Cs Energy Shifts in an Electric Field

在低能物理学中，有一个长期的、富有成果的精确测量历史，被用来回答通常被认为是高能粒子物理学领域的问题。例如，精确的原子宇称不守恒实验以粒子加速器无法达到的方式限制了电弱理论。 另一个例子是寻找原子和分子中的永久电偶极矩（EDM）。如果EDM被发现，这将意味着物理学的标准模型是不完整的，它将指向一个更全面的理论。这里提出的原子测量与这两个例子有关。最好的原子宇称破坏测量使用电场和磁场中的原子铯。为了提取基础物理，必须将原子物理从原子测量中分离出来。在大约20年的时间里，由于原子理论工具不够好，最好的宇称破坏测量无法充分利用。最近的理论进展开始改变这一点，但这些工具需要独立的验证。该项目将测量铯在电场中的不同性质，即其基态张量极化率（GSTP），将该值的实验知识提高至少25倍。铯宇称违反结果所需的计算与预测GSTP所需的计算相似，因此这些测量将有助于以所需的精度验证原子理论。全球贸易优惠制的测量也与铯EDM搜索所需的测量足够相似，它们将是完成这种测量的一个沿着步骤。该实验还将培养研究生在一个非常广泛的实验和理论方法。铯GSTP（并最终铯EDM）将使用激光冷却的铯原子捕获在一对平行的一维远离共振光学晶格陷阱在空间的磁屏蔽区域。 该实验是围绕能够分别测量每个基态磁子级的粒子数而设计的。在同一组原子中，相邻的正磁性子能级之间的直接跃迁可以与相邻的负磁性子能级之间的跃迁同时测量。在750微高斯磁场和33 kV/cm电场中，这两个跃迁的差异量与GSTP成比例，约20 Hz。脉冲时间限制的线宽将为1 Hz，因此可以利用可用的108个原子容易地实现的线分裂将在单次扫描中产生~10-4的灵敏度。最终的精度将受到与光阱相关的系统影响的限制。这些可以很好地控制，足以将现有的8%相对精度提高25倍。新的GSTP测量直接测量基态次能级之间的跃迁，这一事实说明了与以前的测量相比有很大的预期改进，以前的测量在更广泛的光学跃迁中寻找微小的变化。该奖项反映了NSF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。

There is a long, fruitful history of precision measurements in low energy physics being used to answer questions that are usually considered the realm of high energy particle physics. For instance, precision atomic parity non-conservation experiments constrain the electroweak theory in a way that is inaccessible to particle accelerators. Another example is the search for a permanent electric dipole moment (EDM) in atoms and molecules. If an EDM were to be discovered, it would imply that the standard model of physics is incomplete, and it would point the way to a more overarching theory. The atomic measurement proposed here relates to both of these examples. The best atomic parity violation measurement uses atomic cesium in electric and magnetic fields. To extract the fundamental physics, it is necessary to disentangle the atomic physics from the atomic measurement. For about 20 years, full advantage could not be taken of the best parity violation measurement, because the atomic theory tools were not good enough. Recent theoretical advances are starting to change that, but the tools need independent validation. This project will measure a different property of cesium in an electric field, its ground state tensor polarizability (GSTP), improving the experimental knowledge of that value by a factor of at least 25. The calculations needed for the cesium parity violation result are similar to those needed to predict the GSTP, so these measurements will help validate the atomic theory with the required precision. The GSTP measurements are also similar enough to those needed for a cesium EDM search that they will be a step along the way toward completing such a measurement. The experiment will also train graduate students in a very wide range of experimental and theoretical methods.The cesium GSTP (and ultimately the cesium EDM) will be measured using laser-cooled Cs atoms trapped in a pair of parallel 1D far-off-resonant optical lattice traps in a magnetically shielded region of space. The experiment is designed around being able to separately measure the populations of each ground state magnetic sublevel. Within the same set of atoms, direct transitions between adjacent positive magnetic sublevels can be measured at the same time as transitions between adjacent negative magnetic sublevels. In a 750 microGauss magnetic field and a 33 kV/cm electric field, these two transitions will differ by an amount that is proportional to the GSTP, ~20 Hz. The pulse-time-limited linewidth will be 1 Hz, so the line splitting that can be readily achieved with the available 108 atoms will yield ~10-4 sensitivity in a single scan. The ultimate precision will be limited by systematic affects related to the light traps. These can clearly be controlled well enough to improve on the existing 8% relative precision by a factor of 25. The fact that the new GSTP measurement directly measures transitions between ground state sublevels accounts for the large expected improvement over previous measurements, which looked for small shifts in much broader optical transitions.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.