Hydrogen atoms in radiolysis of liquids, solids and ordered systems: Zeolites and mesoporous solids

Abstract

Hydrogen atoms are ubiquitous species in radiolysis of many liquid and solid systems. They serve a very important role in passivation of solid-state defects in silica-based devices and there is concern about the role of radiolytic generation of molecular hydrogen in radioactive waste storage. The authors have made extensive studies of H atoms in water, ice and amorphous silica using conventional and time-resolved magnetic resonance. H atoms are exquisite probes of reaction dynamics and phase structure in these systems. Furthermore, via the study of Chemically Induced Dynamic Electron Polarization (CIDEP), additional insights into the mechanisms of radiolytic generation of H atoms and their fate can be obtained. With this considerable experience they embarked on the study of H atoms in zeolites and mesoporous solids to address the following questions: (1) What is the source of H atoms--bound hydroxyls or confined water? (2) Do the H atom dynamics in the water-saturated powders exhibit kinetics and spin relaxation that is similar to that in bulk silica, liquid water or ice? (3) What are the formation and destruction pathways of H atoms? This could be important for understanding radiolysis in silica-water systems, e.g., nuclear waste