to derive a set of spectroscopic data for N<sub>2</sub>HAr<sup>+</sup> and N<sub>2</sub>DAr<sup>+</sup> using second order perturbation theory. Full six-dimensional (6-D) rotation−vibration computations are also carried out using an analytical representation of the surface for <i>J</i>=0 and 1, in order to deduce the rovibrational spectra of N<sub>2</sub>HAr<sup>+</sup> and its deuterated isotopomer. Our variationally determined anharmonic wavenumbers differ by less than 15 cm<sup>−1</sup> from the most accurate experimental values. Strong anharmonic resonances are found between the rovibrational levels of both cations even at low energies.