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An Experimental Protocol for Femtosecond NIR/UV - XUV Pump-Probe Experiments with Free-Electron Lasers
Published on: October 23, 2018
Two-photon inner-shell ionization in the extreme ultraviolet
V Richardson1, J T Costello, D Cubaynes
1School of Physical Sciences and NCPST, Dublin City University, Dublin 9, Ireland.
Physical Review Letters
|September 28, 2010
Summary
Researchers observed Xenon (Xe) atoms absorbing two extreme-ultraviolet photons, causing inner-shell ionization. This two-photon absorption process was confirmed using photoelectron spectroscopy.
Area of Science:
- Atomic physics
- Quantum mechanics
- Photonics
Background:
- Inner-shell ionization is crucial for understanding atomic structure.
- Extreme-ultraviolet (XUV) photons interact strongly with matter.
- Free electron lasers provide intense, tunable XUV radiation.
Purpose of the Study:
- To investigate the simultaneous absorption of two XUV photons by Xenon atoms.
- To characterize the resulting inner-shell ionization process.
- To analyze the photon energy dependence of the absorption.
Main Methods:
- Experiments conducted at the Short-Wavelength Free Electron Laser Facility (FLASH).
- Photoelectron spectroscopy used to detect and identify ionized electrons.
- Varying pulse energy to study intensity dependence.
Main Results:
- Observed simultaneous absorption of two 93 eV XUV photons by Xe atoms.
- Identified ionization from the Xe 4d subshell.
- Demonstrated a quadratic intensity dependence, confirming two-photon absorption.
Conclusions:
- Two-photon inner-shell ionization of Xe is experimentally verified.
- Results align with theoretical predictions and ion spectroscopy data.
- Provides insights into multi-photon processes in atoms at high intensities.
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