CAREER: Two Photon Laser Cooling of Atomic Hydrogen

本项目将发展原子氢的双光子激光冷却技术。氢是最简单的稳定原子，因此，它提供了一个独特的平台来测试我们最基本的物理理论。对氢跃迁频率的日益精确的测定有助于确定里德伯常数和质子电荷半径，并最终提供量子电动力学的严格测试。虽然测量氢跃迁的实验精度稳步提高，但原子的有限温度仍然是一个严重的限制。因此，通过激光冷却降低温度可以实现更精确的测量，这是这项工作的科学重点。为了实现该项目的教育目标，将在科罗拉多州立大学的物理小商店旁边建立一个互动实验站，以探索激光的相干性，并将提供与研究项目相关的主题的公开讲座。单光子激光冷却氢需要真空紫外线辐射，这是非常困难的生产和操作。这里提出的双光子激光冷却是一种替代方案，它需要同时吸收两个光子，并且只需要一半光子能量的辐射。虽然这种辐射更容易产生，但双光子冷却方案需要高平均功率才能实现快速冷却。因此，增强光腔内的辐射是本研究的一个重要组成部分。腔增强辐射将与磁导内的原子氢束重叠，从而实现一维激光冷却。在演示冷却后，冷氢源将用于确定氢的能量水平，精度提高，系统减少。

For this project, two-photon laser cooling techniques for atomic hydrogen will be developed. Hydrogen is the simplest stable atom and, as such, it provides a unique platform to test our most fundamental physical theories. Increasingly precise determinations of the transition frequencies in hydrogen help to determine the Rydberg constant and the proton charge radius and ultimately provide a rigorous test of quantum electrodynamics. While experiments measuring the transitions in hydrogen have steadily increased in precision, the finite temperature of the atoms has remained a serious limitation. Therefore, a reduction of the temperature through laser cooling would enable much more accurate measurements and is the scientific focus of this effort. For the education objectives of the project, an interactive experiment station will be developed alongside The Little Shop of Physics at Colorado State University to explore the coherence properties of laser light, and public lectures will be offered on topics related to the research program.Single-photon laser cooling of hydrogen requires vacuum ultraviolet radiation that is very difficult to produce and manipulate. The two-photon laser cooling proposed here is an alternative, which requires the simultaneous absorption of two photons and requires radiation with only half the photon energy. While this radiation is much easier to produce, two-photon cooling schemes require high average power to achieve rapid cooling. Therefore the enhancement of this radiation inside an optical cavity is a major component of this research. The cavity-enhanced radiation will be overlapped with an atomic hydrogen beam within a magnetic guide enabling one-dimensional laser cooling. After cooling is demonstrated, the cold hydrogen source will be utilized to determine the energy levels in hydrogen with improved precision and reduced systematics.