On- and off-resonance measurement of the Image State lifetime at the graphene/Ir(111) interface

The image potential state lifetime at the graphene/Ir(111) interface has been measured by tuning the pump photon energy on- and off-resonance for the optical transition between the surface state and the image state. By a joint effort of time resolved non-linear photoemission measurements and Optical Bloch Equations results, we astonishingly show that the depopulation time of the image state becomes four times longer when it is resonantly populated from the surface state.