ENERGY LEVELS OF ER3+ IN LIYF4

A preliminary analysis of the absorption and fluorescence spectra of Er3+ (4f11) in LiYF4 has been made. With the aid of previous work on Er3+ in LaF3, various states have been identified. The Racah parameters giving the best overall agreement between the predicted 'free ion' spectrum and the spectrum of Er3+:LiYF 4 are identical with those for LaF3, that is E1 = 6747 cm-1, E2 = 31·63 cm-1, E 3 = 635·8 cm-1 and ζ = 2345 cm-1. An attempt has also been made to determine the nature of the crystal-field potential by considering the rare earth site as a tetragonally distorted cube. The most suitable crystal-field parameters were found to be B2 0 = -115 cm-1, B40 = -171 cm -1, B44 = -661 cm-1, B 60 = +25·5 cm-1 and B6 4 = -168 cm-1.