Laser spectroscopy

One important field of application of RIMS is optical laser spectroscopy on atoms. The technique’s extremely high selectivity and the efficient detection of single ions enable studies on very small samples of rare species, such as ultra-trace elements or radioactive isotopes.

The precise examination of atomic transitions yields valuable information and facilitate tests of modern theoretical atomic models. One fundamental and characteristic parameter for each element is the ionization potential (IP), which is the binding energy of the outermost electron in the atom. RIMS allows for a highly accurate determination of this important physical parameter via the detailed study of Rydberg series, series of atomic levels with high principal quantum number n in the energetically high-lying region of the atomic spectrum, and their convergence.

In special cases, the atomic spectrum shows a chaotic structure which cannot be described by classical approaches. This type of quantum chaos is only rarely observed and is subject of current research.

Laser spectroscopy does also grant access to nuclear properties. Due to the interaction of the electronic shell with the nucleus, electromagnetic moments, spin, and charge radius of the nucleus can be studied via the hyperfine structure and isotope shift in optical atomic transitions. As the effects are relatively small, these spectroscopic measurements require a special laser system that provides laser radiation with small spectral linewidths of about 20 MHz. Hence, the precise study of hyperfine structure and isotope shifts provide valuable input for theoretical nuclear models and contribute to a better understanding of the structure of the chart of nuclides. Furthermore, the obtained spectra of the transitions can be used to implement isotopically and isomerically selective resonance ionization, which provides great advantages for the selective production of exotic ion beams and ultra-trace analysis of rarest natural or anthropogenic species.

All of the physical parameters mentioned above are of special interest for rare elements, such as astatine or the transuranium elements, and isotopes far off stability. These exotic species are artificially produced and investigated using laser spectroscopy at research facilities like CERN in Geneva.