Modeling Coherent Anti-Stokes Raman Scattering with Time-Dependent Density Functional Theory: Vacuum and Surface Enhancement.

We present the first density functional simulations of coherent anti-Stokes Raman scattering (CARS) and an analysis of the chemical effects upon binding to a metal surface. Spectra are obtained from first-principles electronic structure calculations and are compared with available experiments and previously available theoretical results following from Hartree–Fock polarizability derivatives. A first approximation to the nonresonant portion of the CARS signal is also explored. We examine the silver pyridine cluster models of the surface chemical signal enhancement, previously introduced for surface-enhanced Raman scattering. Chemical resonant intensity enhancements of roughly 10² are found for several model clusters. The prospects of realizing further enhancement of CARS signal with metal surfaces is discussed in light of the predicted chemical enhancements