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Phys. Rev. A 72, 023410 (2005) [9 pages]

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

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A. R. B. de Castro1,2,3, T. Laarmann3,*, J. Schulz3,†, H. Wabnitz3,‡, and T. Möller3,§
1LNLS, P.O. Box 6192, CEP 13084-971 Campinas SP, Brazil
2IFGW UNICAMP, CEP 13083-970 Campinas SP, Brazil
3HASYLAB at DESY, D-22603 Hamburg, Germany

Received 30 August 2004; published 15 August 2005

We consider the problem of a helium atom under the radiation field of the DESY vacuum ultraviolet (VUV) free electron laser (FEL) (Phase I, ℏ≅13 eV). We find by solving numerically the time-dependent Schrödinger 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.

© 2005 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevA.72.023410
DOI:
10.1103/PhysRevA.72.023410
PACS:
42.50.Hz, 33.60.Cv, 32.80.Rm

*Present address: Max-Born-Institute, Max Born Str. 2a, D-12489 Berlin, Germany.

†Present address: MAX-lab, Box 118, 22100 Lund, Sweden.

‡Present address: Centre d’étudies de Saclay, 91191 Gif-sur-Yvette, France.

§Present address: Technische Universität Berlin, D-10623 Berlin, Germany.

See Also

Comment: Alfred Maquet, Bernard Piraux, Armin Scrinzi, and Richard Taïeb, Comment on “Photoionization of helium atoms irradiated with intense vacuum ultraviolet free-electron laser light. Part II. Theoretical modeling of multiphoton and single-photon processes”, Phys. Rev. A 74, 027401 (2006).

Comment: A. R. B. de Castro, T. Laarmann, J. Schulz, H. Wabnitz, and T. Möller, Reply to “Comment on ‘Photoionization of helium atoms irradiated with intense vacuum ultraviolet free-electron laser light. Part II. Theoretical modeling of multiphoton and single-photon processes’ ”, Phys. Rev. A 74, 027402 (2006).

 
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