title: Analytic ab initio calculations of coherent anti-Stokes Raman scattering (CARS).
abstract: We present a theory for the analytic calculation of frequency-dependent polarizability gradients, and apply the methodology to the calculation of coherent anti-Stokes Raman scattering (CARS). The formalism used is based on an open-ended theory for the calculation of frequency-dependent molecular response properties of arbitrary order, also including contributions from perturbation-dependent basis sets. An important feature of our approach is the close connection between the formalism--which is fully matrix-based in an atomic orbital basis--and the implementation, allowing for the rapid implementation of higher-order molecular properties. Care is taken to allow the formalism to be utilized with linearly-scaling Hartree-Fock and density-functional theory codes. By avoiding the evaluation of responses due to geometry distortions, only 9 response equations need to be solved for the calculation of the CARS intensities, independent of the size of the molecular system. The theory is illustrated by calculations on a set of polyaromatic hydrocarbons using a DFT/B3LYP force field and Hartree-Fock polarizability gradients. Good agreement with the experimental CARS spectra of these compounds is obtained.
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø, N-9037, Tromsø, Norway.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Thorvaldsen
authors.forename: Lara
authors.initials: L
authors.lastname: Ferrighi
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ruud
authors.forename: Hans
authors.initials: H
authors.lastname: Agren
authors.forename: Sonia
authors.initials: S
authors.lastname: Coriani
authors.forename: Poul
authors.initials: P
authors.lastname: Jørgensen
mesh_terms: D009930:Organic Chemicals / Q000032:analysis; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman
chemical_list: D009930:Organic Chemicals