ESR studies of defect centers trapped in irradiated calcium chlorate single crystals

Paramagnectic centers trapped in X- or γ-irradiated calcium chlorate dihydrate, Ca(ClO3)(2·2H2O, single crystals have been studied using electron spin resonance methods. The paramagnetic defects produced in this crystal at room temperature are ClO2(I), ClO2(II), Cl2-, O3-. The ClO2 centers are trapped at four magnetically inequivalent sites forming two pairs, viz., ClO2(I) and ClO2(II). The hyperfine parameters for ClO2(I) are slightly different from those of ClO2(II). This difference is attributed to the possible chemical inequivalent of the parent chlorate groups in the lattice. Such chemical inequivalency in this system has been predicted from nuclear quadrupole resonance (NQR) studies. When the irradiated crystal is exposed to 366 nm light from a 100-W mercury discharge lamp, thes ClO2 centers are fully bleached out, giving rise to a Cl2- center. This Cl2- (vk) center is stable at room temperature an dis located at two magnetically inequivalent sites. Both ClO2 and Cl2- centers have revealed "superhyperfine interaction" with one of the protons of water of crystallization. O3- amd O- are two other species identified at room temperature. © 1974.