title: Ultrafast electron diffraction using an ultracold source.
abstract: The study of structural dynamics of complex macromolecular crystals using electrons requires bunches of sufficient coherence and charge. We present diffraction patterns from graphite, obtained with bunches from an ultracold electron source, based on femtosecond near-threshold photoionization of a laser-cooled atomic gas. By varying the photoionization wavelength, we change the effective source temperature from 300 K to 10 K, resulting in a concomitant change in the width of the diffraction peaks, which is consistent with independently measured source parameters. This constitutes a direct measurement of the beam coherence of this ultracold source and confirms its suitability for protein crystal diffraction.
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: M W
authors.initials: MW
authors.lastname: van Mourik
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: W J
authors.initials: WJ
authors.lastname: Engelen
authors.forename: E J D
authors.initials: EJ
authors.lastname: Vredenbregt
authors.forename: O J
authors.initials: OJ
authors.lastname: Luiten