Anharmonic contribution to the static vibrational second hyperpolarizability of linear quadrupolar molecules within the framework VB-2CT and AEEP

E. Squitieri(1) and I. Benjamin(2)

(1) Escuela de Quı´mica, Facultad de Ciencias, Universidad Central de Venezuela, Av. Los Ilustres, Los Chaguaramos, Caracas, Venezuela; (2) Department of Chemistry, University of California, Santa Cruz, California 95064

Anharmonic ðcanhar v Þ and harmonic ðchar v Þ contributions to the static vibrational second hyperpolarizability (cv) of symmetrically substituted quadrupolar p-conjugated molecules are investigated using a three-state (VB-2CT) model and the analytical evaluation of electrical properties (AEEP) method. Calculations show that using strong donors and acceptors for given quadrupolar molecule canhar v can be more important than its electronic counterpart (ce). Additionally, canhar v is comparable in magnitude to char v .