Abstract

The advantages of cold atoms for atomic clocks include a higher line Q and a dramatic reduction of all the limiting systematic errors in room temperature clocks. However, the low temperature also causes a significant problem: the quantum nature of atoms at 1 μK leads to wavelike cross sections of order 10⁻¹⁰ cm² and, in a laser-cooled Cs clock, these lead to collisional frequency shifts as large as δv/v ≈ 10⁻¹².¹ This currently appears to be the most serious systematic error for the accuracy and stability of laser-cooled Cs clocks. The frequency shift for cold Cs atoms is anomalously large due to scattering resonances in the Cs-Cs system.

© 1998 Optical Society of America