The fluorescence lifetime and quantum yield f of isolated red polydiacetylene chains dispersed in their monomer single crystal matrix were measured between 10 and 100 K. increases up to 120 ps at 40 K, then rapidly decreases at higher T. f is a continuously decreasing function of T. The radiative lifetime r is proportional to ͱT in the whole T range studied. This is the expected behavior for a purely one-dimensional system without localization, a behavior which is not usually observed even in semiconductor quantum wires. An order of magnitude of the exciton effective mass m*Ϸ0.3 is inferred. The nonradiative lifetime nr is constant up to 50 K, then decreases exponentially, indicating the opening of a thermally activated decay channel.

The excitonic luminescence of a highly ordered single conjugated polymer chain is studied by microphotoluminescence. At T< or =10 K it consists of a single Lorentzian line. The linewidth increases linearly with T between 6 and 60 K, from 350 microeV at 6 K, indicating a pure dephasing time of approximately 2 ps. Above 10 K, other neighboring regions along the chain direction start to emit at a slightly higher (by approximately 1 meV) energy. This indicates very small inhomogeneous broadening, very long chains ( > or =10 microm), and a long range and very rapid exciton energy transfer ( >10 microm in <100 ps).