Spectra and Energy Levels of Er3+ in YCl3

Abstract

Yttrium chloride is monoclinic with C 2 point symmetry at the site of a Y3+ ion. The point symmetry is approximately octahedral. The absorption and fluorescence spectra of Er3+ in YCl3 are used to find the energy levels of Er3+. The Zeeman effect and the excitation of fluorescence are studied. Assuming a cubic field, the Stark splittings of the Z and Y groups are used to obtain the crystalline field parameters: A 4 〈r 4 〉=175. cm −1 , A 6 〈r 6 〉=10.4 cm −1 . The cubic field gives approximate agreement with the experimental data and explains the clustering of Stark components which is characteristic of rare‐earth ions in YCl3. The total Stark splitting of the free ion levels of a rare‐earth ion is larger in YCl3 than in LaCl3. The centers of gravity of the excited levels of Er3+ are higher in LaCl3 than in YCl3, and this shift increases with increasing wavenumber.