Dichroic Electron Emission Patterns from Oriented Helium Ions
Niclas Wieland, Klaus Bartschat, Filippa Dudda, René Wagner, Philipp Schmidt, Carlo Callegari, Alexander Demidovich, Giovanni De Ninno, Michele Di Fraia, Jiri Hofbrucker, Michele Manfredda, Valerija Music, Oksana Plekan, Kevin C. Prince, Daniel E. Rivas, Marco Zangrando, Nicolas Douguet, Alexei N. Grum-Grzhimailo, Michael Meyer, Markus Ilchen
公開日: 2025/7/23
Abstract
We report a joint experimental and theoretical study using a combination of polarization-controlled free-electron-laser (FEL) and near-infra\-red (NIR) pulses in a synchronized two-color photo\-ionization scheme. Excited He$^+$ ions, created by extreme ultraviolet (XUV) circularly polarized radiation from the XUV-FEL FERMI in the oriented $3p\, (m\!=\!+1)$ state, are exposed to circularly polarized 784-nm NIR radiation with peak intensities from $10^{12}\,\rm W/cm^2$ to $\rm 10^{13}\,W/cm^2$. The angular distribution of the ejected electrons exhibit a strong dichroism depending on the NIR intensity. While the co-rotating case is defined by a single path, for the counter-rotating case, there are two dominant pathways whose relative strength and phase difference are determined.