Investigations toward atomic parity-nonconservation and anapole measurements in francium

自然的基本力量是可以在ISAC研究的引人入胜的学科之一，ISAC是加拿大在TRIUMF的新的世界级放射性束流设施。特别是，导致原子核β衰变的弱力，在呈现宇称破坏现象方面是独一无二的：在自然界中，没有观察到由弱力中介的物理过程的镜像。ISAC为研究Fr中的原子宇称破坏提供了独特的可能性，Fr是一种将非常重的核(Z=87)与简单的、基本上类似氢的碱的价态结构结合在一起的元素。在元素周期表的前103种元素中，FR核是最不稳定的，寿命最长的同位素只在23分钟内衰变。为了最大限度地利用微小样品，Fr原子将被激光减速，并被捕获到一个“磁光”激光陷阱中，该陷阱悬浮在自由空间中，温度比室温低数百万倍。精确的激光光谱学将使我们能够观察宇称破坏的影响。最终目标将是在粒子物理的标准模型之外寻找“新的”物理--到目前为止非常成功。这项实验的巨大技术挑战是实施稳健和极其高效的原子操纵和信号检测方法，以最大限度地利用微小的Fr样品。马尼托巴大学对稳定的Rb原子进行的前驱实验将开发所需的技术，并寻找“负能态”的影响，即创建虚拟的电子-正电子对，对宇称破坏测量中使用的原子跃迁产生影响。

The fundamental forces of nature are one of the fascinating subjects that can be studied at ISAC, Canada's new world-class radioactive beam facility at TRIUMF. In particular, the weak force, causing the beta-decay of nuclei, is unique in exhibiting the phenomenon of parity-violation: the mirror images of physical processes mediated by the weak force are not observed in nature. ISAC offers a unique possibility to study atomicparity-violation in francium (Fr), an element combining a very heavy nucleus (Z=87) with the simple, essentially hydrogenlike, valence structure of an alkali. Fr nuclei are the least stable among the first 103 elements in the periodic table, the longest-lived isotope decays in only 23 minutes. To make optimum use of the minute sample, the Fr atoms will be slowed down with laser light and captured into a `magneto-optical' laser trap, suspended in free space at temperatures millions of times colder than room temperature. Precise laser spectroscopy will allow us to observe the effects of parity-violation. The ultimate goal will be to search for `new' physics outside the - so far very successful - Standard Model of particle physics. The great technical challenge of this experiment is to implement robust and extremely efficient atom-manipulation and signal-detection methods to make optimum use of the minute Fr sample. A precursor experiment with stable rubidium atoms at the University of Manitoba will develop the required techniques and look for the effects of 'negative-energy states', i.e. the creation of virtual electron-positron pairs, on the atomic transition used in the parity-violation measurement.