Ultrafast Nonlinear Double Excitations of He in Intense EUV FEL Fields
1 Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Aichi 464-8602, Japan
2 Department of Environmental Science, Niigata University, Niigata, Niigata 950-2181, Japan
3 Department of Physics, Fu-Jen Catholic University, Taipei 24205, Taiwan
4 Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo, 182-8585, Japan
5 Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8585, Japan
Three-photon double excitation of He in intense EUV FEL fields is studied by the shot-by-shot photoelectron spectroscopy, revealing the enhancement by resonances to the doubly excited states converging to the He+ N=3 level.
© Owned by the authors, published by EDP Sciences, 2013
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