Ground and excited state nonlinear optical properties of poly(-para phenylene vinylene)

We investigate theoretically the nature of higher energy excited even as well as odd   parity states, for various sizes of oligomers of PPV. We study in detail various nonlinear optical properties, like third harmonic generation (THG), two-photon absorption (TPA), electro absorption (EA) of oligomers of PPV within a rigid band correlated Pariser–Parr–Pople (PPP) model Hamiltonian, using the π-electron basis and the powerful multireference single and double configuration interaction (MRSDCI) method. We also use single–double–triple–quadruple configuration interaction (SDTQCI) in limited cases. We show that in THG three kinds of one-photon states 1BuBu, jBujBu and nBunBu (where j