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1.
Charge radius and charge form factors of different charge density distributions for 6,8He are calculated with the relativistic Eikonal approximation. Detailed comparisons and discussions are presented. It is found that the charge form factors curves of 6,8He are much lower than the experimental ones of 4He. This is, in principle, consistent with the experimental fact. Whereas detailed comparison among the charge form factors which correspond to different charge distributions show significant deviations. This indicates that the effects of the correlations between the halo neutrons and the α-core in 6,8He with different charge density distributions are quite different. This result would provide a useful reference for the possible experiments on the next-generation electron-nucleus collider and for the tests of different theoretical models for the exotic nuclei 6,8He. 相似文献
2.
The charge form factors of elastic electron scattering for isotones with N=20 and N=28 are calculated using the phase-shift analysis method, with corresponding charge density distributions from relativistic mean-field theory. The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing. The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions, though the proton numbers change uniformly in two isotonic chains. Meanwhile, the shift regularities of the minima are also discussed, and we give a clear relation between the minima of the charge form factors and the corresponding charge radii. This relation is caused by the diffraction effect of the electron. Under this conclusion, we calculate the charge density distributions and the charge form factors of the A=44 nuclei chain. The results are also useful for studying the central depression in light exotic nuclei. 相似文献
3.
Using the recent empirical information on the deuteron electromagnetic form factors we map out the transverse charge density
in the deuteron as viewed from a light front moving towards the deuteron. The charge densities for a transversely polarized
deuteron are characterized by monopole, dipole and quadrupole patterns. 相似文献
4.
Using only the current empirical information on the nucleon electromagnetic form factors we map out the transverse charge density in proton and neutron as viewed from a light front moving towards a transversely polarized nucleon. These charge densities are characterized by a dipole pattern, in addition to the monopole field corresponding with the unpolarized density. Furthermore, we use the latest empirical information on the N-->Delta transition form factors to map out the transition charge density which induces the N-->Delta excitation. This transition charge density in a transversely polarized N and Delta contains both monopole, dipole and quadrupole patterns, the latter corresponding with a deformation of the N and Delta charge distribution. 相似文献
5.
S. Israel K.S. Syed Ali R. Saravanan 《Journal of Physics and Chemistry of Solids》2009,70(8):1185-1194
The electronic structure and hence the valence charge distribution of germanium at 296 and 200 K has been elucidated from structure factors measured by X-ray diffraction experiment using maximum entropy method (MEM) and multipole model. The methods adopted here are used to extract the fine details of the charge density distribution in the valence region. The charge density evaluated using both the models along the bond path and at the mid bond positions are compared and found to confirm the covalent bond existing in the solid. Topology of the charge density in the crystal is analysed and the critical points determined reveal unique spatial arrangement of valence charge in the direction normal to the bonding direction. The Laplacian of the charge density is also analysed for the understanding of the spatial distribution and the partitioning of the valence charge. The local charge concentration and the mapping of the electron pairs of the Lewis and valence shell electron pair repulsion (VSEPR) models have been done using electron localization function (ELF) and localized orbital locator (LOL). 相似文献
6.
应用相对论Eikonal近似计算了用不同模型给出的6,8He的电荷半径和电荷分布的形状因子, 并将结果与6He和4He的实验结果进行了比较. 结果显示不同模型给出的电荷半径和电荷形状因子差别很大, 表明不同模型给出的晕中子与α核芯的关联有很大的差异. 计算和讨论结果为在下一代电子-原子核对撞机上可能进行的实验提供了理论参考, 同时, 也为现有讨论奇特原子核的理论模型提供了检验. 相似文献
7.
N. Bouarissa 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):153-158
Dependencies of electronic structure and lattice properties of InN with zinc-blende structure on hydrostatic pressure are
presented based on band structures computed using the empirical pseudopotential method. The pressure behavior of the pseudopotential
form factors have been analyzed. The effect of pressure on the density of states has been examined. Trends in bonding and
ionicity under pressure are also discussed. Our results show as well that the absolute value of the Fourier transform of the
valence charge density might be useful in the prediction of the phase transition in zinc-blende materials.
Received 25 May 2001 and Received in final form 16 January 2002 相似文献
8.
The two-pion exchange charge density operators are derived in the static approximation. Their contributions to the charge form factors of 3He and 3H are investigated with the use of simple wave functions and are found to be appreciable at high momentum transfer (3 to 5 fm?1). It is also shown that the exchange charge density modifies the enhancement factor of the electric dipole sum rule by around 10%. The distinguishing feature between the isoscalar and isovector exchange charge densities is pointed out. 相似文献
9.
In this paper,the nuclear longitudinal form factors are systematically studied from the intrinsic charge multipoles.For axially deformed nuclei,two different types of density profiles are used to describe their charge distributions.For the same charge distributions expanded with different basis functions,the corresponding longitudinal form factors are derived and compared with each other.Results show the multipoles C_λ of longitudinal form factors are independent of the basis functions of charge distributions.Further numerical calculations of longitudinal form factors of~(12)C indicates that the C_0 multipole reflects the contributions of spherical components of all nonorthogonal basis functions.For deformed nuclei,their charge RMS radii can also be determined accurately by the C_0 measurement.The studies in this paper examine the model-independent properties of electron scattering,which are useful for interpreting electron scattering experiments on exotic deformed nuclei. 相似文献
10.
Galina Z. Krumova Egle Tomasi-Gustafsson Anton N. Antonov 《Central European Journal of Physics》2008,6(3):491-497
The charge form factor of the 6Li nucleus is considered on the basis of its cluster structure. The charge density of 6Li is presented as a superposition of two terms. One of them is a folded density and the second one is a sum of the 4He and deuteron densities. Using the available experimental data for 4He and deuteron charge form factors, a satisfactory agreement of the calculations within the suggested scheme is obtained
with the experimental data for the charge form factor of 6Li, including those in the region of large transferred momenta.
相似文献
11.
J. Hafner 《Solid State Communications》1978,27(3):263-268
The valence electron density is calculated for aluminum, magnesium, and sodium using an OPW-based pseudopotential method. The Fourier transform of the charge density is used to calculate atomic form factors which compare very well with experimental X-ray scattering form factors. The non-local and energy-dependent nature of the pseudopotential and corrections from the orthogonalization hole are shown to be important. 相似文献
12.
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. 相似文献
13.
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. 相似文献
14.
WANG Zaijun & REN Zhongzhou'''' . Department of Physics Nanjing University Nanjing China . Center of Theoretical Nuclear Physics National Laboratory of Heavy-Ion Accelerator at Lanzhou Lanzhou China Correspondence should be addressed to Ren Zhongzhou 《中国科学G辑(英文版)》2004,47(1)
~~Probing proton halo of the exotic nucleus ~(28)S by elastic electron scattering~~ 相似文献
15.
We investigate the spin-dependent effective electron-electron interactions in a uniform system of two-dimensional electrons to understand the spontaneous magnetization expected to occur at very low density. For this purpose, we adopt the Kukkonen-Overhauser form for the effective interactions which are built by accurately determined local-field factors describing the charge and spin fluctuations. The critical behavior of the effective interaction for parallel spin electrons allows us to quantitatively locate the transition to the ferromagnetic state at rs≈27. When the finite width effects are approximately taken into account the transition occurs at rs≈30 in agreement with recent quantum Monte Carlo calculations. 相似文献
16.
The evaluation of elastic and inelastic electron scattering cross sections is discussed in terms of the Fourier-Bessel expansion of the nuclear ground state and transition charge density, respectively. The method allows one to deduce the charge distributions and the moments as well as the corresponding errors, which originate on the one hand from the uncertainties in the measured data and on the other hand from the lack of knowledge about the large-q behaviour of the form factors; these two contributions are determined separately. The method is described and proved with an evaluation of pseudodata and then applied to 208Pb cross sections. For this nucleus, detailed results concerning the possible structure of the charge density are presented. 相似文献
17.
18.
The deuteron transverse charge density ρC(b) is the two-dimensional Fourier transform of its charge form factor in the impact space. We show that different parameterizations of the charge form factors provide different ρC(b), in particular at the central value of impact parameter (b=0), although all the parameterizations can well reproduce the form factors in the region of small Q2. In addition, we also check the explicit contributions from the different coordinate intervals of the deuteron wave function to its root-mean-square radius. 相似文献
19.
Data for coherent photoproduction of π0 mesons from nuclei ( 12C, 40Ca, 93Nb, natPb), recently measured with the TAPS detector at the Mainz MAMI accelerator, have been analyzed in view of the mass form factors
of the nuclei. The form factors have been extracted in plane-wave approximation of the A(γ,π0)A reaction and corrected for final-state interaction effects with the help of distorted-wave impulse approximations. Nuclear
mass rms radii have been calculated from the slope of the form factors for q2 → 0. Furthermore, the Helm model (hard-sphere form factor folded with Gaussian) was used to extract diffraction radii from
the zeroes of the form factor and skin thicknesses from the position and height of its first maximum. The diffraction radii
from the Helm model agree with the corresponding charge radii obtained from electron scattering experiments within their uncertainties
of a few per cent. The rms radii from the slope of the form factors are systematically lower by up to 5% for PWIA and up to
10% for DWIA. Also the skin thicknesses extracted from the Helm model are systematically smaller than their charge counterparts. 相似文献
20.
《Annals of Physics》1985,159(2):467-480
The three-dimensional Schrödinger equation with an effective mass is solved for a new class of angular momentum dependent potentials with varying depths and shapes. The energy eigen, values and resonances are given in algebraic form as a function of the effective mass and depth and shape of the potential. The eigenfunctions, scattering function, and Green's function are given in closed form in terms of known special functions. The charge density of 208Pb is calculated using eigenfunctions of a particular potential and this charge density is compared to the measured charge density. 相似文献