Effective stimulated emission and excited-state absorption cross-section spectra of poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) and t,t′-didecycloxy-II-distyrylbenzene Original Research Article

Effective stimulated emission cross-section spectra, σem, eff(λ), stimulated emission cross-section spectra, σem(λ), and excited-state absorption cross-section spectra, σex(λ) = σem, eff(λ), are determined in the fluorescence region for the conjugated polymer poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) in tetrahydrofuran, xylene, toluene, and for the model molecule t,t′-(didecycloxy)-II-distyrylbenzene. For theconjugated polymer σem, eff(λ) is found to be small compared to σem(λ) indicating that σex(λ) and σem(λ) are of similar strength and spectral shape, while for the model compound σex(λ) is small compared to σem(λ). In the polymer the laser excitation to the broad S1 absorption band leads to the formation of discrete lattice relaxed exciton conformations extending on the average over four monomer units which are responsible for upper-to-lower-state stimulated emission and lower-to-upper-state (excited-state) absorption.