R. Boscaino et al., ESR AND PL CENTERS INDUCED BY GAMMA-RAYS IN SILICA, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 116(1-4), 1996, pp. 373-377
We have studied the point defects created by gamma irradiation in vari
ous types of commercial silica glasses, including both natural and syn
thetic samples, with different OH content, in the low dose regime (0.0
5-100 Mrad). We found that the growth rate of E' centers depends stron
gly on the silica type, ranging from 2 x 10(15) cm(-3) Mrad(-1) to 6 x
10(17) cm(-3) Mrad(-1). Samples of natural silica are rather suscepti
ble to gamma ray exposure, as E' concentration saturates (typically 5
x 10(17) cm(-3)) for doses as low as a few Mrads. For both synthetic a
nd natural samples, the radiation hardness is higher in wet than in dr
y silica. Moreover, we found a strict correlation between the concentr
ation of E' centers and the gamma-induced absorption band at 5.8 eV. F
inally, exposure to gamma rays generates in all the samples a photolum
inescence band at 4.4 eV, whose excitation spectrum has a maximum at 4
.95 eV. This band exhibits a sublinear growth kinetics in all the inve
stigated samples.