拟合参量计算跃迁概率

根据光谱线相对强度和跃迁特性参数值,通过线性拟合一次函数,得到两个拟合参量.借助于这些参量,计算得到特殊激发态或高激发态谱线的跃迁概率.目前在对NⅡ光谱分析的基础上,得到了一条对耦合激发组态谱线的跃迁概率.为求取一些在理论计算中很难处理的特殊组态或高激发态谱线的跃迁概率,提供了一种最新的、简单可行的半经典计算方法. 关键词： 拟合 跃迁概率 对耦合     

Expectation and transition probability

It is shown that a separating or order-determining set of states on a quantum logic need not determine the expectations of observables. A formula is derived for the transition probability between states. Using this formula, it is shown that the propositions do not determine the transition probability in a certain sense. The form of the transition probability is derived for pure states on Hilbert space, dominated normal states on a von Neumann algebra, and absolutely continuous states on a measurable space. A metric is defined in terms of the transition probability.     

High-temperature superfluidity of fermionic atoms in optical lattices

Fermionic atoms confined in a potential created by standing wave light can undergo a phase transition to a superfluid state at a dramatically increased transition temperature. Depending upon carefully controlled parameters, a transition to a superfluid state of Cooper pairs, antiferromagnetic states or d-wave pairing states can be induced and probed under realistic experimental conditions. We describe an atomic physics experiment that can provide critical insight into the origin of high-temperature superconductivity in cuprates.     

Cosmological dynamics in tomographic probability representation

The probability representation for quantum states of the universe in which the states are described by a fair probability distribution instead of wave function (or density matrix) is developed to consider cosmological dynamics. The evolution of the universe state is described by standard positive transition probability (tomographic transition probability) instead of the complex transition probability amplitude (Feynman path integral) of the standard approach. The latter one is expressed in terms of the tomographic transition probability. Examples of minisuperspaces in the framework of the suggested approach are presented. Possibility of observational applications of the universe tomographs are discussed.     

Study of force-dependent and time-dependent transition of secondary flow in a rotating straight channel by the lattice Boltzmann method

A numerical study using the lattice Boltzmann method has been carried out for flow through a rotating straight channel with a rectangular cross section. With different forces applied, the secondary flow exhibits two-cell states, four-cell states or six-cell states at a range of low rotational Reynolds number, however, within which only the two-cell states have been commonly reported. In addition to the force-dependent flow transition, a time-dependent flow transition of the secondary flow among two-cell states, four-cell states and six-cell states is also discovered during flow development. These newly found flow transitions and their regulations by force application have been analyzed. Based on numbers of case studies, it is found that a dimensionless number, the ratio of the driving pressure gradient to the centrifugal force, regulates such flow transitions. This study not only releases new phenomena of flow transition, but also indicates new applications in flow control, particle separation and heat transfer.     

Phase transitions in 2D and 3D non-Heisenberg ferromagnets with temperature-dependent anisotropy

A model of a non-Heisenberg ferromagnet is considered in which the single-ion anisotropy constant is linearly dependent on temperature. The conditions are found under which phase transitions occur in 2D and 3D non-Heisenberg ferromagnets as the temperature is varied. It is shown that, in the case where the biquadratic interaction is dominant, quadrupole states can occur in the system, which are specified by the orientation of the quadrupole moment. As the temperature is varied, a phase transition between quadrupole states can occur in 2D magnets. Depending on the ratios between the material constants, this transition can be either a second-order phase transition with the continuously changing orientation of the principal axes of the quadrupole moment tensor or a first-order phase transition with hysteresis through a state with a nonhomogeneous distribution of the principal axes of the quadrupole moment tensor. In 3D magnets, the phase transition between quadrupole states is of the first order with hysteresis. Phase diagrams of the system are constructed.     

Investigation of the relation between compression,relaxation, and end losses in the late phases of theta pinch discharges by means of a two-dimensional MHD computer programme

Chemical model reactions are discussed the steady states of which show the phenomenon of non equilibrium phase transitions. One example shows a phase transition of second order, another one shows a phase transition of first order. If diffusion occurs in the case of first order transition, coexistence of two phases in different domains is possible. For plane boundary layers between the domains the coexistence states are found by a construction analogous to the Maxwellian construction of vapor pressure of a Van der Waals gas. For spherical domains the coexistence dates change similarly as vapor pressure of droplets or bubbles with radius.     

Two-Dimensional Wetting Transition Modeling with the Potts Model

A droplet of a liquid deposited on a surface structured in pillars may have two states of wetting: (1) Cassie-Baxter (CB), the liquid remains on top of the pillars, also known as heterogeneous wetting, or (2) Wenzel, the liquid fills completely the cavities of the surface, also known as homogeneous wetting. Studies show that between these two states, there is an energy barrier that, when overcome, results in the transition of states. The transition can be achieved by changes in geometry parameters of the surface, by vibrations of the surface or by evaporation of the liquid. In this paper, we present a comparison of two-dimensional simulations of the Cassie-Wenzel transition on pillar-structured surfaces using the cellular Potts model (CPM) with studies performed by Shahraz et al. In our work, we determine a transition diagram by varying the surface parameters such as the interpillar distance (G) and the pillar height (H). Our results were compared to those obtained by Shahraz et al. obtaining good agreement.     

Preparation of two and four atom entangled states

A scheme for preparing two and four atom entangled states is presented. It is based on atom cavity field interactions. Firatly, the cavity is prepared in the superposition of the number states through the atom undergoing a two photon transition, the secondly, the two or four identical two level atoms, which are all initially in their ground states, are sent through the cavity sequentially and can make resonant single photon transition in the cavity. Then atomic entangled states are created and the cav     

Prospects for making polar molecules with microwave fields

We propose a mechanism to produce ultracold polar molecules with microwave fields. It converts trapped ultracold atoms into vibrationally excited molecules by a single microwave transition and entirely depends on the existence of a permanent dipole moment in the molecules. As opposed to production of molecules by photoassociation or magnetic-field Feshbach resonances, our method does not rely on properties of excited states or existence of Feshbach resonances. We determine conditions for optimal creation of polar molecules in vibrationally excited states of the ground-state potential by changing frequency and intensity of the microwave field. We also explore the possibility to produce vibrationally cold molecules by combining the microwave field with an optical Raman transition or by applying a microwave field to Feshbach molecules. The production mechanism is illustrated for KRb and RbCs.     

Bloch oscillations of path-entangled photons

We show that when photons in N-particle path-entangled |N,0)+|0,N) or N00N states undergo Bloch oscillations, they exhibit a periodic transition between spatially bunched and antibunched states. The period of the bunching-antibunching oscillation is N times faster than the period of the oscillation of the photon density, manifesting the unique coherence properties of N00N states. The transition occurs even when the photons are well separated in space.     

Competitive localization of vortex lines and interacting bosons

We present a theory for the localization of three-dimensional vortex lines or two-dimensional bosons with a short-ranged repulsive interaction which are competing for a single columnar defect or potential well. For two vortices we use a necklace model approach to find a new kind of delocalization transition between two different states with a single bound particle. This exchange-delocalization transition is characterized by the onset of vortex exchange on the defect for sufficiently weak vortex-vortex repulsion or sufficiently weak binding energy corresponding to high temperature. We calculate the transition point and order of the exchange-delocalization transition. A generalization of this transition to an arbitrary vortex number is proposed.     

Energy landscape theory,funnels, specificity,and optimal criterion of biomolecular binding

We study the nature of biomolecular binding. We found that in general there exists several thermodynamic phases: a native binding phase, a non-native phase, and a glass or local trapping phase. The quantitative optimal criterion for the binding specificity is found to be the maximization of the ratio of the binding transition temperature versus the trapping transition temperature, or equivalently the ratio of the energy gap of binding between the native state and the average non-native states versus the dispersion or variance of the non-native states. This leads to a funneled binding energy landscape.     

Inter-state coupling and definitions of bright and dark states

Contrary to a standard definition of diabatic states (i.e., those without momentum-dependent coupling), based on the construction from adiabatic ones, we defined diabatic states as bright and dark states of a given experiment. Namely, they are defined as states providing maximum, respectively, zero value of electronic transition dipole moments projected to a given polarization vector. Second, the state from (or to) which the optical transition is performed is not from the space of investigated electronic excited state manifold, but it is chosen by the observer. It is shown, for this case, that the inter-state coupling is a general function of vibrational coordinates. The explicit dependence of the inter-state coupling on vibrational coordinates is particularly important for system with strong Stokes shift. The role of exact definitions of bright and dark states as well as the inter-state coupling is discussed with respect to the coherent structure of electronic population observed in optical spectroscopy.     

W(110)基底上的铁纳米岛初始自发磁化态的微磁学模拟

用微磁学模拟研究W(110)基底上铁纳米岛的初始自发磁化态的磁畴结构,确定了不规则形状、椭圆形和矩形岛中不同磁畴态之间的各向异性常数的临界点,得到了纳米岛的磁化态作为各向异性常数和厚度函数的完整相图,相图中存在一较宽的过渡区,把双畴态与涡旋态和菱形态分开,过渡区两侧的边界是不确定的.计算结果表明,初始自发磁化态的磁畴结构主要由各向异性及岛的厚度决定,而且岛的边沿形状对涡旋态和菱形态的磁畴结构有重要影响.准确的铁纳米岛的各向异性常数仍有待于进一步确定. 关键词： 初始自发磁化磁畴结构 铁纳米岛 微磁学模拟 各向异性     

Photon emission as a random event

The statistical properties of the random events that correspond to the emission or the detection of a photon spontaneously emitted by a single atom are discussed. This statistics constitutes a full and nontrivial solution of the stochastic theory of random events. The results are most explicit for an atom with two relevant states. The formalism is also generalized to atomic models with nondegenerate states or with more than one driven transition.     

Simple New Axioms for Quantum Mechanics

The space of pure states of any physical system,classical or quantum, is identified as a Poisson spacewith a transition probability. These two structures areconnected through unitarity. Classical and quantum mechanics are each characterized by asimple axiom on the transition probability p. Unitaritythen determines the Poisson bracket of quantum mechanicsup to a multiplicative constant (identified with Planck's constant).     

关于多层超薄共格结构的导电性质

实验表明Nb/Ti多层超薄共格结构有特殊导电行为。我们认为这种行为反映了这类人工材料的超晶格能带结构特性。随着超晶格周期变小,它由金属的性质向半导体或半金属的性质过渡。超晶格调制使多层超薄共格结构中的电子态分为扩展的和在调制方向定域性很强的两种;它们在沿调制方向具有相差很大的有效质量。我们分别考虑两类电子态的贡献,计算了电阻率和电阻温度系数随超晶格周期的变化,结果显示出实验观察的行为。 关键词：     

Three-dimensional confinement in the conduction band structure of InP

Strong quantum confinement in InP is observed to significantly reduce the separation between the direct and indirect conduction band states. The effects of three-dimensional confinement are investigated by tailoring the initial separation between conduction band states using quantum dots (QDs) of different sizes and hydrostatic pressure. Analyses of the QD emission spectra show that the X(1c) states are lowest in energy at pressures of approximately 6 GPa, much lower than in the bulk. The transition to the X(1c) states can be explained by either a sequence of gamma-L and L-X crossings, or by the crossover between strongly coupled gamma and X states.     

Kaleidoscope of life: A 24-neighbourhood outer-totalistic cellular automaton

One of the challenges of cellular automaton research is finding models with a low complexity and at the same time a rich dynamics. A measure of low complexity is the number of states in the model and the number of transition rules to switch between those states. In this paper, we propose a 2-dimensional 2-state cellular automaton that-though governed by a single simple transition rule-has a sufficiently rich dynamics to be computationally universal. According to the transition rule, a cell’s state is determined by the sum of the states of the cells at orthogonal or diagonal distances one or two from the cell (distance-2 Moore neighbourhood), but not by the previous state of the cell itself. Notwithstanding its simplicity, this model is able to generate a great variety of patterns, including several types of stable configurations, oscillators and patterns that move over cellular space (gliders). We prove the computational universality of the model by constructing a universal set of logic gates (NOT and AND) from these patterns. A key element in this proof is the shifting of phases and positions of signals such that they meet the input requirements of the logic gates. Similarities of the model with classical spin systems are also discussed.