Isospin and mixed symmetry structure in 24Mg

The interacting boson model with isospin (IBM-3) has been used to study the isospin excitation states and electromagnetic transitions for 24Mg nucleus. The mixed symmetry states at low spin are also analyzed. The theoretical calculations are in agreement with experimental data. The present calculations indicate that the 3+ state is the lowest mixed symmetry state.     

Isospin structure in 68Ge

The interacting boson model-3(IBM-3) has been used to study the low-energy level structure and electromagnetic transitions of 68Ge nucleus. The main components of the wave function for some states are also analyzed respectively. The theoretical calculations are in agreement with experimental data, and the 68Ge is in transition from U(5) to SU(3).     

Nuclear structure of <Superscript>76</Superscript>Ge from proton-neutron interacting boson model calculations

The properties of low-lying states in ⁷⁶Ge, especially the characteristics of the mixed-symmetry states, have been investigated within the neutron-proton interacting boson model (IBM-2). By considering the relative energy of d proton boson to be different from that of neutron boson, the low-lying positive parity levels and M1, E2 transition strengths have been calculated. The IBM-2 calculated results are in good agreement with the experimental data. Particularly, the mixed-symmetry states have been reproduced quite well. The calculation and systematic analysis demonstrated that the collective character of ⁷⁶Ge lies closest to the SU*_πv(3), with some possible O_πv(6) dynamic symmetry in IBM-2 viewpoint.     

Mixed symmetry states and electromagnetic transition in the N=Z nucleus ~(28)Si

The interacting boson model with isospin (IBM-3) has been used to study mixed symmetry states and electromagnetic transitions at low-lying states for a ²⁸Si nucleus. The theoretical calculations show that the 2₄⁺ state is the lowest mixed symmetry state in ²⁸Si and the 4₃⁺ state is also a mixed symmetry state.     

Mixed symmetry states and isospin excitation in the N =Z nucleus 28Si

The interacting boson model with isospin (IBM-3) has been used to study the isospin excitation states and mixed symmetry states at low spin for 28Si. The theoretical calculations are in agreement with experimental data. The theoretical results show that the 81+ energy is 14.73 MeV.     

The Exploring of New Collective States ——Mixed-Symmetry States in Nuclei

New collective states with mixed-symmetry character of neutron—proton degrees of freedom is reviewed.In the framework of IBM-2,the mixed-symmtry states have been discussed in detail.The full-symmetry states and mixed-symmetry states of Hg,Gd and Nd isotopes,especially the effect of Majorana parameters on these states and M1 transitions,are calculated and analyzed.The results show that the basic properties of mixed-symmetry states of these nuclei are well described by IBM-2.     

Mixed Symmetry States in Even—Even ^96—108Mo Nuclei

Excitation energies and electromagnetic transition strengths in even-even ^96-108Mo nuclei have been described systematically be using the proton-neutron interacting boson model (IBM-2).It appears that the properties of low-lying levels in these isotopes,for which the comparison between experiment and theory is possible,can be satisfactorily described by the IBM-2 model,provided proper account is taken of the presence at low energy of states having a mixed-symmetry character.It seems possible to identify,in each isotope,a few states having such a character,the lowest ones being either 22^ or 23^ levels.It is found that these nuclei are in the transition from U(5) to SU(3).     

Description of Shape Coexistence and Mixed-Symmetry States in ~(96)Mo Using IBM-2

We investigate the level structure and E2,M1 electromagnetic transition properties in an even-even~(96)Mo nucleus within the framework of the proton-neutron interacting boson model(IBM-2).The calculated results of the IBM-2 can reproduce the recent new experimental data on~(96)Mo both qualitatively and quantitatively.It is found that both shape coexistence and mixed-symmetry states in~(96)Mo can be simultaneously described very well with the IBM-2 by taking into account that the relative energy of d neutron bosons is different from that of proton bosons.     

Cd偶同位素集体能谱与价质子空穴激发特性

采用以玻色子展开和MJS(ModifiedJancovici-Schiff)代换为基础的微观IBM-2方案,用直接对角化的计算方法,研究^108—118Cd偶同位素集体能谱.计算结果与实验能谱作了比较,并对近满壳偶偶核中价质子空穴激发特性及影响能谱结构的因素作了讨论.     

Low-lying states and isospin excitation in the Ge isotopes

The level structure of 64-70Ge isotopes has been studied within the framework of the interacting boson model-3 (IBM-3). The symmetry character in the proton and neutron degrees of freedom of the energy levels has been investigated. The isospin excitation states (T>Tz) have been assigned for the 64Ge (N=Z) nucleus. Some intruder states in these nuclei have been suggested. The calculated energy levels and transition probabilities are in good agreement with recent experimental data. The study indicates that the Ge isotopes are in transition from γ-unstable to vibrational.     

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.     

Description of the shape evolution in the yrast states of ~（186）Pt

^186Pt was tested in the framework of IBM-1 and the X（3） model. The results show that ^186Pt is located close to the shape phase transition point, but the B（E2） values little agree with the X（3） model. The shape evolution in the yrast states of186Pt is also discussed in detail. TRS calculation exhibits a flat bottomed potential at low spin states, but a relatively deep minimum at high spin states. It suggests that a shape evolution from vibrational mode to rotational mode happens in ^186Pt. The result is in agreement with the E-GOS calculation.     

Isospin and Symmetry Structure in 36Ar

The interacting boson model-3(IBM-3) has been used to study the isospin excitation states and electromagnetic transitions for ³⁶Ar nucleus. The mixed symmetry states and superdeformed band at low spin are also analyzed. The theoretical calculations are in agreement with experimental data, and the ³⁶Ar is superdeformed rotational nucleus close to the SU(3) limit. The present calculations indicate that the 2₄⁺ state is the lowest mixed symmetry state and the lowest isospin T=1 excitation state and at about 6.2 MeV, and the bandhead of superdeformed band is 0₂⁺ state.     

Vibrations and rotations for the proton-neutron interacting boson model

The interacting proton-neutron boson model (IBM-2) is analyzed in terms of the concepts of a geometrical picture. The centre of mass and relative-motion deformations are determined, and for the deformed systems, rotational and vibrational modes are identified. The parameters in an intrinsic hamiltonian which govern these modes are calculated. For the SU(3) dynamical symmetry a one-to-one mapping is given between low-lying basis states in the geometrical and the algebraic model. The magnetic dipole operator in the geometrical model is derived from its counterpart in IBM-2. This serves as an example for the calculation of static and transition operators, generally.     

A hartree-bose mean-field approximation for IBM-3

A Hartree-Bose mean-field approximation for the IBM-3 is presented. A Hartree-Bose transformation from the spherical to the deformed bosons with charge-dependent parameters is proposed which allows bosonic pair correlations and includes higher angular momentum bosons. The formalism contains previously proposed IBM-2 and IBM-3 intrinsic states as particular limits. Presented by J.E. García-Ramos at the International Conference on “Atomic Nuclei and Metallic Clusters”, Prague, September 1–5, 1997. This work has been supported in part by the Spanish DGICYT under contracts No. PB 95/0123 and PB95-0533, a DGICYT-IN2P3 agreement and by the European Commission under contract CI1*-CT94-0072.     

Comparing some predictions between Davidson-like potentials and interacting boson model: <Emphasis Type="Italic">X</Emphasis>(5) behavior of even-even <Superscript>128–140</Superscript>Nd isotopes

We denote that the level scheme of the transitional nuclei ^128–140Nd also presents the characteristic X(5) pattern, not only in the ground-state band, but also in some low-lying bands. An adequate point of the model leading to the X(5) symmetry is therefore confirmed. We also carry out calculations of positive-parity states of even-mass Nd nuclei within the framework of the interacting-boson model, and then the calculated energy values are compared with the experimental data along with the Davidson potential predictions. By comparing transitional behavior in the Nd nuclei with the predictions of an X(5) critical symmetry, we investigate an achievable degree of agreement between the predictions of the model leading to this symmetry and the interacting-boson model (IBM-1 and IBM-2). They agree well with the predictions of the experimental data. The text was submitted by the authors in English.     

Description of spectrum and electromagnetic transitions in <Superscript>94</Superscript>Mo through the proton-neutron interacting boson model

We investigated the properties of low-lying states in ⁹⁴Mo within the framework of the proton-neutron interacting boson model (IBM-2), with special focus on the characteristics of mixed-symmetry states. We calculated level energies and M1 and E2 transition strengths. The IBM-2 results agree with the available quantitative and qualitative experimental data on ⁹⁴Mo. The properties of mixed-symmetry states can be well described by IBM-2 given that the energy of the d proton boson is different from that of the neutron boson, especially for the transition of B(M1; 4 ₂ ⁺ → 4 ₁ ⁺ ).     

Low-lying states and isospin excitation in the Ge isotopes

The level structure of ^64-70Ge isotopes has been studied within the framework of the interacting boson model-3（IBM-3） . The symmetry character in the proton and neutron degrees of freedom of the energy levels has been investigated. The isospin excitation states（T 〉 Tz） have been assigned for the ^64Ge（N = Z） nucleus. Some intruder states in these nuclei have been suggested. The calculated energy levels and transition probabilities are in good agreement with recent experimental data. The study indicates that the Ge isotopes are in transition from γ-unstable to vibrational.     

Electromagnetic transition properties and isospin excitation in the cross-conjugate nuclei 44Ti and 52Fe

The interacting boson model with isospin (IBM-3) is applied to study the band structure and electromagnetic transition properties of the low-lying states in the cross-conjugate nuclei 44Ti and S2Fe. The isospin excitation states with T=0, 1 and 2 are identified and compared with available data. The E2 and M1 matrix elements for the low-lying states have been investigated. According to this study, the 2+3 state is the lowest mixed symmetry state in the cross-conjugate nuclei 44Ti and 52Fe. The excitation energy of the second 0+2 and 2+2 states with T=0 in the nucleus 52Fe are identified. The agreement between the model calculations and data is reasonably good.     

Isospin and F-spin symmetry structure in low-lying levels of 48，50Cr isotopes

The low-energy level structure and electromagnetic transitions of ^48.50Cr nuclei have been studied using the interacting boson model with isospin (IBM-3). A sequence of isospin excitation bands with isospin T = Tz, Tz 1and Tz 2 has been assigned, and compared with available data. According to this study, the 2^3 and 2^2 states are the lowest mixed symmetry states in ^48Cr and ^50Cr, respectively. In particular, the present calculations suggest that a combination of isospin and F-spin excitation can explain the structure in these nuclei. The transition probabilities between the levels are analysed in terms of isoscalar and isovector decompositions which reveal the detailed nature of the energy levels. The results obtained are in good agreement with recent experimental data.