Imaging of molecules in the gas phase with ultrafast electron diffraction

A two-step algorithm is developed that can reconstruct the full 3-D molecular structure from diffraction patterns of partially aligned molecules in gas phase. This method is applicable to asymmetric-top molecules that do not need to have any specific symmetry. This method will be important for studying dynamical processes that involve transient structures where symmetries, if any, can possibly be broken. A new setup for the diffraction experiments that can provide enough time resolution as well as high currents suitable for gas phase experiments is reported. Time resolution is obtained by longitudinal compression of electron pulses by time-varying electric fields synchronized to the motion of electron pulses.