AB-INITIO MRD-CI STUDY OF ETHANE - 14-25EV PES REGION AND RYDBERG STATES OF POSITIVE-IONS

Ab initio calculations of the MRD-CI type are reported for various states of the C2H6+ ion in two different nuclear geometries and the results are compared with the experimentally observed ethane PES in the 14-25 eV region. The calculated vertical IP values for ionization out of the 1eu, 2a2u and 2a1g MO's respectively agree well with the locations of the three ionization maxima in this spectral range. The analogous findings for excitation out of the relaxed ionic ground state find several relatively low-lying species which occupy a 2pσ* MO in addition to states resulting from simple ionization of the neutral molecule. A number of Rydberg states are also calculated at the relaxed-ion geometry, from which results it is determined that the quantum defects for such species are from 0.40-0.45 units smaller than for their counterparts in neutral systems; these findings are clearly consistent with a decrease in the core penetrability of the Rydberg electron as the effective charge is increased to Z = 2. © 1978.