Search results for "Absorption"
showing 10 items of 2701 documents
Impact of the scattering coefficient of scintillation crystals (LYSO and LSO) on depth of interaction resolution
2008
Intrinsic parameters in scintillation crystals play a crucial role in the measured spatial and energy resolutions. In many cases the measurement of these intrinsic parameters is difficult to be carried out or even there are parameters that need a specific setup to be measured directly, e.g. the intrinsic light yield and the absorption and scattering coefficients. These uncertainties in the parametrization of the characteristics of the scintillation crystals make it quite difficult to evaluate the quality and characteristics of the scintillation crystals and their impact on the resolutions. Results of measurements of depth of interaction and its resolutions for three different scintillation …
XAFS study of interchain and intrachain order inSe1−xTexglasses: Nearest neighbors
1998
XAFS measurements (LURE and NSLS) of ${\mathrm{Se}}_{1\ensuremath{-}x}{\mathrm{Te}}_{x}$ glasses have been carried out on both the Se and Te $K$ edges at low and room temperatures. Using a multishell best-fit analysis procedure, we have reconstructed the Se and Te local environment: first-shell intrachain nearest neighbors $(\mathrm{Se}\ensuremath{-}{\mathrm{Se}}_{1}, \mathrm{Se}\ensuremath{-}{\mathrm{Te}}_{1}, \mathrm{Te}\ensuremath{-}{\mathrm{Se}}_{1},$ and $\mathrm{Te}\ensuremath{-}{\mathrm{Te}}_{1}).$ We conclude that the intrachain chemical order (preferential of Se-Te pairs) increases with Te content in the glasses. On the other hand, we suggest a random distribution of Se and Te atom…
Local structure aroundEr3+inSiO2−HfO2glassy waveguides using EXAFS
2007
${\mathrm{Er}}^{3+}$-doped $\mathrm{Si}{\mathrm{O}}_{2}\text{\ensuremath{-}}\mathrm{Hf}{\mathrm{O}}_{2}$ glassy waveguides with $\mathrm{Hf}{\mathrm{O}}_{2}$ concentrations ranging from $10\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}50\phantom{\rule{0.3em}{0ex}}\mathrm{mol}\phantom{\rule{0.2em}{0ex}}%$ were prepared using the sol-gel route and deposited on $v\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2}$ substrates using the dip-coating technique. The local environment around ${\mathrm{Er}}^{3+}$ ions was determined from Er ${L}_{3}$-edge extended x-ray-absorption fine-structure (EXAFS) measurements. The first coordination shell around ${\mathrm{Er}}^{3+}$ ions is comp…
Optical absorption band at5.8eVassociated with theEγ′centers in amorphous silicon dioxide: Optical absorption and EPR measurements
2008
Line shape modifications induced by thermal treatment in the optical absorption and electron paramagnetic resonance (EPR) signals associated with the ${E}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ center are experimentally investigated in various types of $\ensuremath{\gamma}$-irradiated amorphous silicon dioxide $(a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2})$. The $g$ values of the EPR main resonance line of the ${E}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ center show a shift correlated with the peak energy variation of the absorption band at about $5.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ associated with this defect. These spectroscopic changes are proposed to originate from structu…
Line strengths of the ν2 + ν3 and ν3 − ν2 bands of methane (12CH4)
1992
Abstract The individual linestrengths of two related bands of 12 CH 4 , ν 2 + ν 3 near 4545 cm −1 and ν 3 − ν 2 near 1484 cm −1 , were measured with accuracies of 3% and 5%, respectively. In the analysis, an eight-term expansion of the dipole moment through second order was required to fit the strengths of transitions up to J ′ = 10 in ν 2 + ν 3 and J ′ = 12 in ν 3 − ν 2 and to explain the considerable perturbations observed. Application of this model reduced the rms deviations from 68% (zero-order) to 6.3% with the 248 selected lines of ν 2 + ν 2 and from 37% to 5.8% with 186 lines of ν 3 − ν 2 . The integrated bandstrengths for the two bands, respectively, are 1.84(5) and 0.0085(4) cm −2 …
Solvation of triplet Rydberg states of molecular hydrogen in superfluid helium
2004
We report ab initio interaction potentials, transition dipole moments, and radiative lifetimes for the four lowest triplet states of ${\mathrm{H}}_{2}:$ $b$ ${}^{3}{\ensuremath{\Sigma}}_{u}^{+},$ $c$ ${}^{3}{\ensuremath{\Pi}}_{u},$ $a$ ${}^{3}{\ensuremath{\Sigma}}_{g}^{+},$ and $e$ ${}^{3}{\ensuremath{\Sigma}}_{u}^{+},$ and their response to the perturbation due to approaching ground state He atom. Hybrid density functional\char21{}quantum Monte Carlo calculations employing the ab initio interaction potentials are then used for calculating the liquid structure around the molecular excimers in bulk superfluid ${}^{4}\mathrm{He}.$ Calculations demonstrate a wide variety of possible solvation …
Integrated InGaAlAs/InP laser-modulator using an identical multiple quantum well active layer
2005
We present experimental results on 40 Gb/s large-signal modulation performance of 1.31 μm monolithic integrated laser-modulator in the InGaAlAs/InP material system, exploiting the gain and absorption properties of an identical multiple quantum well (MQW) active layer. In continuous wave operation, at 15◦ C, the devices achieved threshold currents < 28 mA, fiber coupled optical power levels up to +0.4 dBm. The measured small signal modulation bandwidth was about 32 GHz. An air-cavity based Fabry-Perot interferometer has been realized to characterize the spectral chirp of the integrated structures in the time domain up to 40 Gb/s.
The elastic scattering of 25MeV α-particles and neutron shell effects in the A = 50 TO A = 93 mass region
1982
Abstract Experimental elastic scattering angular distributions of 25 MeV α-particles scattered from 28 nuclei ranging from 50Cr to 93Nb have been measured and then analysed in terms of a regular optical model with standard Woods-Saxon geometries for both the real and imaginary potentials. The experimental distributions are well fitted over the whole angular range from 5° to 175° c.m. by the predictions, provided that a smaller than normal diffuseness is used for the imaginary potentials. The usual families of potentials with volume integrals differing by approximately 100 MeV · fm3 are found. The family with volume integral ranging from 540 to 420 MeV· fm3 over the nuclei studied has been c…
On the soft excess in the x-ray spectrum of circinus X-1: Revisitation of the distance to circinus X-1
2005
We report on a 300 ks BeppoSAX (0.12-200 keV) observation of Circinus X-1 (Cir X-1) at phases between 0.62 and 0.84 and on a 90 ks BeppoSAX observation of Cir X-1 at phases 0.11-0.16. Using the canonical model adopted until now to fit the energy spectrum of this source, large residuals appear below 1 keV. These are well fitted using an equivalent hydrogen column of 0.66¿1022 cm-2, adding absorption edges of O VII, O VIII, and Ne IX in the spectra extracted from the observation at phases 0.62-0.84 and adding absorption edges of O VII, O VIII, Mg XI, and Mg XII and absorption lines of O VIII and Mg XII in the spectra extracted from the observation at phases 0.11-0.16. During the observation a…
A Hard Tail in the Broad Band Spectrum of the Dipper XB 1254-690
2001
We report on the results of spectral analysis of the dipping source XB 1254-690 observed by the BeppoSAX satellite. We find that the X-ray dips are not present during the BeppoSAX observation, in line with recent RXTE results. The broad band (0.1-100 keV) energy spectrum is well fitted by a three-component model consisting of a multicolor disk blackbody with an inner disk temperature of ~0.85 keV, a comptonized spectrum with an electron temperature of ~2 keV, and a bremsstrahlung at a temperature of ~20 keV. Adopting a distance of 10 kpc and taking into account a spectral hardening factor of ~1.7 (because of electron scattering which modifies the blackbody spectrum emitted by the disk) we e…