Calculation of the intensity of Touschek electrons in the VEPP-4M storage ring

Formulas for calculating the intensity of intrabeam scattering of electrons in the Born approximation for the one- and two-dimensional collision models have been obtained for the nonrelativistic and relativistic cases. The Baier-Katkov-Strakhovenko two-dimensional relativistic model with Coulomb corrections has been analyzed. Formulas in the ultrarelativistic limit have been obtained using this model. Different models have been compared. The intensities of Touschek electrons and the polarization contribution have been calculated under the conditions of the detection of scattered particles at the VEPP-4M storage ring. The calculations have been compared to experimental data.     

Dispersion properties of surface polaritons at the high-temperature superconductor-insulator interface in the presence of dissipation

The dispersion and energy characteristics of surface polaritons at a high-temperature supercon-ductor-insulator interface have been studied taking into account the dissipation in both media. The dispersions have been found and the criteria for the existence of surface waves have been formulated for temperatures below the phase transition point. The frequency dependences of the depth of penetration of surface polaritons into each medium and their mean free paths have been determined. The characteristic frequencies near which the wave parameters of surface polaritons undergo substantial changes have been revealed.     

Determination of the mass spectrum of quarkonia by the Nikiforov–Uvarov method

The Schr?dinger equation for a potential being the sum of a harmonic oscillator potential, a linear potential, and a Coulomb potential has been solved by the Nikiforov–Uvarov method for large and small distances between particles being in the bound state. Asymptotic expansions have been obtained for the energy levels and wave functions, and also the wave function and the energy of the ground state have been found. The mass spectrum of heavy quarkonia and their radius have been calculated.     

插入生长AlGaAs薄膜对InAs量子点探测器性能的影响

利用分子束外延生长获得的两个InAs量子点样品制备了n型的量子点红外探测器.对于其中一个器件，在InAs量子点有源区的底部和顶部分别插入生长了AlGaAs势垒层.利用透射电阻显微技术研究了两个样品的结构特性；利用光致发光光谱和光电流谱研究了两个器件的光电性质.实验结果表明，AlGaAs层的插入对器件的探测性质有显著的影响.利用有三维效质量近似模型的计算结果，指认了带内光电流谱中峰结构的起源.     

插入生长AlGaAs薄膜对InAs量子点探测器性能的影响

利用分子束外延生长获得的两个InAs量子点样品制备了n型的量子点红外探测器.对于其中一个器件,在InAs量子点有源区的底部和顶部分别插入生长了AlGaAs势垒层.利用透射电阻显微技术研究了两个样品的结构特性;利用光致发光光谱和光电流谱研究了两个器件的光电性质.实验结果表明,AlGaAs层的插入对器件的探测性质有显著的影响.利用有三维效质量近似模型的计算结果,指认了带内光电流谱中峰结构的起源. 关键词： InAs 量子点 AlGaAs薄膜 光致发光光谱 有效质量近似模型     

Estimations of the Free Energy for the Hubbard Model

A series of upper bounds and two lower bounds for the partition function of the Hubbard model have been derived. These bounds are expressible by certain properties of the Falicov-Kimball model. The upper bounds have been derived mainly by the use of the Golden-Thompson inequality and its generalizations, and the Hölder inequality. The lower bounds are based on the Bogoliubov-Peierls inequality. The numerical values of bounds have also been calculated for small systems.     

On the virial coefficients of the equation of state of a system of non-axial molecules

A thermodynamic perturbation theory in which all angle-dependent interactions are considered as a perturbation of the central potential is applied to calculate the second and third virial coefficients of a fluid composed of non-axial molecules. The influence of a large number of anisotropic pair- and three-body non-ādditive interactions has been considered. Experimental values have been used for the dipole moment, quadrupole tensor and for anisotropic polarizability. The parameters for the central Lennard-Jones (12-6) potential have been determined from the viscosity data. The relative contribution of each branch of pair and triplet interactions has been evaluated as a function of temperature for molecules possessing both the axial- and non-axial symmetries. It has been shown that the non-axial approximation is an improvement over the axial one. Theoretical results have been compared with the experimental data of CH₃OH.     

Contributions to the electromagnetic form factors of the deuteron from isobar configurations

A nonrelativistic calculation of the elastic electron deuteron scattering has been performed in which the effects arising from nucleon polarization have been systematically investigated. These effects have been taken into account by admixing isobar configurations into the deuteron wave function. Explicit expressions for the various contributions to the respective deuteron form factors have been given. At higher momentum transfers inclusion of the isobar configurations leads to a substantial increase in the form factors which qualitatively appears to account for at least some of the discrepancies between theory and experiment.     

An analysis of the temperature and pressure dependence of the electrical resistivity in lead

The volume dependence of the high temperature electrical resistivity has been treated in detail for lead. Volume changes caused by external pressure as well as thermal expansion have been considered. Experiments on the volume dependence of the effective electron mass have been reanalysed with an inclusion of electron-phonon interaction. Finally, we have found no experimental support for a net effect from a Debye-Waller factor and multi-phonon processes.     

Analysis of the spectator-angular distribution in the light-nuclei reactions

Angular distributions of spectator particles in dp and ⁴Hep reactions in the region of a few GeV have been studied. Significant asymmetries of the spectator particle distributions have been observed for reactions where π-mesons are produced in the final state. Results of calculations in the framework of a spectator model taking into account the nuclear wave function, flux factor and the energy dependence of the NN elementary cross-sections, have been compared to experimental data. A good agreement has been observed for the fragments momenta, where the one-pole mechanism dominates. Received: 11 February 2000 / Accepted: 29 June 2000     

原子康普顿轮廓的解析计算

利用变分原理和冲量近似,给出了原子康普顿轮廓的解析计算方法。基于该方法具体导出了第一和第二周期元素各轨道电子的康普顿轮廓解析表达式,并绘制了各轨道电子的康普顿轮廓在Q=0-4范围内的变化情况。通过与文献结果的比较,验证了本文计算方法和结论的可靠性。     

On the theoretical description of the chemisorption of the hydrogen atom on the metallic surface. Calculation of energy interaction of H with hcp Co and Ni surface clusters

A model, based on the generalized valence bond theory, capable of describing the interaction of hydrogen atom (H) with large molecular systems is proposed. The accuracy of the model has been checked by calculating the and H₂ systems. Atomic spin densities for clusters having 1243 atoms have been obtained. The surface magnetic and chemisorption property differences between the Ni and Co metals have been analyzed. An extrapolation scheme suitable to obtain H chemisorption energies on infinite systems from the finite ones has been proposed. Size-converged results have been obtained for the Co. Potential energy surfaces of hydrogen, on and below, the Co surface have been provided.     

Molecular dynamics simulation of liquid tetrahydrofuran: on the uniqueness of force fields

Molecular dynamics simulations of liquid tetrahydrofuran have been performed with different force fields to illustrate that there is no unique way to model a given system of molecules. Parameters for the force fields have been taken from existing force fields and have been used as starting guesses for a simplex optimization. In spite of the very different final parameter values, all optimized force fields reproduce properly the physical properties for which they have been optimized, but not necessarily other ones.     

原子康普顿轮廓的解析计算

利用变分原理和冲量近似,给出了原子康普顿轮廓的解析计算方法 .基于该方法具体导出了第一和第二周期元素各轨道电子的康普顿轮廓解析表达式,并绘制了各轨道电子的康普顿轮廓在Q=0-4范围内的变化情况.通过与文献结果的比较,验证了本文计算方法和结论的可靠性.     

Exact solutions of the field equations for Charap’s chiral invariant model of the pion dynamics

The field equations for the chiral invariant model of pion dynamics developed by Charap have been revisited. Two new types of solutions of these equations have been obtained. Each type allows infinite number of solutions. It has also been shown that the chiral invariant field equations admit invariance for a transformation of the dependent variables.     

Study of the H chemisorption on a Cu surface by the recursion method

The electron density of states and the chemisprption energy have been calculated for the case of H on a Cu(111) surface, by means of the recursion method in connection with the continued fraction technique, in a self-consistent Hartree-Fock scheme. The Slater-Koster parameters existing in literature for Cu have been used, while a parametrized form has been taken for the H-metal interaction. The relative role of the d-bands and of the s-band have been investigated. It is shown how, by taking into account the importance of the s-band in the chemisorption process, it is possible to have results which fit well experimental results as well as other theoretical calculations.     

Measurement of the probe impact force of the atomic force microscope operating in the amplitude modulation mode

A method for studying the force interaction in dynamic modes of the atomic force microscope has been considered. Direct measurements of the maximum impact force in the amplitude modulation mode have been performed. It has been shown that the results of analytical calculations are in agreement with numerical simulation, but differ from experimental data by a factor of 1.5. The major factors affecting the results have been analyzed.     

X-ray determination of the Debye-Waller factors and Debye temperatures of europium monochalcogenides

X-ray powder diffractograms of EuS and EuTe have been recorded. The integrated intensites have been measured and corrected for TDS. From an analysis of the intensity data, Debye-Waller factors and Debye temperatures have been evaluated.     

Application of the Nuclear Reaction Analysis Online Technique to Study the Diffusion of Deuterium in Metals

Nuclear reaction analysis online technique has been applied to study the diffusion of deuterium in metals. Investigations ensuring the application of the new method have been performed. These investigations include the development of a device for diffusion annealing of samples in the chamber of an accelerator and an algorithm for taking into account the effect of radiation defects on the diffusion coefficients. Test measurements of the diffusion coefficients of deuterium in nickel in the temperature range from 130 to–60°С have been performed. For negative temperatures, experimental data on the diffusion of a hydrogen isotope in a metal have been obtained for the first time by a direct method and it has been shown that the online nuclear reaction analysis provides reliable data.     

Characteristics of the heating dynamics of a graphite conductor taking into account the skin effect

Calculations for a one-dimensional model of RF heating of a cylindrical graphite conductor have been carried out. The heating dynamics are analyzed in the general form. Conductor temperature profiles and the times for heating up to the graphite sublimation temperature as a function of current and frequency have been obtained. A model of conductor heating with partial return of the energy irradiated by the conductor surface has been considered. Frequency and current ranges have been determined to carry out this graphite sublimation method in a chamber with reflecting walls. The problem is associated with carbon vapor production and subsequent synthesis of fullerenes and other carbon structures.