ESR Analysis of Brownian Motion in V2O5 Xerogels after Adsorption of Water

ESR spectra of V4+ in amorphous vanadium pentoxide appear to be drastically modified when water is adsorbed at the surface of the sample at a constant temperature. An anisotropic powder ESR signal is observed on the xerogel oxide. An isotropic spectrum appears when the sample is Kept under a controlled water pressure. A steady state is obtained after a few hours where an isotropic Brownian diffusion motion can be evinced.