Vibronic analysis of NLO spectra of PDA crystals and films

摘要

A joint analysis of recent NLO spectra of polydiacetylene films and crystals is presented, using vibronic contributions in the Condon approximation and $pi@-electronic states from Pariser-Parr-Pople theory. Raman resonances are shown to be corrections to average excitations. An even-parity state above the photoconduction edge is found in two-photon absorption of PDA-PTS crystals and nondegenerate four-wave-mixing spectra of PDA- 4BCMU films. We incorporate linear and resonance Raman spectra in the joint NLO analysis and emphasize the different roles of electronic and vibrational contributions.