Beta Decay of Highly Charged Ions

Summary

Nuclear beta-decay probabilities are influenced, sometimes dramatically, by the charge state of the corresponding atom, i.e., the number of bound electrons. In the ESR cooler ring at Darmstadt, beta-decay properties of highly charged ions could be measured for the first time. Therewith, it became possible to study beta decays under conditions similar to those prevailing in hot stellar plasmas during nucleosynthesis. An overview of these experiments is given, emphasizing the first observation of bound beta decay in the examples of bare ¹⁶³ Dy and ¹⁸⁷Regions . The latter nuclide, long-lived as a neutral atom (half-life 42 x 10⁹ years), serves as a “clock” for the age of our galaxy. An experiment conducted at the ESR showed that for bare ¹⁸⁷Regions the half-life is shortened by more than nine orders of magnitude. This result enables a “recalibration” of the rhenium aeon clock and thus provides a more reliable lower bound for the age of the galaxy and, a fortiori, for the age of the universe. An outlook is given on experiments which are related to beta decay of highly charged ions and could be conducted soon at ion storage rings.