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MO: Fachverband Molekülphysik

MO 29: Poster: Cold Molecules

MO 29.9: Poster

Dienstag, 20. März 2007, 16:30–18:30, Poster A

Blackbody thermometry with cold molecular ions and possible application to ion-based frequency standards — •Jeroen Koelemeij, Bernhard Roth, and Stephan Schiller — Institut für Experimentalphysik, Universität Düsseldorf

We have used laser spectroscopy to measure the rotational level distribution of trapped molecular HD⁺ ions at translational temperatures in the millikelvin range. Under our experimental conditions, the internal (rotational) degrees of freedom turn out to be independent of the translational degrees of freedom, and an effective rotational temperature close to room temperature is found. The near absence of background-gas collisions allows to relate the rotational temperature directly to the temperature of the ambient blackbody radiation (BBR). This feature suggests the use of molecular ions for BBR thermometry, which may help to improve the accuracy of frequency standards based on trapped atomic ions. We present a detailed proposal for the implementation of BBR thermometry, using CO⁺ molecular ions, in a generic trapped-ion optical clock apparatus. Our proposal includes a method to load CO⁺ by photoionization of neutral CO in the residual gas, while BBR thermometry would be based on a novel scheme for nondestructive detection of rotational states of CO⁺.