Coherent Electron Source for Ultrafast Electron Diffraction and Imaging

We numerically investigate the suitability of photoexcited nanotips as a source of coherent femtosecond single electron pulses for ultrafast surface-sensitive electron diffraction and non-destructive imaging with low-energy electrons. The experimental parameters for realizing hundred femtosecond time resolution are identified by evaluating the effects of vacuum dispersion and beam divergence on the temporal broadening of the electron wave packet during its propagation to the sample