Journal of Chemical Physics, Vol.106, No.12, 5013-5027, 1997
Oriented Molecule Photoelectron Angular-Distributions in the Vicinity of a Photoionization Shape Resonance - Continuum Multiple Scattering-X-Alpha Calculations for Valence Ionization of Cf3Cl
The potential use of fixed molecule photoelectron angular distributions (PADs) as a detailed probe of photoionization dynamics is explored using Continuum Multiple Scattering-X alpha calculations for the molecule CF3Cl. A number of dynamical phenomena (various shape resonances and a Cooper minimum) encountered in the vuv photoionization of CF3Cl up to 70 eV are examined. Cross-sections and asymmetry parameters are also reported and the nature of the low energy shape resonances is examined using eigenchannel plots. These show a clear correspondence between the present scattering calculations and the alternative description of shape resonances as antibonding virtual valence orbitals. PADs from fixed in space molecules are predicted to show a pronounced orientation, favoring electron emission from one end of the molecule. After passing through a shape resonance this orientation can flip direction as a consequence of resonant phase shifts in the interfering partial waves. Resonant electron-ion interactions can also result in greater alignment of the electron’s orbital angular momentum with the molecular axis; the corollary is that the PAD becomes less strongly aligned or oriented along this direction at the resonance energy.
Keywords:ELECTRON-ENERGY-LOSS;ANGLE-RESOLVED PHOTOELECTRON;VIBRATIONAL BRANCHING RATIOS;RAY ABSORPTION-SPECTRA;DISSOCIATIVE PHOTOIONIZATION;CROSS-SECTIONS;VACUUM ULTRAVIOLET;FREON MOLECULES;PHOTON ENERGY;SYNCHROTRON RADIATION