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

Johansson, Allan LU ; Raarup, MK; Li, Zhongshan LU ; Lokhnygin, V; Descamps, D; Lynga, C; Mevel, E; Larsson, Jörgen LU ; Wahlström, Claes-Göran LU and Aloise, S, et al. (2003) In European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics1998-01-01+01:00 22(1). p.3-11
Abstract
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... (More)
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. (Less)
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Contribution to journal
publication status
published
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in
European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics1998-01-01+01:00
volume
22
issue
1
pages
3 - 11
publisher
EDP Sciences
external identifiers
  • wos:000180850000001
  • scopus:0037263791
ISSN
1434-6060
DOI
10.1140/epjd/e2002-00213-1
language
English
LU publication?
yes
id
be754200-c4d8-4a46-82c8-bf5aa403f02d (old id 318685)
date added to LUP
2007-09-13 14:07:11
date last changed
2018-01-07 08:38:00
@article{be754200-c4d8-4a46-82c8-bf5aa403f02d,
  abstract     = {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.},
  author       = {Johansson, Allan and Raarup, MK and Li, Zhongshan and Lokhnygin, V and Descamps, D and Lynga, C and Mevel, E and Larsson, Jörgen and Wahlström, Claes-Göran and Aloise, S and Gisselbrecht, M and Meyer, M and L'Huillier, Anne},
  issn         = {1434-6060},
  language     = {eng},
  number       = {1},
  pages        = {3--11},
  publisher    = {EDP Sciences},
  series       = {European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics1998-01-01+01:00},
  title        = {Two-color pump-probe experiments in helium using high-order harmonics},
  url          = {http://dx.doi.org/10.1140/epjd/e2002-00213-1},
  volume       = {22},
  year         = {2003},
}