A Model for m-LPPP Electronic Structure

We assume that standard Coulomb-correlated models for luminescent polymers [11] properly described the intrachain electronic structure of m-LPPP. In this case intrachain photoexcitation generate singlet excitons with odd parity wave-fimctions (B ), which are responsible for the spontaneous and stimulated emission. Since the pump energy in our experiments is about 0.5 eV larger than the 

Optical gap the initial excitons are expected to be hot states. Intrachain thermalization may, however, occur within the pump pulse duration. 

8 Photophysics of Methyl-Substituted PPP-Type Ladder Polymers 

The PA bands at 1.3 eV (950 nm) and 1.9 eV (650 nm) present different dynamics and a longer lifetime with respect to the singlet exciton. They should therefore be assigned to different photoexcitations. Let us first discuss die PA at 

2 eV would imply a huge singlet-triplet energy separation 1.1 eV, a value that seems to be rather unlikely. 

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