Jahn–Teller Distortion: Magnetic Studies of Vanadium Tetrachloride

Paramagnetic resonance of polycrystalline VCl₄ diluted with TiCl₄ has been observed near 9,24, and 36 GHz below 9°K. Both $g$ values and hyperfine $A$ tensors are axially symmetric and temperature independent with the same principal axes: $g_{\Vert }{\text{\hspace{0.17em}=\hspace{0.17em}1.920, g}}_{\perp }{\text{\hspace{0.17em}=\hspace{0.17em}1.899, | A}}_{\Vert }\text{|\hspace{0.17em}=\hspace{0.17em}72}\mathrm{G}{\mathrm{,\; |\; A}}_{\perp }\text{|\hspace{0.17em}=\hspace{0.17em}120}\mathrm{G}$ . The average $g$ value obtained from susceptibility data is in agreement with the resonance value. The paramagnetic relaxation time $T_1$ varies with temperature as shown by the relation $T_1{\text{\hspace{0.17em}=\hspace{0.17em}2\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−\hspace{0.17em}9}}\exp \text{(25/T)}\sec ,$ indicating the presence of a potential barrier approximately 18 cm^− 1 in height. The results indicate a static Jahn–Teller distortion, but with large zero‐point vibrations. This situation is in between Ballhausen–de Heer's ligand field and Ball‐hausen–Liehr's crystal‐field calculations.