Stimulated Raman Adiabatic Passage for Improved Performance of a Cold   Atom Electron and Ion Source
  We implement high-efficiency coherent excitation to a Rydberg state using stimulated Raman adiabatic passage in a cold atom electron and ion source. We achieve an efficiency of 60% averaged over the laser excitation volume with a peak efficiency of 82%, a 1.6 times improvement relative to incoherent pulsed-laser excitation. Using pulsed electric field ionization of the Rydberg atoms we create electron bunches with durations of 250 ps. High-efficiency excitation will increase source brightness, crucial for ultrafast electron diffraction experiments, and coherent excitation to high-lying Rydberg states could allow for the reduction of internal bunch heating and the creation of a high-speed single ion source. 
B. M. Sparkes, D. Murphy, R. J. Taylor, R. W. Speirs, A. J. McCulloch,   R. E. Scholten
physics.atom-ph quant-ph