Prospects for Incoherent Diffractive Imaging at Compact X-ray Free-electron Lasers
Description
A time-dependent semiclassical formalism is developed for the theory of incoherentdiffractive imaging (IDI), an atomically-precise imaging technique based on the principles of
intensity interferometry. The technique is applied to image inner-shell X-ray fluorescence
from heavy atoms excited by the femtosecond pulses of an X-ray free-electron laser (XFEL).
Interference between emission from different atoms is expected when the XFEL pulse duration
is shorter than the fluorescence lifetime. Simulations for atoms at the vertices of a simple
icosahedral virus capsid are used to generate mock IDI diffraction patterns. These are then
used to reconstruct the geometry by phase retrieval of the intensity correlation function between
photons emitted independently from many different atoms at two different detector
pixels. The dependence of the intensity correlation function on fluorescence lifetime relative
to XFEL pulse duration is computed, and a simple expression for the visibility (or contrast)
of IDI speckle as well as an upper bound on the IDI signal-to-noise ratio are obtained as a
function of XFEL flux and lifetime. This indicates that compact XFELs, with reduced flux
but attosecond pulses, should be ideally suited to 3D, atomic-resolution mapping of heavy
atoms in materials science, chemistry, and biology. As IDI is a new technique, not much has
yet been written about it in the literature. The current theoretical and experimental results
are reviewed, including a discussion of signal-to-noise issues that have been raised regarding
the idea that IDI is suitable for structural biology.
Date Created
The date the item was original created (prior to any relationship with the ASU Digital Repositories.)
2022
Agent
- Author (aut): Shevchuk, Andrew Stewart Hegeman
- Thesis advisor (ths): Kirian, Richard A
- Committee member: Schmidt, Kevin E
- Committee member: Weierstall, Uwe
- Committee member: Graves, William S
- Publisher (pbl): Arizona State University