Collinear laser spectroscopy of 12C4+: towards an all-optical nuclear charge radius determination

For the determination of nuclear charge radii different measurement techniques have been developed over time such as elastic electron scattering or muonic spectroscopy. Atomic spectroscopy has so far been limited to H and He or to the differential nuclear charge radii of short-lived isotopes accessed by collinear laser spectroscopy (CLS). In an all-optical approach we want to determine the absolute charge radii of further He-like ions by exciting them from the metastable 2 3S1 state, which has a lifetime of a few 10-100 ms, to the 2 3PJ states. This experimental value is to be compared with nonrelativistic QED calculations* that are currently being performed. The results will compliment and improve existing measurements of nuclear charge radii. The first high-precision collinear laser spectroscopy measurements of 12C4+ have been carried out at the Collinear Apparatus for Laser Spectroscopy and Applied Physics (COALA) at TU Darmstadt which has recently been upgraded with an electron beam ion source to produce the highly charged ions. This contribution will summarize the current status of the project and present first results which will serve to benchmark the QED calculations.