Final-photon angular distributions in Compton double-ionization

Angular distributions of the scattered-photon in two-electron ionization of helium by Compton scattering are reported. Our calculations are performed as a direct integration over Compton profiles. We show that backward scatte ring is adequately described using an uncorrelated final-state approximatio n as compared with impulse approximation (IA) results. The relation d sigma (c)(2+)/d Omega = R-c d sigma(c)(+)/d Omega is fulfilled within IA at high- photon energies, with R-c the asymptotic shake-off ratio.