Electron and x-ray diffraction reveal the atomic structure of crystalline materials. Pulsed electrons or x-rays provide a snapshot of the crystal structure during the time window the pulses transmit through the sample. We employ femtosecond electron pulses at variable, defined time delay after the sample was excited with an ultrashort light pulse. This technique reveals structural dynamics of a material with femtosecond temporal and sub-atomic spatial resolution.
We developed a highly compact femtosecond electron diffractometer working at electron energies up to 100 keV, see Figure 1. The electron pulse propagation through the setup was simulated with a multi-body particle tracing code (GPT, Pulsar Physics) in order to estimate the electron pulse durations at the sample position (Figure 2). Our simulations show that electron bunches containing few thousands of electrons per bunch are only weakly broadened by space-charge effects and their pulse duration is thus close to the one of a single-electron wave packet. With our compact setup, we can create electron bunches containing up to 5000 electrons with a pulse duration below 100 fs on the sample.
- L. Waldecker, R. Bertoni, and R. Ernstorfer:
Compact femtosecond electron diffractometer with 100 keV electron bunches approaching the single-electron pulse duration limit.
J. Appl. Phys. 117, 044903 (2015) [doi:10.1063/1.4906786]
open access: arXiv:1412.1942
- R.J.D. Miller, R. Ernstorfer, M. Harb, M. Gao, C.T. Hebeisen, H. Jean-Ruel, C. Lu, G. Moriena, G. Sciaini:
Making the molecular movie: first frames.
Acta Cryst. A 66, 137-156 (2010), [doi: 10.1107/S0108767309053926].