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Two-photon (time-resolved or not) photoemission

Two-photon (time-resolved or not) photoemission

Two-photon photoemission consists in the analysis of photoemitted electrons when a sample is illuminated by two photons. The first photon promotes electrons to an excited state. The second photon must be energetic enough to promote the electron over the vacuum level. If the temporal dely between the two photons is zero, it is possible to study the unoccupied states of the system. When a temporal delay exists between the two photons, it is possible to study the desexcitation dynamics. This kind of study need pulsed photon sources, as the femtosecond lasers of FemtoArpes setup or the high harmonic generation sources as Attolab.

Principle of the two-photon photoemission. A first photon excites the system (pump) while a second photon (probe) allows to extract the electron from the excited state. It is therefore possible to study the unoccupied states and the desexcitation dynamics.

Film on the principle of pum-probe experiments. Courtoisy of Julien Bobroff.