Low frequency transition between vibronic levels of V9+2 in crystalline V2O5 from electron spin-lattice relaxation measurements

摘要

We have established the existence of a characteristic energy (0.0013 eV) in undoped crystalline V2O5, by measuring, between 1.3 K and 50 K, the relaxation time of the paramagnetic defect detected at g = 2. In order to interpret this result, we have examined the different models which have been proposed in the past for this defect, and which all imply the existence of a V9+2 molecular ion; taking the recent arguments of Clauws et al. into account, we have finally adopted the model proposed by Perlstein. The energy Δ cannot correspond to the splitting between the bonding and antibonding levels of V9+ 2, since a calculation indicates that the separation between these levels is 0.16 eV. In our interpretation, Δ is the energy separation between the ground vibronic level and the first excited vibronic level of V 9+2.