Precise Lamb Shift Measurements in Hydrogen-Like Heavy Ions—Status and Perspectives
Résumé
The precise determination of the energy of the Lyman 1 and 2 lines in hydrogen-like heavy ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields. For the first time, a calorimetric low-temperature detector was applied in an experiment to precisely determine the transition energy of the Lyman lines of lead ions 207pb81+ at the Experimental Storage Ring (ESR) at GSI. The detectors consist of silicon thermistors, provided by the NASA/Goddard Space Flight Center, and Pb or Sn absorbers to obtain high quantum efficiency in the energy range of 40–80 keV, where the Doppler-shifted Lyman lines are located. The measured energy of the Lyman 1 line, E(Ly-1, 207Pb81+) = (77937±12stat±23syst) eV, agrees within errors with theoretical predictions. The systematic error is mainly due to uncertainties in the non-linear energy calibration of the detectors as well as the relative position of detector and gas-jet target.