RARE-EARTH ION TRANSITIONS IN THE INFRARED

Abstract

“Absorption bands for certain rare-earth ions in solid state solution have been found in the infrared region in the vicinity of $2000-5000 cm^{-1}$. These have been interpreted as electronic transitions arising from crystal field splitting of the ground state. For Ce(III) the absorption (${F}_{\eta 2}\leftarrow {F}_{5/2}$) occurs as a doublet at 2155 and $2250 cm^{-1}$, which is apparently quenched by traces of transition metal ions. The splitting varies with the number of interstitial fluoride ions, as shown by addition of NaF and by x-ray density measurements.”