Probing the evolution of Stark wave packets by a weak half cycle pulse
  We probe the dynamic evolution of a Stark wave packet in cesium using weak half-cycle pulses (HCP's). The state-selective field ionization(SSFI) spectra taken as a function of HCP delay reveal wave packet dynamics such as Kepler beats, Stark revivals and fractional revivals. A quantum-mechanical simulation explains the results as multi-mode interference induced by the HCP. 
H. Wen, S. N. Pisharody, J. M. Murray, and P. H. Bucksbaum