A review of our work that will appear in Physical Review
COMPLEX MOLECULES MADE SIMPLE
Organic molecules are versatile and can be custom tailored for a large variety of applications that span such diverse fields as cell microscopy, cancer therapy, computing technology, or high speed communications, to cite just a few. With this high degree of flexibility comes complications. Even when a system can be reasonably approximated by two excited states, at least 7 parameters are required to predict important properties such as the nonlinear-optical response. In the present work, a combination of sum rules and symmetry constraints has been shown to allow the problem to be reduced to 3 parameters, which can be determined using two simple measurements -- the linear absorption spectrum and a measurement of the hyperpolarizability at just one one wavelength using hyper Rayleigh Scattering. This approach has been applied to the complex molecule AF455, and shown to accurately predict not only the correct shape of the two-photon absorption spectrum, but also its absolute magnitude. Here is a rare instance where two simple measurements accurately predict all the linear and nonlinear optical properties of a molecule. With complexity simplified, new paradigms for making better materials may follow.