Coherent Low-Energy Electron Diffraction Microscopy
is a project aiming at obtaining atomic resolution structural information from oversampled low energy electron diffraction patterns. The principle of object reconstruction by oversampling has already been demonstrated experimentally using x-rays and high-energy electrons with the disadvantage that a number as high as one million molecules are needed in these methods, leadings to an averaged information about the structure.
Low energy electrons do not appear to damage individual biological molecules, in contrast to the methods mentioned above. Therefore, oversampled diffraction patterns of single biomolecules can be recorded. The iteratively recovered object wave will provide the information needed for calculating the three dimensional structure of the molecule.
The main challenge of the project is to find a method to produce a micro electrostatic lens. It will collimate the divergent electrons beam, from a tungsten tip, to a parallel beam, needed to record the diffraction pattern. Because the aberrations of a lens are scaled with its size, we aim great effort to produce electrostatic lens with a size of around 1 micron diameter and therefore reduce dramatically the aberrations.
Contacts: Elvira Steinwand and Jean-Nicolas Longchamp
The work is supported by the Swiss National Science Foundation and carried out in collaboration with John Miao from the University of California at Los Angeles