Photoelectron Diffraction

Abstract

Scattering and diffraction of electrons and X-rays have been employed as a tool for determining structural properties of matter for many decades. In the realm of single molecules in the gas phase, the idea to use the photoelectric effect to emit an electron wave that illuminates the molecule from within emerged from pioneering theoretical work by Dehmer and Dill on molecular photoionization in the late 1970s. However, it was not until the early nineties that “Molecular-Frame Photoelectron Angular Distributions” (MFPADs) of gas-phase molecules became experimentally accessible. This chapter introduces the basic concepts of intra-molecular electron scattering, photoelectron diffraction, and photoelectron angular emission distributions. A short summary of experimental approaches used to study MFPADs is presented together with several examples that trace the development of the field, from its first results to recent time-resolved photoelectron diffraction studies with X-ray free-electron lasers.