Low-temperature evolution of the proton magnetic resonance line shape in β-phase palladium hydride

Measurements of the proton magnetic resonance absorption line shape in β-phase palladium hydride indicate that there is no short-range ordering associated with the order-disorder phase transition that occurs in the neighborhood of 50 K. However, measurements of the line shape in the range 10 30 K show a change from a Gaussian to a non-Gaussian profile. This effect is not related to the order-disorder phase transition. A possible explanation in terms of thermally assisted tunneling is proposed.