Double-octupole states in 208Pb

The states of 208Pb are calculated in a 24 orbit model space which includes all excitations up to two particles and two holes beyond the closed shell. All of the known low-lying states are reproduced by this model. The observed distributions of electromagnetic excitation strength from the ground state to low-lying excited states are well described by the model. The double-octupole excitation strength is calculated and found to be concentrated in 0+, 2+, and 4+ states around 5.2 MeV, but it is fragmented over many 6+ states, in agreement with recent experiments.     

广义振子强度密度

根据Born近似,可以计算高能电子碰撞激发的总截面和微分截面。微分截面是和所谓的广义振子强度成正比的。电子碰撞过程可将靶原子或离子激发至无数的束缚态、自电离态和对应的连续态,多通道量子数亏损理论能够统一地处理这些激发态。因此可以定义每单位激发能内的广义振子强度为广义振子强度密度。本文以Li原子为例,总结其广义振子强度密度随激发能量和动量转移而变化的规律,并和最近精确的实验结果进行了比较,明确了Born近似的适用范围。 关键词：     

Resonance tongues in a system of globally coupled FitzHugh-Nagumo oscillators with time-periodic coupling strength

We investigate the dynamics of a population of globally coupled FitzHugh-Nagumo oscillators with a time-periodic coupling strength. While for synchronizing global coupling, the in-phase state is always stable, the oscillators split into several cluster states for desynchronizing global coupling, most commonly in two, irrespective of the coupling strength. This confines the ability of the system to form n:m locked states considerably. The prevalence of two and four cluster states leads to large 2:1 and 4:1 subharmonic resonance regions, while at low coupling strength for a harmonic 1:1 or a superharmonic 1:m time-periodic coupling coefficient, any resonances are absent and the system exhibits nonresonant phase drifting cluster states. Furthermore, in the unforced, globally coupled system the frequency of the oscillators in a cluster state is in general lower than that of the uncoupled oscillator and strongly depends on the coupling strength. Periodic variation of the coupling strength at twice the natural frequency causes each oscillator to keep oscillating with its autonomous oscillation period.     

Preferred states of open electronic systems

System-environment interaction may introduce dynamic destruction of quantum coherence, resulting in a special representation named as pointer states. In this work, pointer states of an open electronic system are studied. The decoherence effect is taken into account through two different ways which are Büttiker's virtual probe model and strong electron-phonon interaction in the polaron picture. The pointer states of the system with different coupling strength are investigated. The pointer states are identified by tracking the eigenstates of the density matrix in real-time propagation. It is found that the pointer states can emerge for arbitrary coupling strength. And the pointer states deform to the eigenstates of the system in the strong coupling limit, which indicates the vanish of quantumness in the strong coupling limit.     

A schematic model for monopole and quadrupole pairing in nuclei

A schematic Hamiltonian with a pairing interaction plus a quadrupole-quadrupole interaction between nucleons is presented. It is shown that all the states of the fermion system can be classified according to the number of nucleons u not coupled to coherent monopole or quadrupole pairs. The states with u = 0 are shown to have a one-to-one correspondence to the states of the interacting boson model. The spectra for these states are derived analytically for various limits of the pairing strength and the quadrupole strength. Analytical forms for the matrix elements of operators are derived for these limits. The operators in fermion space are mapped onto boson operators. The matrix elements of operators in the fermion space are shown to be equal to matrix elements of the boson operators multiplied by analytical Pauli factors which are state dependent. The two-nucleon transfer strength is calculated in two limits and is compared to experimental values.     

Doorway-state analysis of the fragmentation of the magnetic-dipole strength in SU58 NI observed in high-resolution inelastic electron scattering

The fine structure of the magnetic-dipole strength in ⁵⁸Ni observed in high-resolution inelastic electron scattering at the DALINAC has been analysed under the assumption that the measured distribution of the strong fragmented M1 strength results from a coupling of two doorway states to a large number of more complicated states. From the doorway-state analysis one obtains the coupling matrix elements between doorway states |d〉 and complicated states |q〉. This allows the calculation of the escape width Γ^↑ and the spreading width Γ^↓ of the assumed doorway states. The influence of a coupling between the doorway states via the complicated states (internal mixing) is discussed. An estimate of a mean coupling matrix element between the two doorway states is given.     

Phase and Polarization State of High-Frequency Relic Gravitational Waves

The displaying condition of strength, phase and polarization states of high-frequency relic gravitational waves （HFRGWs） in electromagnetic （EM） detecting systems is studied. It is shown that the displaying condition depends not only on the sensitivity of EM detecting systems and the amplitudes of HFRGWs, but also on the phase, the polarization states of HFRGWs and their matching to the EM detecting systems. In order to display simultaneously the strength, phase and polarization states of the resonant ＂monochromatic component＂ of HFRGWs, an important necessary condition is the utilization of two or more different EM detectors.     

On the second moment of the single-hole strength distribution

The second moment of the strength distribution of single-hole states in finite nuclei is discussed. Theoretical estimates for the second moment of single-hole states near the top of the Fermi sea appear to be larger than experimental values that can be derived from data on knock-out reactions; this indicates that experimentally a part of the single-hole strength has not been observed.     

Experimental and numerical study on the basin stability of the coupled metronomes

The basin stability is an effective parameter to measure the stability of multistable system under perturbations. In this paper, we try to explore the effects of the coupling strength on the basin stability of the coupled metronomes. In two coupled non-identical metronomes, the coupling strength linearly decreases the basin stability of in-phase synchronization while increases that of the anti-phase synchronization. In three coupled metronomes, there are rich coexisting collectively dynamics as in-phase, anti-phase synchronization, quasi-period states and period 4 states. The coupling strength may still change the basin stability of these coexisting dynamics states. The results are observed in experimental systems and numerical models. Our findings are significant on understanding the multistable dynamics under noisy environment.     

Resonance reflection of light from two-dimensional superlattice structures

The exciton Bloch states in a quantum well with a two-dimensional periodic potential are studied theoretically. Expressions are derived for the light reflection coefficient and the exciton oscillator strength for a structure with this type of lateral superlattice. The redistribution of the oscillator strength between exciton states with varying period and depth of the potential is analyzed. The limiting cases where the nearly free exciton and tight-binding approximations are applicable are considered.     

一维无公度系统Aubry模型的Anderson转变

数值计算结果表明,一维无公度系统Aubry模型存在扩展态、中间态和局域态。由扩展态向局域态的转变,要经过处于势强度v=2t附近的一段过渡区。这个新的结果不同于用对偶性理论证明给出的结论,即当势强度V<2t时都是扩展态,而当V>2t时都是局域态,在V=2t存在Anderson转变。 关键词：     

Confinement of an Electron in an Image Potential and an External Electrostatic Field

The quasi-classical approximation is used to determine the positions of the classical turning points upon motion of an electron that is bound by an image field and a constant homogeneous electric field of the same direction. Power expansions of the coordinates of the turning points in a wide range of electron energies and field strengths are obtained. The mechanism of one-dimensional confinement of an electron, which determines a completely discrete spectrum of states, is described. The dependence of the spatial width of the confinement region on the field strength and electron energy is determined. The dependences of the electron energy in different states on the external field strength are calculated numerically. Quasi-classical quantization is performed, and the dependence of the electron energy on the width of the confinement region is determined. The energy interval of a maximum density of electron states is found, which is determined by the dependence of the width of the confinement region on the electric field strength.     

高能多粒子末态的多重分形维数与动力学起伏强度

研究了多重分形维数与动力学起伏强度的关系,给出了一个能直接描述高能多粒子末态动力学起伏强度的特征参量,并指出了这一参量的适用范围以及在实际高能实验中的应用.     

Collective modes in an open microwave billiard

Numerical calculations for a microwave Sinai billiard coupled strongly to a lead are performed as a function of the coupling strength between billiard and lead. They prove the formation of different time scales in an open quantum system at large coupling strength. The short-lived collective states are formed together with many long-lived trapped states.     

Is (3He,t) primarily A (3He,α) (α,t) reaction?

The reaction ⁴⁸Ca(³He, t)⁴⁸Sc to the low-lying even spin states has been studied as a pure sequential (³He, α) (α,t) process using an exact finite-range formalism. It is found that the strength of the cross-sections to these states is under-predicted by large factors. The consideration of second-order processes via the inelastic channels also fails to account for the strength of these states. The (³He, t) discrepancy still exists.     

Disentanglement of Three-qubit States Coupled to an <Emphasis Type="Italic">XY</Emphasis> Spin Chain with Multisite Interaction

The entanglement dynamics of three-qubit states coupled to a general XY spin-chain with a three-site interaction environment is investigated. By using negativity as entanglement measure, we find that the entanglement evolution depends on not only the system-environment couplings but also the strength of three-site interaction. In the strong-coupling region, the three-site interaction can remarkably enhance the decay of the entanglement of three-qubit states. However, in the weak-coupling region, the process of disentanglement depends on the strength of the three-site interaction.     

A weighted network evolution with traffic flow

In this paper, we propose a simple weighted network model that generalizes the complex network model evolution with traffic flow previously presented to investigate the relationship between traffic flow and network structure. In the model, the nodes in the network are represented by the traffic flow states, the links in the network are represented by the transform of the traffic flow states, and the traffic flow transported when performing the transform of the traffic flow states is considered as the weight of the link. Several topological features of this generalized weighted model, such as the degree distribution and strength distribution, have been numerically studied. A scaling behavior between the strength and degree s∼klogk is obtained. By introducing some constraints to the generalized weighted model, we study its subnetworks and find that the scaling behavior between the strength and degree is conserved, though the topology properties are quite sensitive to the constraints.     

Calculation of the spreading widths of the deep-lying hole states in the odd tin isotopes

The experimentally observed deep-lying hole states in (d, t) reactions on the even Sn isotopes are described in terms of a quasiparticle-phonon formalism. The fragmentation of the hole strength is calculated and subsequently the fragments are spread over the many underlying non-collective states in a statistical way. The results of the calculations are in qualitative agreement with experiment, in that the calculated structures are most pronounced for the lighter Sn isotopes. The fact that only a relatively small fraction of the total sum rule strength is exhausted experimentally in the gross structure peak cannot be explained by this Calculation.     

Ionic transitions and oscillator strengths in Debye plasma - a case study

Stability and energy of the excited states of the ion in plasmas are investigated theoretically using the Debye model. The transition energies of and transitions are seen to follow completely opposite trends of variation with the plasma screening strength. The dependence of absorption oscillator strength values on the screening strength is also discussed. Received: 22 October 1997 / Accepted: 9 January 1998