CAREER: Two Photon Laser Cooling of Atomic Hydrogen

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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.