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SYKL: Symposium Kernphysik mit starken Laserfeldern
SYKL 1: Resonant laser-nucleus interactions
SYKL 1.2: Invited Talk
Tuesday, March 11, 2008, 09:00–09:30, 1A
Optical access to the lowest nuclear transition in 229Th* — •Peter G. Thirolf, Michael Bussmann, Dietrich Habs, Hans-Jörg Maier, Jürgen Neumayr, Jörg Schreiber, Michael Sewtz, and Jerzy Szerypo — Ludwig-Maximilians-Universität München and Maier-Leibnitz Laboratory, Garching, Germany
The isomeric first excited state of 229Th is known to be the lowest excitation in the whole chart of nuclei. For a long time its nuclear level energy was reported as 3.5±0.5eV. In a recent experiment this transition energy was remeasured, resulting in an important change of the energy to Eγ=(7.6±0.5) eV, corresponding to a transition wavelength of λ=(163 ± 11)nm [1]. The estimated lifetime of the level is τ= 3-5 hours, which corresponds to a relative line width of about 10−20, 5 to 6 orders of magnitude smaller than typical relative atomic line widths measured in experiments with single laser-cooled ions. The 229mTh transition appears to be the most sensitive probe for studying the time dependence of the fine structure constant α and quark masses. We are presently working on a stepwise approach to confirm the excitation energy and the long lifetime of 229mTh, aiming at a measurement of the transition energy with increasing accuracy. Since possible lasers for λ=(163 ± 11)nm depend very much on the exact transition wave length, the question of directly exciting the nucleus can only be addressed after the transition energy has been determined more accurately in nuclear excitation.
[1]: B.R. Beck et al., PRL 98 (2007) 142501.
* Supported by the DFG Cluster of Excellence MAP (Munich-Centre for Advanced Photonics)