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.

原子核可以根据其拥有的中子和质子的数量来假定不同的形状。许多核球体是球体，但有些是形状像橄榄球（拉伸球体）或南瓜（壁球球）一样变形的形状。在某些情况下，原子核可以变成反射 - 对称或梨形。这发生在核图表的某些局部区域，中子和质子占据了朝着反射形状驱动的特定轨道。具体而言，感兴趣的轨道在3 Hbar的轨道和总角动量上都有差异。占据这些轨道的核子可以通过八极相互作用相互作用，从而产生反射 - 对称或八杆孔的形状。在核图表上，这发生在几个核数字34、56、88和126上。任何具有这些核素数量的核us都容易受到八极相关性的影响，并且在极端情况下，永久性八杆的变形。具有强八极相关性的核具有接近88的质子Z，而中子数则接近126，即光actacinide区域。该区域包括中子不足的辐射（z = 86），镭（z = 88），thorium（z = 90）和铀（z = 92）核。在过去的几十年中，许多这些核已经在实验中进行了研究，它们证明了光谱特征最近的计算表明，在光肌动蛋白区域中八杆杆变形区域可能比以前认为的更延长 - 也就是说，它可能包括中子缺乏的prutium（z = 94）和库层（z = 94）和库层（z = 96）。迄今为止，这些异国情调的核已经超出了实验研究的范围，但是新的实验技术正在使这些核离子融合 - 蒸发反应产生。该博士学位项目将涉及在光actacinide区域中对外来原子核离子的研究，其Z值在该区域的上侧，Z值大于大约94。博士学位项目将使用不同的技术研究这些核，例如，包括衰减光谱谱图，其中激发态在重型离子融合效应 - 衰减后填充了激发态在重型离子衰减后填充了激发态。此类实验将使用芬兰Jyväskylä大学RITU后坐力质谱仪的焦平面上的一系列辐射探测器进行。其他实验还将使用最先进的伽马射线光谱仪进行，例如在芝加哥附近的Argonne国家实验室的数字伽马球，并使用意大利Padova附近Legnaro国家实验室的新的Agata Gamma-ray跟踪光谱仪进行。该博士项目中的工作将包括一个或多个这样的实验，包括计划模拟和建模的实验，设置和运行实验以及数据分析。博士学位项目的结果将使人们更好地理解原子核中外来反射 - 对称变形的发展和演变。