Knowledge Bank

All available microwave and infrared spectroscopic line positions for the ground electronic states of the molecular cations NeH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ and ArH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ were employed in a direct potential fitting procedure to determine compact analytical potential curves and radial functions describing breakdown of the Born-Oppenheimer approximation. For NeH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$, $17$ adjustable parameters were required to represent a total of $183$ line positions for $4$ isotopologues, whereas for ArH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$, $23$ adjustable parameters were required to represent $440$ line positions for $6$ isotopologues. The MLR$3$ potential energy functional form was employed, taking full account of the proper $1/r4$ limiting long-range dependence of the ion-atom dispersion energy interactions. Accurate vibrational energies, rotational constants and centrifugal distortion constants have been calculated for both diatomic cations.