Analysis of the Nonselective Spectra of Photostimulated Electron Emission from the Surface of Irradiated Dielectrics

The methodological aspects of PSEE spectroscopy of the surface of irradiated dielectrics have been considered. A generalized method for processing the nonselective photostimulated electron emission (PSEE) spectra taking into account the effects of radiation electrification and structural disordering is proposed and has been substantiated. The procedure of separation of the emission contribution of discrete radiation centers providing, in the stationary approach, estimation of a number of parameters and the concentration of emission-active defects of the surface layer of the material has been described. The potentialities of the method have been demonstrated with the example of Be₂SiO₄ phenacite crystals and crystalline and glassy SiO₂. Diamagnetic oxygen-deficient centers, body and surface E'-centers, as well as hole O ₁ ⁰ -centers on nonbridging oxygen atoms have been registered. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 381–385, May–June, 2005.     

Spatial distribution of defects produced by boron ion implantation of silicon

A simple technique for the study of the spatial distribution of the damage produced by ion implantation of silicon has been developed. The damage depth distribution for 40 keV boron ions in silicon has been studied at irradiation doses from 7 × 10¹¹ to 3.9 × 10¹⁴ ions/cm² and the relative defect peak depth R _d/R _p = 0.85 determined. An increase of layer conductivity as the surface part of the implanted layer is removed has been revealed. This effect is caused by the presence of radiation defects in the surface region of the layer. The “electrical” cluster diameter is about 28 A and the overlapping cluster dose is close to 1 × 10¹³ ions/cm².     

Calculation of the Loss Coefficient of Amplified Luminescence in the Active Layer of a Laser Diode

A method to calculate the loss coefficient of amplified luminescence _loss ^lum in the active layer of a laser diode on the basis of radiation transfer equations and the balance between emission, amplification, and absorption of spontaneous radiation is suggested. The values of _loss ^lum and also of the density of fluxes of amplified luminescence have been determined in one- and two-dimensional approximations for laser diodes based on GaAs, GaN, and ZnSe compounds with different configurations of resonators.     

NMR Experiments on Ion Permeation in Irradiated Model Membranes

In aqueous solutions of sonicated egg-lecithin vesicles (5 weight-%) the ¹H-NMR parameters line width, area, and chemical shift of the signal of the (CH₃)₃N⁺ group were determined in dependence on the dose of gamma radiation (0 … 12 kGy). The application of curopium ions made it possible, by means of a line shape analysis, to calculate these parameters for the inside as well as for the outside lipid layer.

With increasing ⁶⁰Co-radiation dose the line widths increase linearly. The line width for the outside lipid layer increases significantly more rapidly than for the inside layer. This fact allows us to conclude that there exists a preferred radiation damage of the outside lipid layer. The asymmetry may he a consequence of an indirect radiation action mediated by the radicals of the water radiolysis.

From the temporal change of the NMR parameters information can be obtained about the radiation action on transport processes in the vesicles. Beginning at a threshold value (approx. 5 kGy) the permeation of the En^{+ ++} ions to the (CH₃)₃N⁺ head groups previously not accessible increases significantly.     

Dissociation of molecular hydrogen ions by an IR laser pulse

Dissociation dynamics of the simplest molecular systems, such as H₂ ⁺, D₂ ⁺ and HD⁺ ions, in an intense IR laser field has been investigated by numerical modeling. An n-term approximation has been developed to describe the molecular system dynamics in an intense electromagnetic field. Calculations by the n-term approximation have been compared to an accurate numerical solution of the two-particle problem. The dissociation probability as a function of the frequency and intensity of radiation for different isotopes in a molecular hydrogen ion is discussed. A quasistatic model of molecule dissociation in an IR field has been suggested, and limits of its applicability have been determined. Zh. éksp. Teor. Fiz. 113, 128–143 (January 1998)     

Multiphoton ionization of CF<Subscript>3</Subscript>I clusters by ultraviolet laser radiation

The results of the investigation of the multiphoton ionization of (CF₃I) _n clusters by ultraviolet laser radiation are reported. The yields of the I₂⁺ and I⁺ ions, which are the products of the multiphoton ionization, have been measured as functions of the intensity of the ultraviolet radiation at the wavelengths of 308 and 232.5 nm. The degree of multiphoton ionization has been determined and appears to depend on the wavelength of radiation. The velocity distributions of the products have been measured in detail for various wavelengths and various polarizations of radiation. The anisotropy parameters of the velocity distributions of the produced ions and their kinetic energy have been determined. After analysis of the data, a mechanism of the multiphoton ultraviolet ionization of the clusters under investigation has been proposed. This mechanism depends on the used wavelengths.     

Regularities of ion-electron emission of one-dimensional carbon-based composite material

The temperature dependences of the ion-electron emission yield γ(T), the crystal structure, and morphology of a surface layer of a carbon-based KUP-VM composite material under high-dose irradiation with N ₂ ⁺ 30 keV ions have been investigated. The complex two-stage nature of the dependence γ(T) is caused by the processes of dynamic annealing of radiation damage in structural components of a composite material.     

ESR of gamma irradiated single crystals of cholesteryl acetate and cholesteryl chloroformate

Cholesteryl acetate and cholesteryl chloroformate compounds have been irradiated with ⁶⁰Co-γ rays at room temperatures. The irradiated samples have been examined for paramagnetic resonance, and the observed spectra in several cases have been identified with specific radicals. The results in each case have been considered in relation to the present knowledge of the radiation chemistry of the compound. The single crystals have been investigated between 120 and 300?K. The spectra are found to be temperature independent and radiation damage centers are attributed to ?HCH₂ radical for cholesteryl acetate and ?H₃ and ?HCH₂ CH₂ CH₂ radicals for cholesteryl chloroformate.     

An impact mechanism in diverting energy from absorbing inclusions at laser destruction of transparent dielectrics

A new mechanism of destruction of transparent dielectrics with small highly-absorbing inclusions by using intensive laser emission has been suggested. It has been shown that for experimentally found values of threshold radiation intensity I_th ≈ 1 GW/cm² and impurity concentration n ? 10⁷ cm^-3 radiation absorption outside the front of the impurity-initiated shock wave, when allowing for the collective action of waves, results in great heating of the dielectric surface layer which causes its destruction. The found critical value of impurity concentration is several orders less than the value estimated over a model of heating of an inclusion-surrounding dielectric at the expense of heat conductivity.     

Formation of short-period multilayer W/B4C compositions

The quantitative characteristics of the interlayer interaction in multilayer W/B₄C periodic compositions produced by magnetron sputtering are studied by small-angle X-ray diffraction using CuK _?? radiation and by electron microscopy of transverse cuts. It is found that approximately 0.85 nm of the tungsten layer thickness is consumed for the formation of mixed zones at layer boundaries. The mixed layers have a density of 13.4 ± 0.7 g/cm³ and contain tungsten in a bound chemical state. The effect of these mixed zones on the X-ray reflectivity of multilayer W/B₄C compositions is estimated. A method is proposed to determine the layer thickness at a small number of peaks in an X-ray diffraction pattern.     

Hg蒸汽中通过双光子共振四波差频产生调谐真空紫外辐射

利用Hg原子6¹S₀—6¹D₂和6¹S₀—6³D₂双光子共振的四波差频(2ω₁—ω₃),获得了真空紫外相干辐射(ω₄)。当入射光之一(ω₃)波长调谐时,产生的真空紫外光也是调谐的,调谐范围为184.9-187.5nm.本文对非线性频率变换过程的机 关键词：     

Photoelectron spectra and surface valence fluctuation of Eu in the misfit-layer compound {(EuS)1.15}1.5NbS2

The 1.5Q/1 H type of the misfit layer compound {(EuS)_1.15}_1.5NbS₂ has been studied by X-ray photoelectron spectroscopy. Eu 3d, 4d, 4f and 5p spectra are measured with Al and MgKα radiation. Their intensities are analyzed, taking the escape depth of photoelectrons emitted from the core levels into account. The results indicate that valence transfer of nearly-half Eu²⁺ ions to Eu³⁺ happens in the outermost surface layer and a reduced Eu–S distance brings about surface rearrangement. It is confirmed that Eu²⁺ and Eu³⁺ coexist in a bulk, in consistency with bond valence calculations and Mössbauer spectra. The XPS spectra are well interpreted in terms of the multiplet structures of Eu²⁺ and Eu³⁺.     

DCEMS of neon implantation in yttrium iron garnet

⁵⁷Fe-enriched, epitaxial Y₃Fe₅O₁₂ films have been implanted with 50 keV and 100 keV neon ions with a dose of 4·10¹⁴Ne⁺/cm². Depth-selective conversion electron Mössbauer spectroscopy has been performed at 300 K and 40 K. The results show that the 50 keV-implanted sample can be interpreted as an amorphous layer on top of an almost unperturbed YIG layer. In the 100 keV-implanted film a buried amorphous layer is observed.     

Availability of water glass/Bi2O3 composites in dielectric and gamma-ray screening applications

ABSTRACT

Sodium silicate (Na₂Si₃O₇) also known as water glass is a very low cost material which is used in many industrial applications such as a builder in detergents, as a binder and adhesive etc. But so far the electrical properties of sodium silicate and its ability to screen radiation have never been investigated. In the present study, the frequency dependent electrical properties and gamma-ray shielding performance of water glass based bismuth oxide composites have been studied for the first time. In accordance with this purpose, Na₂Si₃O₇/Bi₂O₃ glassy composites have been prepared for searching their possible applications in electronics and radiation screening. The surface morphology of the samples have been determined by Scanning Electron Microscope (SEM). The frequency dependent electrical properties such as complex impedance, complex dielectric function and conductivity have been analyzed at room temperature between 1 and 40?MHz. As a result of alternative current (ac) electrical analysis, it has been determined that the Na₂Si₃O₇/Bi₂O₃ composites can be utilized as a dielectric layer in capacitors. On the other hand, since bismuth oxide is an anti-radiative material, the gamma-ray screening parameters such as mass attenuation coefficient, half layer and tenth layer values along with mean free path of the composites have been defined experimentally by using NaI(Tl) scintillation detector for the Ba-133 radiation source at 81 and 356?keV. The values of these parameters have also been checked by Monte–Carlo simulation. Since a good agreement has been assigned between experimental and Monte–Carlo simulation results, the related gamma ray shielding parameters have been determined by Monte–Carlo simulation for other gamma photon energies (140?keV, 208?keV, 468?keV, and 661?keV) which are generated from Tc-99, Lu-177, Ir-132, and Cs-137 sources. Ultimately, Na₂Si₃O₇/Bi₂O₃(35%) composite has been suggested as an eco-friendly, lead-free glassy structured material for the gamma radiation shielding in medical applications.     

The optical limitation effect and features of luminescence kinetics in hybrid nanosystems with CdSe/ZnS quantum dots and organic agents

The optical limitation effect in three-component systems formed in colloidal solutions of semiconductor CdSe/ZnS quantum dots with participation of fullerene C₆₀ and perylene, has been experimentally investigated. The first and second harmonics of a YAG:Nd³⁺ laser operating in the single-shot mode with a pulse duration of 7 ns and laser pulses subjected to stimulated Brillouin scattering (SBS)-stimulated Raman scattering (SRS) compression with a duration of about 20 ps near 560 nm have been used as radiation sources. It is shown that the optical limitation efficiency in the systems studied is determined by electron transfer. This is confirmed by the analysis of luminescence quenching.     

Physical, optical, structural and gamma-ray shielding properties of lead sodium borate glasses

Lead sodium borate glasses with compositions xPbO:20Na₂O:(80−x)B₂O₃ (where x=5, 10, 15, 20, 25, 30, 35, 40, 45, 50 and 55 mol%) have been prepared using melt-quenching method and investigated on their optical, physical, structural and gamma-rays shielding properties. The densities of these glass samples were increased with increase in PbO concentration. The FTIR spectra and molar volumes indicate that PbO acts differently on this glass structures over their compositions. For the PbO composition less than 20 mol%, Pb²⁺ is incorporated as network former, while it acts as network modifier for the composition from 20-55 mol%. For gamma-ray shielding properties, parameters such as mass attenuation coefficients, effective atomic number and half value layer were increased with increase in PbO concentration. Our results showed relative difference between theory and experiment of less than 1% between experimental and theoretical values. Moreover half value layers of the glass systems have been compared with some standard radiation shielding materials and they exhibited better shielding properties than barite concrete and ferrite concrete at 15 and 25 mol% of PbO, respectively.     

The orientational mechanism of nonlinearity and the self-focusing of He-Ne laser radiation in nematic liquid crystal mesophase (theory and experiment)

A giant optical nonlinearity of self-focusing type in the oriented mesophase of nematic liquid crystals (NLC) due to the director reorientation under the action of a light wave field is predicted. Self-focusing of He-Ne laser radiation with power ～10^?2 W and power density ～50 W/cm² in a planar oriented 60 μm thick NLC layer has been carried out experimentally. The measured value of the nonlinearity effective constant ?₂ = 0.07 cm³/erg corresponds to theoretical predictions, and turns out to be larger than the CS₂ nonlinearity by ? 10⁹ times.     

Weak antilocalization in a three-dimensional topological insulator based on a high-mobility HgTe film

The up-conversion luminescence of Er³⁺ from the ²H_11/2, ⁴S_3/2, and ⁴F_9/2 levels in nanocrystals of Y_0.95(1?x)Yb_0.95xEr_0.05PO₄ (x = 0, 0.3, 0.5, 0.7, 1) orthophosphates activated with Er³⁺ ions has been studied under the excitation of Yb³⁺ ions to the ²F_5/2 level by 972-nm cw laser radiation. Broadband radiation in the wavelength range of 370–900 nm has been observed at certain power densities of exciting laser radiation; this broadband radiation is absent in the case of excitation of the powders under study by pulsed laser radiation with a wavelength of 972 nm at a pulse repetition frequency of 10 Hz and a duration of a pulse of 15 ns. Experimental data indicating that this radiation is thermal in nature have been presented.     

Formation of GaAsN/GaN cluster nanostructures on the surface of GaAs by the implantation of low-energy nitrogen ions

A nitride nanolayer fabricated on a GaAs (100) surface by implanting ions N ₂ ⁺ (E _i = 1.5 keV) has been studied by high-resolution photoelectron spectroscopy with the use of synchrotron radiation. It has been found that, apart from the dominant GaN wide-gap semiconductor phase, an additional phase of the GaAs_{1 ? x} N _x narrow-gap solid solution (x < 0.10) is present in the nitride layer. It has been shown that the nitride layer created by ion implantation is a nanostructure with an attribute of a system of quantum dots, since it consists of nanoclusters of the narrow-gap semiconductor in the wide-gap matrix.     

Growth and spectral-luminescent study of SrMoO<Subscript>4</Subscript> crystals doped with Tm<Superscript>3+</Superscript> ions

SrMoO₄ crystals doped with Tm³⁺ ions have been produced from a melt using the Czochralski method; their spectral-luminescent characteristics have been studied, and laser radiation has been generated at the wavelength of 1.94 μm using laser-diode excitation. The high absorption section at the wavelength of 795 nm, the fairly high luminescence section, the long lifetime at the upper laser level ³F4 of 1.5 ms, and a wide luminescence band allow one to hope for developing efficient tunable Tm³⁺: SrMoO₄ crystal lasers with diode pumping in the range of 1.7–2.0 μm, which are capable of implementing SRS self-transformation of radiation into the middle IR band.