Spectroscopy of exotic reflection-asymmetric atomic nuclei

奇异反射不对称原子核的光谱学

• 批准号: 2881643
• 金额: --
• 依托单位: University of the West of Scotland
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2881643
• 关键词: Spectroscopy; exotic; reflection; asymmetric; atomic

Atomic nuclei can assume different shapes depending on the numbers of neutrons and protons that they possess. Many nuclei are spherical but some take on shapes that are deformed like a rugby ball (stretched sphere) or a pumpkin (squashed sphere). In some cases atomic nuclei can become reflection-asymmetric or pear shaped. This occurs in certain localized regions of the nuclear chart, where the neutrons and protons occupy specific orbitals which drive towards a reflection shape. Specifically the orbitals of interest have a difference in both orbital and total angular momentum of 3 hbar. Nucleons occupying these orbitals can interact by the octupole interaction which gives rise to a reflection-asymmetric or octupole-deformed shape. On the nuclear chart, this occurs close to nucleon numbers 34, 56, 88, and 126. Any nucleus with these numbers of nucleons is susceptible to octupole correlations and in extreme cases permanent octupole deformation. The nuclei that possess the strongest octupole correlations have proton number Z close to 88 and neutron number N close to 126, which are the light actinide region. This region includes the neutron deficient radon (Z=86), radium (Z=88), thorium (Z=90), and uranium (z=92) nuclei. Over the past few decades a number of these nuclei have been studied in experiments and they have demonstrated the spectroscopic features of octupole deformation such as low-lying negative-parity states, interleaving bands with opposite parities, and strong electric-dipole transitions. Recent calculations have shown that the region of octupole deformation in the light-actinide region maybe more extended than previously thought - that is, it may include the neutron-deficient plutonium (Z=94) and curium (Z=96) isotopes. To date, these exotic nuclei have been out of the reach of experimental investigation, but new experimental techniques are making these nuclei accessible.This PhD project will involve the study of exotic atomic nuclei in the light actinide region with Z values on the upper side of the region with Z values greater than about 94. The PhD project will use different techniques to study these nuclei, for example including decay spectroscopy where excited states are populated following alpha decay in heavy-ion fusion-evaporation reactions. Such experiments will be performed using an array of radiation detectors at the focal plane of the RITU recoil mass spectrometer at the University of Jyväskylä Accelerator Laboratory in Finland. Other experiments will also be performed using state-of-the-art gamma-ray spectrometers such as Digital-Gammasphere at Argonne National Laboratory near Chicago and using the new AGATA gamma-ray tracking spectrometer at the Legnaro National Laboratory near Padova in Italy. The work undertake in this PhD project will include one or more such experiments, including planning for the experiment with simulations and modelling, setting up and running the experiment, and analysis of data. The results of the PhD project will lead to a better understanding of the development and evolution of exotic reflection-asymmetric deformations in atomic nuclei.

原子核可以呈现不同的形状，具体取决于它们所拥有的中子和质子的数量。许多原子核是球形的，但有些原子核的形状像橄榄球（拉伸的球体）或南瓜（压扁的球体）。原子核可能会变成反射不对称或梨形，这发生在核图的某些局部区域，其中中子和质子占据特定的轨道，特别是朝向感兴趣的轨道。轨道和总角动量的差异为 3 hbar。占据这些轨道的核子可以通过八极相互作用相互作用，从而在核图表上产生反射不对称或八极变形形状，这种情况发生在核子编号 34 附近。 56、88 和 126。具有这些核子数量的任何核都容易受到八极相关性的影响，并且在极端情况下是永久性的八极相关性最强的核心，其质子数Z接近88，中子数N接近126，为轻锕系元素区域，该区域包括缺中子氡（Z=86）、镭（Z=）。 88)、钍 (Z=90) 和铀 (z=92) 原子核在过去的几十年里有许多这样的原子核。他们在实验中进行了研究，并证明了八极变形的光谱特征，例如低位负宇称态、具有相反宇称的交错带以及强电偶极跃迁。最近的计算表明，光中的八极变形区域。 - 锕系元素区域可能比之前想象的更广泛 - 也就是说，它可能包括缺乏中子的钚（Z = 94）和锔（Z = 96）迄今为止，这些奇异原子核已经超出了实验研究的范围，但新的实验技术正在使这些原子核变得容易实现。这个博士项目将涉及 Z 值在轻锕系元素区域中的奇异原子核的研究。 Z 值大于约 94 的区域的上侧。博士项目将使用不同的技术来研究这些原子核，例如包括衰变光谱，其中在重离子聚变蒸发反应中的 α 衰变后激发态被填充。此类实验将使用一系列芬兰于韦斯屈莱大学加速器实验室 RITU 反冲质谱仪焦平面上的辐射探测器还将使用最先进的伽马射线光谱仪（例如位于阿贡国家实验室附近的数字伽玛球）进行其他实验。芝加哥并在意大利帕多瓦附近的莱尼亚罗国家实验室使用新型 AGATA 伽马射线跟踪光谱仪。该博士项目中进行的工作将包括一个或多个此类实验，包括规划。用于模拟和建模实验、设置和运行实验以及数据分析。博士项目的结果将有助于更好地了解原子核中奇异的反射不对称变形的发展和演化。