Imaging Polyatomic Molecules in Three Dimensions Using Molecular Frame Photoelectron Angular Distributions

Abstract

We demonstrate a method for determining the full three-dimensional molecular frame photoelectron angular distribution in polyatomic molecules using methane as a prototype. Simultaneous double Auger decay and subsequent dissociation allow measurement of the initial momentum vectors of the ionic fragments and the photoelectron in coincidence, allowing full orientation by observing a three-ion decay pathway, [H$^+$, H$^+$, CH$_2^+$]. Prompt dissociation in the two-ion decay pathway, [H$^+$, H$^+$, CH$_2$], also allows for full three-dimensional orientation of the molecule. We find the striking result that at low photoelectron energies the molecule is effectively imaged by the focusing of photoelectrons along bond directions. Furthermore, we observe a dynamic breakdown of axial recoil behavior in one of the dissociation pathways of the intermediate dication, which we interpret using electronic structure calculations.