Cs Energy Shifts in an Electric Field

电场中铯能量的变化

• 批准号: 1912577
• 负责人: David Weiss
• 金额: $ 48.9万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1912577&HistoricalAwards=false
• 关键词: Cs; Energy; Shifts; Electric; Field

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.

在低能物理中，精确测量被用来回答通常被认为是高能粒子物理领域的问题，这是一个漫长而富有成果的历史。例如，精确的原子宇称非守恒实验以粒子加速器无法达到的方式约束了电弱理论。另一个例子是寻找原子和分子中的永久电偶极矩（EDM）。如果电火花被发现，这将意味着物理学的标准模型是不完整的，它将为一个更全面的理论指明道路。这里提出的原子度量与这两个例子都有关。最好的原子宇称违背测量是在电场和磁场中使用铯原子。要提取基础物理学，就必须把原子物理学从原子测量中分离出来。在近20年的时间里，由于原子理论工具不够完善，无法充分发挥最佳宇称破坏测量的优势。最近的理论进步正开始改变这一点，但这些工具需要独立验证。该项目将测量铯在电场中的另一种特性，即基态张量极化率（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。GSTP的测量也与铯EDM搜索所需的测量足够相似，这将是完成此类测量的一步。该实验还将培养研究生在非常广泛的实验和理论方法。铯GSTP（以及最终的铯EDM）将使用激光冷却的铯原子来测量，这些原子被困在空间磁屏蔽区域的一对平行一维远谐振光学晶格陷阱中。该实验是围绕能够单独测量每个基态磁亚能级的种群而设计的。在同一组原子中，相邻的正磁亚能级之间的直接跃迁可以与相邻的负磁亚能级之间的跃迁同时测量。在750微高斯的磁场和33千伏/厘米的电场中，这两个跃迁的差异与GSTP成正比，约为20 Hz。脉冲时限线宽将为1hz，因此可用的108个原子很容易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有关的系统影响的限制。这些显然可以很好地控制，足以将现有的8%的相对精度提高25倍。新的GSTP测量直接测量基态亚能级之间的跃迁，这一事实说明了比以前的测量有很大的预期改进，以前的测量在更广泛的光学跃迁中寻找小的位移。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。