| 1. |
- Jansik, B., et al.
(författare)
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Relativistic effects on linear and non-linear polarizabilities of the furan homologues
- 2003
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Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0166-1280. ; 633:03-feb, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- First principles calculations including relativistic effects are carried out for dipole moments, polarizabilities, first- and second-order hyperpolarizabilities for the series of furan homologues XC4H4, X = O, S, Se, Te, at three different levels of theory; time-dependent Dirac-Hartree-Fock (DHF), time-dependent Hartree-Fock with a Douglas-Kroll transformed one-component Hamiltonian, and time-dependent Hartree-Fock using effective-core potentials. By comparison with the corresponding non-relativistic results, the influence of relativistic effects on the properties as well as the accuracy of previously reported calculations on these molecules using effective-core potentials for selenium and tellurium can be addressed. The obtained results indicate that relativistic effects can be described with comparable accuracy at all three employed levels, and that non-scalar effects, which are explicitly treated only at the time-dependent DHF level, are of minor importance. Frequency dispersion and relativity are found to be additive at the single-determinant level. We find that relativistic effects cannot make up for the earlier identified mismatch between theory and experiment for the non-linear polarizabilities of the heavier homologues. A Bishop-Kirtman analysis of vibrational effects indicates that the same can be said about these.
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| 2. |
- Luo, Yi, et al.
(författare)
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Nonlinear optical susceptibilities of fullerenes in the condensed phase
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:4, s. 3060-3066
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Tidskriftsartikel (refereegranskat)abstract
- We present results for nonlinear optical susceptibilities of fullerenes, including C-60, C-70, and C-84, in the condensed phase from large-scale nb initio calculations using self-consistent reaction field theory and an analytical local-field method. It is shown that the intermolecular polarization interaction has significant effects on the nonlinear properties of the fullerenes, and that, in some contrast to other organic species, nondipolar contributions to this interaction are important. Based on the theoretical and experimental results for the polarizability of C-60 in the gas phase, a general local-field factor for C-60 film has been obtained, which is found to be quite different from the classical Lorenz-Lorentz local-field factor. The calculated and experimental nonlinear optical susceptibilities of C-60 are in good agreement provided the comparison is made on the same basis, viz at nonresonant frequencies and considering the relevant macroscopic quantities. The dielectric and density dependence of the nonlinear optical susceptibilities of C-70 are discussed.
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| 3. |
- Luo, Y., et al.
(författare)
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Solvent effects on the polarizabilities and hyperpolarizabilities of conjugated polymers
- 1999
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 111:21, s. 9853-9858
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Tidskriftsartikel (refereegranskat)abstract
- Solvent effects on the static polarizabilities and hyperpolarizabilities of conjugated polymers have been studied by means of a semiclassical solvation model using results from ab initio calculations. The solvent-induced changes of the static polarizabilities show maxima at fairly short oligomer lengths, with the main axial contribution decreasing rapidly to a zero value at the geometrically nondistorted polymer limit. Different saturation behaviors of the static polarizabilities of conjugated oligomers in gas phase and in solution are observed. It is concluded that the dipole-dipole interaction is responsible for the solvent-induced property changes of the oligomers. © 1999 American Institute of Physics.
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| 4. |
- Luo, Yi, et al.
(författare)
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Solvent-induced two-photon absorption of a push-pull molecule
- 2000
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 104:20, s. 4718-4722
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Tidskriftsartikel (refereegranskat)abstract
- Solvent-induced two-photon absorption cross sections are calculated for a push-pull molecule in solutions using both self-consistent reaction field and internal finite field approaches. It is shown analytically and numerically that the results from the two methods can be connected through induced local reaction field factors. The two-photon cross sections of the studied push-pull polyene are found to be rather insensitive to the choice of cavity shape. The solvent dependence of the two-photon absorption displays a pattern different from that of the first hyperpolarizability.
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| 5. |
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| 6. |
- Macak, P., et al.
(författare)
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Electronic and vibronic contributions to two-photon absorption of molecules with multi-branched structures
- 2000
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 113:17, s. 7055-7061
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Tidskriftsartikel (refereegranskat)abstract
- The two-photon absorption (TPA) cross-sections of series molecules with multi-branched structures was analyzed using ab initio response theory. The electronic coupling between the different arms of multi-branched molecules was found not very efficient for increasing the TPA cross-sections. In the case of two-dimensional charge-transfer cumulene-containing aromatic molecules, the TPA cross-section was drastically enhanced by increasing the dimensionality of the charge-transfer network. The vibronic coupling, was strong in multi-branched structures, which can result in an enhancement of the TPA cross-section.
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| 7. |
- Macak, P., et al.
(författare)
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Modeling of dynamic molecular solvent properties using local and cavity field approaches
- 2000
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 112:4, s. 1868-1875
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Tidskriftsartikel (refereegranskat)abstract
- Current models of solvent properties using cavity reaction field methods are analyzed and categorized in two groups according to the use of local fields or cavity fields as the perturbing fields. Analytical connections between the two approaches are derived.
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| 8. |
- Macak, P., et al.
(författare)
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Semi-classical modeling of medium effects on NLO molecular properties
- 2000
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Ingår i: Nonlinear Optics. - 1058-7268 .- 1029-2500. ; 25:1-4, s. 177-182
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Tidskriftsartikel (refereegranskat)abstract
- The solute nonlinear optical properties are shown to be quite ambiguous in definition. Connections between different conventions are presented. A general local field factor, differing from the commonly used Lorentz-Lorenz factor, is described. A simplified semi-classical approximation provides reliable results for systems as large as conjugated polymers and fullerenes.
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| 9. |
- Norman, P., et al.
(författare)
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Vibrational contributions to solute molecular properties obtained through a semiclassical model employing ellipsoidal cavities
- 1999
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 110:16, s. 7960-7965
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Tidskriftsartikel (refereegranskat)abstract
- A recently proposed semiclassical model for simulating optical properties of solutions and liquids is extended to encompass vibrational polarizabilities. Taking account of both the electronic and vibrational contributions it is shown that the size of an ellipsoidal cavity of pure liquids can be determined in a way that gives consistency between the predicted microscopic and macroscopic properties. It is found that a good estimate of the vibrational polarizability of the pure liquid can be obtained from experimental data on the molecular, gas phase, infrared (IR) spectrum. The influence of the cavity shapes on the liquid susceptibilities is examined using pure liquid ethanol as a test system.
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| 10. |
- Baev, A., et al.
(författare)
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General theory for pulse propagation in two-photon active media
- 2002
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 117:13, s. 6214-6220
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Tidskriftsartikel (refereegranskat)abstract
- The propagation of laser pulses of different lengths in nonlinear media of organic absorbers is described starting out from a recently suggested dynamical theory for two-photon absorption (TPA) of molecules in solutions [J. Opt. Soc. Am. B 19, 937 (2002)]. The roles of saturation effects and pulse duration on the suppression of TPA are emphasized. The numerical simulations of the pulse propagation are performed for a two-photon active charge transfer molecule using molecular parameters obtained from first principle calculations.
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