Mapping electron beam-induced radiolytic damage in molecular crystals

TL;DR

This study uses advanced electron diffraction techniques to map how molecular crystals undergo radiolytic damage during electron exposure, revealing complex internal structural changes and damage propagation mechanisms.

Contribution

It provides the first detailed spatial and temporal mapping of radiolytic damage progression in molecular crystals at ambient temperature.

Findings

CDZs undergo spatial reorientation during irradiation

Bragg reflection intensities fade nonmonotonically

Damage propagates concentrically beyond initial impact

Abstract

Every electron crystallography experiment is fundamentally limited by radiation damage. Nevertheless, little is known about the onset and progression of radiolysis in beam-sensitive molecular crystals. Here we apply ambient-temperature scanning nanobeam electron diffraction to record simultaneous dual-space snapshots of organic and organometallic nanocrystals at sequential stages of beam-induced radiolytic decay. We show that the underlying mosaic of coherently diffracting zones (CDZs) continuously undergoes spatial reorientation as a function of accumulating electron exposure, causing the intensities of many Bragg reflections to fade nonmonotonically. Furthermore, we demonstrate that repeated irradiation at a single probe position leads to the concentric propagation of delocalized radiolytic damage well beyond the initial point of impact. These results sharpen our understanding of molecular crystals as conglomerates of CDZs whose complex lattice structure deteriorates through a series of dynamic internal changes during exposure to ionizing radiation.