Spin uncoupling in the 6<i>s</i> Rydberg states of methyl iodide. Rotational subband structure in one-photon absorption

Abstract

Molecular constants of electronic states, all origins as well as some vibronic bands, derived from the lowest-energy Rydberg configuration of methyl iodide, are reported. Values of the internal angular momentum parameter ζeff, which is a measure of the strength of Coriolis and vibronic coupling, indicate that the spin of the Rydberg electron is effectively uncoupled from the molecular axis in the pure electronic states and that dynamic interactions between electronic, rotational, and vibrational motions completely quench the internal angular momentum in some vibronic levels. It is concluded that the parameters ζeff, as obtained from one-photon absorption spectra, are approximately those of the alternate levels, 2E3/2 and 2E1/2, of the CH3I+ ion-core ground configuration X̃.