Nonlinear optical evidences of aggregation in asphaltene–toluene solutions

Abstract

Evidences of asphaltene aggregation are presented through the application of the Z-scan technique to study the nonlinear optical response of solutions of asphaltenes in toluene. Strong dependence of the two photon absorption coefficients ( β) with the input intensity was observed for concentrated solutions, as opposed to the observed behavior at low concentration. The results suggest that a change in ( β) occurs as a consequence of aggregation. The results are of importance for the study of dark samples like those relevant for crude oils.