Measured (solid lines) and calculated (dashed lines) photoelectron angular distributions for the second-step photoelectron in the two-photon sequential double ionization of xenon at a photon energy of 24.3 eV

<p><strong>Figure 5.</strong> Measured (solid lines) and calculated (dashed lines) photoelectron angular distributions for the second-step photoelectron in the two-photon sequential double ionization of xenon at a photon energy of 24.3 eV. The left panel is for peak 3 and the right panel for peak 4.</p> <p><strong>Abstract</strong></p> <p>Xenon atoms are double-ionized by sequential two-photon absorption by ultrashort extreme ultraviolet free-electron laser pulses with a photon energy of 23.0 and 24.3 eV, produced by the SPring-8 Compact SASE Source test accelerator. The angular distributions of photoelectrons generated by two-photon double ionization are obtained using velocity map imaging. The results are reproduced reasonably well by the present theoretical calculations within the multi-configurational Dirac–Fock approach.