Spectroscopic characterization of structural isomers of naphthalene: 1-Phenyl-1-butyn-3-ene

► Jet-cooled fluorescence spectroscopy of 1-phenyl-1-butyn-3-ene. ► Structural isomer of naphthalene (C10H8). ► Exhibits strong vibronic coupling and Duschinsky mixing. ► Plays a role in pathways the lead to naphthalene formation.