19F ENDOR measurements of transferred hyperfine interactions in CsCdF3:Gd3+and CsCaF3:Gd3+

Abstract

The transferred hyperfine interaction parameters have been measured at 4.2K by ENDOR for five shells of ¹⁹F neighbours around Gd³⁺ in CsCdF₃:Gd and CsCaF₃:Gd. The parameters for the octahedrally coordinated ligands are rather different from those previously determined from the transferred hyperfine structure of EPR spectra at 300K by Buzare and co-workers (1977). The authors' own EPR measurements show that the separations of the transferred hyperfine-structure lines are rather smaller than those predicted using the ENDOR data. They are only just consistent for CsCdF₃, and they are slightly outside the estimated uncertainty of the EPR data for CsCaF₃. There is no evidence of temperature dependence of the separation of the transferred hyperfine-structure lines in the EPR spectrum. Local distortions are deduced from ¹⁹F second-shell parameters and these distortions and the ligand-shell parameters are compared with those for octahedrally coordinated ¹⁹F ligands in CaF₂ and CdF₂.