Hannover 2003 – scientific programme
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MO: Molekülphysik
MO 8: Photoelektronenspektroskopie, Photodissoziation
MO 8.1: Talk
Thursday, March 27, 2003, 14:00–14:15, B 305
Coherent molecular photoelectron emission from different atomic sites vs. intramolecular scattering — •Daniel Rolles1, Oliver Gessner1,2, Rainer Hentges1, Georg Prümper1, Uwe Becker1, Björn Zimmermann3, and Vince McKoy3 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany — 2Steacie Institute for Molecular Sciences, Ottawa, ON, K1A 0R6, Canada — 3California Institute of Technology, Pasadena, CA, 91125, USA
Photoelectron scattering also known under the more widely used notation No-dqphotoelectron diffractionNo-dq leads to characteristic oscillations in the core-level photoionization cross sections which reflect the particular geometry of the molecule. For free heteronuclear molecules two types of scattering can be distinguished: forward and backward scattering. We show for the case of CO the distinct difference between the two types of behavior. In contrast, homonuclear molecules are not subject to forward and backward scattering due to the mirror symmetry of the system. As a result of this symmetry, these molecules are supposed to emit electrons coherently from two spatially separated places. This coherent superposition gives also rise to oscillating partial cross sections, but instead with a frequency proportional to two times of the bond lengths as for diffraction, with half this frequency corresponding to the distance between the two coherent emitters. The oscillations of the gerade and ungerade components are shifted by π. The incoherent sum of the two should mimic the diffraction pattern of localized core holes. First experimental data testing these theoretical predictions are presented and discussed.