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.

We present lifetime measurements of the 7 p 2 P 3/2 and 7p 2 P 1/2 levels of Fr. We use a time-correlated single-photon counting technique on a cold sample of 210 Fr atoms in a magneto-optic trap. We excite the atoms with the trapping and repumping beams of the magneto-optic trap and detect the decay of the atomic fluorescence. The results are a precision experimental test of the atomic many-body perturbation theory applied to the heaviest alkali metal. The lifetime results are 21.02͑11͒ ns and 29.45͑11͒ ns for the 7p 2 P 3/2 and 7p 2 P 1/2 levels, respectively. This gives a line strength ratio S 1/2 /S 3/2 of 0.526͑3͒ for these levels in Fr. To study sources of systematic errors we measure the lifetimes of 5p 2 P 3/2 and 5p 2 P 1/2 in stable 87 Rb and obtain 26.20͑9͒ ns and 27.64͑4͒ ns, respectively.

We report a method to monitor and control laser frequencies with an optical cavity and a digital feedback system. A frequency-stabilized He-Ne laser provides the reference that is transferred to several other lasers using a scanning Fabry-Pérot cavity. A personal computer-based multifunction data acquisition system generates the scan wave form, and reads the detector outputs synchronously with the cavity scan. The computer determines the positions of all of the peaks in the scan, and generates output signals to control the laser frequencies. It also provides a visual display of cavity spectra. We have successfully used the setup to achieve a long-term lock of the lasers for magneto-optical trapping of radioactive francium atoms.