Darmstadt 2008 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 29: Kernphysik / Spektroskopie

HK 29.9: Vortrag

Dienstag, 11. März 2008, 13:15–13:30, 2G

Measurement of the β⁺ and orbital electron-capture decay rates in fully-ionized, — •Nicolas Winckler for the SLS collaboration — Gesellschaft für Schwerionenforschung GSI, 64291 Darmstadt, Germany — Justus-Liebig-Universität Gießen, 35392 Gießen, Germany

For the first time the β⁺ and orbital electron-capture decay rates of hydrogen-like and helium-like ions have been measured, at the example of ¹⁴⁰Pr. For this purpose, H-like ¹⁴⁰Pr⁵⁸⁺ and He-like ¹⁴⁰Pr⁵⁷⁺ ions were produced by in-flight fragmentation in the Fragment Separator FRS at GSI, injected into the ion-storage ring ESR where they were stored and cooled. The number of both, the mother- and daughter ions generated by EC were monitored continuously as a function of time by exploiting the technique of Schottky spectroscopy. This allowed us to determine the EC decay-constant λ_EC (H-like, He-like) as well as λ_β⁺(bare, H-like, He-like). The measured electron capture decay constant of hydrogen-like ¹⁴⁰Pr⁵⁸⁺ ions is about 50 % larger than that of helium-like ¹⁴⁰Pr⁵⁷⁺ ions. Moreover, ¹⁴⁰Pr ions with one bound electron decay faster than neutral ¹⁴⁰Pr⁰⁺ atoms with 59 bound electrons. This peculiar observation can be fully understood by the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.