State-selective cross sections of multiple photoionization in Ne

Valence double photoionization of Ne atom has been investigated by multielectron spectroscopy. Complete information on energy correlation between ejected electrons allows the identification of ${\mathrm{Ne}}^{2+}$ final states and their formation mechanism. In addition to simultaneous two-electron emission from the valence shells, indirect processes mediated by singly charged excited states have been observed. We have first obtained direct double-photoionization cross sections state-selectively in a wide photon energy region, by evaluating the contributions of the indirect processes. We have also applied the coincidence spectroscopy to three-electron emission from the valence shells. Even in the three-electron emission, the coincidence analysis enables to observe individual ${\mathrm{Ne}}^{3+}$ final states related to the triple-photoionization process and to obtain the state-selective cross sections.