Lifetime measurements of the 7D levels of atomic francium

We present lifetime measurements of the 7D_3/2 and 7D_5/2 levels of Fr. We use a time-correlated single-photon counting technique on a sample of ²¹⁰Fr atoms confined and cooled in a magneto-optical trap. The upper state of the 7P_3/2 trapping transition serves as the resonant intermediate level for two-photon excitation of the 7D states. A probe laser provides the second step of the excitation, and we detect the decay of the atomic fluorescence. Our measurements help extend the knowledge of this class of atomic wave functions in which correlation effects are very significant. We measure lifetimes of 73.6±0.3 ns and 67.7±2.9 ns for the 7D_3/2 and 7D_5/2 levels, respectively.