静电系统受力和力矩计算

具有终端的静设备系统,是一种把电能转移为机械能的换能器。根据能量守恒和转换定律,导出该静电系统受力和力矩的两种计算方法及应用实例。     

用计算机模拟点电荷在二维平面上的静电场

二维平面上的点电荷的静电场是静电场问题的基础，作者独立开发了软件用以模拟，此程序由用户决定点电荷的所有参数，快速地生成视阈内的等势线与电场线，使用户方便的获得电场直观印象，并可以得到任意点的电势与场强，该程序操作简单，对于学生、教师的学与教都能起到很好的辅助作用。     

FTIR and FT‐Raman spectra and density functional computations of the vibrational spectra,molecular geometry and atomic charges of the biomolecule: 5‐bromouracil

FTIR and FT‐Raman spectra of 5‐bromouracil in the powder form were recorded in the region 400–4000 cm⁻¹ and 50–4000 cm⁻¹, respectively. The observed wavenumbers were analysed and assigned to different normal modes of vibration of the molecule. Quantum chemical calculations were performed to support the assignments of the observed wavenumbers. The performance of the B3LYP hybrid density functional (DFT) method was compared with other methods. With the 6–31 G** and 6–311 + G(2d,p) basis sets, the calculated geometry, dipole moments and harmonic vibrations were determined. A comparison with the uracil molecule was made, and specific scale factors were deduced and employed in the predicted wavenumbers of 5‐bromouracil. The total atomic charges and thermodynamic parameters were calculated, and are discussed briefly. Structure and harmonic vibrations of 5‐bromouracil were also calculated in the presence of water within a simple model with one molecule. It is observed that the bromine atom at position 5 exhibits smaller inductive effects than the fluorine atom, producing a small distortion of the electrostatic potential around the ring and a reduction of the molecular dipole moment. Copyright © 2007 John Wiley & Sons, Ltd.     

Advanced adiabatic approximation for momentum distributions of ejected electrons in slow atomic collisions

The problem of determination of momentum distributions of ejected electrons in slow atomic collisions is studied within the impact-parameter method by using a dynamic adiabatic basis which takes into account the correct boundary conditions. An expression is obtained which relates the momentum distribution of the ejected electrons with a coherent sum of the delocalized dynamic adiabatic eigenstates (elementary wavepackets). The form of the momentum distribution exactly coincides with the form of the total wavepacket in configuration space. General formulas are applied to a model problem of electron detachment in the process in which the electron-atom interactions are described by the zero-range potentials. In the example considered, the momentum distribution of ejected electrons, in the center-of-mass frame, exhibits a maximum located in the scattering plane on the circle of radius (in atomic units), where v is the relative collision velocity and is the impact parameter. Received: 5 October 1998     

Non-partial-wave Coulomb-Born theory for the excitation of many-electron atomic ions II: Numerical description and application

A non-partial-wave Coulomb-Born theory is recently formulated to treat the excitation of many-electron atomic ions for impact by an arbitrary charged particle [Y.B. Duan et al., Phys. Rev. A 56, 2431 (1997)]. The multiple expansion of the transition matrix element is decomposed into the target form factor and the projectile form factor. These are the matrix elements of the tensor operators between quantum states so that any complicated wave function for the target ion can be employed. In this formal theory, an infinitesimally small positive quantity is introduced artificially to guarantee the convergence of integrals. As a supplementary part of the theory, we discuss how to choose the value of . It is found that the should be taken as functions of the momentum transfer and multipolarity . Illustrations are carried out by calculating the cross-sections for some typical transitions n _a l _a -n _b l _b of hydrogen-like ions for impact by electron, positron, and proton, respectively. The resulting cross-sections are in good agreement with ones produced by using a method available for ion targets with Slater-type orbitals [N.C. Deb, N.C. Sil, Phys. Rev. A 28, 2806 (1993)]. Comparisons demonstrate that the Coulomb-Born theory with non-partial wave analysis provides a powerful method to treat the excitation of many-electron atomic ions impact by an arbitrary charged particle. Received 6 April 1999     

Mean field methods for atomic and nuclear reactions: The link between time–dependent and time–independent approaches

Abstact: Three variants of mean field methods for atomic and nuclear reactions are compared with respect to both conception and applicability: The time–dependent Hartree–Fock method solves the equation of motion for a Hermitian density operator as initial value problem, with the colliding fragments in a continuum state of relative motion. With no specification of the final state, the method is restricted to inclusive reactions. The time–dependent mean field method, as developed by Kerman, Levit and Negele as well as by Reinhardt, calculates the density for specific transitions and thus applies to exclusive reactions. It uses the Hubbard–Stratonovich transformation to express the full time-development operator with two–body interactions as functional integral over one–body densities. In stationary phase approximation and with Slater determinants as initial and final states, it defines non–Hermitian, time–dependent mean field equations to be solved self–consistently as boundary value problem in time. The time–independent mean field method of Giraud and Nagarajan is based on a Schwinger–type variational principle for the resolvent. It leads to a set of inhomogeneous, non-Hermitian equations of Hartree–Fock type to be solved for given total energy. All information about initial and final channels is contained in the inhomogeneities, hence the method is designed for exclusive reactions. A direct link is established between the time–dependent and time–independent versions. Their relation is non–trivial due to the non–linear nature of mean field methods. Received: 7 January 1998 / Revised version: 20 April 1998