Diffraction of guided waves by the end face of a dielectric slab waveguide terminated with a finite conductive strip

The diffraction of guided waves by the end face of a dielectric slab waveguide short circuited with a finite conductive strip is analyzed. An integral equation technique is employed to formulate the corresponding boundary problem. The unknown term in this integral equations is the electric field E(x) on the terminal plane of the waveguide. The homogeneous term is determined from the incident guided wave. A method of moments technique is employed to compute approximately the electric field E(x) by using Laguerre functions as describing and testing functions. The reflection coefficients of the guided waves are computed by using the approximate expression of the E(x) field. Numerical results are given for several guide and conductor plate dimensions.     

Electric quadrupole and hexadecupole nuclear excitations from the perspectives of electron scattering and modern shell-model theory

Shell-model wave functions obtained from a complete, unified treatment of the structure of the positive parity states in nuclei between ¹⁶O and ⁴⁰Ca are used to calculate the features of inelastic electron scattering to 2+ and 4+ states in this region. These predictions of E2 and E4 form factors, and the corresponding elastic scattering predictions, are compared with the collected experimental data which are available on this topic. The dependence of the calculated results upon alternate models for single-nucleon wave functions and core-polarization transition densities is investigated, as is the consistency between the (e,e′) measurements and the analogous B(E2) measurements.     

Resonance Structure of the Charge-Exchange Strength Function for the Molybdenum Isotopes $${}^{{98,100}}$$ Mo

Physics of Atomic Nuclei - The charge-exchange strength functions $$S(E)$$ for the isotopes $${}^{98,100}$$ Mo are presented. Both experimental data obtained for the strength functions $$S(E)$$ in...     

Approximate Solutions of Dirac Equation with Hyperbolic-Type Potential

The energy eigenvalues of a Dirac particle for the hyperbolic-type potential field have been computed approximately. It is obtained a transcendental function of energy, F(E), by writing in terms of confluent Heun functions.The numerical values of energy are then obtained by fixing the zeros on "E-axis" for both complex functions Re[F(E)]and Im[F(E)].     

Approximate Solutions of Dirac Equation with Hyperbolic-Type Potential

The energy eigenvalues of a Dirac particle for the hyperbolic-type potential field have been computed approximately. It is obtained a transcendental function of energy, F(E), by writing in terms of confluent Heun functions. The numerical values of energy are then obtained by fixing the zeros on "E-axis" for both complex functions Re[F(E)] and Im[F(E)].     

Retardation of E1 transitions and the neutron effective charge in 29Si

The effect of the giant dipole resonance on E1 transition rates is investigated, and an expression is derived which allows E1 effective charges to be calculated using the γ-absorption cross section of the neighbouring even-mass core. It is shown how this expression can be approximated using a sum rule in cases where the absorption cross section is not adequately known. Application is made to ²⁹Si; using wave functions from a particle-core model, calculated E1 transition rates are in excellent agreement with experiment.     

Intermediate-coupling calculation for 10B in a projected Hartree-Fock basis

A shell-model calculation is carried out for ¹⁰B in intermediate coupling. The deformation of the shell-model field is taken into account by using as a basis the functions obtained from a projected Hartree-Fock calculation. The resulting wave functions give an important improvement for the E2 matrix elements with respect to the conventional shell model. Some remaining difficulties are discussed.     

Motional narrowing and ergodic bands in excited superdeformed states of 194Hg

The E(gamma) - E(gamma) coincidence spectra from the electromagnetic decay of excited superdeformed states in (194)Hg reveal surprisingly narrow ridges, parallel to the diagonal. A total of 100-150 excited bands are found to contribute to these ridges, which account for nearly all the unresolved E2 decay strength. Comparison with theory suggests that these excited bands have many components in their wave functions, yet they display remarkable rotational coherence. This phenomenon can be explained in terms of the combination of shell effects and motional narrowing.     

Radiative strength functions in odd-A spherical nuclei

The radiative strength functions for the partial γ-transitions from neutron resonances to the ground and low-lying states of odd-A spherical nuclei are calculated within the quasiparticle-phonon nuclear model. The fragmentation of one-quasiparticle and quasiparticle-plus-phonon states is calculated. This allowed one to calculate γ-transitions between the one-quasi-particle components (valence transitions) and γ-transitions between the quasiparticle-plus-phonon and one-quasiparticle components of the wave functions. The energy dependence of the strength functions $\text{C}$(E1, η) and $\text{C}$(M1, η) is calculated near the neutron binding energy B_n for ⁵⁵Fe and ^{59, 61}Ni. The corresponding experimental data are described qualitatively. The contribution of the valence E1 transitions to the strength function is shown to be from 20% to 90%, and M1 transitions about 1%. The influence of the M1 giant resonance is important for M1 transition probabilities.     

Quark Energy Loss and Shadowing in Nuclear Drell-Yan Process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Dre11-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Dre11-Yan production cross sections are analyzed for 800 GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from those of the FNAL E866, who analyzes the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic IA collisions and pA nuclear Drell-Yan data. Considering the existence of energy loss effect in Drell-Yan lepton pairs production, we suggest that the extraction of nuclear parton distribution functions shoul““““d not include Dre11-Yan experimental data.     

Quark Energy Loss and Shadowing in Nuclear Drell-Yan Process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Drell-Yan production cross sections are analyzed for 800 GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from those of the FNAL E866, who analyzes the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic IA collisions and pA nuclear Drell-Yan data. Considering the existence of energy loss effect in Drell-Yan lepton pairs production, we suggest that the extraction of nuclear parton distribution functions should not include Drell-Yan experimental data.     

等离子体中粒子与cavitons相互作用

从Vlasov-Poisson方程组出发,我们导出了电子慢变分布函数δF_e,慢变场E_s和快变场E之间耦合的动力学方程组,并在一维稳态下解析求解了这一方程组,从而获得了粒子分布函数与soliton作用关系;进一步讨论了高维下δF_e,E_s,E塌缩运动和它们的多个cavitons行为。 关键词：     

Dielectric properties of ice and liquid water from first-principles calculations

We present a first-principles study of the static dielectric properties of ice and liquid water. The eigenmodes of the dielectric matrix E are analyzed in terms of maximally localized dielectric functions similar, in their definition, to maximally localized Wannier orbitals obtained from Bloch eigenstates of the electronic Hamiltonian. We show that the lowest eigenmodes of E (-1) are localized in real space and can be separated into groups related to the screening of lone pairs, intra-, and intermolecular bonds, respectively. The local properties of the dielectric matrix can be conveniently exploited to build approximate dielectric matrices for efficient, yet accurate calculations of quasiparticle energies.     

An approximate projection technique for the calculation of electromagnetic properties of deformed nuclei

A three-dimensional angular momentum projection is carried out for cranking model wave functions. The projected matrix elements of electromagnetic operators are evaluated using a method originally developed by Kamlah for the case of projected energy, which is valid for large deformations and weakly triaxial nuclei. The calculated spectroscopic quadrupole moments deviate substantially from the predictions of a rigid rotor model with axial symmetry. For E2 transitions the deviations are small. Projected values of the magnetic moments are almost identical with those of a semiclassical calculation. Cranking model wave functions are decomposed into its components having good angular momentum.     

Corrected expressions of the electromagnetic transitions in the ϵ-representation of the Nilsson model

Expressions for the E1 and E2 transition operators are given as functions of the stretched coordinates of the particle. Basis-independent relations follow between the corrected and non-corrected matrix elements. The differences between the associated numerical values appear to be most significant in the E2, $\text{Δ, Ω = 0}$ case.     

Nuclear parton distribution functions and energy-loss effect in the Drell-Yan reaction off nuclei

The energy-loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of two typical kinds of quark energy-loss parametrization and the different sets of nuclear parton distribution functions, we present an analysis of the E866 experiments on the nuclear dependence of Drell-Yan lepton pair production resulting from the bombardment of Be, Fe and W targets by 800 GeV protons at Fermilab. It is found that the quark energy loss in cold nuclei is strongly dependent on the used nuclear parton distribution functions. The further prospects of using relatively low energy protons incident on nuclear targets are presented by combining the quark energy-loss rate determined from a fit to the E866 nuclear-dependent ratios versus x ₁, with the nuclear parton distribution functions given from lA deep inelastic scattering (DIS) data. The experimental study of the relatively low energy nuclear Drell-Yan process can give valuable insight in the energy loss of the fast quark propagating through cold nuclei and help to pin down nuclear parton distribution functions.Received: 8 September 2004, Revised: 18 October 2004, Published online: 11 January 2005PACS: 24.85. + p, 13.85.Qk, 25.40.-h, 25.75.Nq     

On Continuous Hochschild comology and Cohomology Groups

Using the method of continuous projective resolutions established by Alain Connes, we calculate the continuous Hochschild homology and cohomology groups of the Fréchet algebra of smooth functions on a manifold M. These (co)homology groups are allowed to take values in the Fréchet space E of smooth sections of a vector bundle E over M and in the strong dual E*. Moreover, we show that in the cohomological case the differential and continuous Hochschild cohomologies are naturally isomorphic.     

Static quadrupole moments and B(E2)(0 → 2) values in 2p-1f shell nuclei

The quadrupole moments of the first excited states and the reduced transition probabilities for E2 transitions in even-even Ti, Cr, Fe and Ni isotopes are calculated from the projected Hartree-Fock-Bogolubov wave functions in the 2p-1f shell. The overall agreement between the calculated and experimental results is quite good.     

中能区40Ar+197Au反应中轻粒子的发射时间测量

本文报道了25MeV/u ⁴⁰Ar+¹⁹⁷Au反应中粒子-粒子关联函数的实验结果.利用三体弹道模型从关联函数提取了轻粒子发射时间.轻粒子的平均发射时间随粒子能量而变化,从低能时的约300fm/c下降至高能时的约100fm/c.     

Si／Ge应变层超晶格的椭偏光谱

测量了几种不同组分的（Ｓｉ）Ｍ／（Ｇｅ）Ｎ应变超晶格材料的椭偏光谱（２．０～５．０ｅＶ），并得到了其介电函数谱；应用介电函数的临界点理论，研究了（Ｓｉ）Ｍ／（Ｇｅ）Ｎ应变超晶格材料的光学性质。发现短周期Ｓｉ／Ｇｅ应变超晶格除了具有明显的Ｅ１和Ｅ２带间跃迁外，还存在与应力和超晶格能带的折迭效应有关的跃迁峰，其能量分别位于２．３～３．０ｅＶ和３．３～４．０ｅＶ范围内