Picosecond transient Raman spectra of S-1 bis(methylstyryl)-benzene: Observation of S-1 <- S-n resonance emission

We have been studying the excited state spectra of several molecules relate d to electroluminescent conducting polymers. The excited state structure co rresponds to the conducting state in these systems. We have obtained data o n 1,4-bis(2,2'-methylstyryl)-benzene (2MSB) as st model system of poly (p-p henylenevinylene) (PPV). We observe both sharp and broad features in the sp ectra. The sharp bands occur at a constant energy shift relative to the pro be wavelength. We attribute the sharp bands to resonance Raman bands of the S-1 state of 2MSB. We assign the broad band at similar to 740nm to resonan ce emission between S-n and S-1. We believe that this is the first observat ion of resonance secondary radiation (RSR) between two electronically excit ed stares in a large molecule.