Helicity Dependence of the Photon-Induced Three-Body Coulomb Fragmentation of Helium Investigated by Cold Target Recoil Ion Momentum Spectroscopy

The angular and energy dependence of circular dichroism in photo-double-ionization of helium at a photon energy of 99 eV is investigated. Using cold target recoil ion momentum spectroscopy the absolute fivefold differential cross section has been obtained by a coincident measurement of the vector momenta of one electron and the recoiling ${\mathrm{He}}^{2+}$ ion covering all relative azimuthal and polar angles. The experimental results are contrasted with numerical calculations using different helium ground state wave functions and forms of the dipole operator.