Research Group Wilfried Nörtershäuser
Experimental Atomic and Nuclear Physics with Radioactive Nuclides

Laser Spectroscopy of Short-Lived Isotopes

Fig. 1: Optical spectrum with a high-resolution representation of a resonance line in atomic mercury. Visible are isotopes, isomers, and hyperfine structure components. The spectral structure depends on the mass of the isotopes (isomers) as well as their ground state properties shown on the right, which can be extracted from the spectrum.

The atomic spectrum contains information about the properties and structure of the nucleus. Resonances of different isotopes appear for example at slightly different frequencies due to redistribution of the nuclear charge, i.e. the protons, when additional neutrons are added. The charge radius of nuclei can be extracted from these shifts. Moreover, an additional splitting of resonance lines, – the hyperfine structure – allows the determination of the nucleus’ spin, its magnetic moments and about its deformation (see Figure 1). Measuring these properties along a chain of isotopes allows us to understand the interactions among the constituents of the nucleus. Such experiments become very challenging when it comes to isotopes far away from the valley of β-stability, where nuclei can be produced only in minute quantities and their lifetime is reduced to only a few milliseconds. Collinear laser spectroscopy is an established tool to study these properties and several detection techniques have been adopted during the last decades to increase accuracy and sensitivity in order to explore more and more exotic regions of the nuclear chart .

We perform collinear laser spectroscopy on short-lived nuclei at several facilities within the following collaborations: