Max Planck Institute of Quantum Optics
Tel. +49 89 32905 282
Research focus: precision laser spectrscopy of hydrogen and hydrogen-like systems
Our group is conducting high resolution laser spectroscopy on simple atomic systems such as atomic hydrogen or hydrogen like helium ions. The primary goal is to compare experimental results with calculations in the framework of quantum electrodynamics (QED). The latter includes constants that cannot be determined theoretically but have to be fixed by measurements. To test whether QED is consistent with observations more measurements than constants are required. Within the CODATA least squares adjustment, two constants, the Rydberg constant and the proton charge radius are obtained from 14 high precision measurements in atomic hydrogen. The values obtained in this way are in disagreement with the measured Lamb shift in muonic hydrogen. We are working on shedding light on this so called proton radius puzzle by improving previous values of experimental transition frequencies in atomic hydrogen. In addition we are working towards laser spectroscopy of hydrogen like helium ions and helium like lithium ions. The latter is coming up for high precision tests of QED as calculations of two electron systems are constantly improving.
Continuous wave laser spectroscopy
For this reason we have been re-measuring the 2S-4P transition frequency using the previous 1S-2S apparatus that is now employed as a source of cold, laser excited 2S atoms. The result is as accurate as all previous hydrogen data combined and confirms the muonic value of the proton charge radius. Hence it is in significant contradiction with the previous hydrogen data. The cause of this discrepancy is as of yet unknown. One may speculate about yet unknown systematic errors of the measurements, errors in QED calculations or even new physics.
Direct frequency comb spectroscopy
XUV direct frequency comb spectroscopy