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Soviet Journal of Quantum Electronics

Integrated cross sections and polarization of photoelectrons in two-photon ionization of alkali metal atoms using two optical beams

R. Parzyński

Published Oct 31, 1980• 0 citations
Publisher

Abstract

General equations are proposed for the integrated cross section and degree of spin polarization of photoelectrons emitted by ground-state alkali metal atoms in two-photon ionization by two different optical beams. The equations, which are derived in the fine-structure approximation, are valid for polarized and unpolarized atoms, parallel experimental geometries, completely polarized (elliptically, circularly, and linearly polarized) and completely unpolarized optical beams, and also near resonance with an nP intermediate doublet level.

DOI
10.1070/qe1980v010n10abeh010518

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We report in detail our complete characterization of atomic photoionization via a single measurement, namely, that of the two-photon photoelectron angular distribution using elliptically polarized light. Through these measurements we are able to determine the atomic parameters necessary to unambiguously describe two-photon ionization of atomic rubidium. These parameters include relative cross sections for photoionization into various outgoing channels as well as the phase difference between the continuum S and D partial waves. We present a derivation of the angular distribution with arbitrarily polarized light in terms of these cross sections and phases, demonstrate the advantages of using elliptically polarized light, discuss details of the experiment, and report the results of our measurements in this paper. While measured phase differences are in excellent agreement with expected values over the entire range of photoelectron kinetic energy of our measurements from 0 to 0.5 eV, ratios of cross sections for photoionization into the two D channels are anomalous, suggesting unexpected fine structure effects in these continua.
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