Suppression of ionization probability due to Rabi oscillations in the resonance two-photon ionization of He by EUV free-electron lasers
- Laboratory of Physics, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, Chiba 274-8501 (Japan)
- Photon Factory, Institute of Materials Structure Science, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)
- RIKEN, SPring-8 Center, Sayo, Hyogo 679-5148 (Japan)
The two-photon resonance ionization probability of atoms in strong extreme-ultraviolet free-electron laser (EUV FEL) pulses has been investigated by the model of time-dependent wave packet propagation of a light-coupled multilevel atom. Under the simulation within the model assuming single-mode FEL pulses, the ionization probability P{sub ion} has shown characteristic dependences on the scaled coupling parameter U{sub gi} between two levels of the ground (g) and intermediate (i) resonance states, namely, P{sub ion}{proportional_to}(U{sub gi}){sup n}, with n being equal to {approx}2, less than 1, and {approx}1 for the small, medium, and large U{sub gi} regimes, respectively. This power dependence of the ionization probability has been interpreted due to Rabi oscillations between g and i states. To compare with recent experimental results on the same condition, the multimode nature of self-amplitude spontaneous emission (SASE) FEL pulses has been managed in the simulation. Then, the recent experimental laser-power dependence of the two-photon resonance ionization of He [Sato et al., J. Phys. B 44, 161001 (2011)] has been well described by that for the large U{sub gi} regime of the simulation, i.e., n{approx} 1. Thus, the observed linear laser-power dependence has been rationalized as being caused by the strong Rabi oscillations between the (2p)-(1s) states.
- OSTI ID:
- 22093568
- Journal Information:
- Physical Review. A, Vol. 84, Issue 5; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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AMPLITUDES
ATOMS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
COUPLING
EMISSION
EXTREME ULTRAVIOLET RADIATION
FREE ELECTRON LASERS
GROUND STATES
OSCILLATIONS
PHOTOIONIZATION
PHOTONS
PROBABILITY
PULSES
RESONANCE
S STATES
TIME DEPENDENCE
VISIBLE RADIATION
WAVE PACKETS