Georg Raithel ( University of Michigan ) Circular - State Rydberg Atoms and the Proton Radius Puzzle

The Rydberg constant is of interest due to its relation to other fundamental constants and its role in calculations of atomic energy levels. Its current relative uncertainty stands at 5.9x10^-12 [1]. However, a large discrepancy involving the proton radius and the Rydberg constant has emerged in muonic hydrogen and deuterium (“proton radius puzzle” [2]). One concern expressed by the leading author of [2] is that “physicists have misgauged the Rydberg constant” [3]. A validation of the Rydberg constant using an independent method is therefore of high value. The work reported here aims at measuring the Rydberg constant and other atomic constants, such as polarizabilities, using long-lived circular Rydberg atoms, which are insensitive to critical systematics that limit the accuracy in spectroscopy of low-lying atomic states (nuclear penetration and QED shifts).