Interplay of pairing and quadrupole correlations in deformed nuclei

We study pairing correlations in deformed nuclei in the framework of the Nilsson+BCS theory. As in the spherical case, the pairing interaction is found to induce strong spacial correlations between the partners of each paired couple. The presence of the deformed mean field gives rise to a non-spherical pair field, whose deformation is governed by the properties of a few single-particle orbitals around the Fermi surface and does not necessarily follow the shape of the mean field. Multipole expansion of the pair field yields all the pair densities associated with the direct two-particle transfer processes to the members of the g.s. rotational band in the A+2 system. The interplay of the deformations of the mean and the pair fields can lead to different relative magnitudes and phases of these densities and therefore to different excitation patterns of the rotational bands in two-particle transfer reactions. In the case of non-collective twoquasiparticles and bands the associated pair densities display large components with high multipoles and the associated transfer processes may be favoured in heavy-ion collisions by kinematical conditions. Examples corresponding to both prolate and oblate cases are considered.     

利用纠缠交换实现多粒子纠缠态纯化

利用纠缠交换的方法实现了两粒子和三粒子纠缠态的纯化,并将该方法推广到多粒子纠缠态的情况,而且得出在所有的情况下从部分纠缠态获得最大纠缠态的概率均为2|b|2。在此过程中我们只使用了幺正变换和Hadam ard变换,而不需要经典通信。     

Triplet cooper pairing in nuclear matter and rotational states of superdeformed nuclei

One hundred and sixty-one rotational bands of superdeformed states in nuclei are considered on the basis of a model that admits triplet Cooper pairing in superfluid nuclear matter. The behavior of the dynamical moment of inertia for such states is investigated within this model, which is shown to comply well with available experimental data and to describe successfully the rotational spectra of superdeformed states.     

Conversion electron cascades in 254(102)No

The spectrum of prompt conversion electrons emitted by excited 254No nuclei has been measured, revealing discrete lines arising from transitions within the ground state band. A striking feature is a broad distribution that peaks near 100 keV and comprises high multiplicity electron cascades, probably originating from M1 transitions within rotational bands built on high K states.     

A microscopic study on shape transition and shape coexistence in superdeformed nuclei

Superdeformed nuclei at high-spin states in several mass regions are investigated within a microscopic approach using cranked Nilsson-Strutinsky formalism to explore the equilibrium deformations in the ground state and their evolution with spin. Shape transition from normal deformed to superdeformed states with increasing spin is studied and a clear picture of shape coexistence is provided. Detailed information on spin, rotational energy, dynamical moment of inertia, and rotational frequency of superdeformed rotational bands is presented and the general features of superdeformed bands in certain mass regions are outlined. Rotational energy and dynamical moment of inertia are compared with available experimental data and the impact of temperature and pairing on superdeformed configuration are discussed.     

非线性一维光学晶格链中的热纠缠

本文对非线性光学晶格链中自旋为1的原子，在两原子以及多原子链中紧邻原子之间的热纠缠问题作了详尽的研究，结果表明非线性耦合和线性耦合系数之间的关系对界定热纠缠是否存在起到关键作用，由于不同的原子这两种耦合对应着不同的关系，这一研究揭示在那些种类的原子中存在热纠缠；这一结果对两粒子以及多粒子体系都是成立的。在多粒子情况下临界温度以及热纠缠仅有少许下降。     

Study ofpf-shell nuclei with a symmetry conserving generator coordinate method

Bands based on the 0⁺ ground state and the first excited 0⁺ pairing vibrational state of⁴⁸Ti,⁵²Cr and⁵⁶Fe are studied with the generator coordinate method. The generating wave functions for each value of the angular momentumJ are angular momentum and particle number projected selfconsistent Hartree-Fock-Bogoliubov states where the constrained amount of pairing correlations serves as the generator coordinate. The interaction is given by reaction matrix elements derived from the Hamada-Johnston force. The basis includes the four lowest oscillator shells. The excitation energies of the pairing vibrational states can be reproduced fairly well by the present choice of the generating wave functions, whereas the ground band is not much improved compared to projected Hartree-Bogoliubov calculations. We find that the strength of the pairing correlations in the 0⁺ and 2⁺ states of the ground state and the pairing vibrational bands can be related to data of two-particle transfer reactions. The angular momentum dependence of the pairing correlations and of the moments of inertia are studied. The results show that for a strongly paired ground state the ground state band and the pairing vibrational band intersect. This may produce in the yrast band the anomaly of the moment of inertia known from rare earth nuclei.     

Limiting Fragmentation Behaviours of Correlation and Fluctuation of Particle Produced in High Energy Oxygen-Nucleus Induced Interactions

The limiting fragmentation behaviour of the single-particle pseudo-rapidity distributions and the two-particle correlations in oxygen-nucleus induced interactions in the energy region from 3.7 to 200A GeV is systematically investigated,and that of the dynamical fluctuations of multi-particle distribution is studied by using the relation between the factorial-moments and the multi-particle pseudo-rapidity distributions.     

Study of giant pairing vibrations with neutron-rich nuclei

We investigate the possible signature of the presence of giant pairing states at an excitation energy of about 10 MeV via two-particle transfer reactions induced by neutron-rich weakly bound projectiles. Performingparticle-particle RPA calculations on ²⁰⁸Pb and BCS + RPA calculations on ¹¹⁶Sn, we obtain the pairing strength distribution for two-particle addition and removal modes. Estimates of two-particle transfer cross sections can be obtained in the framework of the macroscopic model. The weak-binding nature of the projectile kinematically favors transitions to high-lying states. In the case of the (⁶He, ⁴He) reaction, we predict a population of the Giant Pairing Vibration with cross sections of the order of a millibarn, dominating over the mismatched transition to the ground state.     

Deterministic and exact entanglement teleportation viathe W state

Utilizing a three-particle W state, we come up with a protocol for the teleportation of an unknown two-particle entangled state. It is shown that the teleportation can be deterministically and exactly realized. Moreover, two-particle entanglement teleportation is generalized to a system consisting of many particles via a three-particle W state and a multi-particle W state, respectively. All unitary transformations performed by the receiver are given in a concise formula.     

Nonadditivity in moments of inertia of high-K multiquasiparticle bands

The experimental high-K 2- and 3-quasiparticle bands of well deformed rare-earth nuclei are analyzed. It is found that there exists significant nonadditivity in moments of inertia (MOIs) for these bands. The microscopic mechanism of the rotational bands is investigated by the particle number conserving (PNC) method in the frame of cranked shell model with pairing, in which the blocking effects are taken care of exactly. The experimental rotational frequency dependence of these bands is well reproduced in PNC calculations. The nonadditivity in MOIs originates from the destructive interference between Pauli blocking effects.     

Investigation of the two-quasiparticle bands in the doubly-odd nucleus 166Ta using a particle-number conserving cranked shell model

The high-spin rotational properties of two-quasiparticle bands in the doubly-odd ~(166)Ta are analyzed using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency ω are reproduced very well by the particle-number conserving calculations, which provides a reliable support to the configuration assignments in previous works for these bands. The backbendings in these two-quasiparticle bands are analyzed by the calculated occupation probabilities and the contributions of each orbital to the total angular momentum alignments. The moments of inertia and alignments for the Gallagher-Moszkowski partners of these observed two-quasiparticle rotational bands are also predicted.     

Pairing vibrational and isospin rotational states in a particle number and isospin projected generator coordinate method

Pairing vibrational and isospin rotational states are described in different approximations based on particle number and isospin projected, proton-proton, neutron-neutron and proton-neutron pairing wave functions and on the generator coordinate method (GCM). The investigations are performed in models for which an exact group theoretical solution exists. It turns out that a particle number and isospin projection is essential to yield a good approximation to the ground state or isospin yrast state energies. For strong pairing correlations (pairing force constant equal to the single-particle level distance) isospin cranking (-ωT_x) yields with particle number projected pairing wave function also good agreement with the exact energies. GCM wave functions generated by particle number and isospin projected BCS functions with different amounts of pairing correlations yield for the lowest T = 0 and T = 2 states energies which are practically indistinguishable from the exact solutions. But even the second and third lowest energies of charge-symmetric states are still very reliable. Thus we conclude that also in realistic cases isospin rotational and pairing vibrational states may be described in the framework of the GCM method with isospin and particle number projected generating wave functions.     

Shell structure and pairing for interacting fermions in a trap

The shell structures for weakly interacting fermions in harmonic oscillator traps at zero temperature undergo several transitions depending on the number of particles in the trap and their interaction strength. Calculations of the one and two-particle spectra give the pairing gaps, and the many particle state is constructed by the seniority scheme. For sufficiently few particles, N less than or similar to 10(4), the pairing field exceeds the mean-field splitting of single particle levels at the Fermi surface and the greater number of almost degenerate states due to the SU(3) symmetry in the harmonic oscillator shell lead to supergaps. Deformation and rotation are also discussed.     

Intrinsic states and rotational bands in 176Ta and 178Ta

High-spin states in the deformed, doubly odd nuclei, ¹⁷⁶Ta and ¹⁷⁸Ta have been studied by time-correlated γ-ray and electron spectroscopy techniques following (HI,xn) reactions. The new results independently confirm and extend in spin the previously known two- and four-quasiparticle states, albeit with some differences. Many high-seniority structures, most of them with associated rotational bands, have been identified for the first time. Several high-K isomers with half-lives ranging from a few nanoseconds up to hundreds of milliseconds have been discovered. Observation of rotational bands, built upon the intrinsic states has allowed characterization of the configurations, through both the in-band decay properties and alignments. The excitation energies of the observed multi-quasiparticle structures are generally reproduced using calculations based on the Lipkin-Nogami pairing model with inclusion of the effects of blocking and empirical nucleon-nucleon interactions. Some discrepancies in the energies, such as for the 14⁻ and 15⁻ isomers in ¹⁷⁶Ta and ¹⁷⁸Ta, respectively, are attributed to specific configuration mixing. Several anomalously fast K-forbidden transitions are discussed.     

High-spin states and rotation-particle coupling in 179W

The ¹⁷⁸Hf(α, 3n)¹⁷⁹W and ¹⁸¹Ta(p, 3n)¹⁷⁹W reactions are used to populate rotational states in ¹⁷⁹W. Particular attention is paid to the strongly perturbed positive-parity bands. The rotational energies within these bands are successfully explained within the unified model with pairing and Coriolis interactions included if the theoretical Coriolis matrix elements are reduced. The wave functions are calculated from a fit to the experimental energies and the theoretical and experimental transition probabilities are compared. Rotational bands built on the $\text{7}\text{2}$^?[514], $\text{1}\text{2}$^?[521] and $\text{5}\text{2}$^?[512] intrinsic states are also observed.     

Stability of nuclear rotational states

The stability of rotational states described by using a procedure of the Hartree-Fock-Bogoliubov method is discussed. The stability condition is obtained in a general form and some of its properties are examined with the aid of simplifying approximations. It is pointed out in conclusion that the Coriolis force might lead to the instability of rotational states for sufficiently large angular momenta. The instability of rotational states is caused by the instability of the pairing density, and also by that of the nuclear density distribution. In the former case it is shown that below the critical angular momentum, a first-order phase transition takes place and in some cases the rotational band breaks off. In the latter case, it might be considered that the assumption of an axially symmetric deformation is broken or large change of the equilibrium deformation is brought suddenly. Then discontinuous change of the rotational level might be seen at the unstable point.