Research

We investigate fundamental properties and interactions of light exotic systems, especially muonic atoms such as µH and µD or muonic ions such as µHe⁺, µLi⁺⁺ and µBe³⁺, by means of laser and X-ray spectroscopy.

The studies include measurements of nuclear electric charge and magnetization radii, leading to improved determinations of the Rydberg constant, test of QED and improved benchmarks for nuclear physics of light nuclei.

 

	Tritium In the Triton-Radius EXperiment we will first trap atomic hydrogen and perform laser spectroscopy on it. In a second stage this will be done with tritium with the goal to improve the triton charge radius by a factor of 400. The triton is the "missing link" between nuclei of Z=1 (H,D) and Z=2 (He-3 and He-4), all of which we have measured via laser spectroscopy of muonic atoms.
	Lithium We are working on an improved measurement of the Li-6 / Li-7 isotope shift of the D lines, in order to obtain a better charge radius difference of these 2 radii. To this end, we have built a 2D-MOT from which we can extract a cold beam of Li atoms (velocity tunable around 50m/s). We have seen first D-line resonances in Li-6 with good signal/noise ratio.
	1S HFS measurements in muonic hydrogen The measurement of the ground-state hyperfine splitting (1S-HFS) in muonic hydrogenwill determine the magnetic "Zemach" radius of the proton with ~100 times better accuracy. This will both give precise insight into proton structure, and will also improve the QED test using the 1S-HFS measured in ordinary hydrogen more than 50 years ago.
	Lamb shift measurements in muonic hydrogen, deuterium and helium-3/-4 We measure the 2S-2P energy difference (Lamb shift) in muonic hydrogen and deuterium atoms as well as in muonic helium-3 and -4 ions. These measurements allow us to precisely determine the nuclear charge radii of these atoms and to improve the determination of the Rydberg constant. The Lamb shift measurement is therefore a test of bound-state quantum electrodynamics (QED) and additionally gives insight about the nuclear polarizability and other nuclear properties. The measurement in muonic hydrogen has raised the so-called proton radius puzzle.

 

Since 2024 we are proud owners of a Frequency Comb, stabilized to an ultrastable reference cavity, made possible by a Großgeräteantrag funded by the German Funding Agency DFG, Grant number 460938875.

We have two measurement ports, one for 671nm (Li) and one for 972nm (H,D, T spectroscopy).