EPR spectrum of the oxygen vacancy in single crystals V2O5

A new EPR spectrum of V2O5 is reported which is related to the non-stoichiometry of the crystals. Its intensity increases on reduction and decreases on reoxidation. The spectrum is labelled E1. E1 can be described by an S = 1 spin Hamiltonian with parameters gsub(x) = 1.33, gsub(y) = 2.51, gsub(z) = 1.01 (y||b, x and z at angles of 250 to c and a), and D = 200 x 10-20 erg, E = -40 x 10-20 erg. E1 and the near-infrared spectrum F1 (absorption bands at 1.25 and 1.52 eV with E||a) are assigned to the two donor electrons from the oxygen vacancy in V2O5. The electrons are localized on nearest vanadium neighbours of the vacancy. (author)