Timing analysis of two-electron photoemission

Abstract: We predict a significant delay of two-electron photoemission from the helium atom after absorption of an attosecond XUV pulse. We establish this delay by solving the time dependent Schr\"odinger equation and by subsequent tracing the field-free evolution of the two-electron wave packet. This delay can also be related to the energy derivative of the phase of the complex double photoionization (DPI) amplitude which we evaluate by the convergent close-coupling method. Our observations prompt future attosecond streaking experiments on DPI of He which can elucidate various mechanisms of this strongly correlated ionization process.