Resonance-Enhanced Multiphoton Ionization in the X-Ray Regime
- Univ. of Connecticut, Storrs, CT (United States)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; The Hamburg Center for Ultrafast Imaging, Hamburg (Germany)
- European X-ray Free-Electron Laser (XFEL), Schenefeld (Germany); Univ. Kassel (Germany). Inst. fur Physik und CINSaT
- Univ. of Turku (Finland)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Univ. Hamburg (Germany)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Univ. Hamburg (Germany)
- SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS)
- European X-ray Free-Electron Laser (XFEL), Schenefeld (Germany)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamburg Centre for Ultrafast Imaging (Germany); Univ. Hamburg (Germany)
In this work, we report on the nonlinear ionization of argon atoms in the short wavelength regime using ultraintense x rays from the European XFEL. After sequential multiphoton ionization, high charge states are obtained. For photon energies that are insufficient to directly ionize a 1s electron, a different mechanism is required to obtain ionization to Ar17+. We propose this occurs through a two-color process where the second harmonic of the FEL pulse resonantly excites the system via a 1s→2p transition followed by ionization by the fundamental FEL pulse, which is a type of x-ray resonance-enhanced multiphoton ionization (REMPI). This resonant phenomenon occurs not only for Ar16+, but also through lower charge states, where multiple ionization competes with decay lifetimes, making x-ray REMPI distinctive from conventional REMPI. With the aid of state-of-the-art theoretical calculations, we explain the effects of x-ray REMPI on the relevant ion yields and spectral profile.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); European Union Horizon 2020
- Grant/Contract Number:
- SC0012376; AC02-76SF00515; 730872
- OSTI ID:
- 1868364
- Journal Information:
- Physical Review Letters, Vol. 127, Issue 21; ISSN 0031-9007
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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