Mainz 2017 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

A: Fachverband Atomphysik

A 20: Poster Session I

A 20.19: Poster

Tuesday, March 7, 2017, 17:00–19:00, P OG1

Observation of strong non-dipole effects in sequential multi-photon ionization using VUV FEL radiation — •Gregor Hartmann^1,2, Markus Ilchen³, Michael Meyer³, and Jens Viefhaus² — ¹Institut für Physik and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Universität Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany — ²Deutsches Elektronen-Synchrotron, Notkestraße 85, 22607 Hamburg, Germany — ³European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg, Germany

One of the fundamental principles of light-matter interaction is the dipole approximation that is commonly assumed to be valid at low photon energies including the soft X-ray region. Although it has been shown at synchrotron radiation facilities that this approximation has limitations, it has been unclear how they impact the ionization characteristics of ions. Recently, ultrafast and ultra-intense Vacuum UltraViolet pulses from free-electron lasers such as FERMI have been used to efficiently study photoionization properties of noble gas ions by angle resolved photoelectron spectroscopy. We present evidence of a forward-backward symmetry breakdown in such a sequential ionization process in the vicinity of the Cooper Minimum of argon, at 46 eV excitation energy. In particular, we show that the electron angular distribution of ionic argon gains a pronounced forward-backward asymmetry with respect to the beam by interference between the electric dipole and the electric quadrupole amplitudes.