Precision Tests of the Nuclear Wavefunction using Exotic Beams: Measurements of shape co-existence in 182,184Hg using Coulomb excitation

Isolde设施是位于瑞士日内瓦的欧洲核子研究组织国际实验室的一部分，利用所谓的在线同位素分离(ISOL)技术以高强度产生放射性核，这种技术用高强度的高能质子束轰击主要目标。使用不同的主靶，Isolde可以产生70种不同化学元素的700多种同位素的不同强度的束流。该设施在世界范围内是独一无二的，因为它可以产生多样化的可用波束。Isolde最近的一项进展是REX-Isolde设施，它将这些放射性原子核加速到能量，在那里它们开始抵抗固定目标中其他原子核的库仑排斥。在这样的能量下，相互作用发生，使我们能够高精度地探测这些奇异的放射性原子核的结构。对于其中一种机制，库仑激发，相互作用的一些能量被用来激发原子核进入更高的能级。发生这种情况的容易程度反映了核的集体性，这一性质对于变形的核来说通常是最大的，通常具有非球形形状，如橄榄球形状。因此，库仑激发测量使我们能够研究原子核的形状，特别是一类特殊的呈现形状共存的原子核。当特定同位素中的不同状态具有不同的不同形状时，就会出现这种现象。

At the ISOLDE facility, part of the international CERN Laboratory in Geneva, Switzerland, radioactive nuclei are produced with high intensities in the so-called isotope separation on-line (ISOL) technique where a primary target is bombarded with an intense, high energy proton beam. Using different primary targets, ISOLDE can produce beams of varying intensity of over 700 isotopes of 70 different chemical elements. This facility is unique worldwide in the diversity of available beams which it can produce. A recent advance at ISOLDE has been the REX-ISOLDE facility which accelerates these radioactive nuclei to energies where they start to resist the Coulomb repulsion of other nuclei in a fixed target. At such energies, interactions take place which allow us to probe the structure of these exotic radioactive nuclei with high precision. For one of these mechanisms, Coulomb excitation, some of the energy of the interaction goes into exciting the nucleus into higher energy states. The ease with which this takes place reflects the nuclear collectivity, a property which is generally largest for nuclei which are deformed, typically having a non-spherical shape such as a rugby-ball shape. Coulomb-excitation measurements therefore allow us to study the nuclear shape, in particular, a certain special class of nuclei which exhibit shape coexistence. This phenomenon occurs when different states in a particular isotope have different distinct shapes.