Complementarity of ESR and optical absorption of gamma-irrradiated silicate glasses

Radiation defects in alkaline earth silicate glasses are studied by means o f ESR and optical spectroscopies. Previously undiscovered relations between findings of both methods are deduced using four different experimental too ls: (i) variation of chemical glass composition; (ii) isochronal annealing of gamma-irradiated samples; (iii) optical bleaching of gamma-irradiated sa mples; (iv) variation of the gamma-dose Oxygen hole centres are mainly resp onsible for the radiation induced absorption in the visible part of the opt ical spectrum. Previously undescribed electron centres with broad and asymm etric ESR resonances (g' = 1.955) contribute to the optical spectra (200-20 00 nm) in a small way. It is suggested they are electrons trapped on small aggregates of alkaline earth ions. The radiation induced recharging of inco rporated Fe3+ ions is also evidenced by optical and ESR spectroscopies Fe3 ions react as electron traps forming not only Fe2+ but also (Fe3+)- specie s which might be responsible for an absorption band at 300 nm. A correlatio n was found between the changes. of intensity with those of the ESR spectro scopically detected Fe3+ content of the samples.