Photoionization of helium atoms irradiated with intense vacuum ultraviolet free-electron laser light. Part II. Theoretical modeling of multi-photon and single-photon processes

Journal Article · Mon Aug 15 04:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.023410· OSTI ID:20718166

Castro, A R.B. de ^[1]; HASYLAB at DESY, D-22603 Hamburg ^[2]; Laarmann, T; Schulz, J; Wabnitz, H; Moeller, T ^[3]

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1. LNLS, P.O. Box 6192, CEP 13084-971 Campinas SP (Brazil)
2. Germany
3. HASYLAB at DESY, D-22603 Hamburg (Germany)

We consider the problem of a helium atom under the radiation field of the DESY vacuum ultraviolet (VUV) free electron laser (FEL) (Phase I ({Dirac_h}/2{pi}) congruent with 13 eV). We find by solving numerically the time-dependent Schroedinger equation, that there is a large probability for resonant two-photon excitation from the ground state into a low kinetic energy state just above the first He ionization threshold. From this it is possible to go into another quasi-free state higher up, by resonant absorption of an additional photon. There is no double ionization of He. These results are in general agreement with the He photoelectron and time-of-flight (TOF) spectra recorded on March 2002, in the last week of the DESY VUV FEL Phase I operation. A detailed report on the experiments is given in a companion paper.

• OSTI ID: 20718166
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 2 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ATOMS
DESY
EV RANGE
EXCITATION
FAR ULTRAVIOLET RADIATION
FREE ELECTRON LASERS
GROUND STATES
HELIUM
IRRADIATION
KINETIC ENERGY
LASER RADIATION
MULTI-PHOTON PROCESSES
PHOTOELECTRON SPECTROSCOPY
PHOTOIONIZATION
PHOTON-ATOM COLLISIONS
PHOTONS
PROBABILITY
SCHROEDINGER EQUATION
SIMULATION
TIME DEPENDENCE
TIME-OF-FLIGHT METHOD
VISIBLE RADIATION