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Title: Experimental Study of Photodetachment in a Strong Laser Field of Circular Polarization

Abstract

Negative fluorine ions are exposed to a circularly polarized infrared laser pulse with a peak intensity on the order of 2.6x10{sup 13} W/cm{sup 2}. A fundamental difference, as compared to the case of linearly polarized field, is found in the absence of any structure in the photoelectron spectrum that can be associated with the quantum interference effect. This observation is in accord with our recent predictions [S. Beiser et al., Phys. Rev. A 70, 011402 (2004)]. The experiment reveals that the length gauge is appropriate for the description of the field interaction in the frame of the strong field approximation.

Authors:
; ; ;  [1]
  1. Physikalisches Institut, Albert-Ludwigs-Universitaet, D-79104 Freiburg (Germany)
Publication Date:
OSTI Identifier:
20771638
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 95; Journal Issue: 26; Other Information: DOI: 10.1103/PhysRevLett.95.263002; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANIONS; APPROXIMATIONS; ELECTRON DETACHMENT; FLUORINE IONS; INTERFERENCE; LASER RADIATION; PHOTOELECTRON SPECTROSCOPY; PHOTON-ATOM COLLISIONS; POLARIZATION

Citation Formats

Bergues, Boris, Ni Yongfeng, Helm, Hanspeter, and Kiyan, Igor Yu. Experimental Study of Photodetachment in a Strong Laser Field of Circular Polarization. United States: N. p., 2005. Web. doi:10.1103/PhysRevLett.95.263002.
Bergues, Boris, Ni Yongfeng, Helm, Hanspeter, & Kiyan, Igor Yu. Experimental Study of Photodetachment in a Strong Laser Field of Circular Polarization. United States. doi:10.1103/PhysRevLett.95.263002.
Bergues, Boris, Ni Yongfeng, Helm, Hanspeter, and Kiyan, Igor Yu. Sat . "Experimental Study of Photodetachment in a Strong Laser Field of Circular Polarization". United States. doi:10.1103/PhysRevLett.95.263002.
@article{osti_20771638,
title = {Experimental Study of Photodetachment in a Strong Laser Field of Circular Polarization},
author = {Bergues, Boris and Ni Yongfeng and Helm, Hanspeter and Kiyan, Igor Yu.},
abstractNote = {Negative fluorine ions are exposed to a circularly polarized infrared laser pulse with a peak intensity on the order of 2.6x10{sup 13} W/cm{sup 2}. A fundamental difference, as compared to the case of linearly polarized field, is found in the absence of any structure in the photoelectron spectrum that can be associated with the quantum interference effect. This observation is in accord with our recent predictions [S. Beiser et al., Phys. Rev. A 70, 011402 (2004)]. The experiment reveals that the length gauge is appropriate for the description of the field interaction in the frame of the strong field approximation.},
doi = {10.1103/PhysRevLett.95.263002},
journal = {Physical Review Letters},
number = 26,
volume = 95,
place = {United States},
year = {Sat Dec 31 00:00:00 EST 2005},
month = {Sat Dec 31 00:00:00 EST 2005}
}
  • We investigate the photodetachment process in the negative fluorine ion in a strong linearly polarized laser field. Angle-resolved momentum distributions of photoelectrons are measured with the use of an imaging technique for a wide range of laser frequencies and peak intensities. The nonmonotonic structure recorded in photoelectron spectra is interpreted in terms of the quantum interference effect predicted by a Keldysh-like theory. In particular, the dependence of the interference term on the laser parameters is used to explain the origin of the observed spectral features. Our results unambiguously show that the length gauge is the proper one to use inmore » the frame of the strong-field approximation.« less
  • In the recent work of Vanne and Saenz [Phys. Rev. A 75, 063403 (2007)] the quasistatic limit of the velocity gauge strong-field approximation describing the ionization rate of atomic or molecular systems exposed to linearly polarized laser fields was derived. It was shown that in the low-frequency limit the ionization rate is proportional to the laser frequency {omega} (for a constant intensity of the laser field). In the present work I show that for circularly polarized laser fields the ionization rate is proportional to {omega}{sup 4} for H(1s) and H(2s) atoms, to {omega}{sup 6} for H(2p{sub x}) and H(2p{sub y})more » atoms, and to {omega}{sup 8} for H(2p{sub z}) atoms. The analytical expressions for asymptotic ionization rates (which become nearly accurate in the limit {omega}{yields}0) contain no summations over multiphoton contributions. For very low laser frequencies (optical or infrared) these expressions usually remain with an order-of-magnitude agreement with the velocity gauge strong-field approximation.« less
  • The saddle-point analysis of the transition amplitude shows that the quantum interference effect does not occur in the direct process of photodetachment by a circularly polarized laser field. This fact is interpreted in terms of classical electron trajectories. Comparison between the length and velocity gauges is performed by simulating spectra of photoelectrons produced in a focus of a laser pulse. A substantial discrepancy is found in the kinetic energy distribution of photoelectrons. At low energies, only the predictions in the length gauge are consistent with the Wigner threshold law.
  • We study the photodetachment of H{sup -}, F{sup -}, and Br{sup -} in a short laser pulse of 800 nm wavelength and 6x10{sup 14} W/cm{sup 2} peak intensity. Photoelectron spectra, recorded with the use of an imaging technique, reveal a substantial contribution from the sequential process of double detachment of halogen negative ions. The saturation effect is shown to play a crucial role in this process. The role of the alignment of atoms produced by photodetachment is discussed.
  • The angle-resolved photoelectron spectrum of F{sub 2}{sup -}, exposed to a strong infrared laser pulse, is significantly different from the spectrum of F{sup -} obtained under the same experimental conditions. The experimental results are used to test the theory based on the molecular strong-field approximation. Both the dressed and the undressed versions of this theory fail to reproduce the F{sub 2}{sup -} spectrum. One origin for this discrepancy is that photodetachment of F{sup -} produced by strong-field dissociation of F{sub 2}{sup -} needs to be considered.