The calculated asymmetry parameters β2 and β4 for second-step photoelectrons in selected transitions of sequential 2PDI
Figure 2. The calculated asymmetry parameters β2 and β4 for second-step photoelectrons in selected transitions of sequential 2PDI. Solid (black) lines: 2P3/2 → 3P2; long-dashed (red) lines 2P3/2 → 3P0; short-dashed (blue) line: 2P3/2 → 3P1; dot-dashed (green) line: 2P1/2 → 3P2; double-dot-dashed line (magenta): 2P1/2 → 3P0; dotted line (violet): 2P1/2 → 3P1. The β4 parameter is shown for two transitions only: 2P3/2 → 3P2, solid (black) line and 2P3/2 → 3P0, long-dashed (red) line. For other transitions, β4 = 0 (see the text).
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.