PERTURBATION OF THE NONLINEAR OPTICAL-RESPONSE OF A CONJUGATED POLYMER BY AN ADSORBATE-INDUCED ELECTRONIC STATE

The coupling between ground state vibrations and excited electronic states in the polydiacetylene PTS has been investigated using stimulated inverse Raman scattering. Both Raman resonances and optical Stark effects have been measured and the interference between them has been used to determine several exciton-phonon coupling constants. An unexpected narrow (7.5 meV half-width) electronic feature at almost-equal-to 2.23 eV in PTS is observed. An even parity exciton in this spectral region has been postulated before by others. Our work demonstrates that this new electronic feature is resident on the polymer backbone, the same as the odd-parity exciton. This new feature must also possess some odd-parity character. The cause of this odd-parity contribution is likely a complex between molecular oxygen and the diacetylenic backbone.