Energy bunching in soft recollisions revealed with long-wavelength   few-cycle pulses
  Soft recollisions are laser-driven distant collisions of an electron with its parent ion. Such collisions may cause an energy bunching, since electrons with different initial drift momenta can acquire impacts, which exactly counterbalance these differences. The bunching generates a series of peaks in the photo-electron spectrum. We will show that this series could be uncovered peak-by-peak experimentally by means of phase-stabilized few-cycle pulses with increasing duration. 
Alexander K\"astner, Ulf Saalmann, and Jan M. Rost
physics.atom-ph