EPR spectra of irradiated Na2Cr2O7 . 2 H2O crystals

The EPR spectra of X-irradiated Na2Cr2O7 . 2 H2O crystals grown from the aqueous solution at room temperature are studied. Three groups of lines are detected, which marked conventionally as C1, C2 and C3. Each of the C1 and C2 line groups is a superposition of two doublets. The lines are interpreted as due to the Cr5+ ions in the distorted (stretched) oxygenous tetrahedron. The doublet structure is due to hyperfine interaction with nuclei of 1/2 spin which are protons of water. It is shown that the C1 and C2 line groups are due to the centers of the same type with different orientations in the lattice. The principal g-tensor values for these centres were as follows: gsub(z) = 1.916, gsub(y) = 1.978, gsub(x) = 1.986. (author)