Mainz 2017 – scientific programme
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A: Fachverband Atomphysik
A 11: Precision Measurements and Metrology: Optical Clocks (with Q)
A 11.1: Talk
Monday, March 6, 2017, 17:00–17:15, P 104
Decay channels of the 229Th nuclear isomeric state involving atomic electrons — •Pavlo Bilous and Adriana Pálffy — Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, D-69117 Heidelberg, Germany
The thorium isotope 229Th is unique due to its nuclear isomeric (i.e. long living) excited state with the energy of Eiso=7.8 eV typical for optical atomic transitions. Being a bridge between atomic and nuclear physics, this nuclear transition has very narrow width and high stability to external perturbations, so it can be a key to metrology applications such as a nuclear frequency standard. The excitation and decay channels of this transition may well involve the electronic shell due to the very low value of Eiso.
For the neutral atom 229Th, the isomeric state may decay via internal conversion (IC). For 229Th ions this is not the case as the energy Eiso is lower than the corresponding ionization thresholds. However, IC from excited electronic states remains energetically allowed. On the other hand, the energy can be transferred to the electronic shell with excitation of an electron to another bound state accompanied by the absorption or emission of a photon (so called electron bridge). This channel can be strongly enhanced if the electronic and the nuclear transitions are on resonance. Here we consider several channels of decay of the nuclear isomeric state involving the atomic electrons and carry out ab initio calculations of corresponding rates using multi-configurational Dirac-Fock wave functions for the bound atomic electrons.