Search results for " 78.55.Qr"
showing 2 items of 2 documents
Luminescence and absorption spectroscopy of Sn-related impurity centers in silica
2006
We report an experimental study on the absorption and luminescence spectra of oxygen deficient point defects in Sn-doped silica. The absorption band at 4.9 eV (B2β band) and the two related photoluminescence bands at ∼4.2 eV (singlet-singlet emission, S1 → S0) and at ∼3.2 eV (triplet-singlet emission, T1 → S0), linked by a thermally activated T1 → S1 inter-system crossing process (ISC), are studied as a function of temperature from 300 to 20 K. This approach allows us to investigate the dynamics properties of the matrix in the surroundings of the point defects and the effects of local disorder on the two relaxation processes from S1: the radiative channel to S0 and the ISC process to T1. We…
Ultraviolet optical properties of silica controlled by hydrogen trapping at Ge-related defects
2007
We studied the effects induced by the ultraviolet-laser and -lamp exposure sequences on the twofold coordinated germanium (=Ge{sup {center_dot}}{sup {center_dot}}) and the H(II) center (=Ge{sup {center_dot}}-H) in silica. The H(II) centers, generated after the first laser irradiation stage by the trapping of atomic hydrogen H{sup 0} at the (=Ge{sup {center_dot}}{sup {center_dot}}), are destroyed by the subsequent lamp exposure with efficiency depending on photon energy. The H(II) photodestruction is activated from {approx}4 eV, and its cross section is here quantitatively measured, so giving the absorption profile of this center. Consistent with the observed correlated recovering of (=Ge{su…