CAREER: Rotational Cooling of Radioactive Molecules

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。摘要：我们知道，在宇宙之初，存在着我们生存所必需的相互作用，这些相互作用违反了时间对称性。但是，我们还没有发现这些过程是什么。一些重放射性元素有望揭示这些相互作用的本质，因为它们对违反物理学的时间对称性的敏感性增强了。镭就是这样一种元素，当它被掺入分子中时，对时间对称性破坏的敏感性会进一步增强。一项实验将测量两种不同构型下分子状态的能量：当镭核与分子电场对齐时，以及当原子核与电场反对齐时。两种构型之间的能量差限制了违反时间对称的相互作用。由于它们的放射性，镭和镭基分子迄今为止还很少被研究。PI和他的学生将以镭离子的最新进展为基础，提供镭离子重要的低能电子能级的完整图景。此外，该团队将研究镭基分子的旋转结构，并努力以尽可能高的精度控制这些放射性分子。此外，PI和他的学生将领导会议，以改进维基百科科学文章（免费访问），重点是原子物理学领域。这些努力将为研究生、本科生和高中生提供宝贵的培训和学习机会。摘要：在这个项目中，PI和他的学生旨在测量镭离子的基本性质，并研究和控制分子离子RaH+的旋转结构。他们将测量镭离子的7P_1/2、6D_3/2和6D_5/2状态寿命。7P_1/2和6D_3/2的寿命还没有测量过，6D_5/2的寿命只有一个下界。这些测量将提供Ra+重要的低洼激发态的完整图像，这对该离子的高级工作非常重要。除了研究镭离子外，研究小组还将使用Ra+来产生和冷却被捕获的RaH+分子离子。通过光学频率梳，该团队将驱动分子旋转状态之间的受激拉曼跃迁，以研究旋转结构。他们将能够通过可控地驱动旋转状态之间的转换来建立旋转测量，以填充RaH+的目标旋转状态。旋转光谱学和控制技术的进步将为重放射性分子的高精度光谱学打开大门，这将有助于限制时间对称违逆，这对理解重子发生和强CP问题具有重要意义。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). General audience abstract:We know that in the beginning of the Universe there were interactions, necessary for our existence, that violated time symmetry. But, we have yet to discover what these processes were. A few heavy radioactive elements hold promise to uncover the nature of these interactions because of enhanced sensitivity to time symmetry violating physics. Radium is one such element, and when incorporated into a molecule the sensitivity to time symmetry violation is further amplified. An experiment would measure the energy of molecular states in two different configurations: when the radium nucleus is aligned with the molecule’s electric field, and when the nucleus is anti-aligned with the electric field. The energy difference between the two configurations constrains time symmetry violating interactions. Because of their radioactivity radium and radium-based molecules have so far been little-studied. The PI and his students will build on recent advances with the radium ion to provide a complete picture of the ion's important low-energy electronic levels. Further, the team will study the rotational structure of radium-based molecules, and work towards controlling these radioactive molecules with the finest precision possible. Additionally, the PI and his students will lead sessions to improve Wikipedia science articles (freely accessible), with a focus on the field of atomic physics. These efforts will provide valuable training and learning opportunities for graduate students, undergraduate students, and high school students.Technical audience abstract:In this project the PI and his students aim to measure basic properties of the radium ion, and study and control the rotational structure of the molecular ion RaH+. They will measure the radium ion's 7P_1/2, 6D_3/2, and 6D_5/2 state lifetimes. The 7P_1/2 and 6D_3/2 lifetimes have yet to be measured, and there only exists a lower bound on the 6D_5/2 state. These measurements will provide a complete picture of the important low-lying excited states of Ra+, which is important for advanced work with this ion. In addition to studying the radium ion, the team will use Ra+ to produce and cool trapped RaH+ molecular ions. With an optical frequency comb the team will drive stimulated Raman transitions between rotational states of the molecule to study the rotational structure. They will be able to build upon the rotational measurements by controllably driving transitions between rotational states to populate a target rotational state of RaH+. The advances in rotational spectroscopy and control will open the door to high precision spectroscopy of heavy radioactive molecules which are appealing for constraining time symmetry violation that is important for understanding baryogenesis and the strong CP problem.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.