Heidelberg 2015 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 30: Precision spectroscopy of atoms and ions III (with Q)

A 30.4: Vortrag

Donnerstag, 26. März 2015, 11:45–12:00, M/HS1

Search for optical excitation of the low-energy nuclear isomer of 229Th — •David-Marcel Meier, Maksim V. Okhapkin, and Ekkehard Peik — Physikalisch-Technische Bundesanstalt, Braunschweig, Germany

Direct optical excitation of the nuclear transition between ground state and the 7.8 eV isomer in 229Th is the missing link towards a study of this system as a precise nuclear clock. We plan to use two-photon laser excitation via electronic bridge processes in Th+ [1]. The high density of states within the energy range from 7.3 to 8.3 eV [2,3] in Th+ promises a strongly enhanced nuclear excitation rate. Using laser ablation loading of the ion trap and photodissociation of molecular ions that are formed in reactions of Th+ with impurities in the buffer gas, we efficiently load and stably store ions of the radioactive 229Th isotope. We have measured the hyperfine structure and isotope shifts of two resonance lines where one of these lines shows an untypical negative isotope shift compared to all previously known lines in 229Th which show a positive shift. Both lines are suitable as first excitation stages of the electronic bridge.

[1] S. G. Porsev et al., Phys. Rev. Lett. 105, 182501 (2010)

[2] O. A. Herrera-Sancho et al., Phys. Rev. A 85, 033402 (2012)

[3] O. A. Herrera-Sancho et al., Phys. Rev. A 88, 012512 (2013)

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