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Anne L'Huillier

Anne l'Huillier

Professor

Anne L'Huillier

Two-color pump-probe experiments in helium using high-order harmonics

Author

  • Allan Johansson
  • MK Raarup
  • Zhongshan Li
  • V Lokhnygin
  • D Descamps
  • C Lynga
  • E Mevel
  • Jörgen Larsson
  • Claes-Göran Wahlström
  • S Aloise
  • M Gisselbrecht
  • M Meyer
  • Anne L'Huillier

Summary, in English

A pump-probe technique has been applied for measuring the lifetimes and absolute photoionization cross-sections of excited He states. The 1s2p P-1 and 1s3p P-1 states of He are excited by using the 13th and the 14th harmonic, respectively, of a tunable 70 ps dye laser generated in a Kr gas jet. The states are ionized after a varying time delay, by absorption of probe photons with energies between 1.6 and 4.5 eV. Lifetimes of tau(1s2p) = 0.57 ns and tau(1s3p) = 1.76 ns are determined with a precision of about 15%. A significant enhancement of the number of ions present in the lifetime curves at zero time delay for pressures above 6 x 10(-5) mbar is attributed to direct two-photon ionization of He in combination with AC Stark broadening of the excited state and absorption of the XUV light in the medium. Absolute photoionization cross-sections from the He 1s2p P-1 and He 1s3p P-1 states in the threshold region are determined by measuring the saturation of the ionization process with a precision of similar to 25%. In addition, the variation of the relative orientation between the polarization vectors of the pump and probe beams enables the determination of partial photoionization cross-sections.

Department/s

  • Atomic Physics
  • Department of Physics

Publishing year

2003

Language

English

Pages

3-11

Publication/Series

European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics

Volume

22

Issue

1

Document type

Journal article

Publisher

EDP Sciences

Topic

  • Atom and Molecular Physics and Optics

Status

Published

ISBN/ISSN/Other

  • ISSN: 1434-6060