Colloquium: Mohammad Hassan - Attosecond Electron Imaging

Abstract:
In the last decades, the developments in attosecond (attosecond =10^-18second) physics enabled the real-time studies of electron dynamics in matter. Tracing the electron motion in its native time scale becomes crucial for the accurate clocking of microscopic phenomena. The attosecond physics field was based on the generation and exploiting the extreme-ultraviolet (XUV) attosecond pulses for probing the electron dynamics in atoms, molecule, and nanostructure (1). Attosecond spectroscopy provides insights of the atomic and electronic motion in real-time. However, the trajectory of this motion in spatial domain, as the time evolves, remains beyond the reach. Therefore, the ultrafast field called for a new technique to map the atomic and electron motion in both time and space domains. Recently, the development of Ultrafast Electron Microscopy (UEM) and Diffraction (UED) permitted the imaging of atomic motion in real time and space. The temporal resolution in ultrafast electron imaging measurements, typically on the order of a few hundred femtoseconds, is limited by the electron pulse duration and its synchronization with the optical trigger pulse. Ultrafast electron imaging has found a vast range of applications spans chemistry, physics, material science, and biology (3).
In this talk, I will discuss the synthesis of the world first optical attosecond pulses in the visible and nearby ranges and using this tool to control bound electron motion in atoms (2). In addition, I will introduce the ultrafast imaging techniques and how we break the temporal resolution limits in UEM by generating a 30-fs electron pulse exploiting the optical gating approach (4). The obtainingof this few tens femtosecond temporal resolution in UEM opens the door- for the first time- to image the electron dynamics in real time. Finally, I will explain the generation of single-isolated attosecond electron pulses by optical gating to establish the attosecond electron imaging tool which we so-called "Attomicroscopy". Attomicroscopy will enable the imaging of the electron motion, last few hundreds of attosecond to few femtoseconds, in action (5).