Showing papers on "Hyperpolarizability published in 2001"
TL;DR: On the basis of the four-state model, the first hyperpolarizability of the octupolar molecule is found to be linearly proportional to the TPA cross section, and this theoretical relationship is confirmed by using the ab initio calculation results.
Abstract: Two-photon absorption (TPA) cross sections of four representative series of octupolar molecules are theoretically investigated. The general structure−TPA-property relationship is described by using the effective four-state valence-bond three-charge-transfer model. As the charge-transfer character of the ground electronic state increases due to the strong donors or acceptors, (i) the transition dipole matrix elements between the ground and 2-fold degenerate excited states increase, (ii) the energy gap decreases, and consequently (iii) the TPA transition amplitude monotonically increases. Thus, the design strategy to maximize the TPA cross section of the octupolar molecule is established. On the basis of the four-state model, the first hyperpolarizability of the octupolar molecule is found to be linearly proportional to the TPA cross section. This theoretical relationship is confirmed by using the ab initio calculation results. The Hammett correlation analysis of the TPA cross section and first hyperpolariz...
195 citations
TL;DR: In this paper, the relative phase between the vibrationally resonant phenyl ring hyperpolarizability and the Si/SiO2 interface nonresonant hyperpolicizability was measured for polystyrene thin films on oxidized Si substrates.
Abstract: Vibrationally resonant sum frequency generation (VR-SFG) has been used to study the absolute molecular orientational distribution of the pendant phenyl groups at the free surface of polystyrene (PS) thin films on oxidized Si substrates. Characterization of the dependence of the VR-SFG on film thickness allows unique identification of the origin of the signal, e.g., free surface, bulk, or buried interface. For films <400 nm thick, the dominant source of vibrationally resonant signal is the PS/air interface, while the dominant source of the nonresonant background is the Si/SiO2 interface. VR-SFG of a self-assembled phenylsiloxane layer is used to calibrate the relative phase between the vibrationally resonant phenyl ring hyperpolarizability and the Si/SiO2 interface nonresonant hyperpolarizability. It is found that the phenyl groups are ordered at the PS/air interface and are oriented away from the polymer film. Quantitative analyses of the orientational distribution for both the PS free interface and the p...
180 citations
TL;DR: In this paper, the resonance Raman intensities of p-nitroaniline, a prototypical push-pull chromophore with a large first hyperpolarizability (β), have been measured in dilute solution in five solvents having a wide range of polarities (cyclohexane, 1,4-dioxane, dichloromethane, acetonitrile, and methanol) at excitation wavelengths spanning the strong near-ultraviolet charge-transfer absorption band.
Abstract: Resonance Raman intensities of p-nitroaniline, a prototypical “push–pull” chromophore with a large first hyperpolarizability (β), have been measured in dilute solution in five solvents having a wide range of polarities (cyclohexane, 1,4-dioxane, dichloromethane, acetonitrile, and methanol) at excitation wavelengths spanning the strong near-ultraviolet charge-transfer absorption band. The absolute Raman excitation profiles and absorption spectra are simulated using time-dependent wave packet propagation techniques to determine the excited-state geometry changes along the five or six principal Raman-active vibrations as well as estimates of the solvent reorganization energies. The total vibrational reorganization energy decreases and the solvent reorganization energy increases with increasing solvent polarity in all solvents except methanol, where specific hydrogen-bonding interactions may be important. The dimensionless normal coordinate geometry changes obtained from the resonance Raman analysis are conve...
124 citations
TL;DR: In this paper, a hybrid molecular-based ferromagnet of formula [(dmaph)PPh3][MnCr(ox)3], where [(maph)pPh3]+ stands for the (4-dimethylaminophenyl)triphenylphosphonium cation (ox2-being the oxalate anion), has been synthesized.
Abstract: A new hybrid molecular-based ferromagnet of formula [(dmaph)PPh3][MnCr(ox)3], where [(dmaph)PPh3]+ stands for the (4-dimethylaminophenyl)triphenylphosphonium cation (ox2- being the oxalate anion), has been synthesized. It crystallizes in the monoclinic P21 space group, with lattice parameters a = 13.954(2) A, b = 16.297(2) A, c = 14.323(2) A, and β = 99.27(1)°. Refinement based on Fo2 yields R = 0.072 and wR2 = 0.156. The compound exhibits a ferromagnetic interaction between Cr3+ and Mn2+, with a long-range magnetic ordering at TC = 4.5 K. The hyperpolarizability (β) of the cation is calculated within the framework of the INDO/SOS-based method, which indicates a β value comparable to that of p-nitroaniline for an absorption maximum at 306 nm (emax = 28 500 M-1 cm-1). This result is consistent with the observation of a SHG efficiency 4 times that of urea for the parent [(dmaph)PPh3]Br salt, at 1.907 μm. The non-centrosymmetric [(dmaph)PPh3][MnIICrIII(ox)3] derivative is used as a model compound for an inve...
88 citations
TL;DR: The versatility of the method described in this work in the presence of more than one electronic transition contributing to the non-linear optical response is demonstrated.
84 citations
TL;DR: Electric-field-induced second-harmonic generation and harmonic light (hyper-Rayleigh) scattering techniques were used to investigate the vector part of the hyperpolarizability tensor and the two-dimensional character of the molecular nonlinearity, respectively.
Abstract: The synthesis, characterization, and two-dimensional second-order nonlinear optical (NLO) response of a dipolar NiII donor- acceptor Schiff base complex and the related ligand are reported. Electric-field-induced second-harmonic generation and harmonic light (hyper-Rayleigh) scattering techniques, in combination with INDO/SCI-SOS theoretical calculations, were used to investigate the vector part of the hyperpolarizability tensor and the two-dimensional character of the molecular nonlinearity, respectively. Off-diagonal hyperpolarizability tensors can be related to charge-transfer transitions that are polarized perpendicular to the molecular dipolar axis, while parallel transitions account for the diagonal hyperpolarizability tensor. The role of the metal center in enhancing the two-dimensional NLO response of such molecules is twofold since it acts both as the donor and the bridging moiety of the planar donor-(pi-conjugate-bridge)-acceptor system. These dipolar two-dimensional molecules are interesting candidates from the perspective of polarization-independent NLO materials.
79 citations
TL;DR: In this paper, the major linear and nonlinear electric properties of urea and thiourea have been calculated at different levels of approximation with respect to the treatment of the electron correlation contribution.
Abstract: The major linear and nonlinear electric properties of urea and thiourea have been calculated at different levels of approximation with respect to the treatment of the electron correlation contribution. The basis set saturation effects were studied by comparing the results computed in three different basis sets of increasing flexibility. The so-called (first-order) polarized (Pol) basis have been found to give excellent results for dipole moments and dipole polarizabilities. Their performance in calculations of the first hyperpolarizability is also quite good. However, calculations of the second hyperpolarizability require the use of recently developed second-order polarized (HyPol) basis sets. The frequency-dependent dynamic polarizabilities and first and second hyperpolarizabilities of urea and thiourea have been calculated in the time-dependent Hartree–Fock approximation and then scaled to account for the electron correlation contribution and the basis set extension effect. This method gives useful estimates of the magnitude of different nonlinear optical processes. In particular thiourea was found to have attractively high value of the third-order optical susceptibility. The replacement of the C=O group of urea by its sulfur counterpart brings in general quite a large increase of the efficiency of the third-order optical processes.
75 citations
TL;DR: In this paper, the role of phase factors in determining the dipole moment of quasilinear polymers has been investigated, including electron correlation using methods analogous to those employed for molecular systems.
Abstract: Previously we have shown how to obtain the electric properties of a polymer or other periodic system at the coupled Hartree–Fock level by direct, analytical calculation rather than by extrapolation of oligomer results. Here we add computationally simpler noniterative formulas and test the methodology for the longitudinal dipole moment (μ), polarizability (α), first hyperpolarizability (β), and second hyperpolarizability (γ) of five quasilinear polymers: (LiH)n, (FH)n, (H2O)n, trans-polymethineimine (–CNH–)n, and trans-polyacetylene (–CH=CH–)n. The polymer values are in good agreement with large-oligomer calculations. In this connection the role of phase factors, particularly in determining the dipole moment, is elucidated. We are now in a good position to include electron correlation using methods analogous to those employed for molecular systems.
71 citations
TL;DR: The first hyperpolarizability of several Λ-like chromophores including Malachite Green and Brilliant Green were measured by means of Kleinman-disallowed hyper-Rayleigh (harmonic light) scattering (KD-HRS) as discussed by the authors.
70 citations
TL;DR: A simple method to obtain in high yields mixed-ligand nickel-dithiolene complexes, which show strong negative solvatochromism and negative first molecular hyperpolarizability, and the use of Raman spectroscopy to establish the extent of electronic delocalisation in these complexes are reported.
65 citations
01 Jan 2001
TL;DR: In this paper, the second-order and third-order NLO susceptibilities of conjugated organic molecules and polymers in the nonresonant regime are investigated. But the focus of the paper is on the determination of the second and third order NLO properties, β and γ.
Abstract: Publisher Summary This chapter discusses the theoretical approach to the design of organic molecular and polymeric nonlinear optical (NLO) materials. The focus of the chapter is on the determination of the second- and third-order NLO properties, β and γ, of conjugated organic molecules and polymers in the nonresonant regime. At the macroscopic level, these properties are known as the second- order (x(2)) and third-order (x(3)) susceptibilities. For increasingly large oligomers tending toward the polymeric limit, the system is finite in the transverse and perpendicular directions but effectively infinite along the longitudinal direction. In the latter case, it is convenient to define the hyperpolarizability per unit cell, β/N or γ/N, which, in the infinite chain length limit, is equivalent to the nonlinear susceptibility.
TL;DR: In this article, an improved experimental technique for the suppression of the multiphoton fluorescence contribution in hyper-Rayleigh scattering experiments for the determination of the first hyperpolarizability of molecules in solution is presented.
Abstract: An improved experimental technique for the suppression of the multiphoton fluorescence contribution in hyper-Rayleigh scattering experiments for the determination of the first hyperpolarizability of molecules in solution is presented. This improvement allows for a better correction for the fluorescence artifact, so as to eliminate any overestimation for the value of the first hyperpolarizability. The measurement of the demodulation only of the fluorescence as a function of modulation frequency [Olbrechts et al., Rev. Sci. Instrum. 69, 2233 (1998)] is now complemented by the measurement of the phase lag between the intermediate scattering and the time-delayed fluorescence. From the simultaneous data reduction of demodulation and phase shift toward the hyperpolarizability, fluorescence contribution, and fluorescence lifetime, an improvement in precision of 1 order of magnitude is demonstrated. This level of precision has been used to show the relative impact of f-orbital filling and ligands on the molecular second-order nonlinear optical response of lanthanide complexes containing a hemicyanine chromophore.
TL;DR: In this article, a simple multiplicative scheme is proposed for the evaluation of the second-order nonlinear susceptibility of molecular crystals from the knowledge of the first hyperpolarizability of small molecular clusters.
Abstract: A simple multiplicative scheme is proposed for the evaluation of the second-order nonlinear susceptibility of molecular crystals from the knowledge of the first hyperpolarizability of small molecular clusters. The principle of this new scheme is illustrated at the semiempirical AM1 level for 3-methyl-4-nitroaniline crystal.
TL;DR: In this paper, the third nonlinear optical susceptibility (χ〈3〉) of a new family of octupolar molecules with one, two, and three double bonds was measured at 532 in tetrahydrofuran solutions by the degenerate four-wave mixing (DFWM) method.
Abstract: The third nonlinear optical susceptibility (χ〈3〉) of a new family of octupolar molecules with one, two, and three double bonds has been measured at 532 in tetrahydrofuran solutions by the degenerate four-wave mixing (DFWM) method. For comparison, we also measured the analogous dipolar subunits of the molecules. The second hyperpolarizability (γ) for these molecules was deduced. We found that octupolar molecules exhibit large second-order hyperpolarizability (γ) values. The γ values obtained for octupolar compounds are approximately 10 times larger than those of their corresponding dipolar subunits and 104 times larger than those of CS2, which is a reference material for DFWM.
TL;DR: The third-order optical nonlinear response was enhanced by the incorporation of silver d electrons into the delocalized conjugated organic pi system, and its magnitude is highly dependent upon the extent of the pi delocalization.
Abstract: A comparative study of the third-order nonlinear optical properties, via the newly developed heterodyned optical Kerr effect (OHD-OKE) measurements, of silver phenylacetylide and related compounds is reported. [AgC⋮CC6H5]n (1) was found to exhibit efficient third-order nonlinear optical susceptibility χ(3) of 2.4 × 10-14 esu, and second hyperpolarizability γ of 9.07 × 10-32 esu. These results are compared with those of two related silver phenylacetylide compounds, namely, a double salt, (silver phenylacetylide)·(silver tert-butylthiolate) [AgC⋮CC6H5·AgS(t-C4H9)]n complex (2), and a cluster, triphenylphosphine silver phenylacetylide tetramer, [(C6H5)3PAgC⋮CC6H5]4 (3), as well as that of the related organic polymer polyphenylacetylene (4). These four compounds represent different types of phenylacetylide derivatives: 1 is an organometallic polymer, 2 a polymeric double salt, 3 a discrete metal cluster, and 4 an organic polymer. It was found that the third-order optical nonlinear response was enhanced by th...
TL;DR: In this article, the Hartree−Fock and second-order Moller−Plesset levels using the 6-31G atomic basis set were computed for α,ω,nitro,amino-polyacetylene oligomers, containing up to 16 unit cells.
Abstract: Static as well as dynamic electronic and vibrational longitudinal first hyperpolarizabilities ( and ) of α,ω,-nitro,amino-polyacetylene oligomers, containing up to 16 unit cells, have been computed at the Hartree−Fock and second-order Moller−Plesset levels using the 6-31G atomic basis set. The curve of first hyperpolarizability per unit cell versus the number of unit cells presents a maximum that defines the optimal chain length for NLO applications. Modifications in electronic structure occurring when electron correlation is included lead to an increase in the height of the maximum by a factor of 2. A similar enhancement arises from the corresponding change in equilibrium geometry, which, in addition, shifts the position of the maximum toward longer chain lengths. Frequency dispersion also has a major effect on the position and magnitude of the optimal point. The contribution of the vibrational hyperpolarizability is relatively small when correlation and frequency dispersion are included. Our results are...
TL;DR: Large Gaussian-type geminal wave function expansions and direct perturbation theory of relativistic effects have been applied and it has been demonstrated that DPT is superior for this purpose to traditional Breit-Pauli calculations.
Abstract: Large Gaussian-type geminal wave function expansions and direct perturbation theory (DPT) of relativistic effects have been applied to calculate the relativistic contribution to the static dipole polarizability of the helium atom. It has been demonstrated that DPT is superior for this purpose to traditional Breit-Pauli calculations. The resulting value of the molar polarizability of 4He is 0.517254(1) cm3 x mol(-1), including a literature estimate of QED effects. As a by-product, a very accurate value of the nonrelativistic helium second hyperpolarizability, gamma = 43.104227(1) atomic units (without the mass-polarization correction), has been obtained.
TL;DR: Oligo(1,4-phenyleneethynylene)s 1a−e, with solubilizing propoxy side chains, were prepared by use of Hagihara−Sonogashira coupling reactions.
TL;DR: In this paper, the first-order hyperpolarizability of the highly nonlinear organic salt 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST, βzzz=(1540±250)×10-40m4/V at λ = 1542 nm) and the cocrystal 4-2-[1-(2-hydroxyethyl)-4-pyridylidene]-ethylidene}-cyclo-hexa-2,5-
Abstract: We determine the molecular first-order hyperpolarizability β of the highly nonlinear organic salt 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST, βzzz=(1540±250)×10-40 m4/V at λ = 1542 nm) and the cocrystal 4-{2-[1-(2-hydroxyethyl)-4-pyridylidene]-ethylidene}-cyclo-hexa-2,5-dien-1-one)–(methyl 2,4-dihydroxybenzoate) (M2-MDB, βzzz=(1510±250)×10-40 m4/V at λ = 1907 nm) in solution. These values are compared with the molecular first-order hyperpolarizabilities in the solid state, calculated with the measured nonlinear optical coefficient of the crystals. For both materials we show that the molecular nonlinearity in the solid state is considerably smaller than in solution. This lowering of the nonlinearity is attributed to the relatively strong Coulomb interactions in DAST and to the very strong hydrogen bonding in M2-MDB.
TL;DR: In this article, a donor-acceptor conjugated copolymer consisting of the electronaccepting moiety 2,7-diethynylfluorene and the electron-donating moiety tetraphenyldiaminobiphenyl (TPD) was synthesized via Pd-catalyzed coupling reactions.
Abstract: A novel donor−acceptor conjugated copolymer consisting of the electron-accepting moiety 2,7-diethynylfluorene and the electron-donating moiety tetraphenyldiaminobiphenyl (TPD), i.e., poly{(2,7-diethynyl-9,9-di-2-ethylhexylfluorene)-alt-co-[N,N‘-diphenyl-N,N‘-bis(4-phenyl)-1,1‘-biphenyl-4,4‘-diamine]} (TPD-PFE), and its cousins without the alkyne or TPD segments, namely, poly{(9,9-di-2-ethylhexyl-2,7-fluorene)-alt-co-[N,N‘-diphenyl-N,N‘-bis(4-phenyl)-1,1‘-biphenyl-4,4‘-diamine]} (TPD-PF) and poly(2,7-9,9-di-2-ethylhexylfluorenyleneethynylene) (PFE), were synthesized via Pd-catalyzed coupling reactions. The third-order nonlinear optical (NLO) properties of these polymers were characterized using a femtosecond time-resolved optical Kerr effect technique. The ultrafast second-order hyperpolarizability of TPD-PFE was estimated to be as large as 4.5 × 10-30 esu in the nonresonant region, larger than those of its counterparts. The electronic transitions of the fluorene-based polymers can be readily tuned by vary...
01 Jan 2001
TL;DR: In this paper, the first hyperpolarizability β of organic and organometallic molecules for nonlinear optics (NLO) applications has been described and the theoretical methods which have been employed to calculate these properties are discussed.
Abstract: Publisher Summary This chapter focuses on how to design, characterize, and optimize the first hyperpolarizability β of organic and organometallic molecules for nonlinear optics (NLO) applications. The chapter also presents NLO effects and examines the relation between molecular and macroscopic NLO properties. The theoretical methods which have been employed to calculate these properties are discussed. The chapter presents a description of methods for the experimental determination of molecular second-order (SO) NLO parameters with emphasis on the recently widely used hyper-Rayleigh scattering (HRS) technique. The different types of compounds which have been synthesized and characterized for SO NLO are discussed for organic and organometallic molecules, respectively, up to the recent developments in this field. A number of criteria which these compounds have to meet for applications and some materials aspects are also considered in the chapter.
16 Apr 2001
TL;DR: In this article, a set of donor-acceptor complexes derived by functionalizing two organic acceptors with a donor such as ferrocene or an aromatic ring through a hyper-Rayleigh scattering in solution has been measured by hyperpolarizability.
Abstract: First hyperpolarizability ( β ) of a set of donor–acceptor complexes derived by functionalizing two organic acceptors with a donor such as ferrocene or an aromatic ring through a –CN– linkage has been measured by hyper-Rayleigh scattering in solution. Spectral analysis of the second harmonic scattered light reveals that there is a significant two-photon fluorescence (TPF) contribution to the total signal in some compounds. In fact, the TPF contribution was as high as ∼25% in two compounds. The measured β values after correcting for TPF indicate that these molecules possess high second order nonlinearity, much larger than similar organic compounds or charge transfer complexes formed by ferrocenyl donors and organic acceptors. The dispersion free β values of these complexes have been calculated using two different methods depending on the nature of the complex. The conventional nonresonant two-state model which gives a good estimate of the intrinsic second order polarizability away from resonance, has been applied to compounds with no absorption around the second harmonic wavelength. Another model in which a damping parameter related to the inhomogeneous line width of the absorption band near the second harmonic frequency is used for obtaining reliable values of β 0 , has been employed for the other compounds. In conjugation with anthraquinone as acceptor, ferrocene as a donor appears to be a better choice for quadratic nonlinear optics applications than conventional organic donors.
TL;DR: In this article, four kinds of polyurethanes (PUs) containing azo chromophore groups with different molecular hyperpolarizability (β ) as side chains were synthesized and their second-order nonlinear optical (NLO) properties studied.
TL;DR: In this paper, the transient and the instantaneous nonlinear optical (NLO) response of C60 and the higher fullerenes C70, C76, C84 dissolved in toluene using, respectively, the z-scan technique and energy-dependent transmission measurements with 532 nm, 10 ns laser pulses, and the optical Kerr effect with 800 nm, 100 fs laser pulses.
Abstract: We report results on the transient and the instantaneous nonlinear optical (NLO) response of C60 and the higher fullerenes C70, C76, C84 dissolved in toluene using, respectively, the z-scan technique and energy-dependent transmission measurements with 532 nm, 10 ns laser pulses, and the optical Kerr effect with 800 nm, 100 fs laser pulses. The NLO measurements on C76 are the first reported for this fullerene. The second hyperpolarizability γ of the fullerenes has a negative sign in both nanosecond and femtosecond pulse regimes. The transient response value of γ(C70) and the instantaneous response of γ(C76) were much larger than expected from the theoretically predicted smooth dependence of γ on fullerene size. The degree of validity is discussed for factors such as molecular symmetry, molecular volume, aromaticity and other molecular properties previously considered as determining fullerene-size dependence of γ. The observed trends and anomalies are explained, for the transient response, in terms of electronic-state population-dependent photophysical properties and, for the instantaneous response, by inclusion of photon resonance effects.
TL;DR: In this paper, the disappearance of the angular dependence of the nonlinear scattering is shown to be a consequence of the solubilization of the large purple membrane patches into individual protein monomers.
Abstract: From the angular dependence of the second-order nonlinear light scattering (hyper-Rayleigh scattering) from a suspension of purple membrane, bacteriorhodopsin was recently shown to exhibit (nonlinear) photonic crystal properties [Opt. Lett.25, 1391 (2000)]. The optical nonlinearity, i.e., the first hyperpolarizability β, is localized in the small retinal moiety, whereas the optically linear refractive index n is relevant to the large membrane protein. The combination of the nonlinear hyperpolarizability of the retinal decoupled from the linear refractive index of the protein explains the observed angular dependence. The temporal evolution of this angular dependence has now been analyzed. The disappearance of the angular dependence of the nonlinear scattering is shown to be a consequence of the solubilization of the large purple membrane patches into individual protein monomers. This result strongly suggests that decoupling of the optical nonlinearity from the phase-matching condition for coherent second-harmonic generation will result in highly efficient coherent second-harmonic generation in bacteriorhodopsin crystals. In addition, a simulation of the bandgap properties was made for an abstracted structure with a large refractive index for the retinal and with a small refractive index for the protein matrix.
01 Nov 2001
TL;DR: In this paper, a new fluorescent molecule of the HBO family, 2-(2′-hydroxy-4′-aminophenyl)-6-nitrobenzoxazole (BO6), was synthesized, purified and characterized, including solvent environments of distinct polarities.
Abstract: With regard to second-order nonlinear optics (NLO) applications, a new class of 2-(2′-hydroxyphenyl)benzoxazoles (HBO) was designed for a combination of high first hyperpolarizability, β, with good photothermal stability, in association with a fast excited state intramolecular proton transfer (ESIPT) mechanism. Semi-empirical optimization of molecular structures and ab initio calculations of dipole moments were performed. Clear evidence was found that conditions such as conjugation efficiency and electron donor/acceptor strength cannot be evaluated separately, due to structural changes in molecular spatial distribution. Experimentally, a new fluorescent molecule of the HBO family, 2-(2′-hydroxy-4′-aminophenyl)-6-nitrobenzoxazole (BO6), was synthesized, purified and characterized, including solvent environments of distinct polarities. Hyper-Rayleigh scattering, UV–Vis absorption and emission spectroscopy, differential scanning calorimetry and thermogravimetric analysis of BO6 show a significant β (213.4±25.7×10−30 esu in acetone, at 1064 nm) and thermal stability up to 270 °C. Such results, in this first study of ESIPT dyes for second-order NLO to our best knowledge, indicate that the HBO family well deserves further attention towards promising application materials.
TL;DR: Vibrational contributions to the dipole polarizabilities and hyperpolarizabilities of cyclopropenone and cycloprostenethione are reported in this paper, where the results have been analyzed and interpreted in terms of different structural and electronic features of the studied molecules: i.e., oxygen-sulfur replacement, saturation of the carbon ring, and removal of the intramolecular strain.
Abstract: Vibrational contributions to the dipole polarizabilities and hyperpolarizabilities of cyclopropenone and cyclopropenethione are reported Simultaneous calculations have been carried out for the respective saturated and noncyclic counterparts of these molecules The results have been analyzed and interpreted in terms of different structural and electronic features of the studied molecules: ie, the oxygen–sulfur replacement, the saturation of the carbon ring, and the removal of the intramolecular strain For static dipole polarizabilities the vibrational contribution computed at the molecular equilibrium geometry can account for more than 10% of the total value for a given component of the tensor Both the zero-point vibrational average and pure vibrational terms are important for most of the studied molecules In the case of the first dipole hyperpolarizability the total vibrational correction is dominated by the pure vibrational term The vibrational corrections to dipole polarizabilities show certain regularities which can be interpreted in terms of the electronic structure of the investigated molecules Much less clear is the pattern of behavior for the first dipole hyperpolarizability It has been found, however, that the analysis of these data is greatly facilitated by the separate consideration of the nuclear relaxation and curvature terms Limited study of the frequency dependence of the calculated vibrational corrections shows that in the case of the dipole polarizability, they are almost quenched to zero In contrast, at nonzero frequencies, the vibrational contribution to the first dipole hyperpolarizability tensor β(−ω;ω,0), which determines the so-called electro-optic Pockels effect, can be as important as the pure electronic term
TL;DR: In this article, the first hyperpolarizabilities of azobenzene dendrimers were analyzed for three types of dimers: two azobenzenes linked covalently head-to-tail, linear and parallel.
Abstract: To find out why azobenzene dendrimers, which are branched three-dimensional macromolecules with a branch point at each of the donor−acceptor-functionalized azobenzene monomeric units, have large first hyperpolarizabilities, we used theoretical calculations for three types of dimers: (1) two azobenzenes linked covalently head-to-tail; (2) linear dimers where the two azobenzenes are nearly superimposable on the covalently bonded dimers but are not covalently linked; (3) parallel dimers where the two azobenzenes are roughly side by side. We found from ab initio calculations that the optimized geometry is roughly linear for the first type and is nearly parallel and slightly staggered for the third type. We also found that the first hyperpolarizabilities for the linear dimers are larger than those obtained from the sum of the hyperpolarizability tensors for the individual monomers and that those for the parallel dimers are smaller. These findings led us to conclude that the noncentrosymmetric arrangement of t...
TL;DR: In this paper, the first molecular hyperpolarizabilities of a series of thiophene-based organic chromophores were determined using this excitation wavelength to help shed light on their frequency dependence.
TL;DR: In this paper, the dipole moment, parallel dipole polarizability, and the parallel first hyperpolarizability of the coinage metal hydrides (CuH, AgH, AuH) are studied in the context of their vibrational contributions.
Abstract: The dipole moment, parallel dipole polarizability, and the parallel first hyperpolarizability of the coinage metal hydrides (CuH, AgH, AuH) are studied in the context of their vibrational contributions. The partition of the property values into pure electronic, vibrational averaging, and pure vibrational terms is discussed, and the corresponding contributions are calculated by means of the field-dependent Numerov–Cooley integration technique. The potential energy and property surfaces, required for the evaluation of these contributions, follow from different high-level electronic structure calculations. Parallel to the nonrelativistic studies, a relativistic treatment of the investigated properties has been carried out. It has been found that relativistic effects significantly reduce the magnitude of the vibrational corrections to the studied properties. A particularly large relativistic reduction has been found for the vibrational contribution to the first hyperpolarizability. The relativistic effect is enhanced with increasing nuclear charge of the heavy atom, and can be interpreted in terms of the relativistic effect on the potential energy and electric property curves.