Quadrupolar relaxation of hyperpolarized krypton-83 as a probe for surfaces

This work reports the first systematic study of relaxation experienced by the hyperpolarized (hp) noble gas isotope (83)Kr (I=9/2) in contact with surfaces. The spin-lattice relaxation of (83)Kr is found to depend strongly on the chemical composition of the surfaces in the vicinity of the gas. This effect is caused by quadrupolar interactions during brief periods of surface adsorption that are the dominating source of longitudinal spin relaxation in the (83)Kr atoms. Simple model systems of closest packed glass beads with uniform but variable bead sizes are used for the relaxation measurements. The observed relaxation rates depend strongly on the chemical treatment of the glass surfaces and on the surface to volume ratio. Hp (83)Kr NMR relaxation measurements of porous polymers with pore sizes of 70-250 microm demonstrate the potential use of this new technique for material sciences applications.