The c-axis vibrations of hydrogen in yttrium have been measured at various concentrations and temperatures using high-resolution neutron spectroscopy. The unusual splitting of these modes is revealed to be highly sensitive to both conditions and to isotopic dilution. The results indicate that the splitting is caused by hydrogen pairs dynamically coupled across metal atoms and that this interaction is modulated by concentration- and temperature-dependent occupation correlations along the c axis.

• Received 17 August 1987

DOI:https://doi.org/10.1103/PhysRevB.37.4358