Darmstadt 2016 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 45: Postersession
HK 45.10: Poster
Mittwoch, 16. März 2016, 18:30–20:30, S1/05 22-24
Prospects for an energy determination of the 229mTh nuclear isomer via IC electrons — •B. Seiferle1, L. v.d. Wense1, M. Laatiaoui2,3, and P. G. Thirolf1 — 1LMU München, Garching. — 2GSI, Darmstadt. — 3Helmholtz Institut Mainz, Mainz.
Of all known nuclear excited states, the isomeric first excited state of 229Th possesses the lowest excitation energy reported to be E*=7.6(5) eV (=163(11) nm). This opens up the possibility to drive the transition with a laser and makes 229mTh an interesting candidate for future developments linking nuclear and atomic physics, such as a nuclear optical clock or a nuclear γ-ray laser. Still, for a direct laser excitation, the knowledge on the energy and half-life of the isomer is not precise enough. In this work and for the expected transition energy, neutral 229Th decays via the emission internal conversion (IC) electrons with an energy of 1.2 eV (i.e. difference between E* and the 1st ionization potential). A 233U α-recoil source is placed in a buffer-gas stopping cell. 229Th ions, of which 2% are in the isomeric state are recoiled out of the source. RF- and DC electrode structures form an ion beam out of all the recoil ions. Afterwards, 229(m)Th ions are separated from other short-lived daughter isotopes with a quadrupole mass separator and can be prepared for further experiments. The poster gives prospects for an energy determination of the IC electrons emitted during the decay of the isomer and for a corresponding half-life determination with this experimental setup.
This work was supported by DFG grant (Th956/3-1) and by the EU Horizon 2020 grant agreement No. 664732 "nuClock".