High energy Rydberg and ion-pair states, state mixing and excitation dynamics of HI.

Mass resolved multiphoton ionization data for two-photon resonant excitations (REMPI) in the region of 74 000-75 000 cm-1 were recorded for HI. Spectra structures of fragment and molecular ions derived from the data were analyzed to derive information relevant to the energetics and state mixing of ion-pair and Rydberg resonance states as well as for the excitation dynamics. Four new ion-pair vibrational states (V1Σ+(v' = m + i); i = 16-19) and two Rydberg states (j3Σ-(0+; v' = 1) and N1Π1(v' = 2)) were identified and characterized. Spectral perturbations allowed characterization and quantization of both homogeneous and heterogeneous state interactions and mixing of the Rydberg states and ion-pair states. Intensity alterations, with respect to energy level excitations and ion masses, are found to be clear indications of state mixing as well as branching into different fragmentation (both photodissociation and photoionization) channels.