title: Signal-to-noise in femtosecond electron diffraction.
abstract: Pump-probe electron diffraction can directly record atomic-scale motion within molecules or materials. However, the available current in femtosecond experiments is limited, making it challenging to reach the sensitivity required for detecting the fastest structural dynamics, which are encoded in time-dependent diffraction intensities. Here we present a unified analysis of signal-to-noise for an ultrafast electron diffraction apparatus. We characterize the noise of realistic ultrafast electron sources and detectors, test the performance on crystalline and polycrystalline samples and discuss practical approaches for improving measurement sensitivity. The analysis is found sufficient to predict the achievable signal-to-noise ratio in pump-probe electron diffraction before actually starting an investigation.
authors.affiliation: Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748 Garching, Germany; Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.
authors.forename: Catherine
authors.initials: C
authors.lastname: Kealhofer
authors.affiliation: Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748 Garching, Germany; Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Lahme
authors.affiliation: Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748 Garching, Germany; Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.
authors.forename: Theresa
authors.initials: T
authors.lastname: Urban
authors.affiliation: Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748 Garching, Germany; Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany. Electronic address: peter.baum@lmu.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Baum
keywords: 4D microscopy; Electron pulses; Femtosecond crystallography; Pump-probe techniques; Ultrafast electron diffraction