title: A time correlation function theory describing static field enhanced third order optical effects at interfaces.
abstract: Sum vibrational frequency spectroscopy, a second order optical process, is interface specific in the dipole approximation. At charged interfaces, there exists a static field, and as a direct consequence, the experimentally detected signal is a combination of enhanced second and static field induced third order contributions. There is significant evidence in the literature of the importance/relative magnitude of this third order contribution, but no previous molecularly detailed approach existed to separately calculate the second and third order contributions. Thus, for the first time, a molecularly detailed time correlation function theory is derived here that allows for the second and third order contributions to sum frequency vibrational spectra to be individually determined. Further, a practical, molecular dynamics based, implementation procedure for the derived correlation functions that describe the third order phenomenon is also presented. This approach includes a novel generalization of point atomic polarizability models to calculate the hyperpolarizability of a molecular system. The full system hyperpolarizability appears in the time correlation functions responsible for third order contributions in the presence of a static field.
authors.affiliation: Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Neipert
authors.forename: Brian
authors.initials: B
authors.lastname: Space
mesh_terms: D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D055095:Optics and Photonics; D055672:Static Electricity; D013223:Statistics as Topic; D013499:Surface Properties; D013997:Time Factors