The first direct in situ observations of the production and microsegregation of radiolytic interstitial oxygen resulting from electron beam irradiation of crystal and amorphous oxygen deficient SiO2 polymorphs has been made using cathodoluminescence (CL) microanalysis (spectroscopy and microscopy). Previously unreported near-infrared CL emission is observed at 0.968+/-0.003 eV from crystal alpha-SiO2 (quartz) and at 0.971+/-0.003 eV from amorphous a-SiO2 (fused quartz and silica glasses) at 290 K. The energy and width of the near-infrared CL emission from electron-irradiated alpha-SiO2 polymorphs is consistent with the O2 (1)Delta(g)-->(3)Sigma(-)(g) transition associated with molecular oxygen.

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Nanocrystalline BaFCl:Sm3+ is an efficient photoluminescent X-ray storage phosphor. To gain a better understanding of the storage mechanism, the photoluminescence and cathodoluminescence properties of nanocrystalline BaFCl:Sm3+ before and after X-irradiation were investigated. The results were compared with those obtained for microcrystalline BaFCl:Sm3+ prepared by high-temperature sintering. Significant differences in the local coordination environment of Sm3+ ions between the two samples were revealed by comparing the photoluminescence spectra at 2 and 293 K. From the cathodoluminescence microanalysis, it follows that the Sm3+ ions in the as-prepared nanocrystalline BaFCl:Sm3+ are mainly located on or close to the surface of the nanoparticles, whereas those in the microcrystalline sample are distributed homogeneously throughout the microcrystallites. For nanocrystalline BaFCl:Sm3+, the X-irradiation-induced reduction of Sm3+ to Sm2+ ions and the photoionization of Sm2+ to Sm3+ ions during photobleaching were investigated by monitoring the photoluminescence intensities of both Sm2+ and Sm3+ ions. The two processes can be modeled well assuming dispersive first-order kinetics, where the rate constant of the electron transfer is given by an exponential function of the distance between the shallow electron traps and the Sm3+ centers.

Porous layers fabricated by anodic etching of n-GaP substrates in a sulfuric acid solution were studied by electron microscopy and cathodoluminescence ͑CL͒ microanalysis. The morphology of porous layers was found to depend strongly upon the anodization conditions. When the etching process starts at the initial surface, ''catacomb-like'' pores and current-line oriented pores are introduced at low and high anodic current densities, respectively. After the initial development of either kind of pore, further anodization at the current density of about 1 mA/cm 2 favors the propagation of pores along ͗111͘ crystallographic directions. The spatial and spectral distribution of CL in bulk and porous samples is presented. A comparative analysis of the secondary electron and panchromatic CL images evidenced a porosity induced increase in the emission efficiency.

Point defects induced at the exit surface of optical-grade fused silica by high power (>30 J/cm2) 355 nm laser pulses have been investigated to elucidate the nature of laser damage in optics for use at high peak powers (>2 GW/cm2). Six defects have been identified. Eγ′ and E74′ defects were identified using electron spin resonance spectroscopy. The nonbridging oxygen hole center, a self-trapped exciton, an oxygen-deficient center, and interstitial O2 were identified and spatially resolved in the damage craters using cathodoluminescence microanalysis. The defects are associated with the laser generated shock waves and/or thermal explosion.