Odd-even oscillations in first hyperpolarizability of dipolar chromophores: Role of conformations of spacers

An extensive calculation on the effects of spacer length enhancement on the second-order nonlinear optics (NLO) properties of dipolar molecules connected by the CH2 groups is performed. The molecules exhibit a very strong odd-even behavior in the first hyperpolarizabilities, which are reported experimentally on similar systems but the origin of such phenomena remains unclear.