We use time-correlated single-photon counting techniques on a sample of 210 Fr atoms confined and cooled in a magneto-optical trap to measure the lifetimes of the 9S 1/2 , 8P 3/2 , and 8P 1/2 excited levels. We populate the 9S 1/2 level by two-photon resonant excitation through the 7P 1/2 level. The direct measurement of the 9S 1/2 decay through the 7P 3/2 level at 851 nm gives a lifetime of 107.53± 0.90 ns. We observe the decay of the 9S 1/2 level through the 8P 3/2 level at 423 nm and the 8P 1/2 level at 433 nm down to the 7S 1/2 ground level, and indirectly determine the lifetimes of these to be 83.5± 1.5 ns and 149.3± 3.5 ns, respectively.

Neutral fermions present new opportunities for testing many-body condensed matter systems, realizing precision atom interferometry, producing ultra-cold molecules, and investigating fundamental forces. However, since their first observation, quantum degenerate Fermi gases (DFGs) have continued to be challenging to produce, and have been realized in only a handful of laboratories. In this Letter, we report the production of a DFG using a simple apparatus based on a microfabricated magnetic trap. Similar approaches applied to Bose-Einstein Condensation (BEC) of 87Rb have accelerated evaporative cooling and eliminated the need for multiple vacuum chambers. We demonstrate sympathetic cooling for the first time in a microtrap, and cool 40K to Fermi degeneracy in just six seconds -- faster than has been possible in conventional magnetic traps. To understand our sympathetic cooling trajectory, we measure the temperature dependence of the 40K-87Rb cross-section and observe its Ramsauer-Townsend reduction.Comment: 5 pages, 4 figures (v3: new collision data, improved atom number calibration, revised text, improved figures.

Weak interactions within a nucleus generate a nuclear spin dependent, parity violating electromagnetic moment, the anapole moment. We analyze a method to measure the nuclear anapole moment through the electric dipole transition it induces between hyperfine states of the ground level. The method requires tight confinement of the atoms to position them at the anti-node of a standing wave Fabry Perot cavity driving the anapole-induced micro-wave E1 transition. We explore the necessary limits in the number of atoms, excitation fields, trap type, interrogation method, and systematic tests necessary for such measurements in francium, the heaviest alkali.

We measure the hyperfine splitting of the 9S_{1/2} level of 210Fr, and find a magnetic dipole hyperfine constant A=622.25(36) MHz. The theoretical value, obtained using the relativistic all-order method from the electronic wave function at the nucleus, allows us to extract a nuclear magnetic moment of 4.38(5)micro_{N} for this isotope, which represents a factor of 2 improvement in precision over previous measurements. The same method can be applied to other rare isotopes and elements.