Accurate measurements of transition frequencies and isotope shifts of laser trapped francium

An interferometric method is used to improve the accuracy of the 7S-7P transition frequencies of three francium isotopes by I order of magnitude. The deduced isotope shifts for (209-211)Fr confirm the ISOLDE data. The frequency of the D(2) transition of (212)Fr-the accepted reference for all Fr isotope shifts-is revised, and a significant difference with the ISOLDE value is found. Our results will be a benchmark for the accuracy of the theory of Fr energy levels, a necessary step to investigate fundamental symmetries. (C) 2009 Optical Society of Americ