We propose to study hydride ion diffusion in AEH2 (AE = Ca and Ba) using the QENS technique. We have recently demonstrated that the charge carrier in these materials are hydride ions (H-). A previous neutron study employing the new high temperature and conductivity sample environment jointly developed by ISIS and the University of St Andrews for use in ISIS diffractometers further strengthened the case (RB1410181), and QENS will supplement these studies with quantitive data on diffusion mechanistic steps. QENS has been used extensively to study the diffusion of ions in solids. More specifically, proton and hydride ion diffusion have been studied to elucidate diffusion (and conductivity) mechanistic steps such as average ionic jump distances and frequency as well as jump positions.