Image potential states (IPSs) have been observed for various adsorbed carbon
structures, such as graphene or carbon nanotubes. Graphene nanoribbons (GNRs)
are intriguing nanostructures with a significant band gap which promise
applications in nanotechnology. In the present paper we employ two-photon
photoemission (2PPE) to investigate the unoccupied electronic structure and
particularly the IPS of chevron-shaped GNR which are synthesized in a
thermally activated on-surface synthesis on Au(111). Angle- and time-resolved
2PPE are utilized to gain further insights into the properties of the IPS.
Compared to the pristine surface, reduced effective masses between 0.6 and 0.8
electron masses are observed and the lifetimes of the IPS are below the
experimental detection limit, which is in the femtosecond regime. Independent
of the concentration of N dopant atoms introduced in the GNR we observe a
constant binding energy with respect to the vacuum level of the system
