Abstract: Going higher electron beam energy had been one of the major factors to improve electron microscope performance since the invention of electron microscope in 1930s. The ​‘holy grail’ of electron microscope – 1 Å resolution was first demonstrated in 1990s with a 1.2 megaelectronvolt electron microscope. The success of aberration-correction electron optics led to the demise of MV electron microscope.

To meet the challenge of higher time resolution, there is renewed interest in going higher electron beam energy. The megaelectronvolt ultrafast electron diffraction (MeV-UED) is the first step of the renaissance of MeV electron scattering. MeV-UED opened a new paradigm in ultrafast electron scattering - significant reduction in space-charge effects leads to atomic spatial-temporal resolution. MeV-UED had broad and transformative impact to energy science, such as the first 2-D materials ultrafast structure dynamics, light-induced transient states, and the first direct imaging of fundamental chemical processes: canonical interception & ring-opening. In this colloquium, I will first discuss the latest advance of MeV-UED technology and science, such as liquid phase and the first operando experiments. I will speculate next phase of the MeV electron scattering renaissance.

Bio: Xijie Wang is a distinguished scientist at SLAC National Accelerator Laboratory. Dr. Wang graduated from Shaanxi Normal University, Xian China and obtained his PhD from UCLA.