The electron energy and anisotropy parameters β<sub>2</sub> and β<sub>4</sub> measured and calculated for the second-step photoelectrons from Xe in sequential 2PDI

<p><b>Table 2.</b> The electron energy and anisotropy parameters β<sub>2</sub> and β<sub>4</sub> measured and calculated for the second-step photoelectrons from Xe in sequential 2PDI.</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.</p>