Abstract

Virtual π-electron excitations occuring on individual molecular, or polymer chain, sites are responsible for large, ultrafast nonresonant second order β_jjk(-ω₃;ω₁,ω₂) and third order γ_ijKl(−ω₄^;ω₁,ω₂ω₃) noniinear optical susceptibilities of organic conjugated linear chains. It has now been clearly demonstrated that the proper description of β_ijk in such conjugated structures, as well as resonant one-photon and two-photon processes in finite polyenes, requires account of the electron-electron interaction and resulting electron correlation.¹ We present the results of a series of calculations of β_ijk and γ_ijkl of conjugated linear chains in which the π-electronic states are determined by singly and doubly-excited configuration interaction of the π-electron molecular orbitals obtained from an all-valence electron self-consistent field molecular orbital description of the ground state. Thus, the many- electron nature of the virtual electronic excitations is carefully considered.^2,3

© 1988 Optical Society of America