## 2D projection (left) of the momentum distribution of the outgoing photoelectrons from xenon atoms irradiated by EUV FEL pulses at a photon energy of 24.3 eV, and the corresponding slice (right) through the retrieved 3D photoelectron momentum distribution as obtained from an Abel inversion

**Figure 1.** 2D projection (left) of the momentum distribution of the outgoing photoelectrons from xenon atoms irradiated by EUV FEL pulses at a photon energy of 24.3 eV, and the corresponding slice (right) through the retrieved 3D photoelectron momentum distribution as obtained from an Abel inversion.

**Abstract**

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.