Abstract
We report on the experimental observation of a strong-field dressing of an autoionizing two-electron state in helium with intense extreme-ultraviolet laser pulses from a free-electron laser. The asymmetric Fano line shape of this transition is spectrally resolved, and we observe modifications of the resonance asymmetry structure for increasing free-electron-laser pulse energy on the order of few tens of Microjoules. A quantum-mechanical calculation of the time-dependent dipole response of this autoionizing state, driven by classical extreme-ultraviolet (XUV) electric fields, evidences strong-field-induced energy and phase shifts of the doubly excited state, which are extracted from the Fano line-shape asymmetry. The experimental results obtained at the Free-Electron Laser in Hamburg (FLASH) thus correspond to transient energy shifts on the order of a few meV, induced by strong XUV fields. These results open up a new way of performing nonperturbative XUV nonlinear optics for the light-matter interaction of resonant electronic transitions in atoms at short wavelengths.
- Received 28 June 2019
DOI:https://doi.org/10.1103/PhysRevLett.123.163201
© 2019 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
Distorting Helium Atoms with XUV Light
Published 15 October 2019
An extreme-UV (XUV) laser alters the structure of doubly excited helium in experiments that pave the way for improved understanding and control of fundamental light-matter interactions.
See more in Physics