Angle-Resolved Electron Spectroscopy of Laser-Assisted Auger Decay Induced by a Few-Femtosecond X-Ray Pulse

M. Meyer, P. Radcliffe, T. Tschentscher, J. T. Costello, A. L. Cavalieri, I. Grguras, A. R. Maier, R. Kienberger, J. Bozek, C. Bostedt, S. Schorb, R. Coffee, M. Messerschmidt, C. Roedig, E. Sistrunk, L. F. Di Mauro, G. Doumy, K. Ueda, S. Wada, S. Dusterer, A.K. Kazansky, and N.M. Kabachnik European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg, Germany School of Physical Sciences and NCPST, Dublin City University, Dublin 9, Ireland MPSD/CFEL, Notkestrasse 85, D-22607 Hamburg, Germany Max Planck Institut fur Quantenoptik, James Frank Strasse, D-85748 Garching, Germany Ludwig-Maximilians Universitat Munchen, Department of Physics, Am Coulombwall 1, 85748 Garching, Germany Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA Argonne National Laboratory, Argonne, Illinois 60439, USA Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan Department of Physical Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan HASYLAB at DESY, Notkestrasse 85, D-22607 Hamburg, Germany Departamento de Fisica de Materiales, UPV/EHU, E-20018 San Sebastian/Donostia, Spain Donostia International Physics Center (DIPC), E-20018 San Sebastian/Donostia, Spain IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain Institute of Nuclear Physics, Moscow State University, Moscow 119991, Russia (Received 4 October 2011; published 10 February 2012) Two-color (x-rayþ infrared) electron spectroscopy is used for investigating laser-assisted KLL Auger decay following 1s photoionization of atomic Ne with few-femtosecond x-ray pulses from the Linac Coherent Light Source. In an angle-resolved experiment, the overall width of the laser-modified Augerelectron spectrum and its structure change significantly as a function of the emission angle. The spectra are characterized by a strong intensity variation of the sidebands revealing a gross structure. This variation is caused, as predicted by theory, by the interference of electrons emitted at different times within the duration of one optical cycle of the infrared dressing laser, which almost coincides with the lifetime of the Ne 1s vacancy.