Precision lifetime measurement of the cesium $6P_{3/2}$ level using   ultrafast pump-probe laser pulses
  Using the inherent timing stability of pulses from a mode-locked laser, we have precisely measured the cesium $6P_{3/2}$ excited state lifetime. An initial pump pulse excites cesium atoms in two counter-propagating atomic beams to the $6P_{3/2}$ level. A subsequent synchronized probe pulse ionizes atoms which remain in the excited state, and the photo-ions are collected and counted. By selecting pump pulses which vary in time with respect to the probe pulses, we obtain a sampling of the excited state population in time, resulting in a lifetime value of 30.462(46) ns. The measurement uncertainty (0.15%) is larger than our previous report of 0.12% [Phys. Rev. A 84, 010501(R) (2011)] due to the inclusion of additional data and systematic errors. In this follow-up paper we present details of the primary systematic errors encountered in the measurement, which include atomic motion within the intensity profiles of the laser beams, quantum beating in the photo-ion signal, and radiation trapping. Improvements to further reduce the experimental uncertainty are also discussed 
Brian M. Patterson, Jerry F. Sell, Thomas Ehrenreich, Mirela A.   Gearba, George M. Brooke, James Scoville, and Randy J. Knize
physics.atom-ph