Work

Breakdown of the electric dipole approximation at Cooper minima in direct two-photon ionisation

Year: 2020

Type: article

Abstract: We predict breakdown of the electric dipole approximation at nonlinear Cooper minimum in direct two-photon K-shell atomic ionisation by circularly polarised light. According to predictions based on the electric dipole approximation, we expect that tuning the incident photon energy to the Cooper minimum in two-photon ionisation results in pure depletion of one spin projection of the initially bound 1s electrons, and hence, leaves the ionised atom in a fully oriented state. We show that by inclusion of electric quadrupole interaction, dramatic drop of orientation purity is obtained. The low degree of the remaining ion orientation provides a direct access to contributions of the electron-photon interaction beyond the electric dipole approximation in the two-photon ionisation of atoms and molecules. The orientation of the photoions can be experimentally detected either directly by a Stern-Gerlach analyzer, or by means of subsequent Kα fluorescence emission, which has the information about the ion orientation imprinted in the polarisation of the emitted photons.

Source: Scientific Reports

DOI: 10.1038/s41598-020-60206-z

Authors: J. Hofbrucker, A. V. Volotka, S. Fritzsche

Institutions: Helmholtz Institute Jena, GSI Helmholtz Centre for Heavy Ion Research, Friedrich Schiller University Jena

Language: English

Topic: Atomic and Molecular Physics

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,870

Funder: Bundesministerium für Bildung und Forschung