PION SCATTERING FROM WELL-DIFORMED NUCLEI

In the framework of the eikonal theory and using the first order π-nucleus optical potential, the elastic and inelastic scatterings of π^± from well-deformed nuclei are discussed. The virtual excitations to the low-lying levels are taken into account in the calculations of the elastic scatterings by using the closure approximation. The theoretical results of pion scatterings from ¹⁵²Sm at T_π=180MeV are compared with the data.     

Single-Proton Pickup Reaction of the Halo Nucleus ^6He on a ^9Be Target at 25 MeV/nucleon

The inclusive differential cross sections of the ^7 Li nucleus in a reaction induced by ^6He on a ^9Be target are measured at an incident energy of 25 MeV/nucleon. Finite-range distorted-wave Born approximation calculations suggest that these ^7 Li particles are formed in a direct single-proton pickup reaction ^9Be（^6He,^7 Li）^8Li. The experimental data can be well reproduced by taking into account of the contributions of both the ground states and the first excited states of ^7Li and ^8Li.     

Isospin Effect on Level Spacing of N=9 Isotones

The ground-state properties of N=8 and N=9 isotones are investigated in the framework of the single-particle shell model. The isospin effect on the average nuclear potential is taken into account by introducing an isospin-dependent term in the depth of the Woods-Saxon potential. The theoretical results of RMS radii and spin-parity values are in agreement with the experimental data. Especially, the level inversion between neutron levels 2s_1/2 and 1d_5/2 in N=9 isotones is reproduced. A detailed discussion on numerical results is given and one-neutron halos in the ground states of ¹⁴B and ¹⁵C are presented.     

Contribution of One-Photon Annihilation at ψ(2S) in e+e－ Experiment

The continuum one-photon annihilation at ψ(2S) in e⁺e^－ experiment is studied. Such contributions to the measured final states ωπ⁰ and π⁺π^－ at ψ(2S) mass are estimated by phenomenological models. It is found that these contributions must be taken into account in the determination of branching ratios of ψ(2S)→ωπ0 and ψ(2S)→π⁺π^－, as well as other electromagnetic decay modes. The study reaches the conclusion that in order to obtain the correct branching ratios on these decay modes at BES, at least 10pb^－1of data below the ψ(2S) peak is needed.     

INTERACTING BOSON MODEL FOR EVEN-EVEN NUCLEI POSSESSED OF 1+ AND 3+ BANDS IN THE ROTATIONAL RIGION

On the bases of s, d IBM, octupole states are taken into account and the two-quasiparticle excitation is treated as boson-like in the SU(3) limit. The energy spectra are obtained analytically and the nondegenerated 1⁺ and 3⁺ bands are also reproduced. The calculated spectra of eight nuclei, which possess with 1⁺ or 3⁺ bands in their energy spectra in the rotational rigion, agree with the experimental ones fairly good.     

New Low-spin Levels in 76Se and Discussion of Its Yrast Band Structure

The decay of bromine–76 was studied using compton–suppressed spectrometer and high–purity ge detectors in singles and coincidence mode, respectively. bromine–76 was produced via two reactions,i. e.,⁷⁵As(α,3n)⁷⁶Br and ⁷⁶Se(p, n)⁷⁶Br.the results of these experiments verified the previously reported levels and gammas of ⁷⁶Se. in addition to the previously described transitions and levels, 39 new γ–rays and 15 new energy levels were found for the first time. spins and parities for new levels are proposed based on the calculated logft values, de–excitation modes of the observed states, and some nuclear reaction experiment results. a new decay scheme of ⁷⁶Br is proposed in the present work. combining with the high–spin states observed by the in–beam γ–ray spectroscopy of a previous decay work, the positive–parity yrast states were compared with the results from calculations in the framework of the projected shell model.     

Structure Properties of Light Nuclei(Ⅰ)Structure of Li Isotopes

The structure properties of Li isotopes are investigated in the framework of large-basis shell model.0hω calculation can reproduce the structure of ^6,7Li, but for some states of ^8,9 Li far from β-stability line the effect of(0+2)hω excitation should be taken into account for reproducing the experiment at data.For drip line nuclei,enlarging model space or changing the interaction can not reproduce the exotic properties of nucleus ¹¹Li.The exotic properties of some states of nuclei ^6—8Li are also briefly discussed.     

Neutral Higgs Effects on Rare Decay B→Xsl+l－ in the T2HDM

We calculate the new physics contributions to the branching ratios of the rare decays B→X_sl⁺l^－(l=e,μ) induced by neutral Higgs bosons loop diagrams in the top quark two-Higgs-doublet model (T2HDM). From the numerical calculations, we find that (a) the neutral Higgs boson's correction to B→X_sl⁺l^－ decays interferes constructively with its standard model counterpart, but small in magnitude; (b) the neutral Higgs contributions to the branching ratio of B→X_sl⁺l^－ decay can be neglected safely if their masses are larger than 100GeV and tanβ≤40.     

The Expansion Method of Mixed Basis Vectors of Lower-energy States and Harmonic Oscillators in Calculation of Bound States of Few-Body Systems

In this paper,the harmonic oscillator approach to the bound states of few-body ststems is developed and the lower-energy states are introduced as basis vectors and mixed with a part of harmonic oscillator vectors to calculate the binding energy.The lower energy levels of 3-α system and ⁹Be are presented and compared with experiments or other calculations.The results are satisfactory.     

THE SU(6) “UNITARY ENERGY BAND” STRUCTURE IN THE TRIBARYON SYSTEM

A picture of the tribaryon system is proposed based on the papers [1—3]. It is considered that proton, neutron and A hyperon from the basic particles of SU(3) group and form the basic particles of SU(6) group on account for spin. It turns out that there exist "unitary energy band" structure in the tribaryon system. From the mass formula of T₃³ breaking, one can find that the SU(6) symmetry gives the mass relations between different spin levels of the same strangeness analog states. Finally, simple calculations are made and tbere is no discrepancy between tbe results and the experimental data.     

Temperature dependence of the uniaxial magnetic anisotropy of rhombohedral antiferromagnetic crystals with ions in the <Emphasis Type="Italic">S</Emphasis> state

The contributions of the anisotropic exchange to the firstand second-order uniaxial anisotropy constants have been calculated for hematite at T = 0 K and arbitrary temperatures. The results of the calculations and the most significant mechanisms are taken into account in interpreting the temperature dependence of the anisotropy in rhombohedral antiferromagnetic crystals. The first-order anisotropy constant for hematite is described by the dipole interaction, contributions of the “single-ion” nature, and relatively small contributions of the anisotropic exchange. The second-order constant for hematite includes the “single-ion” contribution and the contribution of the anisotropic exchange. For FeBO₃ and MnCO₃ crystals, the main contributions to the first-order anisotropy constant come from the dipole and single-ion mechanisms.     

Particle-number conserving analysis for the 2-quasiparticle and high-K multi-quasiparticle states in doubly-odd 174,176Lu

Two-quasiparticle bands and low-lying excited high-K four-, six-, and eight-quasiparticle bands in the doubly-odd ^{174, 176}Lu are analyzed by using the cranked shell model (CSM) with the pairing correlations treated by a particle-number conserving (PNC) method, in which the blocking effects are taken into account exactly. The proton and neutron Nilsson level schemes for ^{174, 176}Lu are taken from the adjacent odd-A Lu and Hf isotopes, which are adopted to reproduce the experimental bandhead energies of the one-quasiproton and one-quasineutron bands of these odd-A Lu and Hf nuclei, respectively. Once the quasiparticle configurations are determined, the experimental bandhead energies and the moments of inertia of these two- and multi-quasiparticle bands are well reproduced by PNC-CSM calculations. The Coriolis mixing of the low-K (K=|Ω₁-Ω₂|) two-quasiparticle band of the Gallagher-Moszkowski doublet with one nucleon in the Ω = 1/2 orbital is analyzed.     

Partial-Wave Decomposition for Meson-Exchange Currents in Few-Nucleon Systems

 We develop an approach for calculating matrix elements of meson-exchange current operators between three-nucleon basis states in -coupling and a three-nucleon bound state. The contributions generated by π- and ρ-exchanges are included into the consideration. The matrix elements are expressed in terms of multiple integrals in momentum space. We apply a technique of partial-wave decompositions and carry out some angular integrations in closed form. Different representations appropriate for numerical calculations are derived for the matrix elements of interest. The momentum dependences of the matrix elements are studied and benchmark results are presented. The approach developed is of interest for investigations of deuteron-proton radiative capture and ³He photo- and electrodisintegration when the interactions in the initial or final states are taken into account by solving the Faddeev equations. Received April 2, 1999; accepted for publication December 30, 1999     

Microscopic Investigation of High-Spin States for Even-Even Nuclei(Ⅱ) Application to isotones 154Dy,156Er and 158Yb

With the effective interactions consisting of a pairing force,a quadrupole pairing force and a quadrupole-quadrupole force among valence nucleons,the microscopic approach based on the generalized Dyson expansion theory is applied in studying both the low-lying and high spin states for the isotones ¹⁵⁴Dy,¹⁵⁶Er and ¹⁵⁸Yb.In the truncated state space,the configurations(sd)N and (sd)N-1,+neutron-pair are assumed,respectively,for the low-lying and high spin states,although the same values of strength parameters are taken in the numerical calculations in the two subspaces.The calculated results are in good agreement with experiment,especially the data of first backbendings are reproduced satisfactorily.     

对力对于锕系核性质的影响

本文用处理对力的粒子数守恒方法来分析对力对于锕系核性质的影响,其中包括奇A核和偶偶核的内部激发谱、β衰变、α衰变等。文中首先根据实验测得的寄A核的内部激发谱,计及对力的影响,定出了单粒子能级的Nilsson参数(见表3和5)。然后利用此单粒子能级进一步分析了偶偶核的内部激发谱和β衰变。由于现有数据的限制,只分析了Th²²⁸,Th²³⁰,U²³²,U²³⁴和Cm²⁴⁴等核。由能级位置和β衰变的分析,     

Analysis of Three Annihilation Potential andp+ 12C Inelastic Scattering

The inelastic scattering of antiproton (p_lab=600MeV/c) by ¹²C leading to the excitation of the three normal parity T=0 levels is studied in the framework of Glauber model. The transition densities obtained from fitting to the electron scattering data and the three annihilation potentials derived from analysis of pp scattering data are used in the calculation. The inelastic angular distribution for exciting the three lowest normal parity T=0 states in ¹²C at 4.44MeV(J^π=2⁺), 7.66MeV(J^π=0⁺), and 9.63MeV(J^π=3^-) by 600MeV/c antiproton are calculated by selecting potential parameter suitably. The results are seen to be in fairly good agreement with the available experimental data. The results are given by using the elementary two-body amplitudes comparatively.     

Relativistic Multichannel Treatment of Ionic Rydberg States of Lanthanum

Ionic Rydberg energy levels of lanthanum are calculated from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. The present calculated results are in better agreement with the experimental measurements than the previous calculations [J. Phys. B 34 （2001）369] due to the consideration of dynamical polarizations. Moreover, in the experimental spectra achieved by a five-laser resonance excitation via the intermediate state 5d6d^3 F2, a series of weak ionic Rydberg states and some of perturbing states are found and assigned in this work.     

Isospin and Mixed Symmetry Excitations in 60—66Zn Isotopes

The level structure of ^60—66Zn isotopes is studied within the framework of interacting boson model-3 (IBM-3). The mixed symmetry states are investigated in these nuclei by analyzing the wave functions. The isospin excitation states are identified for ⁶⁰Zn (N=Z) nucleus. The calculated energy levels and transition probabilities are compared with available experimental data. The results obtained and the values of parameters used in this calculation indicated that the Zn isotopes are in the transition from vibrational to γ-unstable nuclei.     

Role of the nuclear surface in a unified description of the damping of single-particle states and giant resonances

The damping widths of single-particle states and of giant resonances are estimated in spherical nuclei, based on the excitation of surface modes.A Skyrme III interaction with an effective mass consistent with that resulting from infinite nuclear matter calculations with “realistic” forces $\text{(m}{}^1\text{/m = 0.76)}$, was utilized. The single-particle basis needed to construct the unperturbed nuclear response function for each multipolarity was obtained, treating this force in the Hartree-Fock approximation. Diagonalizing a schematic interaction in this basis, the surface modes were calculated. They are used to dress the single-particle and single-hole states and to renormalize the vertex interaction, taking into account the proper energy dependence of the couplings.The essential new feature of the present calculation as compared to the calculations reported in ref.¹) is that the energy dependence of the real and imaginary part of the self-energy is taken into account. This is done utilizing a strength function model.About 70 % of the damping widths arise from the coupling to specific intermediate states containing one low-lying collective surface vibration. The rest, from the coupling to many nonspecific states.Qualitative agreement is found with the experimental data for spherical nuclei throughout the mass table for both the single-particle states and the giant resonances. The model seems however to predict widths which are smaller than those experimentally observed.     

Lifetimes and transition probabilities of Xe II: Experimental measurements and theoretical calculations

In this work we make an experimental and theoretical investigation of transition probabilities (A) and lifetimes of Xe II. Eighteen A_ij's corresponding to the 6p-6d array were measured using a Laser Produced Plasma (LPP) as the spectroscopic source. The ab initio (AI) and Least Square Fitting (LSF) approaches were used to calculate the atomic parameters. Relativistic corrections and Configuration Interaction (CI) effects have been taken into account using the HFR approach described by Cowan. Whereas the AI parameters corresponding to 6p levels are not very affected by CI effects, several of the 6d levels with J=1/2, 3/2and 5/2 making transitions to the fundamental levels 5p⁵ are affected by CI effects due to both, discrete nd and continuum states, modifying their lifetimes values. An extensive comparison with other measurements and calculations are made. In particular, concerned with branching ratio and forbidden transitions. Received 15 July 1999