基于微观IBM对电子-核散射及核电磁性质的研究(Ⅱ)ME理论方案

Study of Electron Nucleus Scattering and Nuclear Electromagnetic Properties Based on Microscopic IBM (Ⅱ) Theoretical Approach Based on ME Method

从一种微观相互作用玻色子模型 (IBM)玻色子集体态子空间映射出费米子集体态子空间 ,通过假定玻色子算符形式以及使物理算符在两集体态子空间中对应归一化基矢间矩阵元相等 ,给出了从费米子单体算符导出玻色子单体算符的一种微观理论方法 (ME方法 ) .文中以获取玻色子结构函数亦即确定玻色子形式核跃迁电荷 /电流密度算符为例对此作出了详细介绍 .利用微观IBM提供的波函数可在玻色子态空间中求出核跃迁电荷 /电流密度 ,结合电子 -核散射以及核电磁跃迁的形式理论 ,可建立研究电子 -核散射各种形状因子与微分散射截面以及核约化跃迁几率、电磁多极矩、核态 g因子等物理量的理论方案 .在微观sdgIBM 1下利用该方案初步计算了14 6Nd核 2 +1态到 0 +1态的跃迁电荷密度以及约化跃迁几率 。

In this paper a mapping of the collective state subspace in a microscopic IBM onto the fermion collective state subspace is achieved. A microscopic theoretical method (ME method),which is suitable to deduce the boson one body operator from the fermion one body operator,is proposed by supposing the form of the boson operator and making equal the matrix elements of physical operator between the coressponding normal basis vectors of the two different collective state subspaces. In the context, the procedure of obtaining the boson structure function,i.e. the determination of the boson transition charge/current density operator,is taken as an example to give a detailed statement of the method. Thereafter, calculations of the nuclear charge/current densities can be carried out in the boson state space by taking advantage of the eigenfuncitons of the microscopic IBM. Associated with the formal theories of electron nucleus scattering and nuclear electromagnetic transition,a microscopic approach,which can be used to study nuclear transition charge/current densities,various form factors,differential cross sections,reduced transition rates,electromagnetic multipole moments, g factors, and so on,can be built up. Preliminary calculations of transition charge density and reduced transition probability from 2 + 1 to 0 + 1 in 146 Nd are carried out in terms of the approach in the framework of microscopic sdgIBM 1. It is found that the theoretical results fit the experimental data quite well.