title: Practical Model for First Hyperpolarizability Dispersion Accounting for Both Homogeneous and Inhomogeneous Broadening Effects.
abstract: A practical yet accurate dispersion model for the molecular first hyperpolarizability β is presented, incorporating both homogeneous and inhomogeneous line broadening because these affect the β dispersion differently, even if they are indistinguishable in linear absorption. Consequently, combining the absorption spectrum with one free shape-determining parameter Ginhom, the inhomogeneous line width, turns out to be necessary and sufficient to obtain a reliable description of the β dispersion, requiring no information on the homogeneous (including vibronic) and inhomogeneous line broadening mechanisms involved, providing an ideal model for practical use in extrapolating experimental nonlinear optical (NLO) data. The model is applied to the efficient NLO chromophore picolinium quinodimethane, yielding an excellent fit of the two-photon resonant wavelength-dependent data and a dependable static value β0 = 316 × 10(-30) esu. Furthermore, we show that including a second electronic excited state in the model does yield an improved description of the NLO data at shorter wavelengths but has only limited influence on β0.
authors: †Department of Physics, University of Antwerp (campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk-Antwerpen, Belgium.
authors: Jochen
authors: J
authors: Campo
authors: †Department of Physics, University of Antwerp (campus Drie Eiken), Universiteitsplein 1, B-2610 Wilrijk-Antwerpen, Belgium.
authors: Wim
authors: W
authors: Wenseleers
authors: ‡School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics (COPE), Georgia Institute of Technology, Atlanta, Georgia, United States.
authors: Joel M
authors: JM
authors: Hales
authors: ‡School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics (COPE), Georgia Institute of Technology, Atlanta, Georgia, United States.
authors: Nikolay S
authors: NS
authors: Makarov
authors: ‡School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics (COPE), Georgia Institute of Technology, Atlanta, Georgia, United States.
authors: Joseph W
authors: JW
authors: Perry
keywords: TCNQ derivative; second-harmonic light scattering; static first hyperpolarizability; vibronic model