| Abstract: | Resonance Raman excitation profiles of two vibrational modes have been measured for Langmuir-Blodgett films of a polydiacetylene. The polymer films were formed by exposing multilayer samples of the Cd salt of 10,12-pentacosadiynoic acid to ultraviolet radiation. Raman spectra were measured for incident laser photon energies between 1.85 and 2.20 eV (670-564 nm), the region over which the films exhibited optical absorption associated with an electronic transition of the π-electrons on the conjugated backbone. The excitation profiles have been used to determine both the strength of the vibronic coupling and the differences in vibrational frequency between the ground and excited states. The results are in reasonable agreement with those obtained previously for polydiacetylene single crystals. |
