Dynamics of water in confined space (porous alumina): QENS study

Dynamics of water contained in the pores of alumina gel as studied using a combination of the high and medium resolution quasi-elastic neutron scatter ing (QENS) technique at room temperature and extending to the supercooled r egion is reported. In the single particle picture of the dynamics of water molecules in confined geometry (Volino-Dianoux model), two types of water a re found to be present in the pores of alumina gel. Some water molecules ar e attached to the surfaces (localized) and others undergo diffusion within the otherwise available space in the pores. The localization radius and dif fusion constant (D-loc) characterizing the local dynamics and also the diff usion constant (D-t) and residence time (tau (0)) of the water molecules di ffusing inside the alumina gel pores are obtained at different temperatures . Water molecules are found to undergo restricted diffusion in the pores at higher temperatures, which approach the bulk-like behaviour in the superco oled region.