LIFETIME MEASUREMENTS OF THE 7P LEVELS OF ATOMIC FRANCIUM

We present lifetime measurements of the 7p P-2(3?(/?(2) and 7p P-2(1?( /?(2) levels of Fr. We use a time-correlated single-photon counting te chnique on a cold sample of Fr-210 atoms in a magneto-optic trap. We e xcite the atoms with the trapping and repumping beams of the magneto-o ptic trap and detect the decay of the atomic fluorescence. The results are a precision experimental test of the atomic many-body perturbatio n theory applied to the heaviest alkali metal. The lifetime results ar e 21.02(11) ns and 29.45(11) ns for the 7p P-2(3?(/?(2) and 7p P-2(1?( /?(2) levels, respectively. This gives a Line strength ratio S-1?(/?(2 /S-3?(/?(2 of 0.526(3) for these levels in Pr. To study sources of sys tematic errors we measure the lifetimes of 5p P-2(3?(/?(2) and 5p P-2( 1?(/?(2) in stable Rb-87 and obtain 26.20(9) ns and 27.64(4) ns, respe ctively.