Velocity-mapped imaging of electron dynamics in an ultracold laser-induced plasma

We report a time-resolved study on the electron kinetics and dynamics that occur during the formation of an ultracold plasma generated by resonance enhanced multiphoton ionization of krypton in a pulsed supersonic beam. Measurements are performed using a new apparatus that incorporates time-resolved velocity-mapped imaging of the entire electron energy distribution with nanosecond time resolution. We resolve the rapid deceleration and escape of 3.32 eV photoelectrons and the subsequent equilibration, cooling, and escape of electrons that are trapped by the expanding photocation distribution.