EPR spectra of a molybdenum-related structure defect have been observe
d at a temperature of 20 K in CdWO4 scintillator crystal, being as-gro
wn ''blue-coloured''. Mo-95 and Mo-97 isotope superhyperfine (shf) spl
ittings have been resolved. Further splittings in EPR spectra have bee
n interpreted as arising from shf interactions with W nuclea. In the p
resent model of the defect, the unpaired spin is localised in the Cd-s
ite position and molybdenum replaces one of the neighbouring W atoms.
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