NMR AND VORTEX LATTICE MELTING IN YBA2CU3O7

We report Y-89 and O-17 NMR (9 T) echo decays for YBa2Cu3O7 and correc t for contributions from dipolar coupling Cu-63,Cu-65 in, order to iso late effects of vortex dynamics. We confirm vortex localization in the solid state with rms displacements consistent with Langevin dynamical theory, but with motional dynamics at time scales (10-100 mu s) some similar to 10(6) times slower than predicted. Vortex migration over lo nger time scales is restricted to distances less than 1/100 of an inte rvortex spacing over times as long as 100 ms, in contrast with the rap id long range diffusion occurring in the liquid state.