Berlin 2014 – scientific programme
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A: Fachverband Atomphysik
A 9: Precision spectroscopy of atoms and ions II (with Q)
A 9.5: Talk
Monday, March 17, 2014, 15:00–15:15, BEBEL E42
On the 7.8 eV isomer transition in 229Th — •Simon Stellmer1, Matthias Schreitl1, Georg Winkler1, Christoph Tscherne1, Georgy Kazakov1, Andreas Fleischmann2, Loredana Gastaldo2, Andreas Pabinger2, Christian Enss2, and Thorsten Schumm1 — 1VCQ and Atominstitut / TU Wien, Vienna, Austria — 2KIP, University of Heidelberg, Germany
The best atom clocks today employ an optical transition between two electronic states of an atom or ion. It seems tantalizing to utilize a nuclear transition instead, as such a transition would be well-isolated from collisional, electronic, and even chemical perturbations from the environment. In addition, such transitions are expected to be very sensitive probes of drifts in fundamental constants.
The only isotope known to possess an isomer transition in the optical domain is the radioactive element 229Th. Various attempts have been carried out to measure or calculate the transition energy and linewidth. To date, all of these measurements have been refuted, corrected, or at least strongly debated. While a direct evidence of this transition is still pending, its commonly agreed-upon energy is 7.8(5) eV [1].
In this talk, we will present the current status of a novel measurement campaign. In a concerted effort of the Heidelberg and Vienna groups, we use a microcalorimeter to measure the spectrum of gamma photons originating from the decay of excited nuclear states. A double-peaked structure would reveal the existence of the isomer state and allow us to measure its energy with unprecedented precision.
[1] Beck et. al, Phys. Rev. Lett. 98, 142501 (2007)