Photoinduced strain as a probe of acoustical and electronic properties of conducting polymers

We discuss applications of photogenerated strain in transient absorption experiments. These include measurements of sound velocity, phonon dispersion relations, and excited electronic state energy levels. In particular, we have identified a new type of spectroscopy in photoinduced absorption that can be used to detect both allowed and forbidden electronic transitions in thin semiconducting films. This technique was applied to a host of conducting polymers for which we detected energy levels of various excitonic states with odd and even symmetry.