Multi-Electron Processes in ^13C^6＋ Ions with Neon Collisions in Energy Region 4.15-11.08 keV/u

The cross-section ratios of double-, triple-, quadruple-, and the total multi-electron processes to the single electron capture process （σ^DE/σ^SC, σ^TE/σ^SC, σ^QE/σ^SC and σ^ME/σ^SC） as well as the relative ratios among reaction channels in double-electron active, triple-electron active and quadruple-electron active are measured in ^13C^6＋_Ne collision in the energy region of 4.15-11.08keV/u by employing position-sensitive and time-of-flight coincident techniques. It is determined that the cross-section ratios σ^DE /σ^SC, σ^TE /σ^SC, σ^QE /σ^SC and σ^ME /σ^SC are approximately the constants of 0.20 ± 0.03, 0.16 ± 0.04, 0.06 ± 0.02 and 0.42 ± 0.05. These values are obviously smaller than the predictions of the molecular Coulomb over-the-barrier model （MCBM） [J. Phys. B 23 （1990） 4293], the extended classical over-the-barrier model （ECBM） [J. Phys. B 19 （1986） 2925] and the semiempirical scaling laws （SL） [Phys. Rev. A 54 （1996） 4127]. However, the relative ratios among partial processes of DE, TE and QE are found to depend on collision energy, which suggests that the collision dynamics depends on the collision velocity. The limitation of velocity-independent character of ECBM, MCBM and SL is undoubtedly shown.     

Radius studies of 8Li and 8B using the optical-limit Glauber model in conjunction with relativistic mean-field theory

We study the reaction cross sections(σR) and root-mean-square(RMS) radii of 8Li and 8B,the halo-like nuclei,with stable target 12C,27Al and 9Be within the standard optical-limit Glauber model,using densities obtained from relativistic mean-field(RMF) formalisms and other types of distributions.It is found that the experimental σR can be reproduced well at high energy.The RMS radius and △r extracted by RMFtheory and harmonic oscillator distribution are compared.We find that the RMS radius and △r of 8B are larger than those of 8Li.In addition,we analyze in detail the relationship between σR and density distribution.     

Method for measuring prompt γ-rays generated by D-T neutrons bombarding a depleted uranium spherical shell

The prompt γ-ray spectrum from depleted uranium(DU) spherical shells induced by 14 Me V D-T neutrons is measured. Monte Carlo(MC) simulation gives the largest prompt γ flux with the optimal thickness of the DU spherical shells 3–5 cm and the optimal frequency of neutron pulse 1 MHz. The method of time of flight and pulse shape coincidence with energy(DC-TOF) is proposed, and the subtraction of the background γ-rays discussed in detail. The electron recoil spectrum and time spectrum of the prompt γ-rays are obtained based on a 2 ×2 BC501 A liquid scintillator detector. The energy spectrum and time spectrum of prompt γ-rays are obtained based on an iterative unfolding method that can remove the influence of γ-rays response matrix and pulsed neutron shape.The measured time spectrum and the calculated results are roughly consistent with each other. Experimental promptγ-ray spectrum in the 0.4–3 Me V energy region agrees well with MC simulation based on the ENDF/BVI.5 library,and the discrepancies for the integral quantities of γ-rays of energy 0.4–1 Me V and 1–3 Me V are 9.2% and 1.1%,respectively.     

Multiscalar B-L extension based on S4flavor symmetry for neutrino masses and mixing

A multiscalar and nonrenormalizable B-L extension of the standard model(SM)with S₄symmetry which successfully explains the recently observed neutrino oscillation data is proposed.The tiny neutrino masses and their hierarchies are generated via the type-I seesaw mechanism.The model reproduces the recent experiments of neutrino mixing angles and Dirac CP violating phase in which the atmospheric angle(θ₂₃)and the reactor angle(θ₁₃)get the best-fit values while the solar angle(θ₁₂)and Dirac CP violating phase(δ)are in 3σrange of the best-fit value for the normal hierarchy(NH).For the inverted hierarchy(IH),θ13 gets the best-ft value andθ₂₃together withδare in the lσrange,whileθ12 is in 3δrange of the best-fit value.The effective neutrino masses are pre-dicted to be(m_ee)=6.81 meV for the NH and(m_ee)=48.48 meV for the IH,in good agreement with the most re-cent experimental data.     

A Discussion on Whether 15-20C Are All Skin Nuclei via Isospin-dependent Boltzmann-Langevin Equation

A new attempt of calculation for the toted reaction cross sections （σR） has been carried out within the isospindependent Boltzmann-Langevin equation in the intermediate energy heavy-ion collision of isotopes of C. The σR of both stable and exotic nuclei are reproduced rather well. The incident energy and isospin dependencies of σR have been investigated. It is found that the isospin effect is comparatively remarkable at intermediate energy. It is also found that 15-18C are neutron skin nuclei but for 19C and 20C we cannot draw a conclusion whether they have halo structures.     

Multi-Electron Processes in 4.15-11.08 keV/u^13C^6＋ on Argon Collisions

The relative partial cross sections for ^13C^6＋ -Ar collisions at 4.15-11.08 ke V/u incident energy are measured. The cross-section ratios σ^2E/σ^SC, σ^3E/σ^SC, σ^4E/σ^SC and σ^SE/σ^SC are approximately the constants of 0.514-0.05, 0.204-0.03, 0.064-0.03 and 0.024-0.01 in this region. The significance of the multi-electron process in highly charged ions （HCIs） with argon collisions is demonstrated （σ^ME/σ^SC as high as 0.794-0.06）. In multi-electron processes, it is shown that transfer ionization is dominant while pure electron capture is weak and negligible. For all reaction channels, the cross-sections are independent of the incident energy in the present energy region, which is in agreement with the static characteristic of classic models, i.e. the molecular Coulomb over-the-barrier model （MCBM）, the extended classical over-the-barrier model （ECBM） and the semiempirical scaling laws （SL）. The result is compared with these classical models and with our previous work of ^13C^6＋ -Ne collisions [Chin. Phys. Lett. 23 （2006） 95].     

Measurement of ^16O^5＋ Induced L X-Ray Production Cross Sections for Gold

The characteristic L1, Lα, Lβ and Lγ x-rays of Au and energy shifts produced by 20-50 MeV ^16O^5＋ beams on a thick Au film are measured with a Si （Li） detector. Cross-section ratios of σ（Ll）/σ（Lα）, σ（Lβ）/σ（Lβ） and σ（Lγ）/σ（Lα） versus O^5＋ energy show that consistent calculations yield considerably better agreements. Energy shifts L1, Lα, Lβ and Lγ x-rays of Au target increase with more incidence energy. The main application for these measurements is multi-element trace analysis through particle induced x-ray emission.     

Matching Condition in γ-γ Annihilation Absorption

Two-photon annihilation (γ-γ reaction) is an important absorption mechanism in γ-ray physics and γ-ray astronomy. Using the markedly simplified direction-averaged cross section of annihilation σ^-(ω,ω’) for a normal isotropic ambient radiation field around the γ-ray source, we obtain a matching condition for the energies of two interacting photons, which ensures the attainment of the maximum annihilation probability. This is a new result that is helpful to obtain a better understanding for the absorption behaviour in the γ-γ annihilation process,and this predicts some possible line-like absorption structures in the emergent γ-ray continuous spectra. Some inferences of the matching condition are also presented.     

Enhancement of upconversion luminescence of YAlO3：Er^3＋ by Gd^3＋ doping

Two series of Yb3+-doped silica glasses (YA and YAP) are fabricated using the sol-gel method, and their spectroscopic properties are investigated. The longest fluorescence lifetime of 0.96 ms is obtained in YAP2 and YAP3 glasses. The emission cross-section (σemi) and σemi ×τ of Yb3+ in the YAP1 glass are 1.00 pm2 and 0.94 pm2·ms, respectively. Co-doping with Al and P decreases the hydroxyl group content in the glasses because of the reduction in non-bridging oxygen content. The lowest OH content in the YAP3 glass is 9.6 ppm.     

Elastocaloric Effect in PbTiO_3 Thin Films with 180° Domain Structure: A Phase Field Study

The elastocaloric effect of Pb TiO_3 thin films with 180°domain structure is studied using the phase field method.The influence of external stress σ_(33),misfit strain u_m and domain wall energy on the adiabatic temperature change(ΔT_σ)at room temperature are carried out.The calculation results indicate that|ΔT_σincreases as|σ_(33)|or|u_m|increases.The largest ΔT_σ value of-7.8 K is obtained atσ_(33)=2 GPa and u_m=-0.02.Furthermore,thedomain switching behaviors under different gradient coefficients are different,and finally affect the elastocaloriceffect in PTO thin films.These results could provide a guide to choose the substrate and the preparation processin experiments.     

A New CKP Hierarchy with Two Generalized Time Series and ItsReduction

A new C-type subhierarchy for KP hierarchy with two new time series γ_n and σ_k ((γ_n,σ_k)-CKPH), which consists of γ_n-flow,σ_k-flow and mixed γ_n and σ_kevolution equations of eigenfunctions, is proposed. The zero-curvature representation for the (γ_n,σ_k)-CKPH is derived. The reduction and constrained flows of (γ_n,σ_k)-CKPH are studied.     

THE FACTORS FOR THE EMC PHENOMEKON AND THE RATIO RA=(σL/σT)A

The three factors are discussed which may be related to the EMC phenomenon directly, and it is tried to understand the new results on the ratio R^A=(σ_L/σ_T)_A. It is also pointed out that shadowing cannot match the obvious deviation in the small x region between the data obtained by the two categories of experiments PA and eA.     

Study of Defect-Layers Effect in Ferroelectric Thin Film with TransverseIsing Model

By taking into account the two-spin interaction in the transverse Ising model (TIM), the influence of the defect layers (including J_B andΩ_B on the polarization and Curie temperature are calculated numerically, within the framework of the decoupling approximation under Green's function. The numerical results show that the polarization and Curie temperature will both become large sensitively due to the large values ofJ_B and the small value of Ω_B of the defect layers. Meanwhile, the dependence of the crossover values of the exchange interaction J_A, the transverse field Ω_Aof the bulk material on the exchange
interaction J_B and the transverse fieldΩ_B of the defect layers are shown in 3-Dimensional (3-D) figures for the first time. Moreover, the transition features of the ferroelectric thin film with defect layers are presented.     

Ground States of a Generalized Frenkel-Kontorova Model

We studied the modulated structures and commensurate-incommensurate transitions in a generalized Ftenkel-Kontorova (FK) model where the chain is composed of three kinds of atoms. For the classical ground states, the phase diagram and the phonon spectrum show the multi-atomic effects. For the quantum ground states, the multi-atomic effects are reflected by the distribution of atoms in external potential, the phase diagram, the correspondences between the ground states and the orbits of the area-preserving maps, as well as the phonon spectrum and coherence length. For the most incommensurate structure, the critical point K_c at which the transition by breaking of analyticity occurs does not vary monotonically with A. For the case of μ_A= μ_B = 1 and μ_c = 2, with the increasing of A, the critical point K_c first decreases, then increases. The minimum value of K_c occurs at nearly h = 0.035. When K < K_c, the phonon gap Ω_G = 0 and the Lyapunov exponent γ = 0, the system is in the sliding state. When K > K_c, the phonon gap and the Lyapunov exponent show great difference from those of the standard FK model.     

Unusual crystallographic structure and its fluctuation of indium nanoparticles as-deposited and observed with HRTEM using the UHV-DC-TEM system

A UHV-DC-TEM system was developed for direct transportation of samples between an ultra-high vacuum deposition chamber (UHV-DC) and a UHV transmission electron microscope (UHV-TEM). Indium nanoparticles have been deposited onto Si(110) TEM samples at room temperature in UHV-DC and observed in UHV-TEM with high resolution transmission electron microscopy (HRTEM). Freshly made indium nanoparticles were found to be single, twinned, pseudo-twinned crystals and decahedral multiply-twinned particles (MTPs) with their size in the range 8–15 nm. The structure of single crystalline indium nanoparticles is body-centered tetragonal (bct), which is the same as that of bulk indium. In addition to the usual {011} type twins for bct structure, a pseudo-twin was observed to have an orientation relationship as [111]_A//[100]_B and (10 )_A//(0 )_B. The structure of MTP indium is complicated because of the co-existence of bct and fcc structures within one nanocrystal. The structure fluctuation process has been examined using a video recorder with time scale down to 1/60 s. No complete liquid state was seen during this fluctuation.     

γ-α相变中不同晶界特征下铁素体生长形貌的相场模拟

利用多相场模型模拟了奥氏体(γ)-铁素体(α)相变过程中不同晶界特征下铁素体晶粒的形貌与生长动力学.模型中通过能量梯度系数和耦合项系数的协同变化定量表达晶界能与晶界迁移率的各向异性,同时固定相场界面宽度来保证计算精度.模拟结果显示:随着原奥氏体晶界能与铁素体-奥氏体晶界能比值σ_(γ,γ)/σ_(α,γ)的增加,三叉相界面处的平衡角β减小,铁素体晶粒沿原奥氏体晶界与垂直于奥氏体晶界方向的生长速率差变大.铁素体与奥氏体晶粒间的晶粒取向越接近,铁素体生长越缓慢.模拟结果可描述铁素体晶粒生长形貌的多样性,与实验结果符合.     

Classical r-Matrices and Compatible Poisson Structures for Lax Equations on Poisson Algebras

Given a classical r-matrix on a Poisson algebra, we show how to construct a natural family of compatible Poisson structures for the Hamiltonian formulation of Lax equations. Examples for which our formalism applies include the Benny hierarchy, the dispersionless Toda lattice hierarchy, the dispersionless KP and modified KP hierarchies, the dispersionless Dym hierarchy, etc. Received: 10 February 1998 / Accepted: 9 December 1998     

γ射线辐照对含钆磷酸钡玻璃影响的光谱分析

为研制新型γ射线屏蔽材料,采用熔融淬火法制备了xGd₂O₃-(50-x)BaO-50P₂O₅（0≤x≤7 mol%）系列玻璃样品,并经60Co辐照源辐照,利用UV-Vis-NIR,Raman等分析技术研究了玻璃的光学特性和微观结构。结果表明,玻璃在γ射线辐照下产生了磷氧空穴中心（Ⅰ类色心）,呈现棕色;Gd₂O₃能增强磷酸钡玻璃的抗γ辐照能力,玻璃中Gd₂O₃含量越高,γ射线辐照导致的色心数量越少;玻璃产生的色心数量会随着γ射线辐照剂量的增大而增加;Gd₂O₃加入降低了玻璃对可见光和近红外光的透过率;γ射线辐照使玻璃出现了光学吸收带损耗,玻璃在紫外到可见光区的透过率降低;玻璃样品的主要结构为Q2偏磷酸盐结构,伴有少量Q1焦磷酸盐和Q0正磷酸盐结构;玻璃微观网络结构在γ射线辐照下变化不明显。     

First-principles studies of electronic,optical,and mechanical properties of γ-Bi_2Sn_2O_7

The detailed theoretical studies of electronic,optical,and mechanical properties of γ-Bi_2Sn_2O_7 are carried out by using first-principle density functional theory calculations.Our calculated results indicate that γ-Bi_2Sn_2O_7 is the p-type semiconductor with an indirect band gap of about 2.72 e V.The flat electronic bands close to the valence band maximum are mainly composed of Bi-6s and O-2p states and play a key role in determining the electrical properties of γ-Bi_2Sn_2O_7.The calculated complex dielectric function and macroscopic optical constants including refractive index,extinction coefficient,absorption coefficients,reflectivity,and electron energy-loss function show that γ-Bi_2Sn_2O_7 is an excellent light absorbing material.The analysis on mechanical properties shows that γ-Bi_2Sn_2O_7 is mechanically stable and highly isotropic.     

Tight-binding study of ammonia and hydrogen adsorption on magnetic cobalt systems

The semi-empirical self-consistent tight-binding model of ammonia and hydrogen adsorption at Co(0001) and small Co clusters is used to study the chemisorption role in surface magnetism. The adsorbate choice has been suggested by recent experiments. At the Co(0001) surface the atomic magnetization is predicted to diminish locally by 0.26 μ_B due to an isolated hydrogen atom adsorption; for Co₁₃ clusters the change is somewhat smaller but less localized. At H(1×1)–Co(0001) the magnetization of surface Co atoms drops to 0.88 μ_B. The hydrogen magnetic moment is very small and couples antiferromagnetically to Co. Ammonia adsorption is found to reduce the Co atom magnetization locally by 0.1 μ_B or less. We discuss the possibility of adsorbate–metal antiferromagnetic coupling in more detail.