Pressure and temperature dependence of the electronic and vibrational excitations of a conjugated polymer crystal

The pressure dependence of reflection, absorption and resonant Raman spectra of single crystals of toluene sulphonate dicetylene polymer have been measured under hydrostatic conditions to 5 kbars. The peak of the reflection spectrum near 2 eV shifted to lower energies with increasing pressure at a rate of 7.3+or-0.3 meV per kbar. This result is shown to be in qualitative agreement with the prediction of molecular orbital calculations. The temperature and pressure dependence of the resonant Raman spectra are discussed using a simple point mass and anharmonic spring constant model.