Molecular Optics Nonlinear Optical Processes in Organic and Polymeric Crystals and Films. Part 2
Abstract
Comprehensive theoretical and experimental studies of the magnitude, sign, dispersion, and length dependence of the third order molecular susceptibility gamma ijkl(-omega 4; omega 1, omega 2, omega 3) demonstrate that the microscopic origin of the nonresonant third order nonlinear optical properties of conjugated linear chains is determined by the effects of electron correlation due to electron-electron repulsion. Multiple-excited configuration interaction calculations of gamma jkl(-omega 4; omega 1, omega 2, omega 3) for the archetypal class of quasi-one dimensional conjugated structures known as polyenes reveal for the first time the principal role of strongly correlated, energetically high-lying, two photon 1 Ag virtual states in the largest of the two dominant, competing virtual excitation processes that determine gamma ijkl(- omega 4; omega 1, omega 2, omega 3). It is also found in studies of the effects of conformation on gamma ijkl(-omega 4; omega 1, omega 2, omega 3) that the origin of the third order optical properties remains basically the same for the all-trans and cis-transoid polyenes, and the results for the two conformations are unified by a common power law dependence of the dominant tensor component gamma xxxx(-omega 4; omega 1, omega 2, omega 3) on the physical end-to-end length L of the chain with an exponent of 3.5. Calculations for a noncentrosymmetric conjugated chain demonstrate that virtual excitation processes involving diagonal transition moments that are forbidden in centrosymmetric structures lead to a more than an order of magnitude enhancement in gamma xxxx(-omega 4; omega 1, omega 2, omega 3) compared to the analog centrosymmetric structure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1991
- Accession Number
- ADA244899
Entities
People
- A. F. Garito
Organizations
- University of Pennsylvania