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21.
The results of soft-x-ray O Kα emission (XES) and O 1s absorption spectroscopy (XAS) measurements of Pb-implanted glassy and crystalline silica are presented. The x-ray O Kα (2p → 1s electron transition) emission spectra of SiO2 were recorded before and after Pb-implantation with the energy of 30 keV and ion fluence 5 × 1016 ion/cm2. It was found that XES O Kα of implanted samples is sensitive to the disordering degree of the oxygen sublattice. The transformations and peculiarities of the spectra shape of implanted samples are explained by the disordering and amorphization effects in the structure of Pb-implanted SiO2. Comparing the XES O Kα of reference a-SiO2, Pb-implanted SiO2 and binary glassy PbO-SiO2 system, it was established that the ion-beam treatment of oxide matrix does not generate an oxidized Pb as PbO4-type structural units. The energy band gap of 9.2 eV well coincides with previously reported data and was evaluated qualitatively with the help of overlaying the XES O Kα and XAS O 1s to the common energy scale for Pb-implanted SiO2 and binary glassy PbO-SiO2. 相似文献
22.
Zatsepin AF Buntov EA Kortov VS Tetelbaum DI Mikhaylov AN Belov AI 《J Phys Condens Matter》2012,24(4):045301
Results of the investigation of photoluminescence (PL) mechanisms for silicon dioxide films implanted with ions of silicon (100 keV; 7 × 10(16) cm(-2)) and carbon (50 keV; 7 × 10(15)-1.5 × 10(17) cm(-2)) are presented. The spectral, kinetic and thermal activation properties of the quantum dots (Si, C and SiC) formed by a subsequent annealing were studied by means of time-resolved luminescence spectroscopy under selective synchrotron radiation excitation. Independent quantum dot PL excitation channels involving energy transfer from the SiO(2) matrix point defects and excitons were discovered. A resonant mechanism of the energy transfer from the matrix point defects (E' and ODC) is shown to provide the fastest PL decay of nanosecond order. The critical distances (6-9 nm) of energy transport between the bulk defects and nanoclusters were determined in terms of the Inokuti-Hirayama model. An exchange interaction mechanism is realized between the surface defects (E(s)'-centres) and the luminescent nanoparticles. The peculiarities of an anomalous PL temperature dependence are explained in terms of a nonradiative energy transfer from the matrix excitons. It is established that resonant transfer to the luminescence centre triplet state is realized in the case of self-trapped excitons. In contrast, the PL excitation via free excitons includes the stages of energy transfer to the singlet state, thermally activated singlet-triplet conversion and radiative recombination. 相似文献
23.
A. F. Zatsepin V. B. Guseva V. A. Vazhenin M. Yu. Artoymov 《Physics of the Solid State》2012,54(9):1776-1784
Gamma-irradiated alkali silicate glasses of the variable composition 22xNa2O · 22(1 ? x)K2O · 3CaO · 75SiO2 have been studied using the electron paramagnetic resonance (EPR) method. It has been established that, upon the successive replacement Na ?? K in the two-alkali silicate glass, the EPR spectrum of hole centers on nonbridging oxygen atoms can be represented as a superposition of signals from the oxygen centers HC 1(Na), HC 2(Na), HC 1(K), and HC 2(K), which are characteristic of single-alkali silicate systems. The concentration dependences of hole and electron paramagnetic centers do not exhibit specific features that can be interpreted as a manifestation of the ??mixed-alkali effect.?? The results obtained have been discussed taking into account the extended model of centers on nonbridging oxygen atoms. 相似文献
24.
F. F. Khalchukov E. V. Korolkova V. A. Kudryavtsev A. S. Malguin V. G. Ryasny O. G. Ryazhskaya G. T. Zatsepin O. Saavedra 《Il Nuovo Cimento C》1995,18(5):517-529
Summary The production of nuclear-active and electromagnetic particles, as well as long-lived isotopes in nuclear and electromagnetic
showers generated by cosmic-ray muons at different depths underground is discussed. Characteristics of the secondary components
and their dependence on the depth and the muon energy, obtained in experiments and calculations, are presented. 相似文献
25.
26.
The Monte Carlo carbyne model is modified to investigate the glass transition of the simplified polymer chains. The stochastic bombardment between monomers is monitored by Metropolis algorithm with the help of the consideration of hard potential while the mobility of monomers is governed by its mass, scattering rate, and temperature. Our model is capable to show that the glass transition temperature reduces with decreasing film thickness and the formation of critical voids in the thinner polymer contributing to the glass transition that is much easier than the bulk polymer. 相似文献
27.
The problem of charm generation in the interactions of nucleons with nuclei of air atoms at energies inaccessible at present-day accelerators is discussed. Both experimental data on cosmic-ray muons and the predictions of QCD-based theoretical models are used in analyzing the behavior of the differential cross sections for charmed-particle production at high energies. The calculated fluxes of muons and neutrinos arriving at sea level both along the vertical and along the horizontal direction are presented, together with their approximations for the interval 2×102–1010 GeV. 相似文献
28.
Physics of the Solid State - The conversion of the energy absorbed by cubic Gd2O3 nanocrystals doped with Er3+ and codoped with Yb3+ and Zn2+ ions in a temperature range of 95–425 K is... 相似文献
29.
Márcio AF Belo-Filho Franklina MB Toledo Bernardo Almada-Lobo 《The Journal of the Operational Research Society》2014,65(11):1735-1747
Setup operations are significant in some production environments. It is mandatory that their production plans consider some features, as setup state conservation across periods through setup carryover and crossover. The modelling of setup crossover allows more flexible decisions and is essential for problems with long setup times. This paper proposes two models for the capacitated lot-sizing problem with backlogging and setup carryover and crossover. The first is in line with other models from the literature, whereas the second considers a disaggregated setup variable, which tracks the starting and completion times of the setup operation. This innovative approach permits a more compact formulation. Computational results show that the proposed models have outperformed other state-of-the-art formulation. 相似文献
30.
A. F. Zatsepin E. A. Buntov V. S. Kortov V. A. Pustovarov N. V. Gavrilov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2014,8(3):540-544
The luminescence of quartz glass with implanted Pb+ ions is investigated by time-resolved photoluminescence spectroscopy under synchrotron excitation. It is established that the glass layer modified with ions represents a microheterogeneous medium with a variable content of implanted ions predominantly in the form of Pb2+. Three different types of emission centers are detected that are created by radiation-induced defects of the SiO2 matrix and localized electronic states of the amorphous lead-silicate phase. 相似文献