Measurement of first-order hyperpolarizability of several barbituric acid derivatives in solution by hyper-Rayleigh scattering

The hyper-Rayleigh scattering technique is used to determine the first-order hyperpolarizability of a number of newly synthesized barbituric acid derivatives. The technique utilizes the mechanism of thermal fluctuations which instantaneously remove the central symmetric environment at the site of the nonlinear optical chromophore, thereby enabling the second-harmonic-generation signal to be generated as the scattered light. The effect of making different substitutions to the parent barbituric acid molecule on the magnitude of hyperpolarizability is investigated.