title: Circular Dichroism in Multiphoton Ionization of Resonantly Excited He^{+} Ions.
abstract: Intense, circularly polarized extreme-ultraviolet and near-infrared (NIR) laser pulses are combined to double ionize atomic helium via the oriented intermediate He^{+}(3p) resonance state. Applying angle-resolved electron spectroscopy, we find a large photon helicity dependence of the spectrum and the angular distribution of the electrons ejected from the resonance by NIR multiphoton absorption. The measured circular dichroism is unexpectedly found to vary strongly as a function of the NIR intensity. The experimental data are well described by theoretical modeling and possible mechanisms are discussed.
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld Hamburg, Germany.|PULSE at Stanford, 2575 Sand Hill Road, Menlo Park, 94025 California, USA.
authors.forename: M
authors.initials: M
authors.lastname: Ilchen
authors.affiliation: Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311, USA.
authors.forename: N
authors.initials: N
authors.lastname: Douguet
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld Hamburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Mazza
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld Hamburg, Germany.
authors.forename: A J
authors.initials: AJ
authors.lastname: Rafipoor
authors.affiliation: Elettra-Sincrotrone Trieste, I-34149 Basovizza, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Callegari
authors.affiliation: Elettra-Sincrotrone Trieste, I-34149 Basovizza, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Finetti
authors.affiliation: Elettra-Sincrotrone Trieste, I-34149 Basovizza, Italy.
authors.forename: O
authors.initials: O
authors.lastname: Plekan
authors.affiliation: Elettra-Sincrotrone Trieste, I-34149 Basovizza, Italy.|Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, Area Science Park, I-34149 Trieste, Italy.|Molecular Model Discovery Laboratory, Department of Chemistry and Biotechnology, Swinburne University of Technology, Melbourne, Victoria 3122, Australia.
authors.forename: K C
authors.initials: KC
authors.lastname: Prince
authors.affiliation: Elettra-Sincrotrone Trieste, I-34149 Basovizza, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Demidovich
authors.affiliation: Elettra-Sincrotrone Trieste, I-34149 Basovizza, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Grazioli
authors.affiliation: CNR Istituto Struttura della Materia, Via del Fosso del Cavaliere, 100-00133 Roma, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Avaldi
authors.affiliation: CNR Istituto Struttura della Materia, Via del Fosso del Cavaliere, 100-00133 Roma, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Bolognesi
authors.affiliation: CNR Istituto Struttura della Materia, Via del Fosso del Cavaliere, 100-00133 Roma, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Coreno
authors.affiliation: Department of Physics, University of Trieste, I-34128 Trieste, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Di Fraia
authors.affiliation: Istituto di fotonica e nanotecnologie CNR-IFN, 20133 Milano, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Devetta
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld Hamburg, Germany.
authors.forename: Y
authors.initials: Y
authors.lastname: Ovcharenko
authors.affiliation: Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22603 Hamburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Düsterer
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ueda
authors.affiliation: Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311, USA.
authors.forename: K
authors.initials: K
authors.lastname: Bartschat
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld Hamburg, Germany.|Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991, Russia.
authors.forename: A N
authors.initials: AN
authors.lastname: Grum-Grzhimailo
authors.affiliation: Sankt Petersburg State University, Universitetskaya nab. 7/9, Sankt Petersburg 199164, Russia.
authors.forename: A V
authors.initials: AV
authors.lastname: Bozhevolnov
authors.affiliation: Departamento de Fisica de Materiales, UPV/EHU, E-20018 San Sebastian/Donostia, Spain.|IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain.|Donostia International Physics Center (DIPC), E-20018 San Sebastian/Donostia, Spain.
authors.forename: A K
authors.initials: AK
authors.lastname: Kazansky
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld Hamburg, Germany.|Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991, Russia.|Donostia International Physics Center (DIPC), E-20018 San Sebastian/Donostia, Spain.
authors.forename: N M
authors.initials: NM
authors.lastname: Kabachnik
authors.affiliation: European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld Hamburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Meyer