Photoelectron Diffraction from Fixed-in-Space Acetylene Molecules

T.U. Osipov, C.L. Cocke
Kansas State University

A.L. Landers
Western Michigan University

R. Doerner
Institut fur Kernphysik, Universitat Freiburg

T. Weber, O. Jagutski, M. Hattas, A. Demian-Braeuning, H. Schmidt-Boecking
Institut fur Kernphysik, Universitat Frankfurt

H. Braeuning
Institute fur Kernphysik, Universitat Giessen

M.H. Prior
Lawrence Berkeley National Laboratory

A. Cassimi

Free molecules of acetylene C2H2 have been photo-ionized by X-rays just above the carbon K-edge. This photoionization is followed with high probability by an Auger decay and subsequent molecular dissociation. Using a momentum-imaging technique, the momenta of the photoelectron and all charged molecular fragments were measured in coincidence. The photoelectron angular distribution, as a function of molecular orientation with respect to the polarization axis, was then obtained. The photoelectron yield, as a function of X-ray energy, shows the presence of a shape resonance around 15-2O eV above the ionization potential of the carbon K-shell electron. Rom this the complex amplitudes of the partial waves describing the photoelectron outgoing wave were obtained. These amplitudes can be used to provide information about the molecular potential in which the photoelectron moves.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Submitted to DAMOP/DAMP Meeting, May 2001 in London, Ontario.

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