Strong and decoupling structure in transitional odd-odd mass nuclei

The well known decoupling and strong coupling features of the high spin states in the transitional odd mass nuclei are found to persist also in the odd-odd mass nuclei. The simple structure of the levels borne out by the present calculations provides a straightforward understanding of the nature of the electromagnetic transitions.     

Competition between strong and de-coupling in odd-odd mass nuclei

Competition of strong and decoupling is studied systematically for odd-odd mass nuclei as a function of the position of the Fermi surfacesε _F (π) andε _F (υ) and the deformationsβ andγ. As an example we use⁸⁰Br. For a prolate deformation the odd proton likes to decouple while the odd neutron couples strongly. This favours a ground state angular momentum of 5 to 6. The strong coupling is described by the admixture of ad _5/2 nucleon. Only for the neutrons the admixture is so appreciably that it affects the spectrum and improves the agreement between theory and experiment for⁸⁰Br.     

High spin states in the transitional odd-odd nuclei150Eu and152Tb

Zeitschrift für Physik A Hadrons and nuclei - The (7Li, 5n) and (11B, 5n) reactions have been used to study the high-spin states in the two odd-odd nuclei150Eu and152Tb. Three decoupled bands...     

Pairing-isopairing competition in odd-odd nuclei

We discuss the systematics of 0⁺, v = 0, T = |T_Z| + 1 levels in odd-odd nuclei and conclude about the ground state isospin and seniority of these nuclei. For N = Z nuclei starting from the $\text{1f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ shell v_g.s = 0 |T_g.s = |T_z + 1. Otherwise v_g.s = 2, T_g.s = |T_z|.     

A=100区奇奇核旋称反转

利用两准粒子加轴对称转子模型,对A=100质量区两个奇奇核¹⁰²Rh和^{9 8}Rh的旋称反转进行了研究.结果表明,在A=160,130,80三个质量区奇奇核的计算中 已得到证实的、可能的旋称反转机制(即低K空间n-p相互作用和科氏力的相互竞争),对 于A=100质量区奇奇核也是适用的.这暗示在不同质量区奇奇核可能存在一种普遍的旋称 反转机制. 关键词： 奇奇核 旋称反转 两准粒子加轴对称转子模型     

Magnetic properties of odd-odd deformed nuclei

Magnetic moments and Ml transition probabilities depend on the parameters $\text{g}{}_{\mathrm{R}}\text{, g}{}_{\mathrm{\Omega }}{}_{\mathrm{<mtext>p</mtext>}}\text{,}\text{and}\text{g}{}_{\mathrm{\Omega }}{}_{\mathrm{<mtext>n</mtext>}}$ in odd-odd deformed nuclei. The parameter g_R can be obtained from an intraband branching ratio and a magnetic moment. Available data are analyzed and compared with predictions of the unified model.     

Magnetic moments of odd-odd spherical nuclei

We analyze the time-like processes $ \gamma\gamma\rightarrow B\overline{B}$ and $ p\bar{p}\rightarrow\gamma M$ at large Mandelstam variables within the handbag approach, for which the process amplitudes factorize in hard partonic subprocesses and annihilation form factors. The latter represent moments of baryon-antibaryon generalized parton distributions (GPDs). Symmetry relations restrict the number of independent annihilation form factors for the ground state baryons drastically. We determine these form factors from the present BELLE data on $ \gamma\gamma\rightarrow B\overline{B}$ with the help of simplifying assumptions. The knowledge of these form factors allow for predictions of $ p\bar{p}\rightarrow\gamma M$ for various mesons which may be probed at FAIR.     

Chiral doublet bands in odd-odd nuclei

The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Candidate chiral doublet bands in A~100 and 130 odd-odd nuclei were checked against these chiral criteria. Two representative cases, nearly degenerate ΔI =1 doublet bands in ¹²⁶Cs and ¹⁰⁶Rh were investigated in the two quasiparticles coupled with a triaxial rotor model. After including the pairing correlation, good agreement has been obtained between the calculated results and the data available, which supports the interpretation of observed doublet bands as chiral bands.     

Three dynamical boson-fermion symmetries for odd-odd nuclei

For odd-odd nuclei we introduce three dynamical boson-fermion symnetries associated with j_π=3/2, j_υ=3/2 and U^B(5) symmetry of the boson core. The corresponding energy formulas and quantum numbers for low-lying states are explicitly given.     

Quasi-rotation-aligned bands in the odd-odd Au nuclei

Newly observed negative parity bands of the low lying high spin states in the odd-odd Au nuclei (^190,192,194 Au) are explained in the framework wherein the two odd quasi-particles ($\text{π}\text{h}{}_{\mathrm{<mtext>1</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{?v}\text{i}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext><mtext>2</mtext>}}$) are coupled to the gamma deformed core. Interesting physical situations leading to different kinds of level structures and electromagnetic properties are pointed out. The present data are shown to represent the dynamical situation which for the high spin states, due to the energy considerations, does not prefer the mixing of various intrinsic angular momentum states of the two quasi-particle configuration. This property in turn allows the formation of rotational-like bands on these intrinsic states.     

New results on proton emission from odd-odd nuclei

⁷⁸Kr beams were used to bombard ⁵⁸Ni, ⁹²Mo and ⁹⁶Ru, producing three new, odd-odd, proton-emitting isotopes, ¹³⁰Eu, ^164mIr and ¹⁷⁰Au. Preliminary experimental and theoretical results will be presented in this paper. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: mahmud@ph.ed.ac.uk     

Triaxial projected shell model study of chiral rotation in odd-odd nuclei

Chiral rotation observed in ¹²⁸Cs is studied using the newly developed microscopic triaxial projected shell model (TPSM) approach. The observed energy levels and the electromagnetic transition probabilities of the nearly degenerate chiral dipole bands in this isotope are well reproduced by the present model. This demonstrates the broad applicability of the TPSM approach, based on a schematic interaction and angular-momentum projection technique, to explain a variety of low- and high-spin phenomena in triaxial rotating nuclei.     

Chiral bands in odd-odd nuclei with rigid or soft cores

Properties of chiral bands in an odd-odd nucleus, which is treated as a system of an even-even core and a pair of particles in the πh _11/2 ⊗ υh _11/2 ^-1 configuration, are calculated in the frame of the Core-Particle-Hole Coupling (CPHC) model with either a rigid triaxial or a soft core. The results of calculations for the two different cores are compared. The properties of the nucleus with the rigid, maximally triaxial ( γ = 30^°and with the entirely soft core are qualitatively very similar.     

Gamma band in transitional nuclei

The obstinate difficulty of the Davydov-Filippov model in obtaining the correct bunching of states in the γ-band of even-even mass transitional nuclei is explained in an extended version of the model which includes the 2-qp excitations and also the coupling between the 0- and 2-qp states. The important result is that the 0–2qp coupling for even spin states is much stronger than that for odd ones. Due to this effect the bunching of even-odd spin states in the Davydov-Filippov model is destroyed producing either an opposite bunching (now odd-even spin states) or a band wherein the states have similar energy spacings.     

Electron scattering from transitional nuclei

An electron scattering experiment on ¹⁸⁸Os, ¹⁹⁰Os, ¹⁹²Os, ¹⁹⁴Pt and ¹⁹⁶Pt has been performed at momentum transfers q = 0.6 to 3.2 fm⁻¹. Transition charge densities have been determined for the low-lying 2⁺, 3⁻ and 4⁺ states. The 2⁺ densities are well reproduced within the framework of the interacting boson model 2, where we have determined the boson densities α_ν, α_π, β_νv and β_π. The 4⁺ transition densities could not be reproduced indicating the need for including a g-boson. The ground and transition charge densities of ¹⁸⁸Os, ¹⁹²Os and ¹⁹⁶Pt have been compared with a microscopic calculation. The total binding energies and the intrinsic wave functions have been calculated for different values of β and γ with the constrained triaxial Hartree-Fock-Bogoliubov method using the finite range interaction D1SA. These energies are interpreted as potential energy surfaces and used in the Bohr hamiltonian in order to obtain the total nuclear wave functions. We obtain very good agreement with experiment. The calculated potential energy surfaces show these nuclei to be γ-soft with a shallow minimum for triaxial deformations and rigid in the β direction.