Search results for "luminescence."
showing 10 items of 1568 documents
Chromium(iii)-based potential molecular quantum bits with long coherence times
2019
Molecular quantum bits based on copper(ii) or vanadium(iv) have been shown to possess long coherence times on multiple occasions. In contrast, studies in which non-spin-½ ions are employed are relatively scarce. High-spin ions provide additional states that can be used to encode further quantum bits. Furthermore, an optical rather than a microwave readout of molecular quantum bits is highly desirable, because in principle it could allow addressing at the single quantum bit level. The chromium(iii) complex [Cr(ddpd)2]3+ (ddpd = N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine) combines both the large spin (S = 3/2) and optical activity (strong, long lived luminescence). Here we demons…
Differences between photoluminescence spectra of type-I and type-II quantum dots
2008
Semiconductor quantum dots which trap simultaneously electrons and holes are called quantum dots of type-I. Contrary to these structures, empty dots of type-II attract only one type of charged carriers and repel the other. Particularities of confining potential are unaccessible by any direct measurements, thus recognition of quantum dot type by indirect method is highly desired. Our proposal is to distinguish between the two types of quantum dots via a comparison of photoluminescence spectra of these structures, which differ in both cases qualitatively.
Exciton hopping inInxGa1−xNmultiple quantum wells
2005
The dynamics of photoexcited excitons in thin $\mathrm{In}\mathrm{Ga}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ multiple quantum wells (QW's) with different In contents was studied by comparing the experimental data obtained by photoluminescence (PL), PL excitation, and photoreflectance spectroscopy techniques with the results of Monte Carlo simulations of exciton hopping. The temperature dependence of the PL linewidth was demonstrated to be in a fair agreement with the model of phonon-assisted exciton in-plane hopping within In-rich regions with inhomogeneous broadening taken into account. The band potential fluctuations, which scale the dispersion of localized states the excitons are hopping over,…
Anomalous behavior of LiF:Mg,Cu,P (TLD100H) irradiated with electron beams
2006
Abstract Thermoluminescent dosimeters of LiF:Mg,Cu,P (TLD100H) were exposed to 60Co γ -ray, protons, high energy electrons and the glow curves were analyzed. We observed an unusual behavior of the TL response of dosimeters to 7 and 14 MeV electron beam. In fact the relative amplitude between two of the five peaks (2° and 3° peaks) assumes values smaller than the unity for doses up to 5 Gy and values greater than the unity for doses equal to or greater than 10 Gy. A possible explanation of this behavior is given adopting a model of the formation of the peaks 2° and 3° and examining the different ways of energy release in matter for each beam. To perform this analysis we deconvoluted the glow…
First measurement of radioisotopes by collinear laser spectroscopy at an ion-guide separator
1997
The first successful application of an ion-guide separator (IGISOL) for collinear laser spectroscopy of radioisotopes has achieved an efficiency comparable with the best obtained with catcher-ionizer facilities. The ion beam energy spread was determined to be less than 6 eV, allowing laser fluorescence resonance signals for the Ba-140,Ba-142,Ba-144 radioisotopes to be detected with high resolution and sensitivity. Applications of this technique to measuring nuclear properties of refractory elements and short lived isomers promises to be particularly advantageous.
Use of aluminum nitride for UV radiation dosimetry
2007
Abstract An investigation of AlN ceramics for applications in UV radiation detection shows the advantages of using the 480 nm emission band for optically stimulated luminescence signal detection instead of the previously used 400 nm emission band since the rate of decrease of the response signal at room temperature is lower than that of the 400 nm band, and its excitation region falls in the UV-B range.
Glow curve analysis of TLD-100H irradiated with radiation of different LET: Comparison between two theoretical method
2006
In the present paper we show the result of study on the thermoluminescent signal of LiF:Mg,Cu,P (TLD-100H) after irradiation with beams of different LET (photons, electrons and protons). Through the analysis of the glow curve it is possible to obtain information on the LET of the radiation beam. To perform this analysis we have deconvoluted the glow curves adopting general order kinetic equation for the description of the peak shape. In addition a numerical simulation has been performed to find a connection among the physical parameters of the model (OTOR) and the parameters of the empirical expression used in the analysis of the experimental data (GOK). The methodology indicate that the ki…
Discrimination of LINAC photon and sunlight contributions in watch glass analyzed by means of thermoluminescence
2012
Abstract The research described in this paper shows how to extract from the glow curves of watch glasses exposed to LINAC photons and sunlight a contribution sensitive to LINAC photons dose. As first step, the dependence of the TL signal due to sunlight on the exposure duration was studied and a signal saturation was observed after about 20 weeks. The comparison of TL signals due to solar light and to LINAC photons highlights a partial overlap of the two signals. Here, two different analysis procedures of glow curves (general order kinetics deconvolution and principal components analysis) are reported to point out components which depend differently on LINAC photon radiation dose. For both …
Optical properties and spectrometric performance of TlBr detector crystals
2006
Abstract It is shown that preliminary TlBr crystals optical parameters testing can be used for detector crystal selection. Absorption in fundamental spectral region was used for the band gap width definition and determination of homological impurities presence. The luminescence was applied for impurity and defects content study. Radionuclide spectra 241Am were measured using the ionizing radiation detectors with planar electrodes made from TlBr crystals. The detector energy resolution for TlBr detectors produced from different row materials was summarized and the results of detector testing parameters and results of optical investigation were compared.
Optical investigations of TlBr detector crystals
2004
Shift of fundamental absorption edge, the position of main luminescence bands, the luminescence decay and transient absorption spectra in three TlBr crystals were studied. The γ-quanta detector made from TlBr crystals with similar transient absorption and luminescence parameters shows similar detector properties. The iodine impurity in TlBr was detected by optical methods. The role of impurities and crystal defects in γ-quanta detectors manufactured is discussed.