A multichannel Raman spectrometry study of polyacetylene isomerization induced by laser irradiation

The multichannel Raman spectrometry has been used in the study of the isomerization reaction of an 80% cis PA film into a trans PA, using a laser beam for a double purpose. It is employed simultaneously as an activation agent inducing the isomerization reaction and the Raman diffusion. In each experience, the power of the laser beam Pⁱ(λ) was equivalent to the temperature. Twelve spectra have been recorded at different time periods tj = j·dt. The integrations of the Raman intensities related to two selected bands were numerically calculated.We also proposed an original method for the determination of the isomeric composition. A quantitative relationship between the equilibrium temperature and the laser beam power (in the range of laser power: 30 < Pⁱ(λ) < 300 mW) has been found. An estimate number of isomerized molecules N₀ and then a correction factors f_cis and f_trans were also obtained.