On the most accurate measurements of the wavelengths of X-ray spectral lines

The paper discusses the influence of statistical errors in measuring the intensity of a spectral line on the exact determination of its wavelength. Using simplifying assumptions, it is shown that the relative error in measuring the wavelengths of spectral lines of the same type, caused by the statistical character of X-ray intensity measurements and by the influence of the true width of the spectral line, is practically constant under the same conditions, i.e. it is independent of the lattice parameters of the crystals used and of the wavelength of the spectral line. It seems that the latest exact measurements of Bearden confirm this result.The greatest care should therefore be devoted to the neighbourhood of inflection points of the curve representing the spectral line profile when making exact measurements of the spectral position of the lines.The author heartily thanks Professor M. A. Blochin for valuable remarks on this work.     

耳蜗中tip-link张力与静纤毛运动动力学研究

诠释耳蜗的主动感音放大机制一直是未解的医学难题.这种机制与耳蜗中外毛细胞顶端的静纤毛运动密切相关,静纤毛运动又受到tip-link张力与淋巴液流体力的调节.因此,研究静纤毛运动过程中tip-link张力是诠释耳蜗的主动感音放大机制的重要环节.本文把静纤毛视为变形体,基于泊肃叶流动理论并结合分布参数模型,推导了静纤毛运动的解析解.研究了盖膜剪切荷载作用下静纤毛和淋巴液相互作用的动力响应以及tip-link张力的变化规律.研究发现:当静纤毛的杨氏模量减小时,在小于峰值频率的区域,tip-link张力显著增大,f₂的峰值频率减小.以往的研究将静纤毛作为刚体,势必导致低频声音信号作用减弱.当系数c=0 (无黏性阻力)时,f₂频率选择特性存在;当μ=0(无压力)时,f₂频率选择特性消失,因此淋巴液可能是通过在静纤毛间产生压强的方式来调节毛束的频率特性的.另外,盖膜剪切荷载频率越高,静纤毛轴弯曲越明显,发束内外域的压强差也越大.     

线型分子的电子能级之Λ分裂的新解释

认为电子态能级发生Λ分裂虽然是角动量引起的,但不是耦合而是运动牵连作用的结果.从这一认识出发,利用欧拉方程和拉格朗日方程分别得到了包含Λ分裂的分子转动哈密顿函数和哈密顿算符,所得结果与Van.Vleck的著名结论完全一致 关键词： Λ分裂 线型分子 欧拉方程 哈密顿算符     

Nonlinear optical response of an atom in the field of femtosecond laser pulses with near-atomic intensity

A theory of the nonresonant response of a single atom in a state with arbitrary magnitude and direction of the angular momentum of an atomic electron with respect to the polarization vector of the acting electromagnetic field has been developed. It has been shown that the atomic response current has a tensor structure and depends both on the direction of the angular momentum of the atom and on the polarization vector of the external field. The tensor character of the response is due to the effects of the anisotropy of probability density distribution of the atomic electron as compared to the case of the free atom. The selection rules for the axisymmetric problem of the atom in the field have been analyzed. The manifestation of the selection rules in the angular spectra of photoelectrons has been demonstrated. The probability of the ionization of the atom has been analyzed as a function of the amplitude and duration of the pulse. It has been shown that the width of the generation spectrum is a nonlinear function of the field strength and is saturated in the region of nearly atomic fields. Methods for controlling the parameters of the atomic response spectrum have been proposed on the basis of the use of a sequence of laser pulses with various time profiles, carrier frequencies, and polarization states. It has been shown that the generation of terahertz radiation is possible in the preionization regime, where the generation mechanism is attributed to atomic nonlinearity.     

Statistical theory of a solvated electron in an electrolyte

The behavior of a solvated electron in an electrolyte is investigated. The formalism of the theory is based on variational estimation of path integrals. It reduces the problem to the investigation of the self-consistent mean field produced by the ions and the electron. Mayer cluster expansions make it possible to take account of the short-range interactions and to find expressions for the effective potential of the electron and the electron-ion and electron-neutral atom correlation functions as a function of the macro-and microscopic parameters of electrolytes. In the limit of high ion densities the behavior of the electron is determined solely by the Coulomb interaction, which results in the formation of a polaron state. This state of the electron is virtually independent of the thermodynamic parameters of the electrolyte. In the opposite limit of low ion densities the electron forms a cavity state. The presence of ions results in additional localization of the electron and is manifested experimentally as a shift of the absorption band in the direction of high energies. The estimated shift for a hydrated electron agrees with the experimental data. Zh. éksp. Teor. Fiz. 115, 1463–1477 (April 1999)     

固体火箭发动机羽流辐射光谱测温方法研究

固体火箭发动机羽流具有高温、高速与强辐射特征,羽流温度是发动机工作状态与性能的重要表征参数。准确测量固体火箭发动机羽流温度对了解发动机内部燃烧情况以及发动机综合性能具有重要的参考价值。随着激光与光谱学的发展,激光光谱技术逐步应用于固体推进剂燃烧及发动机羽流温度测量。辐射光谱测温法通过测量火焰辐射光谱来实现温度的非接触在线测量,具有测温范围宽、响应快及可靠性高等优点,可应用于固体火箭发动机羽流温度测量。在此提出了基于火焰辐射光谱的固体火箭发动机羽流温度测量方法,采用350～1 000 nm波段光纤光谱仪搭建了发动机羽流火焰辐射光谱测量系统,利用标准辐射黑体炉开展光谱仪响应系数标定,获得响应系数随波长的变化曲线,并以此用作羽流辐射光谱数据修正。之后将该测量系统应用于标准Φ118固体火箭发动机地面试验,开展典型12%铝质量含量推进剂发动机羽流辐射光谱实验测量,选取不同时刻羽流辐射光谱分析了发动机羽流辐射光谱特征,并利用双色法灰性判断原理对羽流火焰灰体特性进行讨论,验证在675～745 nm波段发动机羽流火焰辐射可近似认为灰体,该波段辐射率随波长变化最大相对偏差为4.01%,相对均方差为1.53%。因此,基于普朗克辐射定律开展辐射光谱拟合参数获得不同时刻羽流温度与辐射率参数,并讨论测量结果与发动机工作状态的关系。最后,开展12%,15%与19%铝质量含量的不同推进剂配方固体火箭发动机羽流辐射光谱测量,将辐射光谱法温度测量值与理论热力计算值进行比较,两者最大偏差值为5.40%,讨论了不同铝含量推进剂发动机羽流辐射光谱特征,并结合温度与辐射率测量结果,分析了固体推进剂铝含量对辐射光谱、羽流温度及辐射率的影响。通过固体火箭发动机羽流辐射光谱测温方法研究,为固体火箭发动机性能评估及推进剂配方优化等研究提供了有效的羽流参数测量手段。分析获得的推进剂铝含量对发动机羽流辐射光谱、温度及辐射率参数的影响,为降低固体发动机羽流特征信号提供了重要的实验数据支撑。     

强耦合表面激子内部激发态的性质

采用线性组合算符和幺正变换方法,研究极性晶体中强耦合表面激子内部激发态的性质.计算了表面激子的激发态能量、激发能量和平均声子数.     

高速模型尾迹流场及其电磁散射特性相似性实验研究

高速目标再入大气层或在临近空间飞行时,空气电离形成的等离子体鞘套和尾迹对目标的雷达散射特性会产生影响.为了研究不同模型尾迹流场及其电磁散射特性规律和相似性,以氧化铝球模型为研究对象,在弹道靶设备上开展了双尺度参数相同的条件下高速球模型尾迹流场及其电磁散射相似性实验研究.由二级轻气炮发射模型,模型直径分别为8.0、10.0、12.0、15.0 mm,速度约6 km/s,靶室压力分别为6.3,5.0,4.2,3.3 k Pa,采用阴影照相系统测量模型激波脱体距离、电子密度测量系统测量模型尾迹的电子密度分布、X波段单站雷达系统测量在视角为40?的模型及流场的雷达散射截面(RCS)分布.实验结果表明:在速度不变、双尺度参数相同的条件下,随着模型尺寸的增加,激波脱体距离逐渐增加,激波脱体距离与模型直径之比近似相同;不同模型尾迹电子密度测量曲线的趋势和数量级一致,表明不同模型的尾迹流场适用于双缩尺律;不同尺寸模型尾迹的总体RCS与分布RCS均不相同,表明不同模型尾迹的电磁散射不适用于二元缩尺律;高速球模型全目标电磁散射能量分布在模型及其绕流区域、等离子体尾迹区域;高速球模型全目标电磁散射能量在模型及绕流场区域出现1个强散射中心,在模型湍流尾迹区域出现多个散射中心;高速球模型尾迹的RCS测量信号呈现随机性分布特性,幅度脉动和频率脉动均没有周期性;随着模型尺寸的增加,模型尾迹的总体RCS增加,尾迹脉动频率的变化范围减小.     

Photomagnetism of metals. first observation of dependence on polarization of light

We report the first observation of the polarization dependence of the d.c. photocurrent induced by illumination in Cu. The dependence of a d.c. photocurrent on the direction of the plane of light polarization is measured. In agreement with the theoretical considerations, the current parallel to the plane of light incidence is a symmetric function of the angle between this plane and the plane of light polarization. The angular-dependent part of the current perpendicular to the plane of light incidence is an antisymmetric function of the angle.     

Dynamics of Spin Temperatures in EPR on Rapid Switching of the Frequency Detuning of a Saturating Field

In the framework of the spin temperature in EPR in the absence of interaction with the lattice, the time-dependent change in the spin temperatures of the Zeeman subsystem and dipole-dipole reservoir has been investigated theoretically in the high-temperature approximation. It is shown that amplification in the system can be obtained by switching the detuning of the saturating field frequency. The approach to the solution of the problem is based on the fact that during the process of switching and establishment of both temperatures the total energy of the Zeeman subsystem and of the dipole-dipole reservoir is preserved. It has been established that the values of absorption or amplification in the system depend on the frequency detunings of the saturating field. In the presence of a probe field, the possibility of determining the value of the local magnetic field related to the time of transverse relaxation of the system is demonstrated.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 2, pp. 171–175, March–April, 2005.     

Numerical simulation of low-frequency oscillations of the space charge and potential in the electron-optical system of a gyrotron

We present the results of simulating magnetron-injection guns of gyrotrons using the PIC technique for large values of the pitch factor, in which case intense oscillations of the space charge cloud and the related oscillations of the potential in the beam are observed. Time dependences are found for the charge located in the adiabatic trap. The temporal evolution of the potential in different cross sections of the beam and the corresponding frequency spectra are calculated. The process of reflected-particle bombardment of the cathode and the role of the secondary electron emission in the process of particle accumulation in the trap are studied. The beam parameters for regimes with a great share of trapped particles are found and compared with those calculated within the framework of the static model. Time dependences of the current of the beam entering the operating space are analyzed and the electron energy distribution at the input of the gyrotron cavity is found. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 872–879, October 2006.     

Relative contribution of various factors to the formation of the energy spectrum of fast, medium-energy, charged particles and ions transmitted through a thin target with fluctuations of the target thickness

The characteristics of the energy spectra of kiloelectron-volt protons transmitted through a free-standing foil are investigated theoretically and experimentally as functions of the angle of incidence of the beam on the target. Analytical expressions for the average characteristics of the transmitted-particle energy spectrum are determined for the case of small-angle scattering. The combined influence of various factors affecting the formation of the energy spectra is taken into account: systematic stopping of particles in the medium, fluctuations of the particle energy losses in inelastic collisions, bending of the particle trajectories due to multiple elastic scattering, and fluctuations of the target thickness. It is shown that the contributions of these factors to the width of the transmitted-particle energy spectrum depend differently on the angle of incidence of the beam on the target surface. On the basis of this differentiation it is inferred from the experimental dependence of the width of the energy spectra of kiloelectron-volt protons transmitted through a free-standing foil on the angle of incidence of the beam that fluctuations of the particle energy losses in inelastic collisions are the predominant factor in the formation of the proton energy spectra. Zh. Tekh. Fiz. 67, 81–93 (May 1997)     

Longitudinal Current Induced by a Plane Electromagnetic Wave in a Single Atom

The change in the polarization state of the atomic response due to the appearence of the longitudinal component, which has been predicted in [A. Andreev, S. Stremoukhov, and O. Shoutova, Europhys. Lett. 120, 14003 (2017)], has been studied. The dependence of the vector properties of the atomic current induced in an atom with unit angular momentum in the ground state on the properties of a two-color laser field with orthogonally polarized components has been analyzed. It has been shown that the variation of the delay time between the frequency components of the laser field makes it possible to efficiently control the polarization of the components of the atomic response field. The effect of the mutual orientation of the electric component of the laser field and the angular momentum of the atom on the longitudinal component of the atomic current and on the polarization properties of the generated radiation has been demonstrated.     

On the influence of the voltage pulse profile on the process of particle trapping in the adiabatic trap of the gyrotron

We analyze the process of stabilization of electron beam parameters in a gyrotron for different profiles of the front of the accelerating-voltage pulse and the case of a large space charge trapped in the adiabatic trap. The duration of the portion of the pulse front, within which the electrons are reflected from the magnetic mirror and trapped, is at least an order of magnitude shorter than the entire length of the pulse front and is comparable with the characteristic time of potential oscillation development in the trap at great values of the pitch factor. The results of numerical analysis of the electron beam within the framework of models with finite durations of the voltage pulse front and instantaneous switch-on of the voltage showed that the steady-state values of the beam parameters are only weakly dependent on the pro.le of the pulse front. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 425–433, May 2008.     

An ionization gauge with plane electrode system and emission current modulation

The paper is devoted to the study of an ionization gauge with parallel plane electrodes. It deals with the emission current modulation by means of a low-frequency signal, and in particular with the question of the ratio of the anode current to the total emission current and with the effect of this ratio on the ion current. Next it presents the calibration curves of gauges without and with the emission current modulation, and discusses the effect of the capacity between the ion collector and the modulator grid on the lower limit of the gauge measuring range. The results of the gauge calibration in a magnetic field, which prove the usefulness of the gauge for pressure measurements in magnetic fields of variable magnitude, are given in the conclusion of the paper.In conclusion the atuhor wishes to express his thanks to Professor Dr. V. Kunz! for the stimulus to the preparation of this paper, and to A. Ryska and J. Bla~ek for the construction of experimental gauges and for the making of some of the preliminary experiments.     

The dynamics of a slider-crank mechanism with a Fourier-series based axially periodic array non-homogeneous coupler

In industry, many applications of planar mechanisms such as slider-crank mechanisms have been found in thousands of devices. Typically due to the effect of inertia, these elastic links are subject to axial and transverse periodic forces. Vibrations of these mechanisms are the main source of noise and fatigue that lead to short useful life and failure. Hence, avoiding the occurrence of large amplitude vibration of such systems is of great importance. Recently, the use of specified materials, which are periodically embedded into structures, to satisfy designing requirement has been the subject of many interests. Therefore, the objective of this paper is to present analytical and numerical methodologies to study the dynamics of a slider-crank mechanism with an axially periodic array non-homogeneous coupler; the proposed passive system is introduced to reduce the region of parametric resonance of the mechanism. The Fourier-series based approach and Newtonian mechanics are employed in the analysis. An attention is given to the influence produced by the in-homogeneity of materials of the periodic array to the primary region of dynamic instability of the system.Result of present study indicates that under the same operational condition, the commensurability between the natural frequency of the mechanism and the excitation frequency can be weakened by varying the material properties of the periodic array. The in-homogeneity of materials of the periodic array can be treated as a tuning parameter of the natural frequency of the slider-crank mechanism. With proper choice of the material properties and thickness of the embedded laminas of the periodic array, the occurrence of parametric resonance can be suppressed such that the growth of small amplitude vibration into large motion regime is attenuated.     

The nonequilibrium Lorentz gas

We study the conductivity of a Lorentz gas system, composed of a regular array of fixed scatterers and a point-like moving particle, as a function of the strength of an applied external field. In order to obtain a nonequilibrium stationary state, the speed of the point particle is fixed by the action of a Gaussian thermostat. For small fields the system is ergodic and the diffusion coefficient is well defined. We show that in this range the Periodic Orbit Expansion can be successfully applied to compute the values of the thermodynamic variables. At larger values of the field we observe a variety of possible dynamics, including the breakdown of ergodic behavior, and later the existence of a single stable trajectory for the largest fields. We also study the behavior of the system as a function of the orientation of the array of scatterers with respect to the external field. Finally, we present a detailed dynamical study of the transitions in the bifurcation sequence in both the elementary cell and the fundamental domain. The consequences of this behavior for the ergodicity of the system are explored. (c) 1995 American Institute of Physics.     

多光子Jaynes-Cummings模型中与Glauber-Lachs态相互作用原子的熵压缩

利用全量子理论,研究了多光子Jaynes-Cummings模型中与Glauber-Lachs态相互作用的混合态原子的信息熵压缩。讨论了相干平均光子数、热平均光子数、跃迁光子数、原子初态参量对原子信息熵压缩的影响。结果表明原子信息熵 分量没有熵压缩性质;相干平均光子数取值适当时,原子信息熵 分量呈现熵压缩效应;热平均光子数、跃迁光子数会破坏原子信息熵 分量的熵压缩效应;原子初态参量对原子信息熵 分量能否呈现熵压缩效应没有决定性作用;伴随双光子跃迁时,原子的熵压缩因子的时间演化曲线呈现周期性。