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Q: Fachverband Quantenoptik und Photonik

Q 41: Precision Measurement and Metrology 1

Q 41.5: Talk

Wednesday, March 16, 2011, 17:30–17:45, HÜL 386

Using (Δ F=1, Δ m_F=± 1) transitions as a diagnostic tool for atomic fountain clocks — •Nils Nemitz, Vladislav Gerginov, Stefan Weyers, and Robert Wynands — Physikalisch-Technische Bundesanstalt, Braunschweig

Atomic caesium fountain clocks provide the most accurate realization of the SI second by making use of the |F=3,m_F=0 ⟩ to |F=4,m_F=0 ⟩ hyperfine transition.

A leading contribution to their uncertainty budget arises from the effects of phase gradients in the microwave cavity. A better understanding of the atomic distribution during each of the two cavity passages would help in putting stricter limits on this uncertainty.

We have recently investigated a new method of obtaining information on the center-of-mass position during either cavity passage for the fraction of atoms contributing to the actual frequency measurement. It is based on a position-dependent change of the Δ m=± 1 spectra when the normally vertical quantization field is tilted slightly. This type of spectra is normally not investigated in fountain clocks.

We will present experimental evidence and an analytical model that promises an achievable accuracy of the measured center-of-mass position of better than 0.3 mm.