München 2004 – scientific programme

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A: Atomphysik

A 9: Poster 1

A 9.27: Poster

Tuesday, March 23, 2004, 14:00–16:00, Schellingstr. 3

Fragment Distributions From the Photo-ionization and Dissociation of Aligned H₂ and D₂ Molecules — •Lutz Foucar^1,2, M. H. Prior¹, M. Schöffler², L. Ph. H. Schmidt², R. Dörner², H. Schmidt-Böcking², A. Landers³, T. Osipov³, E. P. Benis³, and C. L. Cocke³ — ¹Lawrence Berkeley Nat. Lab, California, USA — ²Institut für Kernphysik der J. W. Goethe-Universität Frankfurt am Main — ³Kansas State University, USA

The angular distributions of photoelectrons in the molecular frame have been measured for processes leading to the single ionization and dissociation of H₂ and D₂ molecules. Linearly polarized photons ranging in energy from 27 to 60 eV were used at Beamline 9.3.2 of the LBNL Advanced Light Source in conjunction with the ion-electron coincident momentum spectroscopic technique (COLTRIMS) . Energy correlation spectra, between the heavy fragments and the photoelectron, reveal doubly excited and direct-ionization channels that lead to neutral atoms (H or D) in ground or excited states. Coincident measurements of the momenta of the heavy particles and the electron allow resolution of these states. A large isotope effect is observed in the energy correlation between the fragment kinetic energy release and the electron energy when exciting the dominent Q1 autoionizing channel near 30 eV photon energy. At 36 eV photon energy, the electron angular distributions in the molecular frame, for chosen alignments of the molecular axis with respect to the light polarization axis, vary substantially for the different ionization pathways (direct or autionizing) leading to the H or D(n=1) final state.