Magnetically trapped atoms for compact atomic clocks

International audienceWe investigate the hyperfine transition of magnetically trapped non-condensed atoms. The two principal frequency shifts, the second order Zeeman effect and the mean field interaction are considered. Analytic models of the mean frequency and its trap induced spread are developed. Comparisons with existing experiments evaluate the role of the atoms' oscillatory motion. The analytic model proves to be equivalent to existing Monte Carlo simulations. The formulae provide a simple tool for optimising the design of a new experiment. Applied to the two-photon transition | F=1, m <SUB> F </SUB>=-1>-->| F=2, m <SUB> F </SUB>=1> in <SUP>87</SUP>Rb and the conditions of a typical atom chip experiment, a line spread as small as 11 mHz is predicted giving a quality factor of 10<SUP>12</SUP>. The system is promising for application in precision instruments such as compact atomic clocks