Scientific Reports (Nov 2024)

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
https://doi.org/10.1038/s41598-024-75459-1
Journal volume & issue
Vol. 14, no. 1
pp. 1 – 11

Abstract

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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.