Optical, EPR, and ENDOR Studies of CdF2:V3+, V2+

Single crystals of CdF₂ containing either V³⁺ or V²⁺ ions have been prepared and studied by optical, EPR, and ENDOR techniques. As expected, the properties of V³⁺ in the eight‐coordinated (cubal) environment closely resemble those of Ni²⁺ in octahedral sites. The ENDOR data show that $M_s\text{\hspace{0.17em}=\hspace{0.17em}±\hspace{0.17em}1}$ , confirming the identification of the ion as V³⁺. The V²⁺ ions, produced by heating samples containing V³⁺ in Cd vapor, exhibit evidence for a large trigonal Jahn–Teller distortion of the cubal site. On the basis of the EPR and optical data it is suggested that the environment about the V²⁺ ions may be more nearly octahedral than cubal, thus reflecting the presence of a static trigonal field comparable in magnitude to the (undistorted) cubic field. Some optical and EPR data are presented for isoelectronic Cr³⁺ ions, which also display a strong Jahn–Teller effect.