ESR studies of Ba(ClO4)2x3H2O and Ba(ClO4)2x3D2O single crystals #betta# irradiated at 77 K

The paramagnetic defect centers observed in Ba(ClO4)2x3H2O and Ba(ClO4)2x3D2O single crystals #betta# irradiated at 77 K are identified as ClO3 and ClO42-. ClO42- occurs at three chemically inequivalent conformations. Two of them are metastable and occur at three magnetically inequivalent sites each. The third one is relatively more stable and occurs at only one site with axial symmetry. It is found that the ESR spectra of these centers could be well understood in terms of the (ClO3-, O-) model proposed for these centers in KClO4 by Byberg. The temperature up to which the metastable configurations of these radicals are stable has increased to 135 K in the hydrated crystals and to 183 K in the deuterated crystals when compared to a value of 100 K in KClO4. The observation of the ClO3 indicates that the radiation damage mechanisms in this lattice are essentially different from those in KClO4. These observations are attributed to the effect of waters of hydration in the present lattice. The orientation and the proton superhyperfine interaction of the (ClO3-, O-) radicals has also been discussed