Exciton–surface plasmon coupling: An experimental investigation

Langmuir–Blodgett monolayer assemblies, which contained dye molecules, have been deposited on silver films. Exciton–surface plasmon interactions have been studied with attenuated total reflection (ATR) spectroscopy. Reflectivity and dispersion curves for plasmon surface polaritons (PSP’s) at the metal interface are reported for both angular and wavelength scans. In agreement with theory dispersion curves from angle scans exhibit a double ‘‘back bending’’ at the transverse exciton frequency ωT (due to PSP interaction with the in plane component of the dye transition dipole moment) and at the longitudinal frequency ωL (due to PSP interaction with a perpendicular component). Correspondingly, dispersion curves from wavelength scans break into separate branches at these frequencies.