MG14 - Talk detail

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Abstract

The electromagnetic transition between the almost degenerate 5/2+ and 3/2+ states in 229Th is expected to be very sensitive to changes in the fine structure constant alpha. State of the art Hartree-Fock and Hartree-Fock-Bogoliubov calculations are performed to compute the difference in Coulomb energies of the two states. This difference determines the amplification of variations in alpha into variations of the transition frequency. The kinetic energies are also calculated which reflect a possible variation in the nucleon or quark masses. A generalized Hellmann-Feynman theorem is proven including the use of density-matrix functionals. As the two states differ mainly in the orbit occupied by the last unpaired neutron the Coulomb energy difference results from a change in the nuclear polarization of the proton distribution. This effect turns out to be rather small and to depend on the nuclear model. Nevertheless the amplification is large and varies for different models between about +4x10^4 and -4x10^4. Much more effort must be put into the improvement of the nuclear models before one can draw final conclusions from a measured drift in the transition frequency on a temporal drift of fundamental constants.

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