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Abstract:
Similar to the optical diffraction of light passing through a material grating, the Kapitza-Dirac effectoccurs when an electron is diffracted by a standing light wave. In its original description, theeffect is time independent. Here, we extended the Kapitza-Dirac effect to the time domain. Bytracking the spatiotemporal evolution of a pulsed electron wave packet diffracted by a 60-femtosecond(where one femtosecond = 10−15 seconds) standing wave pulse in a pump-probe scheme, we observedtime-dependent diffraction patterns. The fringe spacing in the observed pattern differs from thatgenerated by the conventional Kapitza-Dirac effect. By exploiting this time-resolved diffraction scheme,we can access the time evolution of the phase properties of a free electron and potentially imageionic potentials and electronic decoherences
