FREE-ELECTRON MODEL FOR OPTICAL POLARIZABILITIES - ROLE OF DIMENSIONALITY

The free electron model proposed by Rustagi and Ducuing to explain the enhancement of the second-order hyperpolarizabilities of pi-conjugate d linear molecules with increasing conjugation length has been extende d to two and three dimensions. The sign and magnitude for the linear ( alpha) and third order (gamma) polarizabilities as a function of the s ize and electron density of the systems have been obtained. Some simpl e general conclusions on the role of dimensionality in the nonlinear r esponse have been obtained.