High-resolution in-beam particle spectroscopy --New results on prompt proton emission from 58Cu

Prompt proton decay lines in ⁵⁸Cu have been studied by means of high-resolution in-beam particle-γ coincidence spectroscopy using the GAMMASPHERE Ge-detector array in conjunction with a dedicated set of ancillary detectors including four ΔE-E silicon-strip telescopes. High-spin states in ⁵⁸Cu have been populated via the heavy-ion fusion-evaporation reaction ²⁸Si(³⁶Ar, 1α1p1n) at 148 MeV beam energy. The full-width at half maximum for the proton peak could be reduced significantly compared to earlier experiments. The results indicate that only one prompt proton decay branch exists in the decay-out of the well-deformed band of ⁵⁸Cu. Received: 11 March 2002 / Accepted: 10 April 2002     

Localization of electrons and excitations

Electrons, electron holes, or excitations in finite or infinite ‘multimer systems’ may be localized or delocalized. In the theory of Hush, localization depends on the ratio Δ/λ (Δ/2 = coupling; λ = reorganization energy). The latter theory has been extended to the infinite system [S. Larsson, A. Klimkāns, Mol. Cryst. Liq. Cryst. 355 (2000) 217]. The metal/insulator transition often takes place abruptly as a function of Δ/λ. It is argued that localization in a system with un-filled bands cannot be determined on the basis of Mott–Hubbard U alone, but depends on the number of accessible valence states, reorganization energy λ and coupling Δ (=2t). In fact U = 0 does not necessarily imply delocalization. The analysis here shows that there are many different situations for an insulator to metal transition. Charge transfer in doped NiO is characterized by Ni²⁺ − Ni³⁺ exchange while charge transfer in pure NiO is characterized by a disproportionation 2Ni²⁺ → Ni⁺ + Ni³⁺. In spite of the great differences between these two cases, U has been applied without discrimination to both. The relevant localization parameters appear to be Δ and λ in the first case, with only two oxidation states, and U, Δ and λ in the second case with three oxidation states. The analysis is extended to insulator-metal transitions, giant magnetic resistance (GMR) and high T_c superconductivity (SC). λ and Δ can be determined quite accurately in quantum mechanical calculations involving only one and two monomers, respectively.     

Suppression of band crossing in the neutron-rich nuclei 172, 173Yb due to the absence of a static pair field

High-spin states in the neutron-rich nuclei ^172,173Yb have been populated in a ¹⁷⁰Er(⁷Li,(p,d,t)xn) incomplete-fusion reaction and the emitted γ-radiation was detected with the GASP array. The signature partners of the 7/2⁺[633] rotational band of the odd-N ¹⁷³Yb isotope have been newly established and were observed up to spin values of (45/2⁺) and (43/2⁺), respectively. The ground-state band of the even-even nucleus ¹⁷²Yb has been observed up to a spin value of (22⁺). No band crossings were found in these bands. To explain this observation, it is proposed that the static pair field is absent, considering that the neutron odd-even mass differences reach for these nuclei very small values and that the band crossing is absent in cranked shell modell calculations without pairing. The results indicate, however, that strong dynamic correlations are still present.     

Investigation of Dynamical Parameters of Exciton Confined in CdS Spherical Quantum Dots with a B-Spline Technique

Exciton energies as a function of radii of quantum dots in the range of 5-35 A are calculated based on effective mass approximation model with the B-spline technique and compared with experimental and other theoretical data for the CdS dots. This method leads to accurate and fast convergent exciton energy, which are in good agreement with experimental data in the whole confinement regime. The effect of penetration of wave function from the inside to the outside of the dots and the effect of dielectric constants are taken into account. The magnitudes of dynamical parameters are discussed. It is found that the different materials surrounding the CdS quantum dot affect not only the potential energy and Coulomb interaction energy of the system, but also the effective masses. The comparison shows that the effective mass approximation model can describe very well the quantum size effects observed experimentally on the exciton ground state energy.     

硅锗混合团簇GemSin(m+n≤10)的非正交紧束缚模型研究

Menon等[1]提出的非正交紧束缚模型(以下简称M-S NTB模型), 是基于s及p轨道的成键特征, 考虑了sp3杂化轨道间的非正交性对成键的贡献, 将计算量置于常规计算手段可接受的范围之内, 更适合于对碳族元素如C60[2], Sin[3]及Gen[4]等微团簇的研究. 这些工作表明, M-S NTB法是一种可信度较高、 计算量适中的半经验方法.     

Projected shell model study of neutron-deficient 122Ce

The observed excited states of ¹²²Ce nucleus have been studied in the framework of projected shell model (PSM). The yrast band has been studied up to spin 26ħ. The first band crossing has been predicted above a rotational frequency of 0.4 MeV/ħ that corresponds to first backbending. The calculation reproduces the experimentally observed ground state band up to spin 14 ħ. The electromagnetic quantities, transition quadrupole moments and g-factors are predicted and there is a need to measure these quantities experimentally.     

Observation of a πh9/2 ⊗ νi13/2 oblate band in 188Tl

Excited states in ¹⁸⁸Tl have been studied experimentally using the ¹⁵⁷Gd (³⁵Cl, 4n) reaction at a beam energy of 170MeV. A rotational band built on the πh _9/2 ⊗ νi _13/2 configuration with oblate deformation has been established for ¹⁸⁸Tl. Based on the structure systematics of the oblate πh _9/2 ⊗ νi _13/2 bands in the heavier odd-odd Tl nuclei, we have tentatively proposed spin values for the new band in ¹⁸⁸Tl. The πh _9/2 ⊗ νi _13/2 oblate band in ¹⁸⁸Tl shows low-spin signature inversion, and it can be interpreted qualitatively by the two-quasiparticle plus rotor model including a J-dependent p-n residual interaction.     

Spectroscopy and single-particle structure of the odd- Z heavy elements 255Lr, 251Md and 247Es

The odd-Z isotope ²⁵⁵Lr, its daughter ²⁵¹Md and grand-daughter ²⁴⁷Es were studied in two experiments performed at GANIL and the University of Jyv?skyl?. The ²⁵⁵Lr nuclei were produced using the cold fusion-evaporation reaction ²⁰⁹Bi(⁴⁸Ca, 2n)²⁵⁵Lr at a bombarding energy of 217MeV. The single-particle structure and decay properties were investigated using α, γ and electron spectroscopy. The ground-state spin and parity could be assigned for ²⁵⁵Lr (1/2^-) and ²⁵¹Md (7/2^-). States corresponding to the 7/2⁺[633], 7/2^-[514] and 1/2^-[521] Nilsson orbitals were observed. Results are compared to experimental data obtained in neighbouring isotopes and to Hartree-Fock-Bogoliubov calculations using the Skyrme interaction SLy4 and a density-dependent pairing interaction. The position of the 1/2^-[521] orbital from the spherical 2f _5/2 shell is discussed.     

AGS和RHIC能区核-核碰撞中的领头粒子效应与双柱模型

在总结双柱模型计算结果的基础上, 用该模型对交变梯度同步加速器(AGS)和相对论性重离子对撞机(RHIC)能区核－核碰撞中的领头粒子效应进行了统一分析. 结果表明:在AGS和RHIC能区, 不同中心性核－核碰撞中带电粒子(赝)快度分布的不同, 主要由领头粒子的贡献影响; 如果扣除领头粒子的贡献, 不同中心性核－核碰撞中带电粒子的(赝)快度分布有相同的形状.     

Model of the physical properties of halides with complete graph‐based indices

We describe the computation of dispersion constants using variational subspace methods to solve the perturbation theory equations in the tensor product space of the interacting molecules, treated separately at a (full) configuration interaction (CI) level. These new techniques are more accurate than the numerical quadrature of the Casimir Polder integral at the expense of a small additional computational cost. We also show how to compute the norm of the residual of the perturbative solution in the tensor product space to check convergence. The methods are tested on LiH and BH. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005