Correlated Coulomb-Volkov approach and its application to the angular distributions of two-photon double ionization of helium

Abstract

We investigate the double-ionization process of helium in brief and intense laser fields of 10, 16, and 40 optical cycles, linearly polarized with an intensity of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>5</a:mn><a:mo>×</a:mo><a:msup><a:mn>10</a:mn><a:mn>12</a:mn></a:msup><a:mspace width="4.pt"/><a:mtext>W</a:mtext><a:mspace width="0.16em"/><a:msup><a:mtext>cm</a:mtext><a:mrow><a:mo>−</a:mo><a:mn>2</a:mn></a:mrow></a:msup></a:mrow></a:math>. We calculate the total two-photon double-ionization cross section for photon energies ranging from 39.5 to 54 eV and the triple-differential cross sections at a photon energy of 42 eV, using the correlated Coulomb-Volkov approach, which takes into account the interaction of the laser field with each electron (Volkov phase) and interactions of Coulombian nature between electrons and between electrons and the nucleus. The proposed wave function has the advantage of being much less time consuming due to the fact that it does not require a numerical propagation of the wave packet. The results of our calculations obtained for the nonsequential double photoionization are compared with previously reported data and good agreement is found with approaches using projections onto uncorrelated continuum states. This indicates that the disagreements that remain between some theoretical models for the process studied cannot simply be attributed to the electronic correlation in the continuum states. Published by the American Physical Society 2024