PHOTOLUMINESCENCE AND OPTICAL-ABSORPTION IN NEUTRON-IRRADIATED CRYSTALLINE QUARTZ

Optical absorption measurements in the 3.5-6.5 eV spectral range and p hotoluminescence spectra, excited in the 4-8 eV range have been perfor med on neutron irradiated synthetic crystalline quartz as a function o f temperature and of neutron fluence. The Gaussian deconvolution of th e radiation-induced absorption spectrum in the 4.5-6 eV region reveals a complex structure: five distinct components, peaking at 4.85, 5.06, 5.35, 5.62, and 5.96 eV are detected. The complexity of the absorptio n pattern finds a correspondence in photoluminescence spectra excited in the 5 eV region: a detailed analysis of the emission spectra as a f unction of excitation energy indicates the presence of three emission bands centered at 3.91, 4.23, and 4.46 eV, excited at 5.25, 4.83, and 5.03 eV respectively. Excitation in the 5.62 and 5.96 eV absorption pe aks does not produce emission. The features of the 4.23 eV and of the 4.46 eV bands are very similar to those of the alpha(intrinsic) emissi on, already well studied in amorphous SiO2: this suggests a possible c orrelation between these bands and the alpha(intrinsic) center. The 3. 98 eV band does not find a correspondence in amorphous SiO2, and so th e responsible defect appears specifically related to the crystalline s tructure. The emission spectra excited in the E absorption band (appro ximate to 7.6 eV) present a weak band centered at 4.83 eV: its depende nce on neutron irradiation dose suggests the attribution to an intrins ic center different from those responsible for the emission in the 3.8 - 4.5 eV region.