Double photoionization of helium at an excess energy of 60 eV using left- and right-elliptically-polarized light

Abstract

Helium double photoionization (γ,2e) triple differential cross sections (TDCSs) were measured at an excess energy of 60 eV using a dual toroidal spectrometer and synchrotron radiation from a helical undulator (BL-28A, Photon Factory, Japan). Energy-sharing ratios (R=E 2 /E 1 ) for the two ejected electrons of 5 and 11 are studied with both right- and left-handed elliptically polarized light. The TDCSs are found to be in good agreement with those obtained using the hyperspherical R matrix with semiclassical outgoing waves theory. The circular dichroism for a limited mutual angular range (Φ 1 2 110°-200°) is determined from the experimental data for both R= 5 and 11, and compared to theoretical calculations performed over the complete range of mutual angles. No dynamic nodes are found in either the experimental (within the explored Φ 1 2 range) or theoretical circular dichroism for these R values at this excess energy.