Complementary TDCS for the photo-double ionization of He at 40 eV above the threshold in unequal energy-sharing conditions

Photo-double ionization (PDI) of helium at 40 eV above the threshold has been studied for unequal energy-sharing in the complementary kinematics obtained in two measurements by the interchange of the kinetic energies E1leftrightarrowE2 of the two photoelectrons. The triple differential cross sections (TDCS) were measured in the plane perpendicular to the photon direction using the multicoincidence end-station of the gas-phase photoemission beam-line of the Elettra storage ring. The measured TDCSs were compared with previous experimental results using a practical parametrization proposed by Cvejanovic and Reddish (2000 J. Phys. B: At. Mol. Opt. Phys. 33 4691) and with predictions of the 3C and convergent close-coupling calculations. Satisfactory agreement with the previous experimental data was found. The comparison with the two theoretical models shows that the TDCSs is the complementary kinematics still present a challenge for PDI theory.