EFFECTS OF INTERMEDIATE DISSOCIATION IN THE 2-PHOTON THRESHOLD PHOTOIONIZATION OF CH3I

In the threshold photoionization spectrum of CH3I obtained by one-color two-photon excitation, intermediate resonance with the CH3 + I dissociative continuum manifests itself in an expanded Franck-Condon envelope of accessible cation vibrational states together with the production and accompanying near-threshold two-photon photoionization of atomic iodine. The spectrum of the atomic photoproduct shows a new system of iodine autoionizing resonances converging to the P-3(1) state of I+. Two series are identified, [P-3(1)]np and [P-3(1)]nf Both are distinguished by narrow line widths and high two-photon cross sections, which combine to produce distinctive signatures for these states in which electrons produced by autoionization are trapped for delayed detection in the space charge of resonantly produced I+.