Rydberg states of of radical

We study Rydberg states of radical in adiabatic (rotational Born–Oppenheimer) approximation as well as in the inverse limit. The needed value, $d$ = 0.833, of the OH$^+$ cation's dipole moment was calculated using the RCCSD(T)/aug-cc-pV5Zmethod. Our calculations show that a dipole moment of this magnitude influence weakly on the energies of the Rydberg states. The exception are the states originating from $s$-states in the central-symmetric field, which are influenced significantly by the cation dipole moment. In the inverse Born–Oppenheimer limit, we study in detail the dependence of the Rydberg spectrum upon the total angular momentum, $J$, of the molecule. This dependence substantially differs from the well-known dependence, $\sim J(J + 1)$, of the rotating top energy on its total momentum.