Investigation of low-lying isovector octupole excitations in spherical nuclei

球形核中低位等矢量八极激发的研究

• 批准号: 230773711
• 负责人: Professor Dr. Thorsten Kröll
• 金额: --
• 依托单位: Institut für Kernphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/230773711?language=en
• 关键词: Investigation; low; lying; isovector; octupole

Aim of the project is to conduct experiments with neutron-induced reactions to determine the spectroscopic properties of recently proposed first candidates for low-lying isovector octupole excitations in spherical nuclei. Due to historical reasons the analogue low-lying isovector excitations in the quadrupole sector are commonly referred to as mixed-symmetry states. For a firm assignment of the nature of the states proposed as candidates, it is mandatory to determine the B(M1) value of the transition connecting the candidate with the first excited 3- state, the isoscalar octupole phonon, with a high level of accuracy. Therefore, it is necessary to measure for this transition the multipole mixing ratio, the relative intensity and the radiation character which has been done already in the project with the EXILL spectrometer. In addition, for the absolute B(M1) value the lifetime is needed which will be measured with the GAMS spectrometer at ILL as it is suited best for the expected lifetime in the femtosecond range. Establishing this new kind of low-lying collective mode in spherical nuclei offers several theoretical models, such as, for example, the Quasiparticle Phonon Model (QPM) or modern beyond mean-field models, the opportunity to fix the coupling constant of theisovector part of proton-neutron residual interaction in the octupole part of the multipole expansion of the effective nuclear force.

该项目的目的是用中子诱导的反应进行实验，以确定球形核中低洼层异载体八极激发的最近提议的第一候选物的光谱特性。由于历史原因，四极杆部门中的低洼等线激发通常称为混合对称状态。为了确定提议为候选人的国家性质的坚定分配，必须确定将候选人与第一个激动的3个状态（Isoscalar octupole phonon）相连的b（m1）值，其精度很高。因此，有必要测量此过渡的多极混合比，相对强度和辐射特征在项目中已经使用外观光谱仪完成的。此外，对于绝对B（M1）值，需要使用ILL的GAM光谱仪来测量寿命，因为它最适合于飞秒范围内的预期寿命。在球形核中建立这种新型的低洼集体模式提供了几种理论模型，例如，例如，准粒子声子模型（QPM）或Modern Beyter Measter Meason模型，有机会固定质子 - 内分子残留质量互动的Theisovector部分的耦合常数，该部分在Octupole的多层繁殖型核力量的Octupole一部分中。