Accurate ab initio potential for HO 2 + : CBS extrapolated energies and direct-fit diatomic curves

Highlights: • The potentials of ${\text{HO}}_2^{+}$ and its dissociation products are calculated at CBS ab initio level. • The extrapolated energies are globally modeled analytically with cm⁻¹ accuracy. • The predicted spectroscopic parameters show unprecedented agreement with experimental data. A potential energy surface is reported at the complete basis set limit for the ground electronic state of ${\text{HO}}_2^{+}$ via a four dimensional interpolation in relaxed hyperspherical coordinates. The dissociated products ${\text{OH}}^{+}$ and ${\text{O}}_2^{+}$ have also been studied at the complete basis set level and subsequently analytically modelled. In the case of ${\text{O}}_2^{+}$, the vibrational states predicted from the model potential have also been directly included in the fit. The potential form so obtained matches the RKR levels with a root mean square deviation below $1{\text{cm}}^{-1}$. Spin orbit + relativistic effects have also been taken into account for the ${\text{O}}_2^{+}$ ion.