PM: Cold Radioactive Molecules for Precision Measurements.

宇宙是由物质构成的，却不包含反物质，这是一个谜。没有人知道什么物理过程导致了早期宇宙中物质的产生，但我们知道它可以以一些不寻常的方式表现出来。一种方法是通过改变原子核的电磁特性，这可以在桌面设置中使用激光控制原子和分子进行精确的研究。一些原子核比其他原子核对这些效应更敏感，几十年来，人们已经知道，在元素周期表的最后一行含有某些重的、不稳定的原子核的极性分子，与目前最先进的实验相比，将这种新物理效应放大了大约一百万倍。然而，这些成果仍未实现；即使是最简单的分子的复杂性，再加上实验室中可以获得和处理的数量有限的不稳定原子核，使得这项研究非常具有挑战性。事实上，第一次基于激光的放射性分子精确测量是在几年前进行的。在目前的研究中，PI将带领一组学生开发和演示一种新方法来合成，冷却和精确研究含有镭的分子的结构和性质-镭是对新基础物理最敏感的原子核之一。研究小组将结合激光驱动的化学反应、低温氦气冷却和精密光谱学的新方法来研究多原子含镭分子，这些分子的化学结构经过调整，使先进的量子控制能够研究这些奇异的原子核。此外，该方法将广泛适用于含有不稳定或稀有原子核的分子，用于核结构、放射化学和核天体物理的研究。含有重的八极子形变原子核的分子，如镭，提供了强子cp违逆的极端增强。分子间电磁环境和原子核形状变形的结合导致对违反cp的核希夫矩的灵敏度比使用具有球形原子核的原子的最先进实验提高了大约一百万倍。此外，许多含镭的分子被预测为可激光冷却的，这意味着它们为高灵敏度测量的先进量子控制提供了一条途径。然而，研究这些物种的困难阻碍了他们的研究；事实上，直到最近几年，精密光谱学才被应用于任何短寿命放射性分子物种。该研究计划的目标是通过结合激光驱动的化学合成、低温缓冲气体冷却以及使用非常少量材料的宽带和窄带光谱新方法，合成、冷却和光谱研究含镭的多原子分子，包括RaOH。该方法将产生在静态缓冲气池中旋转和平移冷却到约4 K的分子，从而将它们置于光谱，激光冷却和精密测量的起点。此外，这些方法将是非常通用的，可以应用于含有外来核的各种各样的分子，或者只能获得微量的分子。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。

The fact that the Universe is made from matter, yet contains no anti-matter, is a mystery. Nobody knows which physical process was responsible for generation of matter in the early Universe, but we do know that it can manifest itself in some unusual ways. One way is by modifying the electromagnetic properties of nuclei, which can be studied precisely in a table-top setting using laser-controlled and atoms and molecules. Some nuclei are more sensitive than others to these effects, and it has been known for decades that polar molecules containing certain heavy, unstable nuclei in the last row of the periodic table amplify the effects of this new physics by around a million times compared to current state-of-the-art experiments. However, these gains remain unrealized; the complexity of even the simplest molecule, combined with the limited amounts of unstable nuclei which can be obtained and handled in the laboratory, made this research very challenging. Indeed, the first precise laser-based measurement of any radioactive molecule was first performed a few years ago. For this present study, the PI will lead a team of students to develop and demonstrate a new method to synthesize, cool, and precisely study the structure and properties of molecules containing radium – one of the nuclei with the highest sensitivity to new fundamental physics. The research team will combine laser-driven chemical reactions, cryogenic helium gas cooling, and new approaches to precision spectroscopy to study polyatomic radium-containing molecules, whose chemical structures are tuned to enable advanced quantum control to study these exotic nuclei. Furthermore, the method will be widely applicable to molecules containing unstable or rare nuclei for studies in nuclear structure, radiochemistry, and nuclear astrophysics.Molecules containing heavy, octupole-deformed nuclei, such as radium, offer extreme enhancement of hadronic CP-violation. The combination of the intermolecular electromagnetic environment and the shape deformation of the nucleus result in around a million-fold enhancement in sensitivity to CP-violating nuclear Schiff moments compared to state-of-the-art experiments using atoms with spherical nuclei. Furthermore, many radium-containing molecules are predicted to be laser-coolable, meaning that they offer an avenue to advanced quantum control for highly sensitive measurements. However, the difficulty of working with these species has stifled their study; indeed, only in the last few years has precision spectroscopy been performed on any short-lived radioactive molecular species. The goal of this research program is to synthesize, cool, and spectroscopically study radium-containing polyatomic molecules, including RaOH, by combining laser-driven chemical synthesis, cryogenic buffer gas cooling, and new approaches to both broadband and narrowband spectroscopy with very small quantities of material. The method will produce molecules which are rotationally and translationally cooled to around 4 K in a static buffer gas cell, thereby placing them at a starting point for spectroscopy, laser cooling, and precision measurements. Furthermore, the methods will be very general, and can be applied to a wide variety of molecules containing exotic nuclei or otherwise available only in trace amounts.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.