Chiral approach to theK L −K S mass difference

A complete analysis of the long range part of theK _L –K _S mass difference in next-to-leading-order of chiral perturbation theory is presented. We find a large positive contribution from transitions via S=2 vertices and irreducible loop diagrams involving two separate weak interactions. Single-particle pole contributions are small if an approximate nonet symmetry for the couplings of the singlet ₁ holds. They tend to cancel the short distance contribution from box diagrams. In total, good agreement with experiment is obtained. In a second part we study theK _L –K _S mass difference in a phenomenological model of nonleptonic weak transitions which explains the I=1/2 rule in terms of non-perturbative quark-quark correlations. The numerical results agree well with those presented before.     

ВЛИЯНИЕ СОДЕРЖАНИЯ К ИСЛОРОДА НА ЭЛЕКТРИЧЕСКИЕ И ТЕ РМОЭЛЕКТРИЧЕСКИЕ СВОЙСТВА ТРОЙНОЙ СИС ТЕМЫ Вi2Те3−x Sе x

, Bi₂Te_3–x Se _x . , , . , , . .

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Influence of oxygen content on electric and thermoelectric properties of ternary system Bi₂Te_3–x Se _x

A study is made of the influence of oxygen, contained in the semi-conducting system Bi₂Te_3–x Sé _x , on the electric and thermoelectric properties. It is shown that the addition of oxygen to the prepared samples Bi₂Te_2.4Se_0.6 causes a decrease in electric conductivity while the thermoelectric force remains unchanged. This influence is connected with a decrease in the mobility of the electrons but their concentration is not influenced by the presence of oxygen. Conclusions are reached as to the influence of oxygen on the efficiency of the conversion of thermal energy into electric energy and vice versa.

     

S = −1 resonances in two meson-one baryon systems

We study the two meson-one baryon systems by solving Faddeev equations, using chiral dynamics. The calculations, carried out for the $\pi \overline{K} N$ system and its coupled channels for the case of strangeness = ?1, in the S-wave, lead to a dynamical generation of many strangeness = ?1 resonances in the 1500–1800?MeV region. While building the formalism, we found important cancellations between different sources of three-body forces.     

Lattice dynamics of ZnSe x S1 − x semiconductor crystals

Recently ultrabroadband infrared solid state lasers based on a new vibronic material Cr²⁺:ZnSe _x S_1–x were demonstrated [1–3]. Cr²⁺ ion substitutes the metal ion (tetrahedral sites), the crystal field of the solid solution is responsible for large inhomogeneous broadening of Cr²⁺ electron states. The crystal field can be reconstructed by investigation of lattice dynamics — optical phonon parameters and dielectric function in IR. We paid special attention to investigation of vibrational and infrared spectroscopic properties of ZnSe _x S_{1 ? x} crystals. A very interesting and somewhat unexpected result of these studies was the existence in the crystals of effective S-Se dipoles, which generate an additional deep dynamically charged level in the forbidden gap of the semiconductors. The results of the first-principles calculations of both the phonon structure and the electron localization in ZnSe _x S_1–x crystals as well as acceptor levels in Cr²⁺: ZnSe crystal are discussed.     

S = −1 dibaryon formation in the ∑−D atom

An estimate of the formation rate of the strangeness S = −1 dibaryons D_s and D_t via “∑⁻-capture” in a ∑⁻d atom is presented. Reasonable branching ratios are expected for formation from the atomic P orbitals. The ∑⁻d atom experiment is found to be sensitive to the formation of D_s dibaryons in a mass range of only 10 MeV starting at the ∑⁻p mass, while for the D_t dibaryons in a range of 30 MeV is expected.     

Magnetotransport effects in paramagnetic Gd x Mn1 − x S

The electrical resistance of Gd _x Mn_{1 ? x} S solid solutions with x = 0.1, 0.15, and 0.2 has been measured at magnetic field H = 0.8 T and at zero magnetic field within the 100 K < T < 550 K temperature range. The magnetoresistance peak is observed above room temperature. On heating, the composition with x = 0.2 exhibits the change of magnetoresistance sign from positive to negative and the magnetoresistance peak near the transition to the magnetically ordered state. The experimental data are interpreted in the framework of the model involving the orbital ordering of electrons and the arising electrical polarization leading to the changes in the spectral density of states for electrons in the vicinity of the chemical potential in the applied magnetic field.     

Analysis of the K S K S system from the reaction π − p → K S K S n at 40 GeV

On the basis of experimental data from the 6-m spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow), an amplitude analysis of 40 553 events of the reaction π ^? p → K _S K _S n induced by a negatively charged pion of energy 40 GeV is performed over a broad momentumtransfer range by using a new procedure. The results for |t| > 0.1 GeV² are obtained for the first time. In particular, resonances of mass 1700 and 1900 MeV and width 120 MeV are discovered in the D ₊ wave (there were no such resonances for |t| < 0.1 GeV²). In the region of low momentum transfers, the S wave exhibits a structure that lies in the mass region around 1370 MeV and which requires three resonances for its explanation. Two of these (that of mass 1234 ± 6 MeV and width 47 ± 33 MeV and that of mass 1478 ± 6 MeV and width 119 ± 10 MeV) were found in the studies of A. Etkin et al. [Phys. Rev. D 25, 2446 (1982)] and O.N. Baloshin et al. {Yad. Fiz. 43, 1487 (1986) [Phys. At. Nucl. 43, 959 (1986)]}. The third has a mass of 1389 ± 9 MeV and a width of 30 ± 24 MeV. At high momentum transfers, the S wave is found to feature resonances that have the following parameters: M = 1328 ± 8 MeV and Γ = 237 ± 20 MeV, M = 1440 ± 6 MeV and Γ = 121 ± 15 MeV, and M = 1776 ± 15 MeV and Γ = 250 ± 30 MeV. For the D ₀ wave, it is found that, in addition to the well-known resonances f ₂, a ₂, and f′ ₂, there appear the following resonances in this wave: a resonance of mass 2005 ± 12 MeV and width 209 ± 32 MeV and a resonance of mass 2270 ± 12 MeV and width 90 ± 29 MeV at low |t| and a resonance of mass 1659 ± 6 and width 152 ± 18 and a resonance of mass 2200 ± 13 MeV and width 91 ± 62 MeV at high |t|.     

Photoluminescence in amorphous Ge2S3 and GexSe1−x

Photoluminescence from amorphous Ge₂S₃ and Ge_xSe_1–x has been studied at 77°K. Photoluminescence results obtained with amorphous Ge₂S₃ and Ge₂Se₃ at 4.2°K are presented here for the first time. All the semiconductors studied in this work had one broad photoluminescence band with its peak at E Eg/2. A strong electron-phonon interaction in these samples is indicated by the strong exponential temperature dependence observed in the photoluminescence intensity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 7–10, October, 1981.We wish to express our deep appreciation to Academy of Sciences Corresponding Member Kh. I. Amirkhanov for useful advice during discussions of this work.     

Thermoelectric properties of n-Bi2Te3 − x − y Se x S y solid solutions under high pressure

The thermoelectric properties of n-Bi₂Te_{3 ? x ? y} Se _x S _y solid solutions with atomic substitutions in the tellurium sublattice (x = 0.27, 0.3, y = 0, and x = y = 0.09) have been studied under a pressure to 8 GPa. It has been found that the Seebeck coefficient and the resistance decrease with increasing P, and power factor χ increases in all compositions and becomes maximal at pressures of 2–4 GPa. It has been shown that the power factor χ, which is proportional to the product of the effective mass of the density of states m/m m/m ₀ and the charge carrier mobility μ₀ in the form (m/m ₀)^3/2μ₀, increases with increasing pressure mainly due to the increase in the mobility and also depends on the solid solution composition. In the composition with substitution Te → Se + S (x = y = 0.09), the peculiarity of the dependence of m/m ₀ on P in the pressure range corresponding to maximal values of the power factor can be explained by the existence of an electronic topological transition. The increase in the power factor under pressure in n-type Bi₂Te_{3 ? x ? y} Se _x S _y solid solutions combined with similar data for p-type Bi_{2 ? x} Sb _x Te₃ solid solutions obtained earlier, including the estimations of possible changes in the thermal conductivity with increasing pressure, give grounds to design thermoelements with improved value of the thermoelectric figure-of-merit, which can be 50–70% at pressures of 2–4 GPa.     

Radiation-stimulated changes in the transmission of chalcogenide glasses of As2S3−Ge2S3

The radiative-optical properties of chalcogenide glass-like semiconductors of the As₂S₂−Ge₂S₃ system in the region of a topological 2D-3D-phase transition are investigated. It is shown that γ-irradiation of samples by an absorbed dose of 4.4 · 10⁶ Gy leads to a longwave shift of their optical-transmission edge in the spectrum. The effect observed depends on the structural type of the glasses investigated and changes considerably near the 2D-3D-phase transition. Two components of the transmission-edge shift are detected: a static component, which remains unchanged for a long time after irradiation of the samples, and a dynamic one, which gradually fades in 2–3 months. It is suggested that the microstructural mechanism of these changes is attributable to processes of coordination defect formation in the structural skeleton of the samples. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, pp. 657–660, September–October, 1999.     

Fluorene Based Ferric Complex as Colorimetric and Fluorometric Probe for Highly Selective Detection of CN− and S2− Anions

Journal of Fluorescence - A series of new chemosensor molecules bearing benzothiazole-, quinoline- and phthalazine-functionalized fluorene derivatives were synthesized and their complexation...     

Thermovoltaic effect in samarium sulfide-based Sm1 − x Eu x S heterostructures

The thermovoltaic effect in samarium sulfide-based Sm_{1 ? x} Eu _x S bulk heterostructures in the temperature interval 300–520 K is considered. It is shown that this effect is due to an artificially produced samarium ion concentration gradient, rather than to an external temperature gradient.     

Magnetic and electric properties of Yb x Mn1 − x S alloys

Results from investigating the structural, magnetic, and electrical properties of Yb _x Mn_{1 ? x} S alloys (0 ≤ x ≤ 0.2) synthesized on the basis of manganese monosulfide are presented. Substituting manganese for ytterbium increases the concentration of charge carriers and lowers the activation energy. The observed anomalies in the temperature dependence of resistivity are explained by an impurity semiconductor model with donor 4f levels.     

Birefringence of CuGa(S1−x Sex)2 single crystals

The magnitude and dispersion of birefringence of single crystals of CuGa(S_1?x Se_x)₂ solid solutions is studied in the spectral region of 0.5–2.5 μ at T=300 K. The effect of the substitution of selenium for sulfur on special features of birefringence dispersion is analyzed within the framework of the single-oscillator model.     

Vibrational spectra of CuAl x Ga1−x S2 solid solutions

Investigations of the IR reflection and Raman spectra in polarized light are carried out on single crystals of the ternary compounds CuAlS₂ and CuGaS₂ and solid solutions based on them grown by the method of chemical transport reactions. The frequencies of longitudinal and transverse phonons are determined, the IR intensities and damping factors of phonons (ε₀, ε_∞) are calculated, and their concentration dependences are constructed. It is established that optical vibrations in the solid solutions manifest a mixed behavior. Belarusian State University of Information Science and Radioelectronics 6 P. Brovka Str., Minsk, 220072, Belarus; e-mail: kafchim@gw.bsuir.unibel.by. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 800–803, November–December, 1999.     

Magnetic properties of FexMn1−x S sulfides exhibiting the magnetoresistive effect

The magnetic, electrical, and thermal (derived from DTA data) properties of Fe_xMn_1?x S polycrystalline sulfides (0≤x≤0.38) synthesized based on α-MnS (NaCl cubic lattice) and exhibiting colossal magnetoresistance were studied. The studies were conducted at temperatures from 77 to 1000 K and magnetic fields of up to 30 kOe. As the degree of cation substitution in the Fe_xMn_1?x S system was increased, the magnetic order was found to change from antiferromagnetic to ferromagnetic. In the high-temperature domain (550–850 K), the samples undergo two phase transitions with critical temperatures $T_{c_1 }$ and $T_{c_2 }$ , which are accompanied by reversible anomalies in the magnetization and thermal (DTA) properties and by a semiconductor-metal transition.     

Studies on the synthesis and characterization of Zn1− x Cd x S and Zn1− x Cd x S:Mn2+ semiconductor quantum dots

Quantum dots (3–4?nm) of Zn_{1? x} Cd _x S (both free of Mn²⁺ and with Mn²⁺ incorporated) were synthesized through a novel solvothermal-microwave irradiation technique. Detailed structural analysis of the Zn_{1? x} Cd _x S and Zn_{1? x} Cd _x S:Mn²⁺ (x?=?0, 0.25, 0.5, 0.75 and 1) materials was carried out using powder X-ray diffraction technique. For all the compositions, the crystallite size was controlled to less than 1.5?nm. The optical energy gap for Zn_{1? x} Cd _x S was found to vary from 3.878 to 2.519?eV and for Zn_1?x Cd _x S:Mn²⁺ it varies from 3.830 to 2.442?eV when x is increased from 0 to 1. Overall, the optical energy gap could be tuned from a minimum of 2.442?eV to a maximum of 3.878?eV. DC conductivity analysis (from 40°C to 150°C) and electrical energy gap analysis for all the compositions were also performed. The dc conductivity for Zn_{1? x} Cd _x S solid solutions varies from 0.3840?×?10^?10 to 8.7782?×?10^?10?mho/m at 150°C and for Zn_{1? x} Cd _x S:Mn²⁺ it varies from 0.5751?×?10^?10 to 9.8078?×?10^?10 mho /m at 150°C (for x?=?0 to x?=?1). The method of synthesis and the results observed in this investigation may assist in the fabrication of optical devices when the required operational performance falls under the range observed in the study.     

Decay τ − → φπ − ν τ and ω−φ mixing

The decay process τ ^? → φπ ^? ν _τ is investigated on the basis of the method of chiral phenomenological Lagrangians. It is shown that the calculated value of the decay probability is very sensitive to variations in the angle of ω?φ mixing. The resulting value of this probability is compared with available experimental data and with the results of other theoretical calculations.