Dresden 2011 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 41: Precision Measurement and Metrology 1
Q 41.6: Vortrag
Mittwoch, 16. März 2011, 17:45–18:00, HÜL 386
Laser spectroscopy of trapped thorium ions — •Óscar-Andrey Herrera-Sancho1, Maxim Okhapkin1, Kai Zimmermann1, Alexey Taichenachev2, Valeriy Yudin2, Christian Tamm1, and Ekkehard Peik1 — 1Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany — 2Institute of Laser Physics, Siberian Branch of RAS, Novosibirsk 630090, Russia
In our experiment more than 105 232Th+ ions are stored in a linear Paul trap after creation by laser ablation from thorium metal. Single-frequency laser excitation in the complex spectrum of Th+ poses the problem that spontaneous decay populates a number of metastable levels that are decoupled from the laser. Helium and Argon buffer gas are used for collisional cooling and quenching of those levels. We observe laser excitation of the strong resonance line at 401.9 nm with an extended-cavity diode laser and laser excitation of several other transitions around 400 nm and 270 nm with harmonics of a pico-second Ti:Sa laser. In a theoretical analysis we approximate the dense electronic level structure of Th+ ions by just four levels: the ground state and an excited state are coupled by the primary laser, one metastable state is depopulated by a repumper laser and one level by collisions only. The model agrees with experimental results for the fluorescence rate as a function of the laser intensities and can be used to deduce populations and quenching rates. First investigations on two-photon excitation of the Th+ electron shell to the energy range 7.8 eV of the nuclear transition of 229Th are in progress.