M. Leone et al., LOW-TEMPERATURE PHOTOLUMINESCENCE SPECTROSCOPY RELATIONSHIP BETWEEN 3.1 AND 4.2 EV BANDS IN VITREOUS SILICA, Journal of non-crystalline solids, 216, 1997, pp. 105-110
We report experimental results on the thermal behavior, in the tempera
ture range 350 to 10 K, of the two correlated photoluminescence bands
centered at 4.2 and 3.1 eV in a-SiO2. The spectral features and their
temperature dependence are compatible with a scheme of optical transit
ions from two excited electronic states, a singlet and a tripler, pert
aining to a single point defect and strictly connected via intersystem
crossing. The analysis of the interconversion process between the sin
glet and triplet stare, as a function of temperature, suggests the pre
sence of local environments (conformational substrates) surrounding th
e chromophore that are frozen at low temperature and reach thermal equ
ilibrium above T similar or equal to 120 K. (C) 1997 Elsevier Science
B.V.