正反重强子对构成的强子分子态能谱

近二十年来,世界上众多高能物理实验发现了大量超出传统夸克模型的共振结构。为了理解 这些性质奇特的共振结构,科学家们提出了很多方法和模型。其中,因为实验上发现的这些奇特态 大多处在一对强子阈值附近,强子分子态的观点得到了很多关注。本文我们将以粲{反粲强子对为例 来探究哪些系统可以形成分子态,进而给出粲{反粲强子分子态的能谱。我们考虑了所有由 S 波粲 介子、粲重子以及窄的 P 波粲介子构成的粲{反粲强子对。我们假定它们之间的相互作用由介子交 换主导,在最低阶近似下可简化为常数。通过求解常数相互作用的 Bethe---Salpeter 方程,我们可以 找到振幅的极点进而确定该系统分子态的质量。最终我们发现,那些通过轻矢量介子交换在阈值附 近产生吸引力的系统,会存在一个靠近阈值的极点。不同的系统,由于其相互作用强度不同,极点 可能会处于能量复平面的第一黎曼面或者第二黎曼面,分别对应于束缚态或者虚态。我们总共发现 了 229 个强子分子态。很多实验上发现的那些位于粲---反粲强子对阈值附近的共振结构可以很好地 与我们的结果吻合。另外,我们需要强调所预言的一个 ΛcΛc  分子态,这个态可以很好地解释北京正负电子谱仪 (BESIII) 上测量的数据。     

相对论Birkhoff系统的平衡稳定性

研究相对论Birkhoff系统的平衡稳定性.给出相对论Birkhoff自治系统、半自治系统和非自治系统的平衡方程、受扰运动方程和一次近似方程;给出判定平衡稳定性的一次近似方法及其判据;讨论相对论Birkhoff系统平衡稳定性和经典Birkhoff系统平衡稳定性的关系.给出实例以说明方法的应用 关键词： 相对论 Birkhoff系统 平衡稳定性 一次近似方法     

Equation of state of long chain molecules and rings

An equation of state for long chain molecules has been proposed using statistical associating fluid theory (SAFT). The formalism derived here is based on the assumption that the chain is formed by the pairs of trimers. The equations of state for 48-mers and 192-mers are formulated and compared with Monte Carlo results. The theory has been developed to treat hard sphere molecules with two attraction sites to form a ring molecule. The equations of state for trimer, hexamer and 12-mer ring molecules have been formulated. There is excellent agreement with available Monte Carlo results. Second virial coefficients of tangent chain molecules and ring molecules have been determined numerically and compared with simulation results.     

转动相对论Birkhoff系统的平衡稳定性

研究转动相对论Birkhoff系统的平衡稳定性，给出转动相对论Birkhoff自治系统、半自治系统和非自治系统的平衡方程和转动相对论Birkhoff自治系统的受扰运动方程和一次近似方程；给出转动相对论Birkhoff自治系统平衡稳定性的一次近似方法及其判据；并给出转动相对论Birkhoff自治系统平衡稳定性的直接方法及其判据；讨论转动相对论Birkhoff系统平衡稳定性和经典转动Birkhoff系统平衡稳定性的关系.给出实例以说明方法的应用. 关键词： 相对论 转动Birkhoff系统 平衡稳定性 一次近似方法     

Equation of state for fused-hard-sphere fluid mixtures

This paper develops a theoretically-based equation of state for fused-hard-sphere fluid mixtures on the basis of an equation of state previously derived for hard-convex-body fluid mixtures. The equation uses as a reference the equation of state for an equivalent hard-sphere fluid mixture in which each component has the same molecular volume as the effective molecular volume of one of the components of the fused-hard-sphere mixture. The two parameters required by the theory, namely the averaged effective molecular volume of the molecules in the mixture and the corresponding effective non-sphericity parameter, are obtained from the geometrical characteristics of the molecules that form the mixture. The results are, on the whole, in closer agreement with simulation data than those obtained with other theories developed for this kind of mixture.     

Perturbation theory and the excess properties of mixtures of simple liquids

One of the most successful theories of single-component simple liquids is perturbation theory which is based on the assumption that the structure of a liquid is primarily determined by the repulsive forces between its molecules, so that a liquid may be regarded as a system of hard spheres with the attractive forces providing a uniform background energy. Our earlier extension of these ideas to liquid mixtures was only partially successful. In this paper we show that this problem was due to the use of a somewhat unsatisfactory equation of state for the reference hard-sphere mixture. If a more satisfactory equation of state is used, perturbation theory yields results in close agreement with Monte Carlo and experimental results, even when the molecules of the mixture differ appreciably in size.     

Dynamics to the universal structure of one-dimensional self-gravitating systems in the quasi-equilibrium state

We investigate the quasi-equilibrium state of one-dimensional self-gravitating systems. If the null virial condition is satisfied at initial time, it is found that the number density around the center of the system at the quasi-equilibrium state has the universality similar to two- and three-dimensional self-gravitating systems reported in Refs. [1], [2]. The reason why the null virial condition is sufficient for the universality is unveiled by the envelope equation. We present a phenomenological model to describe the universal structure by using a special Langevin equation with a distinctive random noise to self-gravitating systems. Additionally, we unveil a mechanism which decides the radius of the system.     

The solution of the diffusion equation with a sink term using the radiation boundary condition

The diffusion equation with an added sink term describing the energy transfer by a dipole-dipole mechanism was solved under steady state conditions using the radiation boundary condition. An equation for the non-radiative energy transfer rate constant between organic fluorescent molecules was obtained. This general equation contains the particular cases of a total reflecting boundary condition and the so-called Smoluchowski boundary condition already obtained by other authors.     

Rotational effect on the thermodynamic properties of isotopes

It is shown that the differences in the thermodynamic properties of HT and D₂ is due to the fact that, for the same total mass, the distribution of mass between the two atoms is not the same. This fact introduces for the heteronuclear molecules a correlation between translational and rotational degrees of freedom. This is a pure quantal effect. A quantum-mechanical perturbation calculation shows that the energy of the ground state is higher for assemblies of heteronuclear molecules than for assemblies of homonuclear ones. On account of this the equation of state of heteronuclear hydrogen molecules is different from that of homonuclear hydrogen molecules. This permits an understanding, for example, of the higher vapour pressure of HT compared to D₂ and the anomalous behaviour of HD.     

Role of rotational state-selected for nonadiabatic alignment: OCS molecules in femtosecond laser fields

Nonadiabatic alignment by intense nonresonant laser fields is a versatile technique to manipulate the spatial direction of molecules. By solving the time-dependent Schrödinger equation numerically the degree of alignment of the molecules initially in different rotational state are calculated and the results show that the degree of alignment strongly depends on the initial rotational state. Thus, the present study indicates that, for obtaining a high degree of alignment for molecules, appropriate selection of molecular rotational states is necessary.     

Integral equation for the angular distribution function of an anisotropic fluid taking account of short-range order in a quasichemical approximation

An integral equation for the one-particle angular distribution function of nonspherical molecules is formulated on the basis of the thermodynamically closed system of equations obtained earlier for the occupation numbers of a multicomponent mixture of molecules with internal degrees of freedom. It is shown that this equation goes over into a known equation of Vlasov-Onsager type for large coordination numbers (for strongly elongated molecules), and yields a known rigorous result which does not contain a phase transition into the anisotropic state in the one-dimensional case. The criterion for such a transition is formulated in the form of an eigenvalue problem for the kernel of the equation obtained. In the case of single-axis molecules, an explicit expression is given for its kernel which takes account of the anisotropy in both the attraction and repulsion as well as the finite compressibility of the substance. For a binary liquid-crystal mixture, an equation is obtained in explicit analytic form within the framework of the XYZ-model for the transition line of an isotropic fluid (IF) into a nematic liquid crystal (NLC), which agrees with experiment for individual NLC. Formulas are hence obtained for a computation of the parameters of the interaction anisotropy in terms of the IF-NLC transition line parameters, and also specific results for para-azoxyanisole (PAA).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 114–118, September, 1977.The author is grateful to V. K. Semenchenko for kindly providing the necessary publications of experimental material and to B. U. Chotchaev for assistance in processing the results of the experiment.     

爆轰产物物态方程（Ⅱ）——爆轰的ZND理论不成立吗?（上）

 爆轰的ZND理论,作为一个理论是需要经过严格检验之后才能承认其成立的。美国科学家做了这样的检验,但由于缺乏对爆轰产物物态方程的了解,没有能得出肯定的检验结论。用分子间有强排斥作用与分子作完全自由平动的液态物态方程（R-T物态方程）所做的检验表明爆轰的ZND理论是成立的。     

Coherent transients in the femtosecond photoassociation of ultracold molecules

We demonstrate the photoassociation of ultracold rubidium dimers using coherent femtosecond pulses. Starting from a cloud of ultracold rubidium atoms, electronically excited rubidium molecules are formed with shaped photoassociation pump pulses. The excited state molecules are projected with a time-delayed probe pulse onto molecular ion states which are detected in a mass spectrometer. Coherent transient oscillations of the excited state population are observed in the wings of the pump pulse, in agreement with the time-dependent solution of the Schr?dinger equation of the excitation process.     

Methodology for the solutions of some reduced Fokker‐Planck equations in high dimensions

In this paper, a new methodology is formulated for solving the reduced Fokker‐Planck (FP) equations in high dimensions based on the idea that the state space of large‐scale nonlinear stochastic dynamic system is split into two subspaces. The FP equation relevant to the nonlinear stochastic dynamic system is then integrated over one of the subspaces. The FP equation for the joint probability density function of the state variables in another subspace is formulated with some techniques. Therefore, the FP equation in high‐dimensional state space is reduced to some FP equations in low‐dimensional state spaces, which are solvable with exponential polynomial closure method. Numerical results are presented and compared with the results from Monte Carlo simulation and those from equivalent linearization to show the effectiveness of the presented solution procedure. It attempts to provide an analytical tool for the probabilistic solutions of the nonlinear stochastic dynamics systems arising from statistical mechanics and other areas of science and engineering.     

On the dielectric theory of a crystalline slab of point molecules

We discuss the dielectric response of a crystalline slab of point molecules to an incident plane electromagnetic wave. The slab is assumed to be made up of non-polar, polarizable molecules (a) lying at points of a simple cubic lattice and (b) interacting only via the electromagnetic field. Expressions for the dispersion relations, polarisation and electric fields and the transmission coefficient are derived. Conditions under which a point dielectric equation of state holds are obtained. This simple system exhibits three resonances near the transverse optic frequency.     

Equation of state for fullerite C60

A new equation of state for fullerite C₆₀ is derived in the framework of the quantum-statistical method. This equation includes two Grüneisen parameters responsible for vibration–rotational and intramolecular contributions of fullerene molecules, which are represented in the form of isotropic quantum oscillators. The intramolecular vibrations of carbon atoms are described by the Debye heat capacity theory, and the cold contribution to the free energy is calculated using the Lennard–Jones pair potential for fullerene molecules. The theory is in a very good agreement with the experiment.

     

水高温高密度状态方程理论研究

 采用MCR方法计算由exp-6势描述的水分子作用体系的pVT状态方程。与MD数值模拟结果比较后发现，由于水分子间强烈的吸引作用有利于分子有序化过程的发生，在较高温度（2 000~4 000 K）条件下，水分子作用体系仍呈现出固态特征。该物相区内体系的热力学性质不能用MCR理论描述但MCR理论准确预言了水分子作用体系高温液相区pVT状态方程。