Although the energy formula of Rydberg series is a result of hydrogen-like atom structure, Rydberg states are also present in molecules. Wave functions of high Rydberg states are very diffuse and span diameters that approach infinity.
The Rydberg series formula, although derived from hydrogen-like atom structure, also applies to molecules. The wave functions of high Rydberg states in molecules are highly diffuse and extend over diameters that approach infinity.