Condensation of vibrational excitation and properties of Raman scattering by conjugated-polymer chains

Assuming the possibility of 'detachment' of the excited vibrational level from the level specified by temperature, the experimental data on Raman scattering of light in conjugated polymers are interpreted. It is shown that upon optical pumping, vibrational excitations in a chain of alternating C–C and C=C bonds are combined to form a vibrational 'condensate' and a 'quantum gas', which are localised at one of the bond types due to the spontaneous violation of symmetry. Scattering by the condensate and a part of the quantum gas captured by the condensate explains the appearance of the low-frequency wing of the anti-Stokes line in the Raman spectrum of conjugated polymers and the anomalous relation between the intensities of the Stokes and anti-Stokes components at temperatures up to room temperature.