Mechanism of hydration induced gamma ray degradation in ion beam figured fused silica

We show that surface hydration significantly reduces the damage threshold of irradiated IBF samples, whereas non-hydrated counterparts remain stable. Degradation follows a coupled pathway where IBF induced deoxygenation creates reactive Si-rich surfaces that hydrate into Si-OH groups.

Gamma irradiation subsequently ruptures O-H bonds to generate non-bridging oxygen hole centers (NBOHCs), enhancing ultraviolet (UV) absorption. ReaxFF simulations validate this microscopic transition from Si-rich defects to hydrated structures. Our results reveal a mechanism involving deoxygenation, hydration, and defect formation, highlighting the critical role of surface hydration in the radiation stability of high-precision optics.