Speaker: Peter Abbamonte, University of Illinois
Program Description
The attosecond regime is widely regarded as the frontier of ultrafast science. Driven by recent advancements in attosecond lasers based on high harmonic generation, the new field of 'attoscience' is revealing, for the first time, the microscopic dynamics of many-electron systems in real time.
In this talk I will describe an alternative approach to attoscience that is based on inelastic x-ray scattering (IXS). For many years x-rays have been used to obtain atomic-level density maps, for example of protein structures, by providing diffraction patterns that may be inverted by solving the "phase problem." I will argue that there is an analogous inverse problem for IXS that, when solved, yields the density "propagator," which quantifies how a system responds to an idealized, point disturbance, in effect providing angstrom level spatial imaging with attosecond time resolution. I will describe our first, crude applications of this approach to study plasmon excitations in liquid water,[1] image the birth of a exciton in an insulator,[2] and to measure the effective fine structure constant of graphene.[3] I will close by arguing that the *proper* approach is to do IXS with a standing wave x-ray source, which allows true, crystallographic refinement of the collective excitations of a system.[4]
[1] P. Abbamonte, et al., PRL 92, 237401 (2004) [2] P. Abbamonte, et al., PNAS 105, 12159 (2008) [3] J. P. Reed, et al., Science 330, 805 (2010) [4] Y. Gan, et al., arXiv:1205.5915
