Accurate internuclear potential energy functions for the ground electronic states of NeH⁺ and ArH⁺

All pure rotational and vibrational-rotational spectroscopic line positions available on the ground X1Σ⁺ electronic states of the rare gas hydride cations NeH⁺ and ArH⁺ have been employed in weighted least-squares direct fits to the potential energy functions, together with auxiliary functions describing breakdown of the Born-Oppenheimer approximation. All radial functions are represented by compact analytical models, and the spectroscopic line positions are reproduced to within the associated experimental uncertainties by the quantum-mechanical eigenvalues of the derived Hamiltonians. The potential energy functions are constrained to approach the theoretical radial behavior at long-range. Accurate vibrational term values and rotational and centrifugal distortion constants are provided for all stable isotopologues of NeH⁺ and ArH⁺ included in the least-squares fits.