Lifetime measurements of the7Dlevels of atomic francium

Abstract

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 ${}^{210}\mathrm{Fr}$ 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 $73.6\ifmmode\pm\else\textpm\fi{}0.3 \mathrm{ns}$ and $67.7\ifmmode\pm\else\textpm\fi{}2.9 \mathrm{ns}$ for the ${7D}_{3/2}$ and ${7D}_{5/2}$ levels, respectively.