HIGH-ENERGY NEUTRON SPECTROSCOPY OF RARE-EARTHS

With spallation neutron sources it is now feasible to observe intermultiplet transitions in the rare-earth metals of energies up to about 1 eV. As well as measuring the dipolar J &rarr J + 1 transition in metallic praseodymium and neodymium, we have also identified several non-dipolar, inter-term transitions in Pr. The energies of the inter-term transitions are significantly reduced by approximately 50 meV from their free-ion values. This is ascribed to an increase in the conduction-electron screening of the on-site Coulomb interaction between 4f electrons in rare-earth metals.