Ultrafast Electron Microscopy Analysis

Ultrafast Electron Microscopy has been demonstrated to be an effective table-top technique for imaging the temporally-evolving dynamics of matter with subparticle spatial resolution on the time scale of atomic motion. A stringent enhancement of the UEM temporal resolution is demanded for recording snapshots of the electron motion which will provide a real-time access to all microscopic motions outside the atomic core and radically change our insight into the workings of the microcosm. Here, we demonstrate an order of magnitude enhancement in the temporal resolution of UEM by generation ~ 30 fs electron pulse (200 KeV) by the optical-gating approach using a visible laser pulse with the strength for probing the matter dynamics. Moreover, the …show more content…
It can be explained as follows; the ultrafast electron pulses with a duration of couple hundreds of femtosecond are generated by the photoemission process by illuminating the photocathode inside the microscope by UV laser pulses. These electron pulses are accelerated inside the microscope and incident on the sample under study together with visible laser pulses. The photon-electron coupling between the optical pulses and the electron pulses takes place when the energy-momentum conservation condition is satisfied (27, 28). This inelastic interaction leads to gain/loss of photon quanta via electron packets, which can be resolved in the electron energy spectrum consisting of discrete peaks, spectrally separated by multiples of photon energy (nћω), on both sides of the zero loss peak (ZLP). The electron that gain or loss energy due to the coupling only exists in the presence of the optical laser pulse. In another word, the optical laser pulse acts as a temporal gating of these electrons and the time window of this gating is the optical pulse duration. These gated electrons can be filtered out providing a magnificent enhancement of the temporal resolution in electron microscopy. Another optical laser pulse can be utilized to trigger the ultrafast dynamics of matter which can be envisaged by gated-electrons in different modes i.e. diffraction, electron …show more content…
At the spatiotemporal overlapping between the two pulses, the coupling between the visible and electron pulses take place. The signature of the electron-photon coupling can be revealed by measuring the electron energy spectrum by the electron energy spectrometer in the microscope. The measured electron spectrum is shown in Fig. 2A. The red white part of the spectrum represents the ZLP while blue part shows the gated electron