Metastable Trapped Ions for Clockwork and Probing Nuclear Structure

科学家们用来了解宇宙的一些最灵敏的探测器实际上是单个原子。为了获得这种灵敏度，带电原子（离子）被单独隔离在真空室中，用激光冷却到接近绝对零度，并悬浮在称为离子阱的电磁场中。镱离子可以说是这类科学中最受欢迎的，它可以在一种独特的（人们知之甚少的）“亚稳态”激发态下储存能量多年。据预测，在这种亚稳态中存在罕见的原子效应，这对于制造原子钟和观察微小原子核的形状特别有利。该计划首次通过实验研究这些影响，以深入了解这种不寻常状态提供的高精度测量能力。该计划旨在观察和研究两个不寻常的特征，这些特征被预测存在于相对未开发的（I=5/2）钇-173同位素的低洼2F7/2状态中。首先，理论上预测，超细诱导态混合173Yb+可以将2F7/2态的六个超细能级中的四个的寿命减少大约两个数量级（与171Yb+相比），达到实验所需的几天的水平。该小组正在测量每个受影响的超精细状态的影响，以确定当该系统取代目前的171同位素作为时钟时，交流斯塔克位移系统误差的相应减少幅度有多大。其次，该小组正在展示一种方案来测量173Yb+在2F7/2状态下的超精细结构（目前未知）。电子态和原子核的大自旋使得这台“原子核电子显微镜”有可能显示其电磁多极矩的特征，包括核磁八极矩、电六极矩，甚至可能是磁32极矩。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Some of the most sensitive probes scientists have for learning about the universe are in fact single atoms. To access this sensitivity, charged atoms (ions) are individually isolated in vacuum chambers, cooled to nearly absolute zero by lasers, and levitated in electromagnetic fields known as ion traps. Ytterbium ions, arguably the most popular for this type of science, can store energy for years in a unique (and poorly understood) "metastable" excited state. Rare atomic effects have been predicted to exist in this metastable state that should make it particularly good for building atomic clocks and seeing the shape of the atom's tiny nucleus. This program is experimentally studying these effects for the first time to gain insight into the high precision measurement capabilities offered by this unusual state.This program seeks to observe and study two unusual features that have been predicted to exist in the low-lying 2F7/2 state of the relatively unexplored (I=5/2) ytterbium-173 isotope. First, hyperfine-induced state mixing 173Yb+ has been theoretically predicted to reduce the lifetime of four of the six hyperfine levels of the 2F7/2 state by approximately two orders of magnitude (as compared to 171Yb+) to the experimentally-desirable level of a few days. The group is measuring this effect for each affected hyperfine state to determine how large the corresponding reduction in ac Stark shift systematic error will be when this system is used in place of the current 171 isotope as a clock. Second, the group is demonstrating a scheme to measure the (currently unknown) hyperfine structure in the 2F7/2 state of 173Yb+. The large spin of both the electronic state and the nucleus allows the possibility that this "electron microscope for the nucleus" will show signatures of its electromagnetic multipole moments, including the nuclear magnetic octupole, electric hexadecapole, and possibly even the magnetic 32-pole moment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.