06/10/21

The development of high-brightness electron sources made it feasible to explore megaelectronvolt electrons for Ultrafast Electron diffraction and Microscopy (MeV-UED/UEM) [1]. MeV-UED has led to a new paradigm in ultrafast electron scattering: higher electron beam energy significantly reduces space-charge effects hence leads to atomic spatial-temporal resolutions [2-3]. Furthermore, MeV electrons experience less multiple-scattering, and possess “real” flat Ewald-sphere; MeV-UED is a platform for  total electron scattering.   MeV-UED had broad and transformative impact on ultrafast science, such as the first 2-D materials ultrafast structure dynamics [5], light-induced transient states [6,7], and the first direct imaging of fundamental chemical processes: canonical interception & ring-opening [8-9].  In this seminar, I will discuss the latest advancements of MeV-UED technology and science, such as the first operando experiment in ultrafast [10] and hydrogen bond dynamics of liquid water [11].   

1. X.J. Wang et al, Phys. Rev. E , 54, No.4, R3121 -3124 (1996).
2. X.J. Wang et al, Proceedings of the 2003 Particle Accelerator Conference, 2003, pp. 420-422 Vol.1, doi: 10.1109/PAC.2003.1288940.
3. P Zhu et al, New Journal of Physics 17 (6), 063004 (2014).
4. S. Weathersby et al, Rev. Sci. Instrum. 2015, 86, 073702−073707.
5. E. M. Mannebach et al, Nano Lett. 15, 6889 (2015) doi: 10.1021/acs.nanolett.5b02805.
6. Edbert J. Sie et al, Nature 565,61–66(2019).
7. A. Kogar et al, Nat. Phys.16, 159 (2019) doi: 10.1038/s41567-019-0705-3.
8. J. Yang et al, Science 361, 64 (2018) doi: 10.1126/science.aat0049.
9. T. J. A. Wolf et al, Nat. Chem. (2019) doi: 10.1038/s41557-019-0252-7.
10. J A. Sood et al, Science 373, 352 (2021) doi: 10.1126/science.abc0652.
11. J. Yang et al., Nature 596, 531–535 (2021). https://doi.org/10.1038/s41586-021-03793-9.

Wednesday 6th October 2021 (4 pm BST)