X-ray-laser interaction with matter and the role of multiphoton ionization: Free-electron-laser studies on neon and helium
- 3 May 2007
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review A
- Vol. 75 (5), 051402
- https://doi.org/10.1103/physreva.75.051402
Abstract
At the soft-x-ray free-electron laser FLASH in Hamburg, we have studied multiphoton ionization on neon and helium by ion mass-to-charge spectroscopy. The experiments were performed in a focused beam at 42.8 and photon energy and irradiance levels up to . Direct, sequential, and resonant two-, three-, and four-photon excitations were investigated by quantitative measurements as a function of the absolute photon intensity. The atomic and ionic photoionization cross sections derived indicate a clear dominance of sequential compared to direct multiphoton processes.
Keywords
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