Circular dichroism in multiphoton ionization of resonantly excited helium ions near channel closing

René Wagner; Markus Ilchen; Nicolas Douguet; Philipp Schmidt; Niclas Wieland; Carlo Callegari; Zachary Delk; Alexander Demidovich; Giovanni De Ninno; Michele Di Fraia; Jiri Hofbrucker; Michele Manfredda; Valerija Music; Oksana Plekan; Kevin C Prince; Daniel E Rivas; Marco Zangrando; Alexei N Grum-Grzhimailo; Klaus Bartschat; Michael Meyer

doi:10.1038/s41598-024-75459-1

Circular dichroism in multiphoton ionization of resonantly excited helium ions near channel closing

Sci Rep. 2024 Nov 8;14(1):27232. doi: 10.1038/s41598-024-75459-1.

Authors

René Wagner^{1

2}, Markus Ilchen^{1

2

3

4}, Nicolas Douguet⁵, Philipp Schmidt¹, Niclas Wieland², Carlo Callegari⁶, Zachary Delk⁷, Alexander Demidovich⁶, Giovanni De Ninno⁶, Michele Di Fraia⁶, Jiri Hofbrucker⁸, Michele Manfredda⁶, Valerija Music^{1

3

4}, Oksana Plekan⁶, Kevin C Prince⁶, Daniel E Rivas¹, Marco Zangrando^{6

9}, Alexei N Grum-Grzhimailo¹⁰, Klaus Bartschat¹¹, Michael Meyer¹²

Affiliations

¹ European X-Ray Free-Electron Laser Facility, 22869, Schenefeld, Germany.
² Department of Physics, Universität Hamburg, 22607, Hamburg, Germany.
³ Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607, Hamburg, Germany.
⁴ Institut für Physik und CINSaT, Universität Kassel, 34132, Kassel, Germany.
⁵ Department of Physics, University of Central Florida, Orlando, FL, 32816, USA.
⁶ Elettra-Sincrotrone Trieste S.C.p.A., 34149, Basovizza, Trieste, Italy.
⁷ Department of Physics, Kennesaw State University, Marietta, GA, 30060, USA.
⁸ Helmholtz-Institut Jena, Fröbelstieg 3, 07743, Jena, Germany.
⁹ CNR Istituto Officina dei Materiali, Laboratorio TASC, 34149, Basovizza, Trieste, Italy.
¹⁰ Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
¹¹ Department of Physics and Astronomy, Drake University, Des Moines, IA, 50311, USA.
¹² European X-Ray Free-Electron Laser Facility, 22869, Schenefeld, Germany. [email protected].

PMID: 39516212
DOI: 10.1038/s41598-024-75459-1

Abstract

The circular dichroism (CD) of photoelectrons generated by near-infrared (NIR) laser pulses using multiphoton ionization of excited He⁺ ions in the 3p(m= +1) state is investigated. The ions were prepared by circularly polarized extreme ultraviolet (XUV) pulses. For circularly polarized NIR pulses co- and counter-rotating relative to the polarization of the XUV pulse, a complex variation of the CD is observed as a result of intensity- and polarization-dependent Freeman resonances, with and without additional dichroic AC-Stark shifts. The experimental results are compared with numerical solutions of the time-dependent Schrödinger equation to identify and interpret the pronounced variation of the experimentally observed CD.