Detection of Molecular Chirality using different Optical Second-Harmonic Generation Techniques

Abstract

In the past, second-harmonic (SH) studies of monolayers have often been applied to systems with C∞ υ -symmetry, in most cases to systems consisting of rodlike molecules [1]. These samples are axialsymmetric with respect to the surface and possess a mirror plane of symmetry normal to the surface. If the molecules are replaced by chiral molecules of one enantiomer, this mirror symmetry is broken and the system C∞-symmetry. In the following, this is called surface chirality. Because these monomolecular films are very thin, this symmetry break can hardly be detected using linear optical techniques such as optical activity measurements. However, if the molecular chirality influences the part of the nonlinear structure responsible for SH generation, surface chirality can be detected by using nonlinear optical techniques.