Vibrational autoionization of hot bands in methyl iodide

Abstract

The photoionization of gaseous CH3I below the first ionization potential has been studied as a function of pressure and temperature. Structural features that exhibit a Maxwell-Boltzmann temperature dependence are observed as far as 0.17 eV below threshold. They are identified as nd Rydberg transitions originating in excited vibrational levels of the electronic ground state and autoionizing, with hv=-1 and-2, into the vibrational ground state of the ion. From these results along with the simultaneously measured absorption spectrum, we obtained the v2 and v3 vibrational frequencies of the d Rydberg states.