Bochum 2009 – wissenschaftliches Programm
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HK: Fachverband Hadronen und Kerne
HK 67: Poster Session
HK 67.42: Poster
Donnerstag, 19. März 2009, 14:00–16:00, Audi-Max
Towards optical access to the lowest nuclear transition in 229mTh† — •P.G. Thirolf1, M. Bussmann1,3, D. Habs1, J. Neumayr1, T. Schaetz2, H. Schmitz1,2, J. Schreiber1,4, J. Szerypo1, L. Trepl1, and H.-F. Wirth1 — 1LMU München, Garching, Germany — 2MPI für Quantenoptik, Garching, Germany — 3FZ Dresden, Dresden, Germany — 4Imperial College, London, UK
229mTh exhibits the lowest-lying nuclear excitation with an excitation energy of only 7.6(5) eV (163(11) nm) and an isomeric lifetime of ∼ 104 s, giving rise to an extremely sharp relative line width of the ground state transition of ∼ 10−20. This transition qualifies as an extremely sharp frequency standard, allowing to build a nuclear clock with unprecedented accuracy. Moreover, theoretical calculations predict an enhancement of the sensitivity to time dependent variations of fundamental constants like the fine structure constant α by about 106. Laser excitation of the 7.6 eV transition requires a precise knowledge of the transition energy. Therefore the 229mTh isomers are populated via α decay from 233U in a buffer gas cell, from where they are selectively extracted and collected. The UV fluorescence photons are then collimated via a MgF2 lens and sharp filters onto an MCP detector and secondary electrons are registered on a phosphorous screen by a CCD camera. In order to prepare for subsequent sympathetic laser cooling in a 24Mg+ Coulomb crystal, a laser setup consisting of an Yb fibre laser and a frequency quadrupling stage is presently under construction.
†Supported by the DFG Cluster of Excellence MAP (Munich-Centre for Advanced Photonics).