Dispersion dipole between rare-gas atoms

Accurate calculations of the dispersion dipole coefficient D ₇ and its components are described for the systems HeH and HeHe, and used to check an approximate formula for D ₇ developed in a previous paper [1]. By means of a further approximation for a new atomic property, values of D ₇ are obtained for the rare-gas diatoms, based on semi-empirical Van der Waals C ₆ coefficients, Hartree-Fock expectation values and sum-rule values for the atoms. The dispersion contributions to the dipole are compared with the Hartree-Fock contributions [35], and at the conventional collision diameters are found to be of comparable magnitude but usually of opposite sign.     

混合漫射近似模型的漫反射理论及其模拟实验研究

研究了一个改进的漫射近似模型.该模型将漫射近似中的漫射系数D用描述P₃近似的漫射系数D_asym替代.推导了这个混合的漫射近似模型在单点源近似和外推边界条件下的反射率R_Hybrid(ρ)的解析表达式,比较了有效反照率a′对标准漫射近似R_DA(ρ)和R_Hybrid(ρ关键词： 漫射近似 P₃近似')" href="#">P₃近似 混合漫反射模型 强吸收     

Yangian double

Studying the algebraic structure of the doubleDY(g) of the Yangian Y(g), we present the triangular decomposition ofDY(g) and a factorization for the canonical pairing of the Yangian with its dual inside Y⁰(g). As a consequence, we describe a structure of the universalR-matrixR forDY(g) which is complete forDY(s1₂). We demonstrate how this formula works in evaluation representations of Y(sl₂). We interpret the one-dimensional factor arising in concrete representations ofR as a bilinear form on highest-weight polynomials of irreducible representations of Y(g) and express this form in terms of -functions.Partially supported by ISF grant MBI000 and Russian Foundation for Fundamental Researches     

H<Superscript>+</Superscript> and He<Superscript>2+</Superscript> impact charge transfer cross sections of magnesium

H⁺ impact single and He²⁺ impact single and double electron capture cross sections of magnesium atoms have been calculated in the modified binary encounter approximation (BEA). The accurate expressions of ion impact s_DE\sigma _{\Delta {E}} (cross section for energy transfer DE\Delta E) and Hartree-Fock momentum distributions of the target electrons have been used throughout the calculations. On the basis of the present work it is concluded that inner shell captures by H⁺ and He²⁺ ions incident on magnesium atoms contribute partly to single electron capture and partly to transfer ionization cross sections. The calculated He²⁺ impact double electron capture cross sections of magnesium are in reasonably good agreement with the experimental observations. This indicates the success of the present theoretical approach in study of charge transfer cross sections of atoms as indirect mechanisms do not interfere with double electron capture processes in this case.     

Scattering of acoustic phonons by rare earth substitutional atoms in yttrium aluminum garnets

The diffusive maxima of phonon signals, and in particular their arrival timest _m are examined for a number of solid solutions of rare earth atoms in yttrium aluminum garnets. The phonon pulses are generated by metallic films of the characteristic lengthl _h heated by current pulses to the temperatureT _h slightly higher than the ambient temperatureT. The injected phonons travel in wafers of the thicknessL _z. They are scattered by substitutional atoms of rare earth occupying the yttrium dodecahedral sites, rare earth and yttrium atoms occupying the aluminum octahedral sites and by another lattice imperfections generated in the process of sample growing. The qualitative analysis based on our exact formula for the diffusion coefficientD allows us to extract the contribution of rare earth atoms substituting the Y atoms toD. Considering the dependence oft _m/L _z ² on the temperature and the ratiol _h/L_z we conclude thatD∼T _h ⁻⁴ and that the energy of phonons forming the diffusive maxima ranges from 3.2k _BT_H to 4.2k _BT_H, which is in reasonable agreement with the existing estimates.     

The influence of excited levels on the circumstellar gas ionization rate

It is shown that the gas surrounding a hot star is excited mainly by the stellar radiation field. The contribution of the excited states to the ionization rate R _exc can noticeably exceed that of the basic state R _base. A simple approximation formula is obtained for the ratio R _exc/R _base.     

Electron-impact excitation of barium atoms from metastable 5 <Superscript>3</Superscript><Emphasis Type="Italic">D</Emphasis><Subscript><Emphasis Type="Italic">J</Emphasis></Subscript> states

The excitation of spectral transitions of barium atoms from the 5³ D _J states by electron impact has been studied experimentally. The absolute values of the interaction cross sections and their energy dependences have been determined. The results obtained have been compared with theoretical calculations both by the classical Born approximation method and by the R-matrix method using the multiconfiguration Hartree-Fock wave functions of a target.     

Scale transformations for renormalized field operators: Discussion of the soluble model

We discuss the operator formulation of the Zachariasen-Thirring model, describing the chain approximation to the propagator (the sum of three-particle massless bubbles) in massless λ⁴ theory. Such a model is formally scale-invariant and explicitly soluble. All intermediate steps of conventional renormalization procedure, regularization, introduction of appropriate counterterms, and cut-off free limit, are explicitly performed. In every step the scaling properties are discussed and respective dilatation currents are written down. After the proper choice of scale transformations for the renormalized field operator, we obtain the nonlocal dilatation current, defining the renormalized dilatation generator D_Λ^R(t). In the cut-off free limit Λ → ∞ the ET commutator of D_Λ^R(t) with renormalized field operators reproduces the Callan-Symanzik modification of “naive” canonical scale transformations. The renormalized scale transformations coincide in the cut-off free limit with renormalized dimensional transformations and define the exact symmetry of the renormalized theory.     

Interface resistances and AC transport in a Luttinger liquid

We consider a Luttinger liquid (LL) connected to two reservoirs when the two sample-reservoir interface resistances R_S and R_D are arbitrary (not necessarily quantized at half-the-quantum of resistance). We compute exactly the dynamical impedance of a Luttinger liquid and generalize earlier expressions for its dynamical conductance in the following situations. (i) We first consider a gated Luttinger liquid. It is shown that the Luttinger liquid parameters u and K and the interface resistances R_S and R_D can be experimentally determined by measuring both the dynamical conductance and impedance of a gated wire at second order in frequency. The parallel law addition for the charge relaxation resistance R_q is explicitly recovered for these non-trivial interface resistances as R_q^-1 = R_S^-1 + R_D^-1. (ii) We discuss the AC response when only one electrode is connected to the LL. (iii) Thirdly we consider application of an arbitrary AC electric field along the sample and compute the dynamical response of the LL with arbitrary interface resistances. The discussion is then specialized to the case of a uniform electric field.Received: 19 May 2003, Published online: 30 January 2004PACS: 73.23.-b Electronic transport in mesoscopic systems - 71.10.Pm Fermions in reduced dimensions(anyons, composite fermions, Luttinger liquid, etc.) - 72.30. + q High-frequency effects; plasma effects     

钪原子的自电离里德伯能级3d4s(1D2)nf2 D3/2,3d4s(1D2)nf2 F5/2和3d4s(1D2)np2 D3/2<

在多通道量子亏损理论框架下,利用相对论多通道理论,分别在冻结实近似和考虑偶极极化下计算钪原子的J^π=(3/2)^-,(5/2)^-的三个收敛于 3d4s(¹D₂)的自电离里德伯系列的能级.对3d4s(¹D₂)np²D_3/2和3d4s(^{1 关键词： 相对论多通道理论 多通道量子亏损理论 电子-电子关联 自电离里德伯系列}     

M2Sn17(M=Ni，Mn)及其阴离子的几何结构、电子结构和磁性的计算研究

采用密度泛函理论(density functional theory, DFT)中的广义梯度近似(generalized gradient approximation, GGA) 对Ni₂Sn₁₇，Mn₂Sn₁₇，［Ni₂Sn₁₇］^4-和［Mn₂Sn₁₇］^2-三种同分异构体的几何结构、电子 关键词： 2Sn₁₇')" href="#">Ni₂Sn₁₇ 2Sn₁₇')" href="#">Mn₂Sn₁₇ 几何结构 电子结构和磁性 密度泛函理论     

Transition Moments betweenΔg,Πg, andΠuStates of the H2Molecule

Electronic transition moments are computed for dipole transitions between theCandD¹Π_u,IandR¹Π_gandJandS¹Δ_gstates of the hydrogen molecule for internuclear distancesR∈ [1, 15] bohr. The character of the wavefunctions at large internuclear distances is investigated. It is shown that in theDandRstates the asymptotic configurations are strongly mixed forR≤ 15 bohrs. TheSstate has mixed character even atR= 40 bohr.     

PdCO分子结构与势能函数

用密度泛函理论的B3LYP方法,对钯原子采用LANL2DZ收缩价基函数,碳原子和氧原子采用AUG-cc-pVTZ基组,对PdC,PdO和PdCO体系的结构进行优化,计算表明：PdC分子基态为¹Σ⁺态,键长为R_e=0.17285nm,离解能为4.919eV.PdO分子基态的平衡核间距为0.18546nm,其电子态为³Π,离解能为2.455eV,并拟合得到Murrell-Sorbie势能函数;PdCO分子有两 关键词： PdCO 分子结构 势能函数     

Matter-wave propagation in optical lattices

Coherent propagation of atomic-matter waves in a one-dimensional optical lattice is studied. Wave packets of cold two-level atoms propagate simultaneously in two optical potentials in a dressed-state basis. Three regimes of the wave-packet propagation are specified by the quantity Δ² /ω _D , where Δ and ω _D are the dimensionless atom–laser detuning and the Doppler shift, respectively. At Δ² /ω _D ≫ 1, the propagation is essentially adiabatic, at Δ² /ω _D ≪ 1, it is (almost) resonant, and at Δ² ≃ ω _D , the wave packets propagate nonadiabatically, splitting at each node of the standing wave. The latter means that the atom makes a transition from one potential to the other one when crossing each node, and the probability of that transition is given by a Landau–Zener-like formula. All the regimes of propagation are studied with δ-like and Gaussian wave packets in the momentum and position spaces. Varying the control parameters, we can create wave packets trapped in a well of optical potentials and moving ballistically in a given direction in close analogy with point-like atoms. Within some range of the parameters, we force the atom to move in a pure quamtum-mechanical manner in such a way that a part of the packet is trapped in a well, and the other part propagates ballistically. The propagation modes are found to be characterized by different types of time evolution of the uncertainty product and the Wigner function.     

Accurate studies on dissociation energies of diatomic molecules

The molecular dissociation energies of some electronic states of hydride and N2 molecules were studied using a parameter-free analytical formula suggested in this study and the algebraic method (AM) proposed recently. The results show that the accurate AM dissociation energies DeAM agree excellently with experimental dissociation energies Deexpt, and that the dissociation energy of an electronic state such as the 23△g state of 7Li2 whose experimental value is not available can be predicted using the new formula.     

Excited state dynamics of Eu3+ in the partially disordered crystals La3Ga5SiO14 and La3Ga5.5Ta0.5O14

The spectroscopic properties of two partially disordered crystals, langasite (LGS) and langatate (LGT), doped with Eu³⁺ were investigated. The fluorescence lifetimes of the ⁵D₀ and ⁵D₁ excited levels are measured. The spectral overlapping between the luminescence from the ⁵D₀ and ⁵D₁ levels was eliminated using pulsed excitation at 532 nm and suitable delays in order to improve the precision of the calculation of the spectroscopic figures of merit R₀, R₂ (the areas of the electric-dipole transitions ⁵D₀→⁷F₀ and ⁵D₀→⁷F₂, respectively, divided by the area of the magnetic-dipole one—⁵D₀→⁷F₁). The maximum splitting of the ⁷F₁ level (ΔE) is calculated from the luminescence spectra and the B₂₀ crystal field parameter is determined. We obtain R₀(LGS)>R₀(LGT), R₂(LGS)<R₂(LGT), and ΔE(LGS)>ΔE(LGT), and we discuss these results taking into account structural data, covalency and J-mixing effects.     

Evolution of dislocation structure during deformation of γ-irradiated LiF crystals

The effect of γ irradiation on the mechanical characteristics and dislocation structure of slip bands in LiF crystals is studied at doses D⩽7.3×10⁸ R. Irradiation causes a substantial increase (up to a factor of 30) in the yield stress τ _y of the crystals, with τ _y ∝ D ^0.4 in the first approximation. The deformation shear increases in the slip bands of irradiated crystals, as do the densities of the screw and edge dislocation components, while the dislocation mean free paths decrease. Irradiation also raises the probability of twinning cross slip for screw dislocations. The observed effects are assumed to be related to the formation of a different kind of defects in the irradiated crystals, primarily clusters of implanted atoms. Fiz. Tverd. Tela (St. Petersburg) 39, 1072–1075 (June 1997)     

Calculation of the diffusion coefficient in acoustic turbulence

The first (Born) approximation commonly used to calculate the diffusion coefficient D_T of a passive scalar in acoustic turbulence is shown to be insufficient. Even for a small main parameter—the Mach number, M?1—the next approximation gives a larger contribution to D_T than does the first approximation, but negative in sign. We present a procedure for correctly calculating D_T based on the solution of a nonlinear DIA (direct interaction approximation) equation for the mean Green’s function of the problem. We include an additional term in the general formula for D_T that directly describes the compressibility of acoustic turbulence. This term has not been known previously and has been disregarded even in the Born approximation. A positive value was obtained for D_T=CM³u₀/p₀. The spectrum E(x) was assumed to be smooth at distances Δ x～M²?1.     

Constructing unified models based on E8 in ten dimensions

The vacuum energy is calculated for Yang-Mills (YM) system defined inD dimensional space-time ofS ¹×R ^d (D=d+1), where the possibility of the YM fields to acquire the vacuum expectation values onS ¹ is taken into account. The vacuum energy has already been obtained to the order of one-loop in many people. Here we calculate the vacuum energy inD dimensions to two-loop order. With an intention to reach higher loops, an approximation method is proposed, which is especially effective in higher dimensions. By this method, we can treat the higher-loop contributions of YM interactions as easily as we treat one-loop effect. As a check, we show reproduction of the two-loop contribution (D-dependence of the coefficient as well as the functional form) when the coupling constant is small. This approximation method is useful not only for the Kaluza-Klein theories but also for the finite temperature-density system (as a quark-gluon plasma).Minami-Ohsawa Hachioji-shi, Tokyo 92-03 Japan     

The importance of gravitational self-field effects in binary systems with compact objects. II. The “static two-body problem” and the attraction law in a post-post-Newtonian approximation of general relativity

The attraction force of two massive bodies connected by a rod is calculated in a post-post-Newtonian approximation. As far as we know this is the first calculation in such an order of approximation. Although the result already shows a complicated field-field interaction, we reproduce Newton's attraction forceM ₁ M ₂/R ² as the leading term in powers of 1/R.