Deciphering the hydrogen shuttle-mediated kinetic memory of Ge-related defects in UV-grade fused quartz via in situ EPR with 3D imaging.

This study elucidates the photo-induced defect dynamics in standard UV-grade fused quartz (JGS2) by synergizing in situ electron paramagnetic resonance (EPR) spectroscopy with 3D volumetric imaging. We identify a hydrogen shuttle mechanism driving the interconversion between Ge-E' and Ge-E'H centers, which triggers a significant kinetic memory effect dramatically increasing the generation rate of Ge-E' by 20-fold in subsequent UV cycles. 3D EPR imaging, effectively mapping the internal defect distribution, demonstrates that defect activation is precisely confined to the UV-illuminated volumes. Long-term tracking confirms that while Ge-E' is unstable, Ge-E'H remains highly persistent for several months. A potential energy landscape is proposed to unify these spatiotemporal observations, providing a robust thermodynamic framework for evaluating the radiation resilience and long-term stability of high-purity silica in advanced optical applications.