QUANTUM DIFFUSION OF HYDROGEN

A brief overview is given on low temperature diffusive behaviour of H in Nb(OH)(x), measurement of diffusion, primarily by neutron scatterin g. We go in some derail into recent work on calculations of neutron st ructure factor as well as the diffusion coefficient of hydrogen, influ enced by two-level excitations. Both the Electronic and phononic contr ibutions are covered. The importance of similar two-level excitations in insulating and metallic glasses is also pointed out.