E.S.R. of X-iradiated Na2SO4 doped with NaClO4

The E.S.R. spectra of X-irradiated Na2SO4 crystals doped with NcClO4 are studied at X-band using a Varian E-4 spectrometer. A stable paramagnetic radical, ClO42-, is found to be trapped at two magnetically inequivalent sites in the crystal. A very weak hyperfine coupling with two equivalent sodium nuclei is observed at 77 K. The principal g and A-values are presented for this radical along with those of other radicals, SO4- and O3- trapped in the crystal. Thermal bleaching of the crystal has revealed that ClO42- gets bleached with the formation of two additional SO4- centres with different direction cosines. All the paramagnetic centres are completely bleached at 2000C. The ground state of ClO42- is deduced to be 2A1 and this agrees with the deduction from CNDO calculations. (author)