Low frequency Raman spectrum of ZrSi04:V(4+): An impurity-induced dynamical distortion.

We report the Raman scattering spectrum of vanadium-doped zircon in the spectral region 0--200 cm(-1). At low temperatures we observe three lines associated with V(4+) ion, one of which we interpret in terms of tunneling between two equivalent equilibrium positions for the ion. These positions correspond to a B2 distortion of the crystal, induced by the presence of the V (4+) ion.