From Event: SPIE Optical Engineering + Applications, 2016
Ultrafast electron diffraction (UED) is a powerful technique that can be used to resolve structural changes of gas molecules during a photochemical reaction. However, the temporal resolution in pump-probe experiments has been limited to the few-ps level by the space-charge effect that broadens the electron pulse duration and by velocity mismatch between the pump laser pulses and the probe electron pulses, making only long-lived intermediate states accessible. Taking advantage of relativistic effects, Mega-electron-volt (MeV) electrons can be used to suppress both the space-charge effect and the velocity mismatch, and hence to achieve a temporal resolution that is fast enough to follow coherent nuclear motion in the target molecules. In this presentation, we show the first MeV UED experiments on gas phase targets. These experiments not only demonstrate that femtosecond temporal resolution is achieved, but also show that the spatial resolution is not compromised. This unprecedented combination of spatiotemporal resolution is sufficient to image coherent nuclear motions, and opens the door to a new class of experiments where the structural changes can be followed simultaneously in both space and time.
Jie Yang, Markus Guehr, Theodore Vecchione, Matthew S. Robinson, Renkai Li, Nick Hartmann, Xiaozhe Shen, Martin Centurion, and Xijie Wang, "Relativistic ultrafast electron diffraction from molecules in the gas phase
(Conference Presentation)," Proc. SPIE 9956, Ultrafast Nonlinear Imaging and Spectroscopy IV, 995603 (Presented at SPIE Optical Engineering + Applications: August 28, 2016; Published: 2 November 2016); https://doi.org/10.1117/12.2238559.5170791510001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon