Dynamics of hydroxyl deuterons and bonded water molecules in NaDY(0.8) zeolite as studied by means of deuteron NMR spectroscopy and relaxation

Deuteron spin–lattice relaxation and spectra were measured for NaDY (0.8) zeolite containing some heavy water. Two subsystems of deuterons with different mobility were disclosed at low temperatures with their respective relaxation rates differing by two orders of magnitude. Spectra exhibit different shapes related directly to a specific motional model. Hydroxyl deuterons perform incoherent tunneling along the hydrogen bond, then on increasing temperature jumps to excited states and over the barrier appear. Hydrogen bonded water molecules perform 180° rotational jumps about the twofold symmetry axis. Spectral amplitudes are consistent with the water content of 13 D₂O molecules per unit cell. Above about 240 K translational mobility becomes significant and finally water molecules diffuse across the free space of cages. Diversity in temperature dependence of hydroxyl deuteron dynamics may indicate location of adsorbed molecules.