Angular anisotropy parameters for sequential two-photon double ionization of helium

We evaluate photoelectron angular anisotropy parameters for the process of sequential two-photon double electron ionization of helium within the lowest-order time-independent perturbation theory. Our results indicate that for photoelectron energies outside the interval Eslow,Efast , where Eslow= −VHe+ and Efast= −VHe, there is a considerable deviation from the dipole angular distribution, thus indicating the effect of electron correlation.