<br/>Direct visualization of dynamic processes in materials with high spatiotemporal resolution is essential for understanding fundamental phenomena with underlying mechanisms. In principle, most of the dynamic processes are irreversible in nature. Compared to ultrafast spectroscopy and diffraction techniques, 4D electron microscopy is capable of imaging dynamics in both space and time with the highest temporal resolution down to femtosecond. This technique has two modes, stroboscopic mode for reversible processes while single-pulse mode for irreversible ones. In this talk, I will present our recent results on the phase reaction dynamics in Au-GaAs materials [Fig. 1, left] and then the motion behavior of nanoparticles in liquid environment [Fig. 1, right] using single-pulse mode of 4D electron microscopy. The involved processes were initiated with a single optical pulse, while a single electron pulse was used to image the irreversible structural evolution on the nanosecond time scale. To characterize these structural changes, images were recorded in three time domains: before, during and after the process ended. From the observed results, the mechanisms that account for the phase reaction and motion (rotation and translation) dynamics of nanostructures will be elucidated. Successful applications of single-pulse imaging to irreversible systems open new venues for studying a wide variety of nanoscale dynamic processes in chemistry, physics, materials and biology.

Irreversible dynamics imaged in space and time

256th National Meeting (2018)

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