Title

Time-resolved photoelectron angular distributions and cross-section ratios of two-colour two-photon above threshold ionization of helium

Document Type

Article

Publication Date

10-1-2010

Abstract

Time-resolved anisotropy parameters and cross-section ratios of the positive and negative sidebands from two-colour two-photon above threshold ionization of helium atoms are measured using photoelectron velocity map imaging with the selected 19th high-order harmonic at 29.1 eV in an 810 nm perturbative dressing field. The intensities of both the sidebands and the single-photon ionization depletion follow a Gaussian correlation function where the photoelectron angular distributions and cross-section ratios of the sidebands do not change as a function of the temporal delay between the extreme ultraviolet and infrared pulses. The experimental results are compared with theoretical predictions using the soft-photon approximation, showing poor agreement, and analytical expressions are derived using second-order perturbation theory to determine the relative magnitudes of the resulting S and D partial waves of the above threshold ionization features. © 2010 Taylor & Francis.

Publication Source (Journal or Book title)

Molecular Physics

First Page

1241

Last Page

1251

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