Use of attosecond electron pulses to image electronic motion in atoms and molecules

We investigate theoretically the direct imaging of coherent electronic motion in atoms and molecules using attosecond electron pulses. The theories of time-resolved ultrafast electron diffraction and (e, 2e) momentum spectroscopy as well as the requisite conditions for carrying out time-resolved measurements to obtain time-dependent images are discussed. Results of simulations showing images of the motions of coherent superposition states in both the hydrogen atom and the hydrogen molecular ion are shown, thus indicating the capability of ultrafast electron pulses to investigate time-dependent electron dynamics.