title: Holstein-Peirls-Hubbard trimer as a model for quadrupolar two-photon absorbing dyes.
abstract: The linear and nonlinear optical properties of a Donor-Acceptor-Donor system have been investigated by using a two-electron three-point-site model system. Some basic features of electron correlations are included in the model by means of a bi-electronic density matrix. The polarizabilities and second hyperpolarizabilities have been computed with a modified version of the Collective Electronic Oscillators (CEO) method which allowed us to include the electron-phonon coupling. Both singly- and doubly-excited states are taken into account in the computation of (hyper-)polarizabilities. The effects of electron-phonon coupling on the two-photon absorption and on the third harmonic generation in the infrared region are discussed.
authors.affiliation: Consorzio INSTM, UdR Padova, Department of Chemical Sciences, Via Marzolo 1, 35131 Padua, Italy. roberto.pilot@unipd.it
authors.forename: Robertino
authors.initials: R
authors.lastname: Pilot
authors.forename: Renato
authors.initials: R
authors.lastname: Bozio