Hannover 2010 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 7: Precision Measurements and Metrology I
Q 7.1: Talk
Monday, March 8, 2010, 14:00–14:15, M 11
How to determine the blackbody shift in Sr optical lattice clocks — •Thomas Middelmann, Christian Lisdat, Stephan Falke, Joseph Sundar Raaj Vellore Winfred, Fritz Riehle, and Uwe Sterr — Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
Optical clocks have surpassed 133Cs microwave clocks in stability and systematic uncertainty. The 1S0−3P0 clock transition of 88Sr and 87Sr is investigated as atomic reference in an optical lattice clock. Currently the largest contribution to the uncertainty of 1 · 10−16 is due to the ac Stark effect from ambient blackbody radiation. In good approximation the blackbody shift is proportional to the differential static polarizability of the two clock states and to the fourth power of the environmental temperature.
To reduce the uncertainty of the blackbody shift we prepare to measure the differential static polarizability in a dc electric field. Moreover, we want to reduce the blackbody shift itself by a low temperature environment. Trapped in a horizontal 1-D optical lattice the strontium atoms will be transported into a dc electric field or a liquid nitrogen cooled environment respectively. It is necessary to move the interference pattern together with the focus position to ensure invariant trap depth. This is achieved by moving the lattice optics, which are on opposite sides of the vacuum system, with two air bearing stages. The current status of the experiment will be presented in the talk.
The work is supported by the Centre for Quantum Engineering and Space-Time Research (QUEST) and the ERA-NET Plus Programme.