Spectroscopic mesopore size characterization and diffusion measurement in closed porosity by xenon NMR

Nuclear magnetic resonance measurements of Xe-129 chemical shifts in a larg e variety of nonionic calibrated microporous and mesoporous silica glasses with open porosity provide a calibration of spectroscopic mesopore size mea surements. The pore size dependence of the xenon chemical shift is quantita tively interpreted,by considering both fast exchange and van der Waals inte ractions at the surface, which cause chemical shifts. The temperature depen dence of the chemical shift supports the proposed model and characterizes t he enthalpy of adsorption at the pore surface. The xenon NMR measurement is also useful for very low or even quasi-closed porous systems and may provi de assessment of the macroscopic xenon diffusion coefficient in xerogels.