Showing papers on "Hyperpolarizability published in 1998"

Assessment of Conventional Density Functional Schemes for Computing the Polarizabilities and Hyperpolarizabilities of Conjugated Oligomers: An Ab Initio Investigation of Polyacetylene Chains

Abstract: DFT schemes based on conventional and less conventional exchange-correlation (XC) functionals have been employed to determine the polarizability and second hyperpolarizability of π-conjugated polyacetylene chains. These functionals fail in one or more of several ways: (i) the correlation correction to α is either much too small or in the wrong direction, leading to an overestimate; (ii) γ is significantly overestimated; (iii) the chain length dependence is excessively large, particularly for γ and for the more alternant system; and (iv) the bond length alternation effects on γ are either underestimated or qualitatively incorrect. The poor results with the asymptotically correct van Leeuwen–Baerends XC potential show that the overestimations are not related to the asymptotic behavior of the potential. These failures are described in terms of the separate effects of the exchange and the correlation parts of the XC functionals. They are related to the short-sightedness of the XC potentials which are relatively insensitive to the polarization charge induced by the external electric field at the chain ends.

Structure−Property Relationships in Third-Order Nonlinear Optical Chromophores

Abstract: Scientists have sought for over two decades to incorporate the necessary attributes of transparency, stability, and high nonlinear susceptibilities into optimized organic or organometallic chromophores for third-order nonlinear optical (NLO) applications. These investigations have provided an ever-expanding understanding of structure−function relationships for the second hyperpolarizability γ and the bulk third-order nonlinear optical susceptibility χ(3) in organic materials, which are reviewed herein. Contributing to this understanding are the studies of the third-order NLO properties displayed by an array of structurally related organic chromophores based on the conjugated carbon skeletons of hex-3-ene-1,5-diynes (1,2-diethynylethenes, DEEs) and 3,4-diethynylhex-3-ene-1,5-diynes (tetraethynylethenes, TEEs). A comprehensive series of donor (D) and/or acceptor (A) substituted derivatives of DEEs and TEEs has been measured by third-harmonic generation (THG) experiments, and the investigations on these one-...

A systematic study of basis set, electron correlation, and geometry effects on the electric multipole moments, polarizability, and hyperpolarizability of HCl

Abstract: The electric multipole moments, dipole and quadrupole polarizability and hyperpolarizability of hydrogen chloride have been determined from an extensive and systematic study based on finite-field fourth-order many-body perturbation theory and coupled-cluster calculations. Our best values for the dipole, quadrupole, octopole and hexadecapole moment at the experimental internuclear separation of Re=2.408 645a0 are μ=0.4238ea0, Θ=2.67ea02, Ω=3.94ea03, and Φ=13.37ea04, respectively. For the mean and the anisotropy of the dipole polarizability ααβ we recommend ᾱ=17.41±0.02 and Δα=1.60±0.03e2a02Eh−1. For the mean value of the first dipole hyperpolarizability βαβγ we advance β=−6.8±0.3e3a03Eh−2. Extensive calculations with a [8s6p6d3f/5s4p2d1f] basis set at the CCSD(T) level of theory yield the R-dependence of the Cartesian components and the mean of the second dipole hyperpolarizability γαβγδ(R)/e4a04Eh−3 around Re as γzzzz(R)=1907+1326(R−Re)+570(R−Re)2+10(R−Re)3−40(R−Re)4, γxxxx(R)=3900+747(R−Re)−65(R−Re)2−38...

Measurement of the electric quadrupole moments of CO2, CO, N2, Cl2 and BF3

Abstract: The electric quadrupole moments of a number of molecules have been determined from measurement of the birefringence induced in a gas by an electric field gradient. The values obtained are: carbon dioxide (− 14·27 ± 0·61)x 10−40 C m2, carbon monoxide (− 9·47 ± 0·15)x 10−40 C m2, nitrogen (− 4·65±0·08)x 10−40 C m2 and boron trifluoride (12·6±0·7)x 10−40 C m2. In the calculation of the moments for carbon monoxide and boron trifluoride the small hyperpolarizability contribution was neglected in the absence of known values. By means of the Jones calculus a detailed analysis was made of the effects of strain birefringence in the cell windows and imperfect orientation of polarizing components in the light path. This analysis led to a measurement procedure which yielded results significantly different from previously reported ones obtained with essentially the same apparatus. The probable error in the earlier procedure is identified.

Remarkable NLO response and infrared absorption in simple twisted molecular π-chromophores

Abstract: Computational modeling reveals that, by substitutional modification of interplanar dihedral angles in a series of quinopyrans, both the optical absorption cross section and the first hyperpolarizability can be widely tuned in both frequency and magnitude. This is a promising structural control scheme for modulating molecular nonlinear optical and infrared absorption properties. The maximum nonresonant μβ estimated for a tetraalkyl-substituted 4-quinopyran, the full AM1-optimized interplanar dihedral angle of which is 104°, is ∼70000 × 10-48 esu, at an excitation energy of 0.10 eV. This is 4 orders of magnitude larger than that of the archetypical NLO chromophore, 4-N,N‘-(dimethylamino)-4‘-nitrostilbene, at the same excitation frequency. The effects of conjugation pathway, strength of the electron donor/acceptor groups, and auxiliary donor and acceptor on the molecular response properties have also been analyzed. The optical absorption at a twist angle of 90°, when the molecule can be described as two disj...

Solvent dependence of the first hyperpolarizability of p-nitroanilines: Differences between nonspecific dipole-dipole interactions and solute-solvent H-bonds

Abstract: In this paper, the influence of solvents on the first hyperpolarizability β of nonlinear optical (NLO) molecules is studied at 25 °C for solutions of p-nitroaniline and N,N-dimethyl paranitroaniline in some 50 solvents belonging to different classes. The hyperpolarizabilities deduced from measured hyper-Rayleigh scattering are the relative ones with as reference that of paranitroaniline in 1,4-dioxane. Taking for the latter the literature value of 16.9 10−30 esu, the β values vary from 14.4 to 29.9 10−30 esu for paranitroaniline and from 28.7 to 46.2 10−30 esu for N,N-dimethyl paranitroaniline. A selection of the solvents is made on the basis of the fraction of the time γ0 during which the NLO molecule is not involved in H-bonding with the solvent molecules. γ0 can be determined from the solubility in the given solvent. The formation of specific solute–solvent interactions as H-bonds always increases the hyperpolarizability β. In the absence of such interactions, the hyperpolarizability increases with the...

Electronic Stark Effect Studies of a Porphyrin-Based Push−Pull Chromophore Displaying a Large First Hyperpolarizability: State-Specific Contributions to β

Abstract: Electroabsorption or Stark effect spectroscopy has been applied to a pair of porphyrin-based chromophores with the aim of deriving a detailed understanding of the origin of the remarkable first hyperpolarizability, β, of one of the chromophores: [5-[[4‘-(dimethylamino)phenyl]ethynyl]-15-[(4‘‘-nitrophenyl)ethynyl]-10,20-diphenylporphinato]zinc(II). The measurements show that significant changes in molecular dipole moment, Δμ, accompany excitations of x-polarized transitions of the aminophenyl (donor)/nitrophenyl (acceptor) functionalized chromophore, but are absent for a related chromophore lacking the donor and acceptor groups. For linear chromophores, changes in dipole moment are a prerequisite to effective molecular first hyperpolarization and incident light frequency doubling behavior. A more detailed consideration of the available |Δμ| data, within the context of a conventional two-level model, has yielded the following: (a) specific information about the roles of each of seven electronic and vibron...

Solvent Effects on Linear and Nonlinear Optical Properties of Donor−Acceptor Polyenes: Investigation of Electronic and Vibrational Components in Terms of Structure and Charge Distribution Changes

Abstract: We investigate the influence of solvation media upon the relationship among structure, spatial distribution of electron density, and linear and nonlinear electric properties for two series of push−pull π-conjugated molecules. The analysis is performed on both electronic and vibrational components of static polarizability and first hyperpolarizability, and the effects solvent induce on them are analyzed singularly within the framework of the polarization continuum model. Solvent is found to affect the extent of charge separation induced in the ground state of these molecules. This charge separation leads to a geometric distortion, measured by the bond-length-alternation (BLA) parameter, which shows a solvent-induced evolution of the molecular geometry from a neutral, bond-alternated polyene-like structure, to a partially ionic cyanine-like structure, and ultimately to an ionic bond-alternated structure. As a consequence large changes in the linear and nonlinear response properties are found, in both their ...

Relationship between static vibrational and electronic hyperpolarizabilities of π-conjugated push–pull molecules within the two-state valence-bond charge-transfer model

Abstract: The two-state valence-bond charge-transfer (VB-CT) model for π-conjugated push–pull molecules is analyzed to yield several parameter-independent relations between vibrational and electronic hyperpolarizabilities. Ab initio computational tests show that these relations are not satisfied. As a byproduct of the ab initio calculations, we have found cases where the static vibrational first hyperpolarizability is much larger than the static electronic first hyperpolarizability. Our results also shed light on a controversy regarding normal coordinate polarizability derivatives.

Calculation of macroscopic first-, second-, and third-order optical susceptibilities for the urea crystal

Abstract: Macroscopic first-, second-, and third-order susceptibilities of the urea crystal are calculated using static and frequency-dependent ab initio molecular (hyper)polarizabilities at the self-consistent field (SCF) and second-order-Mo/ller–Plesset (MP2) levels. Environmental effects are taken into account using a rigorous local-field theory and are compared with the anisotropic Lorentz field factor approximation. The electric field arising from the permanent dipoles of the surrounding molecules is explicitly taken into account using a self-consistent approach. The dipole moment and the first hyperpolarizability are particularly strongly dependent on this field, but the crystal structure leads to a fortuitous cancellation of the field effect on the second-order susceptibility. The experimental linear susceptibility is accurately reproduced, while differences remain for the quadratic susceptibility. Dispersion curves for the first-order susceptibility, and results for quadratic electrooptic effect (QEO), elec...

Simple finite field method for calculation of static and dynamic vibrational hyperpolarizabilities: Curvature contributions

Abstract: In the static field limit, the vibrational hyperpolarizability consists of two contributions due to: (1) the shift in the equilibrium geometry (known as nuclear relaxation), and (2) the change in the shape of the potential energy surface (known as curvature). Simple finite field methods have previously been developed for evaluating these static field contributions and also for determining the effect of nuclear relaxation on dynamic vibrational hyperpolarizabilities in the infinite frequency approximation. In this paper the finite field approach is extended to include, within the infinite frequency approximation, the effect of curvature on the major dynamic nonlinear optical processes.

Molecular Polarizability and First Hyperpolarizability of Octupolar Molecules: Donor-Substituted Triphenylmethane Dyes

Abstract: Molecular polarizabilities and hyperpolarizabilities of a series of octupolar molecules that are donor-substituted triphenylmethane dyes are calculated. The four-state model of an octupolar molecul...

Octupolar versus dipolar crystalline structures for nonlinear optics: A dual crystal and propagative engineering approach

Abstract: A new type of crystalline structure for nonlinear optics whereby octupolar symmetry features are displayed at both molecular and crystalline levels is exemplified by the prototype 2,4,6-triaryloxy-1,3,5-triazine (TPOT) crystal and analyzed in terms of both individual molecular responses and crystal packing features. Polarized harmonic light scattering permits the full determination of the molecular β hyperpolarizability tensor and confirms the octupolar trigonal symmetry of the TPOT molecule. An oriented gas model is used to infer therefrom an estimate of the crystalline nonlinear d tensor which is predicted to be of the same order as that of the reference dipolar N-4-nitrophenyl-(L)-prolinol crystal. The concept of optimal packing toward quadratic nonlinear optics, which had been initially introduced in the realm of quasi-one-dimensional structures, is revisited and enlarged to encompass more isotropic uniaxial structures potentially amenable, in the case of octupoles, to larger optimal values than in the one-dimensional case. Moreover, considerations pertaining to phase matching which had been left aside in the earlier one-dimensional optimization framework are now considered and the various type I and type II configurations compared for both one-dimensional and octupolar uniaxial structures. Application perspectives of octupolar structures toward short pulse nonlinear optics are discussed: their structurally built-in polarization independence is outlined as a major asset in contrast with the more traditional one-dimensional structures.

Versatile optical materials: fluorescence, non-linear optical and mesogenic properties of selected 2-pyrazoline derivatives

Abstract: A study of the structure-property relationships in a series of 3-(4-n-decyloxyphenyl)-1-(p-X-phenyl)-2-pyrazolines has been performed. By simply changing the substituent in the 1-phenyl ring we were able to tune the physical properties of the compounds. If this ring is non-substituted or substituted with a 4-methoxy, 4-chloro or 4-carboxy group, the pyrazoline compounds are fluorescent. If the ring is 4-nitro- or 2,4-dinitro-substituted, the compounds have interesting second-order non-linear optical properties. The first hyperpolarizability has been measured using the Hyper-Rayleigh Scattering technique in solution. The 4-nitro derivative displays liquid crystalline behaviour, showing a monotropic smectic A phase with a partial bilayer structure due to an antiparallel arrangement of molecules as confirmed by X-ray studies in the mesophase.

New class of high hyperpolarizability organic chromophores and process for synthesizing the same

Abstract: A new class of high hyperpolarizability organic chromophores and a process for synthesizing the same. The chromophores incorporate at least one organic substituent and are formed in consideration of molecular shapes and a spatial anisotropy of intermolecular interactions. The chromophores are processed into hardened material lattices to lock-in poling induced electric-optic activity. Preferred organic substituents are alkyl, aryl, and isophorone groups. A composite including the organic chromophore, in a preferred embodiment, includes a polymer such as a poly(methylmethacrylate), polyimide, polyamic acid, polystyrene, polycarbonate or polyurethane. The optimized chromophores result in hardened electro-optic polymers suitable for electro-optic modulators and other devices such as optical switches. These modulators can be configured to work at high frequencies and in arrays for applications in communications and network connections. In addition, they can be implemented in series and parallel combinations in phased array radar, signal processing and sensor technology applications.

Conformation and Solvent Dependence of the First Molecular Hyperpolarizability of Pyridinium-N-Phenoxide Betaine Dyes. Quantum Chemical Calculations

Abstract: The static and frequency-dependent first hyperpolarizabilities (β) of Reichardt's betaine dye and two simplest pyridinium-N-phenoxide betaines were computed in the gas phase and in aqueous solution. The sum-over-state formalism was used to calculate individual components of the β-tensors. The solvent effect was included via the Langevin dipoles/Monte Carlo approach. The influence of the molecular geometry on the β values of the betaine dyes was investigated as well. The calculations demonstrate that the β values strongly depend on the interplanar angle between the pyridinium and the phenoxide ring. Moreover, we observed dramatically decreased values of β (for all investigated betaines) in aqueous solution as compared to the gas phase.

Nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties by means of electrical property expansions: Application to HF, CH4, CF4, and SF6

Abstract: Electrical property derivative expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any molecule) makes an important contribution to the static second vibrational hyperpolarizability of CF4 and SF6. A comparison between calculated and experimental values for the difference between the (anisotropic) Kerr effect and electric field induced second-harmonic generation shows that, at the Hartree–Fock level, the nuclear relaxation/infinite frequency approximation gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small.

Electric and magnetic properties of fullerenes

Abstract: We present fully analytical ab initio calculations of the electric polarizability, the second hyperpolarizability, and the magnetizability of the fullerenes C70 and C84 at the self-consistent field level of theory using large basis sets and—in the case of the magnetizability—London atomic orbitals in order to obtain gauge-origin independent results. These calculations are the first ab initio studies of such properties for C70 and C84, and all results are expected to be of near Hartree–Fock limit quality. By comparison with similar results reported earlier for C60, valuable insight into the electronic structure of the fullerenes is obtained.

Hyper-Rayleigh scattering study of η5-monocyclopentadienyl–metal complexes for second order non-linear optical materials

Abstract: A series of ionic η5-monocyclopentadienyl–metal compounds possessing p-substituted benzonitrile ligands has been studied by hyper-Rayleigh scattering at the fundamental wavelength of 1.064 µm. Upon systematic variation of the metal ion, the first hyperpolarizability β was found to increase along the sequence Co, Ni, Ru, Fe, with about a three-fold increase from Ru to Fe. This yields very high values for the iron complexes, e.g., β=410×10–30 esu for [Fe(η5-C5H5)(dppe)( p-NCC6H4NO2)]+ [PF6 ]– dissolved in methanol. The high β values are attributed to π back-donation resulting in an extension of the conjugated π-system from the FeII organometallic fragment, acting as a good donor group, via the nitrile to the acceptor group NO2 . Complexes with single phenyl rings as conjugated chains perform better than their biphenyl analogues, which is explained in terms of non-planarity of the coordinated biphenyl ligands in solution. By comparing complexes with electron donor and acceptor substituted ligands it is demonstrated that the organometallic moiety can be used as an extremely effective donor group but not as a good acceptor group.

Nonlinear Optical Properties of Correlated Chromophores in Organic Mesoscopic Superstructures

Abstract: A new design strategy for enhanced nonlinear optical properties, based on a simple vector model and situated at the mesoscopic level, between the microscopic molecular level and the macroscopic bulk, is explained and exemplified by a number of organic superstructures. The second-order nonlinear optical properties of the structures are analyzed in terms of the corresponding properties of the individual monomeric chromophores that constitute the structure. The chromophores can be considered as electronically independent with a high symmetry. A simple vector model can then account for the large secondorder nonlinear optical polarizability of the mesoscopic superstructure. Another important advantage that is clear from the vector analysis is the improved chromophore alignment, owing to the enlarged mesoscopic dipole moment. Organic molecular materials have been proposed as potential candidates for constructing a number of nonlinear optical (NLO) devices, such as frequency-doublers, electrooptic modulators, all-optical modulators, and holography devices. The former two are situated in the field of secondorder nonlinear optics. Such devices are already heavily used in information transmission and two-dimensional data storage, albeit on an inorganic basis. The latter two devices, based on organic materials, are on the verge of being used for information handling and three-dimensional data storage, based on third-order NLO effects. In our modern society with ever increasing need for information retrieval, handling, and storage capacity, there is a need for fast devices that can manipulate all-optical information. Owing to the purely electronic nature of the NLO response in organic molecular materials, devices based on organics are inherently fast. Modulation bandwidths of 100 GHz for electrooptic modulation in a polymer have been reported. The magnitude of the nonlinear response at the molecular level can also be extremely large. Incorporation of the individual molecules, with their large molecular first hyperpolarizability and fast response, into bulk devices with large and stable NLO susceptibilities, is not so straightforward as inorganic crystal growth. In this article, we will describe a strategy to enhance the NLO response at the mesoscopic

Third-order nonlinear optical properties of new bisdithiafulvenyl-substituted tetrathiafulvalene

Abstract: We measured the third-order susceptibilities χijkl〈3〉 of new bisdithiafulvenyl-substituted tetrathiafulvalene, using the degenerate four-wave mixing method. From these measurements we deduced the values of the second-order hyperpolarizabilities γ and their molecular and electronic contributions. We compared the third-order optical properties of these new extended tetrathiafulvalene derivatives with the properties of acetylenic and ethylenic analogs of tetrathiafulvalene that we studied previously. All organic molecules studied here revealed large third-order nonlinear optical hyperpolarizability.

Nonlinear optical response of molecules in a nonequilibrium solvation model

Abstract: The response equations governing nonequilibrium solvation in the continuum approach are derived and implemented for second order in response theory. Applications to a simple benchmark system consisting of a solvated water molecule are presented. We consider the role of nonequilibrium solvent configurations on the first hyperpolarizability. Effects of solvation parameters, such as optical and static dielectric constants, and frequency dispersion are discussed.

Second molecular hyperpolarizability of 2,2′-diamino-7,7′-dinitro-9,9′- spirobifluorene: An experimental study on third-order nonlinear optical properties of a spiroconjugated dimer

Abstract: Nonlinear optical properties of a fixed molecular dimer, 2,2′-diamino-7,7′-dinitro9,9′-spirobifluorene (ANSF), have been investigated in solution by the degenerate four-wave mixing technique. It has been observed that the orientationally averaged second molecular hyperpolarizability of ANSF in THF is enhanced ten times in comparison with its monomer unit, 2-amino-7-nitrofluorene. Since electronic coupling between monomer units in ANSF is negligible owing to symmetry, we attribute the large enhancement to the orientational effect of the two constituting dipoles with possible involvement of vibronic coupling and spiroconjugation.

Aspects of Intervalence Charge Transfer in Cyanide-Bridged Systems: Modulated Electric Field Assessment of Distances, Polarizability Changes, and Anticipated First Hyperpolarizability Characteristics

Abstract: Electroabsorption studies of the systems (CN)5MII−CN−M‘III(NH3)51- (M = Fe, Ru, Os; M‘ = Ru, Os) reveal that the metal-to-metal or intervalence charge-transfer transitions are associated with a change in dipole moment, |Δμ|, ranging from 11 to 17 D. This change corresponds to a charge-transfer distance of ca. one-half to two-thirds of the geometric separation between the donor and acceptor metals. This result has consequences for electron transfer parameters, where electronic coupling energies are now upwardly revised to as high as 3000 cm-1. The result is also pertinent in the context of nonlinear optics, where Δμ can be utilized in a two level model to estimate wavelength-dependent molecular first hyperpolarizabilities. The change in polarizability (Δα) accompanying the optical intervalence transitions varies from −10 to +310 A3. Comparing the experimental results to a simple two state model suggests that the two state picture is seriously deficient for these systems and that a multitude of available ad...

Dual Influence of H-Bonding on the Solid-State Second- Harmonic Generation of a Chiral Quinonoid Compound

Abstract: A new chiral push−pull quinonoid compound, 7,7-bis(3(R)-hydroxypyrrolidino)-8,8-dicyanoquinodimethane (BHPDQ), has been synthesized. Powder studies indicate an appreciable second harmonic generation (SHG) capability, and crystal structure analysis reveals extensive intermolecular H-bonding in BHPDQ. The influence of H-bonding and molecular chirality on the dipole alignment in the crystal is described. The H-bonds play an unusual role of modifying the molecular structure by producing an enhanced molecular twist in BHPDQ; this in turn affects the molecular hyperpolarizability. Thus we describe a novel instance wherein the powder SHG in a molecular material is determined by the dual influence of intermolecular H-bonding on the crystal structure as well as on the molecular structure and hyperpolarizability. The new dimension that this observation adds to the general theme of molecular materials design is highlighted.

Synthesis and (Non)linear Optical Properties of a Series of Donor-Oligopyrrole-Acceptor Molecules,

Abstract: The Pd-catalyzed cross-coupling reaction involving organostannanes (Stille reaction) is applied to prepare a series of N-t-BOC-protected D−π−A oligopyrroles. After purification, oligomers with one to four pyrrole units inserted between a 4-nitrophenyl and a 4-methoxyphenyl group are isolated in yields between 20 and 47%. Only minor differences in the linear optical properties are observed for the four oligomers. The charge-transfer band around λmax = 365 nm shows a small, unexpected, hypsochromic shift, while the π−π* band around λmax = 285 nm shows a small, expected, bathochromic shift upon elongation of the molecule. Their nonlinear optical properties, however, show a surprising proceeding; going from the D−π−A oligomer with one pyrrole unit to that with three pyrrole units, the hyperpolarizability, as measured by hyper-Rayleigh scattering, increases additionally with the number of pyrrole units within the oligomer, up to 277 × 10-30 esu in case of the trimer. On the basis of the assumption that both tr...

Static electric properties of lih : explicitly correlated coupled cluster calculations

Abstract: Explicitly correlated MBPT-R12 and coupled cluster [up to CCSD(T)-R12] methods have been used in calculations of various (vibrationless) electrical properties for the LiH molecule, including the dipole and quadrupole moments, dipole and quadrupole polarizability tensors, dipole hyperpolarizability tensors, and the second dipole hyperpolarizability tensors. Generally, with extension of the basis set the R12 method did not lead to faster convergence for the calculated properties towards the basis limit. Nevertheless, R12 calculations serve as useful indicators to judge the reliability of the results, and substantially help in determining the accuracy. Results obtained with the 11s8p6d5f/9s8p6d5f basis and CCSD(T)-R12 calculated within this work should be close to the basis set limit.