Precision Determination of g-Factors with an Atomic Fountain Clock

• Applicant: Privatdozent Dr. Robert Wynands
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2007 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 35368585

Atomic fountain clocks constitute the most accurate instruments in existence for absolute measurements. Residual uncertainties of less than 1 part in 1015 for the realization of the SI second have been achieved. But fountain clocks are also attractive from an atomic physics or laser spectroscopy viewpoint. They can provide the experimentalist with a sample of free atoms at microkelvin temperature, with all atoms in one specific |F, m〉 ground state chosen by the experimenter. The atoms fall freely under gravity, but nonetheless an observation time of the atom cloud of about one second is possible, leading to very narrow resonance linewidths. The cold atoms can be manipulated by a combination of well-defined static magnetic fields, microwave radiation, and laser radiation at various points along their trajectory. With this project we would like to exploit the possibilities offered by such a precise and flexible instrument to determine the ratio of electronic to nuclear g-factor in the ground state of the caesium atom and the nuclear g-factor itself, with a residual uncertainty hundredfold better than the literature value. Along the way, we will obtain precise information on so-called “cold collisions” in the atom cloud for certain, previously unexplored combinations of atomic states with the possibility of evaluating the magnetic field dependence (Feshbach resonances). We can also look for collision-induced modifications of the electronic g-factor. The experiment proposed here makes use of the unique situation in the atomic clock laboratory at Physikalisch-Technische Bundesanstalt (PTB), where two fountain clocks are located side by side so that one can serve as a reference for the other.

• DFG Programme: Research Grants