  The bottom-up fabrication graphene nanoribbons (GNRs) has opened new
opportunities to specifically control their electronic and optical properties
by precisely controlling their atomic structure. Here, we address excitations
in GNRs with periodic structural wiggles, so-called Chevron GNRs. Based on
reflectance difference and high-resolution electron energy loss spectroscopies
together with ab-initio simulations, we demonstrate that their excited-state
properties are dominated by strongly bound excitons. The spectral fingerprints
corresponding to different reaction stages in their bottom-up fabrication are
also unequivocally identified, allowing us to follow the exciton build-up from
the starting monomer precursor to the final ribbon structure.
