Optical Absorption in Polyacetylene: A Direct Measurement Using Photothermal Deflection Spectroscopy

Abstract

We present direct measurements of the optical absorption in undoped and ammoniatreated polyacetylene utilizing the technique of photothermal deflection spectroscopy. Our spectra show an Urbach-type edge and a broad, N${\mathrm{H}}_{3}$-sensitive sub-band-gap absorption. Quantitative comparisons of absorption and spin-resonance results do not show the predicted midgap absorption from neutral solitons.