Molecular Rydberg states. XI. Quantum defect analogies between molecules and rare gases

The s and d Rydberg series of hydrogen iodide and methyl iodide are reported. These series are assigned using analogies to the corresponding series in xenon. It is shown that a comparison between molecular spectra and pertinent atomic data provides a facile assignment technique for molecular Rydberg spectra. Using the phase amplitude method, the Rydberg data are analyzed in an attempt to provide information on the residual atomic and molecular potentials and to categorize them qualitatively as attractive/repulsive, long range/short range. It is shown that, for l?2, the centrifugal barrier inhibits ingress of the Rydberg electron into the core and that the molecule is effectively spherically symmetric.