Triaxial Superdeformation in Nuclei Near N=100

N=100 附近原子核的三轴超变形

• 批准号: 0300673
• 负责人: Daryl Hartley
• 金额: $ 2.65万
• 依托单位: United States Naval Academy
• 依托单位国家: 美国
• 项目类别: Interagency Agreement
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0300673&HistoricalAwards=false
• 关键词: Triaxial; Superdeformation; Nuclei; Near; N=100

Atomic nuclei are known to exist in a variety of shapes whichinclude spherical, prolate (like a football), oblate (like a doorknob), and octupole (like a pear). Although these are different shapes, theyall have one common factor: they are all symmetric about at least one axis. Somewhat surprisingly, the most difficult nuclear shape to identify is one inwhich there is no symmetry axis, which would look like a kiwi fruit. Anucleus with this asymmetric shape is often said to possess ``triaxialdeformation'' or have ``triaxiality.'' In fact, only a few nuclei haveestablished cases of triaxial deformation. However, this shape only occurs in thesenuclei when it is in a highly excited state. Here, the nucleus issignificantly more elongated or more deformed than when in a less excited state. This phenomenon is known as ``superdeformation,'' and therefore when thenucleus is also triaxial it is said to have triaxial superdeformation. Itwas once thought triaxial superdeformation would only occur in nuclei withneutron numbers near N = 94, but recently we discovered possible triaxialdeformation in an isotope of hafnium having N = 102. In order to confirm thisshape, we must perform another experiment with higher statistics than thefirst, to search for the presence of wobbling excitations. These are thequantum equivalent to an asymmetric top being spun which would display awobbling motion. We will also begin a search for evidence of triaxial superdeformation in the neighboring tantalum nuclei with neutronnumbers near N = 100. Therefore, it is our intent to firmly establish thisregion of nuclei as having stable triaxial deformation.We will also participate and possibly lead experiments utilizingneutron-rich radioactive beams at Oak Ridge National Laboratory. Until recently,these species of isotopes could not be studied easily as few methodsexisted for exciting the neutron-rich nuclei. However, Oak Ridge can nowproduce beams of these rare isotopes for further analysis. Participation inthese experiments will better prepare the principal investigator topropose future experiments at this facility and eventually at the Rare IsotopeAccelerator. In addition, a make-shift radioactive beam can be used at theFlorida State University laboratory to study select neutron-rich nuclei.Undergraduate involvement will be vital in all of these projects. Students will learn basic nuclear physics techniques at the Naval Academy,and then apply this knowledge at the laboratories where this work will becompleted. The opportunity to use world-class facilities will hopefully propelthese students into scientific careers.

众所周知，原子核以各种形状存在，包括球形、长圆形(像足球)、扁圆形(像门把手)和八极(像梨)。尽管它们是不同的形状，但它们都有一个共同的因素：它们都至少围绕一个轴对称。有些令人惊讶的是，最难识别的核形状是一个没有对称轴的核，看起来像一个猕猴桃。这种不对称形状的原子核通常被说成具有“三轴变形”或“三轴”。事实上，只有少数几个原子核存在三轴形变的情况。然而，这种形状只出现在处于高激发态的核中。在这里，与处于较低激发态时相比，原子核明显更长或更变形。这种现象被称为“超变形”，因此，当原子核也是三轴时，它就被称为三轴超变形。它曾经被认为只会在中子数N=94附近的原子核中发生三轴超形变，但最近我们发现在N=102的一个氦的同位素中可能发生三轴形变。为了确认这一形状，我们必须用比第一次更高的统计量进行另一次实验，以寻找摆动激发的存在。这些量子相当于一个不对称的顶部被旋转，会显示出令人敬畏的运动。我们还将开始寻找在邻近的中子数N=100附近的钽核中存在三轴超形变的证据。因此，我们的意图是坚定地确定这一区域的原子核具有稳定的三轴形变。我们还将参与并可能领导在橡树岭国家实验室利用富含中子的放射束进行的实验。直到最近，由于激发富中子核的方法寥寥无几，这些同位素还不容易被研究。然而，橡树岭现在可以产生这些稀有同位素的光束，用于进一步分析。参与这些实验将使首席研究人员更好地为在这个设施以及最终在稀有同位素加速器提出未来的实验做好准备。此外，佛罗里达州立大学的实验室可以使用临时转换的放射性束流来研究精选的富含中子的原子核。在所有这些项目中，本科生的参与都将是至关重要的。学生们将在海军学院学习基本的核物理技术，然后在完成这项工作的实验室应用这些知识。使用世界级设施的机会有望推动这些学生进入科学职业生涯。