Time resolved ARPES
In time resolved ARPES (tr-ARPES) experiments, unoccupied or excited states of samples and their dynamics are examined. A first photon pulse (pump pulse) populates initially unpopulated electronic states in the sample, a second photon pulse (probe pulse) is used to do photoelectron spectroscopy on these states. Usually pump-probe schemes with Laser sources are applied in this context. The time resolution enters the experimental scheme via a variable time delay time between the pump and the probe pulse. In this way it is, for example, possible to measure the time constants of the excited states that have been generated by the pump-pulse.