Dynamic Jahn-Teller Effect in a Rare-Earth Compound: CeAl2

Abstract

Measurements of the neutron-energy-loss spectrum of Ce${\mathrm{Al}}_2$, made using a triple-axis spectrometer, reveal the existence of two inelastic lines in the paramagnetic regime. Only a single line (${\Gamma }_7\to {\Gamma }_8$) is expected from the cubic symmetry of the crystal field. The origin of the two lines is attributed to the removal of the degeneracy of the excited ${\Gamma }_8$ electronic state by the action of the dynamic Jahn-Teller effect.