Infrared Absorption of Some Hexagonal Rare-Earth Chlorides

Abstract

The polarized absorption spectra of anhydrous SmCl₃, DyCl₃, HoCl₃, and ErCl₃ diluted with LaCl₃ were obtained at 2°K with high resolution between 3000 and 10 000 cm^—1. Approximate values for the f values of the transitions lie between 10^—9 and 10^—6. The selection and polarization rules indicate induced electric dipole transitions except for the transitions between the two lowest components of the ground multiplet which are partly due to magnetic‐dipole transitions. Weak infrared fluorescence was observed for DyCl₃. The results from the infrared measurements confirm and supplement data on the same energy levels obtained from fluorescence.