共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
M. Neubert 《Zeitschrift fur Physik C Particles and Fields》1991,50(2):243-253
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. 相似文献
3.
, Bi2Te3–x
Se
x
. , , . , , . .
Influence of oxygen content on electric and thermoelectric properties of ternary system Bi2Te3–x Se x
A study is made of the influence of oxygen, contained in the semi-conducting system Bi2Te3–x Sé x , on the electric and thermoelectric properties. It is shown that the addition of oxygen to the prepared samples Bi2Te2.4Se0.6 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.相似文献
4.
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. 相似文献
5.
E. A. Vinogradov B. N. Mavrin N. N. Novikova V. A. Yakovlev D. M. Popova 《Laser Physics》2009,19(2):162-170
Recently ultrabroadband infrared solid state lasers based on a new vibronic material Cr2+:ZnSe x S1–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 S1 ? 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 S1–x crystals as well as acceptor levels in Cr2+: ZnSe crystal are discussed. 相似文献
6.
《Nuclear Physics A》1986,453(4):525-541
An estimate of the formation rate of the strangeness S = −1 dibaryons Ds and Dt 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 Ds dibaryons in a mass range of only 10 MeV starting at the ∑−p mass, while for the Dt dibaryons in a range of 30 MeV is expected. 相似文献
7.
The electrical resistance of Gd x Mn1 ? 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. 相似文献
8.
V. V. Vladimirsky V. K. Grigor’ev I. A. Erofeev O. N. Erofeeva Yu. V. Katinov V. I. Lisin V. N. Luzin V. N. Nozdrachev V. V. Sokolovsky G. D. Tikhomirov Yu. P. Shkurenko 《Physics of Atomic Nuclei》2006,69(3):493-509
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|. 相似文献
9.
A. A. Babaev 《Russian Physics Journal》1981,24(10):899-902
Photoluminescence from amorphous Ge2S3 and GexSe1–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. 相似文献
10.
I. V. Korobeinikov L. N. Luk’yanova G. V. Vorontsov V. V. Shchennikov V. A. Kutasov 《Physics of the Solid State》2014,56(2):263-269
The thermoelectric properties of n-Bi2Te3 ? 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 Bi2Te3 ? x ? y Se x S y solid solutions combined with similar data for p-type Bi2 ? 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. 相似文献
11.
O. I. Shpotyuk E. R. Skordeva R. Ya. Golovchak V. D. Pamukchieva A. P. Kovalskii 《Journal of Applied Spectroscopy》1999,66(5):749-753
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. 相似文献
12.
Journal of Fluorescence - A series of new chemosensor molecules bearing benzothiazole-, quinoline- and phthalazine-functionalized fluorene derivatives were synthesized and their complexation... 相似文献
13.
The thermovoltaic effect in samarium sulfide-based Sm1 ? 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. 相似文献
14.
S. S. Aplesnin A. M. Kharkov O. B. Romanova K. I. Yanushkevich A. I. Galyas V. V. Sokolov 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(10):1252-1254
Results from investigating the structural, magnetic, and electrical properties of Yb x Mn1 ? 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. 相似文献
15.
The magnitude and dispersion of birefringence of single crystals of CuGa(S1?x Sex)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. 相似文献
16.
I. V. Bodnar 《Journal of Applied Spectroscopy》1999,66(6):928-933
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. 相似文献
17.
G. A. Petrakovskii L. I. Ryabinkina G. M. Abramova A. D. Balaev O. B. Romanova G. I. Makovetskii K. I. Yanushkevich A. I. Galyas 《Physics of the Solid State》2002,44(10):1925-1928
The magnetic, electrical, and thermal (derived from DTA data) properties of FexMn1?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 FexMn1?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. 相似文献
18.
Quantum dots (3–4?nm) of Zn1? 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 Zn1? x Cd x S and Zn1? 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 Zn1? x Cd x S was found to vary from 3.878 to 2.519?eV and for Zn1?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 Zn1? x Cd x S solid solutions varies from 0.3840?×?10?10 to 8.7782?×?10?10?mho/m at 150°C and for Zn1? 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. 相似文献
19.
20.
K. R. Nasriddinov B. N. Kuranov G. G. Takhtamyshev T. A. Merkulova 《Physics of Atomic Nuclei》2001,64(7):1326-1328
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. 相似文献