Kinetics of ions in a neutral gas upon abrupt application of an electric field. I. CEM model

A new method for calculating matrix elements of the collision integral is used for solving problems of the mobility of ions against the background of atoms and for constructing the distribution functions for ions upon an abrupt application of an electric field. It is shown how the stationary distribution function can be constructed using the nonstationary moments method in the case when the stationary moments method is completely inapplicable. The solution to the nonstationary problem for the CEM model corresponding to resonant charge exchange with a constant collision frequency, which is constructed analytically, is used for analyzing the limits of applicability of the nonstationary moments method.     

Influence of kinematical constraints on multiplicity distributions and neutral charged correlations in the independent cluster emission model

Energy-momentum conservation in the cluster production process is introduced in the independent cluster emission model using the generating functional formalism. In a simple version of the model clusters are produced which decay into a fixed number of pions. The ?? model and a model with isospin conservation in the cluster decay are used to calculate the charge distribution among the secondaries of cluster decay. Multiplicity characteristics like average multiplicity, second moments and associated average neutral multiplicities and second moments are calculated. The results are compared with experimental data.     

Chemisorption of Li and Na on iridium surfaces: An investigation with nuclear spin polarized atoms

The chemisorption of Li and Na on clean and oxygen covered polycrystalline iridium was investigated using nuclear spin polarized alkali atoms. During adsorption on the surface the moments of the nuclei act as microscopic probes. The nuclear quadrupole moments of the alkali atoms are interacting with the electric field gradient. The interaction reflects the charge distribution around the nucleus. The nuclear magnetic moments are interacting with magnetic fields generated by the magnetic moments of electrons.     

Fluctuations of Induced Charge in Hemispherical Detectors

Detectors with hemispherical geometry are used to eliminate the contribution from the hole component to the signal of a detector based on a compound semiconductor operating at room temperature. In this work, the random process of charge induction on electrodes of a detector with hemispherical geometry is theoretically considered with allowance for capture of electrons by traps. Formulas are obtained for the first two moments of the distribution function for the induced charge on the detector electrodes. These formulas help analyze the contribution of the electron transport in detectors with hemispherical geometry.     

自仿集的势论和分析性质

研究了关于自仿集上电荷分布的势论及有关分析性质。指出电荷分布、势及其Fourier变换的构造性质;明确给出了三分Cantor集上二项分布及其矩、Fourier变换、势的具体表达式;并给出一些数值结果。     

强外电场作用下CCl3F物理特性与光谱

运用密度泛函理论在6-311++G（d,p）基组上进行优化并在x轴方向增加电场（F=-0.025~0.025 a.u.）,对CCl₃F分子结构、偶极矩、总能量、电荷分布和能隙、C-Cl键特征吸收峰进行研究.结果表明：随着外场强度的增加,C-Cl键键长逐渐减小,偶极矩先减小后增大,总能量先增大后减小,Cl原子的电荷分布逐渐增大,当F=-0.015 a.u.时,由负电性转变为正电性,达到新的亲核亲电反应作用点.而能隙在没有外加电场时也达到最小值,此时最容易发生电场降解反应.C-Cl键的红外特征吸收峰随着负电场的增强出现蓝移.     

Charge-drift and dispersion in deep inelastic collisions in an equilibrium model

First and second moments of the charge distribution for the reaction⁸⁶K +¹⁶⁶Er have been calculated assuming a thermal equilibrium model. The moments are calculated microscopically on the basis of a realistic two-center shell model as a function of distance as well as of excitation energy. The experimentally observed constancy of the first moments is reproduced.     

Extracting double layer charge density distributions using themethod of moments

Using the method of moments, it is shown that the charge distribution can be directly extracted from a measured potential profile. The technique is described and placed on a theoretical foundation. The predicted charge distribution for a potential profile V=V₀ tanh (x/L) using this technique is compared with a direct solution of Poisson's equation. It is shown that similar results are obtained even if random noise is present in the system     

Kinetics of dipole moments of polyatomic molecules

The relations that link the time dependences of the dipole moments of the ground and excited states of a molecular system whose charge distribution is nonstationary with the correlation functions of the shift of the absorption and emission spectra of this system are derived on the basis of of the well-known equations of solvatochromism. The calculated dependences of the kinetics of the dipole moments of the excited singlet states of dimethylaminobenzonitrile and 4-dimethylamino-4′-cyanostilbene in some polar solvents are presented.     

Ground state correlations and the nuclear charge distribution

Combining a sum rule approach and the generator coordinate model we evaluate the influence of ground state correlations on the moments of the radial charge distribution. The isotopic and isotonic differences of the moments come out to be particularly sensitive to fluctuations of the ground state correlations due to changes in the low energy spectrum. A comparison with the experimental results for the isotopes of Ca, Fe, Ni and Zn shows a fair agreement and confirms the importance of the ground state correlations for isotopic and isotonic differences of radial moments.     

Elastic charge density representation of the interaction via the nematic director field

The interaction between particle-like sources of the nematic director distortions (e.g., colloids, point defects, macromolecules in nematic emulsions) allows for a useful analogy with the electrostatic multipole interaction between charged bodies. In this paper we develop this analogy to the level corresponding to the charge density and consider the general status of the pairwise approach to the nematic emulsions with finite-size colloids. It is shown that the elastic analog of the surface electric charge density is represented by the two transverse director components on the surface imposing the director distortions. The elastic multipoles of a particle are expressed as integrals over the charge density distribution on this surface. Because of the difference between the scalar electrostatics and vector nematostatics, the number of elastic multipoles of each order is doubled compared to that in the electrostatics: there are two elastic charges, two vectors of dipole moments, two quadrupolar tensors, and so on. The two-component elastic charge is expressed via the vector of external mechanical torque applied on the particle. As a result, the elastic Coulomb-like coupling between two particles is found to be proportional to the scalar product of the two external torques and does not directly depend on the particles' form and anchoring. The real-space Green function method is used to develop the pairwise approach to nematic emulsions and determine its form and restrictions. The pairwise potentials are obtained in the familiar form, but, in contrast to the electrostatics, they describe the interaction between pairs (dyads) of the elastic multipole moments. The multipole moments are shown to be uniquely determined by the single-particle director field, unperturbed by other particles. The pairwise approximation is applicable only in the leading order in the small ratio particle size-to-interparticle distance as the next order contains irreducible three-body terms.     

Magnetic multipole moments

Literature definitions of magnetic multipole moment operators are shown to be at variance, and new definitions are formulated which are consistent with a general multipole interaction hamiltonian and with the radiation field of a dynamic charge distribution. The applicability of traceless multipole moments is examined.

The multipole hamiltonian is used to derive expressions for some magnetic quadrupole distortion tensors. For those describing the quadrupole moment induced by a magnetic field and by a field gradient the number of independent components for various molecular symmetries is evaluated.     

Vanishing of the fusion-like process in heavy-ion collisions

With high resolution collinear fast beam laser spectroscopy in the 451 nm-line of Indium nuclear moments and the change in the mean square radii of the nuclear charge distribution of^105,106 In have been determined.     

Shallow center in AgBr: Theoretical investigation by sum rules

In AgBr, an absorption band at 168 cm^?1 can be attributed to absorption by an electron bound in an electrostatic potential. The comparison between the experimental values of the moments of the absorption coefficient and their theoretical expressions gives the ground state mean radius, mean kinetic energy and mean charge density seen by the electron. The ionization energy and electron charge distribution of this center are also obtained.     

potential theory and analytic properties of self-similar fractal and multifractal distributions

By the use of recursion relations and analytic techniques we deduce general analytic results pertaining to the electrostatic potential, moments, and Fourier transform of exactly self-similar fractal and multifractal charge distributions. Three specific examples are given: the binomial distribution on the middle-third Cantor set, which is a multifractal distribution, the uniform distribution on the Menger sponge, which illustrates the added complication of higher dimensionality, and the uniform distribution on the von Koch snowflake, which illustrates the effect of rotations in the defining transformations.     

Proton electromagnetic-form-factor ratios at low Q2

We study the ratio R identical with muG_{E}(Q2)/G_{M}(Q2) of the proton at very small values of Q2. Radii commonly associated with these form factors are not moments of charge or magnetization densities. We show that the form factor F2 is correctly interpretable as the two-dimensional Fourier transformation of a magnetization density. A relationship between the measurable ratio and moments of true charge and magnetization densities is derived and used to show that the magnetization density extends further than the charge density, in contrast with expectations based on the measured reduction of R as Q2 increases.     

Oscillations of the magnetic polarization in a Kondo system at finite magnetic fields

The electronic properties of a Kondo impurity are investigated in a magnetic field using linear response theory. The distribution of electrical charge and magnetic polarization are calculated in real space. The (small) magnetic field does not change the charge distribution. However, it unmasks the Kondo cloud and generates a Kondo polarization. The weight of the d-electron components with their magnetic moment up and down is shifted and the compensating moments of the s-electron clouds don’t cancel any longer (a requirement for an experimental detection of the Kondo cloud). In addition to the polarization cloud (of the conduction electrons) an oscillating polarization component with a period of half the Fermi wave length is observed. This represents an internal electronic structure of the Kondo impurity.     

Impact parameter dependence of electronic energy loss

Energy-loss moments of the electronic energy loss are calculated as functions of impact parameter for protons of 1 to 7 MeV incident upon Be, Al, Cu, Ag, and Ta targets. The Lindhard dielectric-function formalism is used, in the local-density approximation. The target-atom electron densities are Lenz-Jensen, and the projectile is a point charge. The moments are fitted by a simple algebraic function, and the energy and Z₂ dependence of the parameters of this function are given.     

Static observables of relativistic three-fermion systems with instantaneous interactions

We show that static properties like the charge radius and the magnetic moment of relativistic three-fermion bound states with instantaneous interactions can be formulated as expectation values with respect to intrinsically defined wave functions. The resulting operators can be given a natural physical interpretation in accordance with relativistic covariance. We also indicate how the formalism may be generalized to arbitrary moments. The method is applied to the computation of static baryon properties with numerical results for the nucleon charge radii and the baryon octet magnetic moments. In addition, we make predictions for the magnetic moments of some selected nucleon resonances and discuss the decomposition of the nucleon magnetic moments in contributions of spin and angular momentum, as well as the evolution of these contributions with decreasing quark mass.