A binary (e, 2e) spectroscopy investigation and detailed analysis of the 4d5/2 and 4d3/2 inner shell ionization of Xe

We report the momentum profiles for the binary (e, 2e) reaction of the Xe 4d5/2 and 4d3/2 inner shell ionization transitions. The experiment has been performed at an incident electron energy of 1270 eV, using a highly sensitive multichannel electron momentum spectrometer with a coverable momentum range up to 9 a.u. The experimental results were compared with the associated theoretical profiles calculated by the plane wave impulse approximation (PWIA), the distorted wave impulse approximation (DWIA), and the distorted wave Born approximation (DWBA) models, using the relativistic and non-relativistic Kohn-Sham orbitals as the target electron orbitals. The superiority of the DWBA model over not only the PWIA but also the DWIA was found for the whole momentum range up to 9 a.u., demonstrating that the interaction between the projectile and target electrons, as well as the distorted wave effect, plays an important role in explaining the momentum profile of inner-shell ionization. Furthermore, it was experimentally revealed that the branching ratio of the 4d5/2 and 4d3/2 ionizations slightly deviates from the value of the non-relativistic ratio and is only weakly dependent upon the momentum over the momenta investigated, indicating that the relativistic effect on the Xe 4d wavefunction is fairly small, as predicted by the theory. These results would provide detailed insight into the relativistic effect on electron distributions and (e, 2e) reaction dynamics for the inner-shell ionization.