Raman gain saturation, pump depletion and two-photon absorption in pTS

Summary form only given. Single crystals of the polydiacetylene, poly[2,4-hexadiyne-1,6-diol-bis(p-toluenesulfonate)] (pTS) have been studied in the near resonant regime by transient absorption spectroscopy. We show the changes observed in the absorption spectra at short times surrounding the arrival of the 726-nm laser pulse. The experiment is performed by monitoring the transmission of a continuum probe in the presence of a /spl sim/1-ps high intensity pump pulse. The prominent negative going peaks are due to stimulated Raman scattering arising from the carbon-carbon double and triple bonds along the polymer backbone. The broad induced absorption is the result of population of an excited state produced through two-photon excitation.