Intermultiplet transitions in praseodymium using neutron spectroscopy.

Abstract

Intermultiplet transitions with energies up to 810 meV in praseodymium metal have been observed by neutron spectroscopy. Both dipolar ($^{3}H_{4}\ensuremath{\rightarrow}^{3}H_{5}$) and, for the first time, nondipolar, interterm ($^{3}H_{4}\ensuremath{\rightarrow}^{3}F_{2,3,4}$) transitions have been identified. The energies of the interterm transitions are significantly reduced by approximately 50 meV from their free-ion values. This gives direct evidence of conduction-electron screening of the (on-site) Coulomb interaction between $4f$ electrons in rare-earth metals.