R. Boscaino et al., SPECTRAL AND KINETIC-PROPERTIES OF THE 4.4-EV PHOTOLUMINESCENCE BAND IN ALPHA-SIO2 - EFFECTS OF GAMMA-IRRADIATION, Physical review. B, Condensed matter, 54(9), 1996, pp. 6194-6199
Spectral and decay properties of the photoluminescence (PL) emission i
n the range 3.5-5.0 eV are investigated in various types of silica (a-
SiO2), as grown and after gamma irradiation. We report experimental re
sults on the ultraviolet (5.0 eV) absorption, on the emission and exci
tation spectra of the stationary FL, excited by ultraviolet (5.0 eV) a
nd vacuum ultraviolet (6.0-8.5 eV) light, on the decay times of the tr
ansient PL emission, at room temperature, and at 10 K. Our results sho
w that gamma irradiation causes the appearance of a PL band, centered
at 4.37 eV, which can be excited at 5.0 eV and at 6.8 eV. This band, w
hich is induced in all the investigated samples, brings a close simila
rity to the PL band alpha(1) that is peculiar of unirradiated oxygen-d
eficient natural silica. However, small but appreciable differences be
tween the two bands can be inferred from our experimental data. The re
sults are consistent with an energy level scheme with two singlet-sing
let transitions. We tentatively ascribe the small differences between
the two PL bands to different dynamic environments surrounding the int
rinsic and the gamma-induced centers.