Search results for "Solid"

Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time…

2008

The article describes an experimental method that allows to estimate the inhomogeneous and homogeneous linewidths of the photoluminescence band of a point defect in an amorphous solid. We performed low temperature time-resolved luminescence measurements on two defects chosen as model systems for our analysis: extrinsic Oxygen Deficient Centers (ODC(II)) in amorphous silica and F+ 3 centers in crystalline Lithium Fluoride. Measurements evidence that only defects embedded in the amorphous matrix feature a dependence of the radiative decay lifetime on the emission energy and a time dependence of the first moment of the emission band. A theoretical model is developed to link these properties to…

Inhomogeneous width of oxygen-deficient centers induced by electron irradiation of silica

2009

We report a study of the luminescence activity of oxygen-deficient centers stabilized in as-grown synthetic silica, as compared with the same defects induced by $\ensuremath{\beta}$ irradiation at increasing doses, ranging from $1.2\ifmmode\times\else\texttimes\fi{}{10}^{3}$ to $5\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{kGy}$. We experimentally observe a progressive broadening of the luminescence band with increasing total electron dose released on samples. By analyzing our data within a theoretical model capable of separating homogeneous and inhomogeneous contribution to the total luminescence linewidth, we observe that the increasing of the width is entirely ascribable to t…

Photoluminescence and diffusion properties of O2 molecules in amorphous SiO2 nanoparticles

2013

An experimental study by Raman and Photoluminescence (PL) spectroscopies on the emission and diffusion properties of O2 molecules in amorphous SiO2 nanoparticles of commercial origin with diameters from 14 to 40 nm is reported. Stationary and time resolved PL measurements have been carried out to characterize the Near Infrared (NIR) emission at 1272 nm of O2. Emission features similar to those of bulk silica systems with a sharp PL band and excitation channels in the NIR, at 1070 nm, and in the visible, at 765 and 690 nm are found, with peculiarities arising from embedding O2 in nanostructures. The study of the NIR PL lifetime as a function of temperature down to 10 K enabled to reveal the …

Twofold coordinated Ge defects induced by gamma-ray irradiation in Ge-doped SiO2

2008

We report an experimental study by photoluminescence, optical absorption and Electron Paramagnetic Resonance measurements on the effects of exposure of Ge-doped amorphous SiO2 to gamma ray radiation at room temperature. We have evidenced that irradiation at doses of the order of 1 MGy is able to generate Ge-related defects, recognizable from their optical properties as twofold coordinated Ge centers. Until now, such centers, responsible for photosensitivity of Ge-doped SiO2, have been induced only in synthesis procedures of materials. The found result evidences a role played by gamma radiation in generating photosensitive defects and could furnish a novel basis for photosensitive pattern wr…

Growth and optical properties of transition metal oxides single crystal solid solutions

2007

Abstract NiO, CoO, MnO single crystals and single crystal solid solutions of Ni c Mg 1− c O, Co c Mg 1− c O and Mn c Mg 1− c O were grown by the method of chemical transport reaction (the “sandwich” technique). The nature of the observed absorption and luminescence bands is explained in terms of the electronic transition of bivalent nickel, cobalt and manganese. The fine structure of the observed bands in NiO and MnO are connected to the pure exciton transition and to the exciton-magnon excitation.

Different natures of surface electronic transitions of carbon nanoparticles

2017

The photoluminescence behaviour of carbon-based nanodots is still debated. Both core and surface structures are involved in the emission mechanism, and the electronic transitions can be modified by external agents such as metal ions or pH, but the general relation between the structure and the optical function is poorly understood. Here, we report a comparative study on the effects of these variables, changing the core structure from crystalline to amorphous, and modifying the surface structure by different passivation procedures. Our results highlight that the emission mechanism of the tunable visible fluorescence is identical for crystalline and amorphous samples, indicating the independe…

Recombination luminescence of oxygen-deficient centers in silica

2008

Abstract The luminescence of silica glass, prepared by plasma chemical vapor deposition (PCVD) and quartz glass of type IV (trade mark KS-4V) methods, were studied while irradiated with pulses of ArF laser (193 nm) light in the range of sample temperatures between 10 and 300 K. The samples contain less than 0.1 ppm metallic and hydroxyl impurities. The samples synthesized by PCVD were of two kinds. The first one (amorphous) was as-deposited from plasma at a substrate tube temperature of ∼1200 °C. The second one (fused) was prepared from the first by the tube collapsing with an external burner. In this process, a section of the substrate tube with the deposited glass was installed in a lathe…

Note on the Unit Solid Angle

1964

Charge reconstruction in large-area photomultipliers

2018

Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single PMT in a few tens/hundreds of nanoseconds, resulting in several photoelectrons (PEs) to pile-up at the PMT anode. In such scenario, the signal generated by each PE is entangled to the others, and an accurate PMT charge reconstruction becomes challenging. This manuscript describes an experimental method able to address the PMT charge reconstruction …

Photon reconstruction in the ATLAS Inner Detector and Liquid Argon Barrel Calorimeter at the 2004 Combined Test Beam

2011

The reconstruction of photons in the ATLAS detector is studied with data taken during the 2004 Combined Test Beam, where a full slice of the ATLAS detector was exposed to beams of particles of known energy at the CERN SPS. The results presented show significant differences in the longitudinal development of the electromagnetic shower between converted and unconverted photons as well as in the total measured energy. The potential to use the reconstructed converted photons as a means to precisely map the material of the tracker in front of the electromagnetic calorimeter is also considered. All results obtained are compared with a detailed Monte-Carlo simulation of the test-beam setup which i…