Kerr constants, depolarization ratios, and hyperpolarizabilities of substituted methanes
TL;DR: In this article, the static Kerr constants of eight substituted methanes in the gas phase have been measured by a low-frequency null technique, and the magnitudes of the hyperpolarizabilities obtained are in good agreement with the values obtained from second harmonic generation measurments.
Abstract: The static Kerr constants of eight substituted methanes in the gas phase have been measured by a low‐frequency null technique. Combining these results with gas phase depolarization ratio measurements we show that the hyperpolarizability contributions to the Kerr constant are small except for CH3F. The magnitudes of the hyperpolarizabilities obtained are in good agreement with the values obtained from second harmonic generation measurments. In the case of nitromethane the electric birefringence and depolarization ratio measurements are combined to obtain the three principal values of the polarizability tensor.
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TL;DR: In this article, a basis set of moderate size optimized for the computation of the dipole polarizability of reasonably large molecules consisting of hydrogen and p-block elements up to iodine is presented.
Abstract: The development is described of a basis set of moderate size optimized for the computation of the dipole polarizability of reasonably large molecules consisting of hydrogen and p-block elements up to iodine. The mean polarizability, polarizability anisotropy and dipole moment for hydrides of the first four rows of the periodic table, obtained at both the SCF and MP2 levels, are compared with those obtained using the previously developed 6–31 G(+ sd + sp) basis set, as well as larger basis sets, and with experiment. For the series of diatomic halogens, X2, and the halomethanes, CH3X (X = F, C1, Br, I), electric properties are obtained in excellent agreement with those resulting from use of larger basis sets, and also with experiment.
232 citations
TL;DR: In this paper, Coupled Hartree-Fock perturbation theory has been applied to evaluate the first hyperpolarizability in the molecules H2O, NH3, CH4, and CO. A group-theoretical approach has been employed, which makes it possible for a reduced file of symmetry distinct integrals to be processed at each iteration with reduced computer efforts.
Abstract: Coupled Hartree–Fock perturbation theory has been applied to evaluate the first hyperpolarizability in the molecules H2O, NH3, CH4, and CO. A group‐theoretical approach has been employed, which makes it possible for a reduced file of symmetry distinct two‐electron integrals to be processed at each iteration with reduced computer efforts. Several very large basis sets, including up to 4f functions on the heavy atom and 3d on hydrogen, have been retained, which yield SCF energies, dipole moments, polarizabilities, and first hyperpolarizabilities very near to the corresponding HF quantities. Except in the case of CO, large discrepancies with respect to experimental data have been found.
71 citations
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TL;DR: In this article, the frequency-dependent polarizabilities and first and second hyperpolarizabilities of the haloform series have been performed within the framework of the time-dependent coupled perturbed Hartree-Fock method.
66 citations
TL;DR: In this paper, an interacting segment model (ISM) is applied to a full-scale treatment of the electric dipole moments, isotropic and anisotropic polarizabilities, and hyperpolarizabilities of a series of 12 halogenated methane molecules CXnY4−n(X,Y = H,F,Cl; n = 0-4).
Abstract: A previously developed interacting segment model [ISM—see J. Chem. Phys. 67, 2109 (1977)] is applied to a full‐scale treatment of the electric dipole moments, isotropic and anisotropic polarizabilities, and hyperpolarizabilities of a series of 12 halogenated methane molecules CXnY4−n(X,Y = H,F,Cl; n = 0–4). The ISM scheme enables the molecular properties considered to be fitted in terms of a set of ’’bare’’ electric tensor parameters for each bond, which are modified (’’dressed’’) by intramolecular electrostatic interactions. The computed results of the ISM scheme, and of a corresponding interaction‐free bond additivity model, are discussed in relation to the following: choice of geometric and bond parameters, quality of fit to experimentally determined molecular and bond properties, and predictive potential and general physical validity of the model. It is concluded that the ISM approach represents a substantial improvement over simple bond additivity as a basis for understanding molecular electric tenso...
45 citations
TL;DR: In this article, constrained anisotropic dipole oscillator strength distribution techniques are discussed and applied to obtain reliable results for a wide variety of the Anisotropic and isotropic dipole properties of H2 and N2.
Abstract: Constrained anisotropic dipole oscillator strength distribution techniques are discussed and applied to obtain reliable results for a wide variety of the anisotropic and isotropic dipole properties of H2 and N2. These include the dipole oscillator strength sumsS
k, k=2, 1, −1/2(−1/2) −2, −3, −4, ..., the logarithmic dipole sumsL
k and mean excitation energiesI
k, k=2(−1) − 2, and, as a function of wavelength, the dynamic polarizability and the associated anisotropy, the total depolarization ratio, the Rayleigh scattering cross section, and the Verdet constant. The anisotropic components of the DOSD for a molecule are obtained from a given recommended isotropic DOSD by using a constrained least squares procedure and a series of known anisotropic constraints. Assuming that sufficient input is available, the constrained DOSD approach used in this paper is the only available method for the reliable evaluation ofall the relevant anisotropic and isotropic dipole properties for a wide variety of atoms and molecules.
35 citations
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TL;DR: In this paper, the depolarization of light scattered from the beam of a helium-neon gas laser at low pressures was measured and the results of these measurements were reported.
Abstract: Measurements of the polarization of light scattered from the beam of a helium-neon gas laser at low pressures are described. The intensity, polarization and parallelism of the beam permit high accuracy, and new values for the depolarization ratios of twenty-four simple species are reported. The general quantum theory of scattering is discussed and applied in detail to the evaluation of a formula for the depolarization ratio of the scattered light. It is found that quantum corrections to the classical formula arise from ( i ) the effects of frequency changes due to rotational Raman scattering, ( ii ) changes in the molecular polarizability with rotational state due to centrifugal distortion, ( iii ) approximations inherent in the polarizability scattering formula, and ( iv ) vibrational Raman scattering. Effect ( i ) reduces the depolarization of hydrogen to 91% of its classical value; ( iii ) is unimportant unless the frequency of the light is near an absorption frequency of the molecule. The depolarization measurements have been combined with refractivity data to yield the anisotropies in molecular polarizabilities of the molecules studied.
579 citations
TL;DR: In this paper, the authors used the technique of static field induced second harmonic generation in liquids to determine the second order hyperpolarizability β and the third order hyper polarization γ, for a wide range of conjugated and nonconjugated organic molecules.
Abstract: We have used the technique of static field induced second harmonic generation in liquids to determine the second order hyperpolarizability β, and the third order hyperpolarizability γ, for a wide range of conjugated and nonconjugated organic molecules. The adequacy of the Onsager local field formulation was tested as was the accuracy of the bond additivity approximation. The large π‐electron nonlinearities which are possible in substituted benzene molecules were investigated by measuring a large number of benzene derivatives and subtracting out the σ‐electron contributions.
529 citations
TL;DR: In this article, molecular refractivity and polarizability of a particle is defined as the dipole moment induced by an electric field of unit intensity, and the principal polarizabilities of molecules can be analyzed in terms of anisotropic bond polarisation.
Abstract: Publisher Summary This chapter discusses molecular refractivity and polarizability. Refractive indices ( n ) of pure substances are more accurately measurable than any other optical properties. The refractive index of a substance varies with its physical state, temperature t , and wave-length λ of the light by which n is observed. The first two of these effects are attributed to the density d . The specific refraction r of a substance multiplied by the molecular weight is referred as molecular refraction. Polarizability of a particle is defined as the dipole moment induced by an electric field of unit intensity. The polarizabilities of monatomic ions and molecules are generally independent of field direction. The principal polarizabilities of molecules can be analyzed in terms of anisotropic bond polarizabilities. Polarizabilities are also responsible for the birefringence, which appears whenever the orientations of anisotropic molecules in an assemblage are derandomized or changed by any disturbing force.
344 citations
TL;DR: In this article, the dispersion of the gas phase depolarization ratio of Rayleigh scattered light for 12 linear and symmetric top molecules was measured and the frequency dependence of the polarizability anisotropy was obtained.
Abstract: We have measured the dispersion of the gas phase depolarization ratio of Rayleigh scattered light for 12 linear and symmetric top molecules Combining these data with known refractive index data we obtain the frequency dependence of the polarizability anisotropy For all molecules studied we find that the polarizability anisotropy increases more rapidly with increasing frequency than the bulk polarizability We have correlated this behavior with the oscillator strength and direction of the first electronic transition We have also compared our zero frequency extrapolated anisotropies with the anisotropies determined from static fields with the Kerr effect and the Stark effect in microwave spectroscopy
319 citations