Showing papers on "Hyperpolarizability published in 2009"
TL;DR: Intramolecular charge transfer responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally and the first hyperpolarizability of the molecule is calculated.
279 citations
TL;DR: The Coulomb-attenuating method (CAM-B3LYP) was found to remove to large parts the overestimation observed for standard methods and in many cases provides results close to those of coupled cluster calculations.
Abstract: The polarizability and second hyperpolarizability of polyacetylene oligomer chains of increasing size up to C24H26 were investigated by means of the Coulomb-attenuating method (CAM-B3LYP) using response theory. It was found that this long-range corrected density functional removes to large parts the overestimation observed for standard methods and in many cases provides results close to those of coupled cluster calculations. A direct comparison to experimentally observed dynamic hyperpolarizabilities is made to estimate the accuracy of the method. A basis set study revealed a noticeable contribution of diffuse orbitals to the hyperpolarizability also for larger oligomers. Furthermore, CAM-B3LYP is also confirmed to provide molecular geometries close to experimentally observed structures, especially for longer chain lengths.
260 citations
TL;DR: The most fascinating feature of this Li doping is its loosely bound valence electron, which has been pulled into the cavity of the B(10)H(14) basket and become diffuse by the electron-deficient morphological features of the open end of the boron basket.
Abstract: An innovative type of lithium decahydroborate (Li@B10H14) complex with a basketlike complexant of decaborane (B10H14) has been designed using quantum mechanical methods. As Li atom binds in a handle fashion to terminal electrophilic boron atoms of the decaborane basket, its NBO charge q (Li) is found to be 0.876, close to +1. This shows that the Li atom has been ionized to form a cation and an anion at the open end of B10H14. The most fascinating feature of this Li doping is its loosely bound valence electron, which has been pulled into the cavity of the B10H14 basket and become diffuse by the electron-deficient morphological features of the open end of the B10H14 basket. Strikingly, the first hyperpolarizability (β0) of Li@B10H14 is about 340 times larger than that of B10H14, computed to be 23 075 au (199 × 10−30 esu) and 68 au, respectively. Besides this, the intercalation of the Li atom to the B10H14 basket brings some distinctive changes in its Raman, 11B NMR, and UV−vis spectra along with its other e...
249 citations
TL;DR: It was found that when the helices reached a certain length, the number of peptide units in the helix should not alter the data analysis substantially, and thus the orientation determination method presented here is general and thus can be applied to study other helices as well.
Abstract: In this paper, we systematically presented the orientation determination of protein helical secondary structures using vibrational spectroscopic methods, particularly, nonlinear sum frequency generation (SFG) vibrational spectroscopy, along with linear vibrational spectroscopic techniques such as infrared spectroscopy and Raman scattering. SFG amide I signals can be collected using different polarization combinations of the input laser beams and output signal beam to measure the second-order nonlinear optical susceptibility components of the helical amide I modes, which are related to their molecular hyperpolarizability elements through the orientation distribution of these helices. The molecular hyperpolarizability elements of amide I modes of a helix can be calculated based on the infrared transition dipole moment and Raman polarizability tensor of the helix; these quantities are determined by using the bond additivity model to sum over the individual infrared transition dipole moments and Raman polarizability tensors, respectively, of the peptide units (or the amino acid residues). The computed overall infrared transition dipole moment and Raman polarizability tensor of a helix can be validated by experimental data using polarized infrared and polarized Raman spectroscopy on samples with well-aligned helical structures. From the deduced SFG hyperpolarizability elements and measured SFG second-order nonlinear susceptibility components, orientation information regarding helical structures can be determined. Even though such orientation information can also be measured using polarized infrared or polarized Raman amide I signals, SFG has a much lower detection limit, which can be used to study the orientation of a helix when its surface coverage is much lower than a monolayer. In addition, the combination of different vibrational spectroscopic techniques, for example, SFG and attenuated total reflectance Fourier transform infrared spectroscopy, provides more measured parameters for orientation determination, aiding in the deduction of more complicated orientation distributions. In this paper, we discussed two types of helices, the alpha-helix and 3-10 helix. However, the orientation determination method presented here is general and thus can be applied to study other helices as well. The calculations of SFG amide I hyperpolarizability components for alpha-helical and 3-10 helical structures with different chain lengths have also been performed. It was found that when the helices reached a certain length, the number of peptide units in the helix should not alter the data analysis substantially. It was shown in the calculation, however, that when the helix chain is short, the SFG hyperpolarizability component ratios can vary substantially when the chain length is changed. Because 3-10 helical structures can be quite short in proteins, the orientation determination for a short 3-10 helix needs to take into account the number of peptide units in the helix.
149 citations
Book•
19 Feb 2009TL;DR: Second-order nonlinear optical imaging techniques as mentioned in this paper have been used to study second-order polarizabilities and susceptibilities beyond the electric-dipole approximation, and to determine the symmetry of interfaces, surfaces, and thin films.
Abstract: General Aspects of Second-Order Nonlinear Optics Linear optical phenomena Nonlinear optical phenomena Examples of nonlinear optical phenomena Symmetries in second-order nonlinear optics Second-order polarizabilities and susceptibilities Beyond the electric-dipole approximation Determination of Molecular Symmetry with Hyper-Rayleigh Scattering Hyper-Rayleigh scattering: general principles Experimental techniques and equipment Determination of molecular symmetries Switching the first hyperpolarizability at the molecular level Probing aggregation and supramolecular structure in solution Characterization of Interfaces, Surfaces, and Thin Films Second-harmonic generation and sum-frequency generation from surfaces: general principles Experimental techniques and equipment Probing the symmetry of interfaces, surfaces, and thin films Molecular orientation at surfaces Surface adsorption and surface reactions Characterization of Surface Chirality by Second-Harmonic Generation and Sum-Frequency Generation Chirality and second-order nonlinear optics: general principles Experimental procedures Second-harmonic generation in nanostructures Applications to biological systems Molecular origin Relation with the Faraday effect Second-Order Nonlinear Optical Imaging Techniques General principles Experimental techniques and equipment Applications Appendix Index References appear at the end of each chapter
142 citations
TL;DR: It is found that two DFT functionals with the larger fraction of Hartree-Fock exchange (BMK and especially M05-2X) provide the best agreement to the experiment, comparable to that of the MP2 method.
Abstract: We investigate the molecular first hyperpolarizability (β) for donor/acceptor (D/A) substituted π-conjugated organic molecules with different D/A groups and π-systems (including up to eight π-bonds). The results of the MP2 and density functional theory (PBE0, BMK, M05, M05-2X) calculations are compared to those obtained from experimental data. The goal of this study is to select a protocol with optimal quality/cost ratio to be used for systematic prediction of molecular nonlinear optical (NLO) properties. This goal is closely related to the way in which theoretical βs are compared to experimental ones and to the accuracy and consistency of experimental hyperpolarizabilities used to test theoretical predictions. We found that two DFT functionals with the larger fraction of Hartree−Fock exchange (BMK and especially M05-2X) provide the best agreement to the experiment, comparable to that of the MP2 method. Due to high computational cost of MP2 method, we recommend to use the M05-2X functional as a tool for s...
128 citations
TL;DR: Molecular switches: Highly efficient acido- and photoswitchable frequency doublers (see scheme) based on the indolinooxazolidine core are studied by means of hyper-Rayleigh experiments and quantum-chemical calculations.
Abstract: Molecular switches: Highly efficient acido- and photoswitchable frequency doublers (see scheme) based on the indolinooxazolidine core are studied by means of hyper-Rayleigh experiments and quantum-chemical calculations.
To optimize the nonlinear optical (NLO) contrast, a series of indolinooxazolidine derivatives with electron-withdrawing substituents in the para position on the indolinic residue have been synthesized. Their linear and nonlinear optical properties have been characterized by UV-visible absorption and hyper-Rayleigh scattering measurements, as well as by ab initio calculations. The two-way photo- or pH-triggered switching mechanism has been demonstrated by comparing the absorption spectra of the zwitterionic and protonated open forms (POF). Hyper-Rayleigh measurements have revealed that the second-order NLO contrast between the closed indolinooxazolidine and the open π-conjugated colored forms remain very large upon substitution. Theory and measurements show that for the POFs the amplitude of the first hyperpolarizability follows the Hammett parameters of the withdrawing groups. However, because the measurements are performed in resonance, to recover this behavior, elaborate procedures including homogeneous and inhomogeneous broadenings, as well as single-mode vibronic structures are necessary to extrapolate to the static limit.
127 citations
TL;DR: The present investigation provides a new kind of candidates for the high-performance NLO materials.
Abstract: The interesting radical ion pair salts M2˙+TCNQ˙− (M = Li, Na, K) are a particular class of charge transfer complexes with excess electron. The ground states of these complexes are triplet. The C2v symmetry geometrical structures of the M2˙+TCNQ˙− (M = Li, Na, K) with all-real frequencies are obtained at the density functional theory (DFT) B3LYP/6-31+G(d) level. All calculations of electric properties in this paper have been carried out at the restricted open-shell second order Moller–Plesset perturbation theory (ROMP2) level. Owing to existing excess electron (from the polarized alkali metal atoms) these charge transfer complexes exhibit large nonlinear optical (NLO) responses dominated by excess electron transitions.
For these radical ion pair salts M2˙+TCNQ˙−, the static first hyperpolarizabilities (β0) are large. The order of β0 values is 19 203 (M = Li) < 24 140 (M = Na) < 29 065 a.u. (M = K). Specially, the second hyperpolarizability (γ0) of the complexes with excess electron is obtained for the first time. These static second hyperpolarizabilities are also large. The order of γ0 values is 2 213 006 (M = Li) < 3 136 754 (M = Na) < 7 905 623 a.u. (M = K). Among the three structures, K2˙+TCNQ˙− has the largest γ0 value to be 7.9 × 106 a.u. (3982 × 10−36 esu), which is about 9 times larger than that of the intramolecular charge transfer complex σ-arylvinylidene trans-[Ru(4-CCHC6H4CCC6H4NO2)Cl(dppm)2]PF6 [Hurst et al., Organometallics, 2001, 20, 4664]. The present investigation provides a new kind of candidates for the high-performance NLO materials.
123 citations
TL;DR: In this article, a comprehensive investigation on the intramolecular charge transfer (ICT) of an efficient π-conjugated potential push-pull NLO chromophore, 1-(4-methoxyphenyl)-3-(3,4-dimethoxymhenyl)2-propen-1-one to a strong electron acceptor group through the πconjugation bridge has been carried out from their vibrational spectra.
101 citations
TL;DR: Using a wide variety of quantum-chemical methods, it is observed that the double harmonic vibrational contribution to the static beta is much larger than its electronic counterpart and for the intensity-dependent refractive index the vibrational and electronic terms are comparable.
Abstract: Using a wide variety of quantum-chemical methods we have analyzed in detail the linear and non-linear optical properties of [60]fullerene−chromophore dyads of different electron-donor character. The dyads are composed of [60]fullerene covalently linked with 2,1,3-benzothiadiazole and carbazole derivatives. Linear scaling calculations of molecular (hyper)polarizabilities were performed using wave function theory as well as density functional theory (DFT). Within the former approach, we used both semiempirical (PM3) and ab initio (Hartree−Fock and second-order Moller−Plesset perturbation theory) methods. Within the latter approach only the recently proposed long-range (LRC) schemes successfully avoid a large overshoot in the value obtained for the first hyperpolarizability (β). Calculations on model fullerene derivatives establish a connection between this overshoot and the electron-donating capability of the substituent. Substitution of 2,1,3-benzothiadiazole by the triphenylamine group significantly incre...
96 citations
TL;DR: It is concluded that the large collagen nonlinear response originates in the tight alignment of a large number of small and weakly efficient harmonophores, presumably the peptide bonds, resulting in a coherent amplification of the nonlinear signal.
Abstract: We performed Hyper−Rayleigh Scattering (HRS) experiments to measure the second-order nonlinear optical response of the collagen triple helix and determine the physical origin of second harmonic signals observed in collagenous tissues. HRS experiments yielded a second-order hyperpolarizability of 1.25 × 10−27 esu for rat-tail type I collagen, a surprisingly large value considering that collagen presents no strong harmonophore in its amino acid sequence. Polarization-resolved experiments showed intramolecular coherent contributions to the HRS signal along with incoherent contributions that are the only contributions for molecules with dimensions much smaller than the excitation wavelength. We therefore modeled the effective second-order hyperpolarizability of the 290 nm long collagen triple helix by summing coherently the nonlinear response of well-aligned moieties along the triple helix axis. This model was confirmed by HRS measurements after denaturation of the collagen triple helix and for a collagen-lik...
TL;DR: The second-order NLO properties of a series of monoTTF-porphyrins and metalloporphyrins have been calculated by density functional theory (DFT) combined with the finite field (FF) method and it is shown that these compounds possess considerably large static first hyperpolarizabilities.
Abstract: The redox-active tetrathiafulvalene (TTF) is a good electron donor, and porphyrin is highly delocalized in cyclic π-conjugated systems The direct combination of the two interesting building units into the same molecule provides an intriguing molecular system for designing nonlinear optical (NLO) molecular materials In the present paper, the second-order NLO properties of a series of monoTTF-porphyrins and metalloporphyrins have been calculated by density functional theory (DFT) combined with the finite field (FF) method Our calculations show that these compounds possess considerably large static first hyperpolarizabilities, ∼400 × 10−30 esu Since the TTF unit is able to exist in three different stable redox states (TTF, TTF•+, and TTF2+), the redox switching of the NLO response of the zincII derivative of monoTTF-metalloporphyrin has been studied, and a substantial enhancement in static first hyperpolarizability has been obtained in its oxidized species according to our DFT-FF calculations The β valu
TL;DR: The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule and the energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) results complements with the experimental findings.
TL;DR: A model was obtained that correctly describes a variety of thermodynamic, dynamic, and dielectric properties of water while still preserving the simplicity of the COS model, which allows a straightforward introduction of explicit polarization into (bio)molecular force fields.
Abstract: A new charge-on-spring (COS) model for water is introduced (COS/D). It includes a sublinear dependence of the induced dipole on the electric field for large field strength to include the effect of hyperpolarizability by damping the polarizability. Only two new parameters were introduced to define the damping of the polarizability. In the parametrization procedure, these two damping parameters, the two Lennard-Jones parameters, the charge on the oxygen, and the distance between the virtual site and the oxygen atom were varied to reproduce the density, the heat of vaporization, the dielectric permittivity, and the position of the first peak in the radial distribution function of liquid water at room temperature and pressure. In this way, a model was obtained that correctly describes a variety of thermodynamic, dynamic, and dielectric properties of water while still preserving the simplicity of the COS model, which allows a straightforward introduction of explicit polarization into (bio)molecular force fields.
TL;DR: Comparison of the observed fundamental vibrational frequencies of 3,5-DMP with calculated results show that 6-311++G(d,p) superior to other basis sets for molecular vibrational problems.
TL;DR: With minimal trapping field perturbation provided by the blue-detuned lattice, the fractional uncertainty due to the hyperpolarizability effects was found to be 2x10;{-19} in the relevant clock transition.
Abstract: We investigated the properties of optical lattice clocks operated with a repulsive light-shift potential. The magic wavelength, where light-shift perturbation for the clock transition cancels, was experimentally determined to be 389.889(9) nm for $^{87}\mathrm{Sr}$. The hyperpolarizability effects on the clock transition were investigated theoretically. With minimal trapping field perturbation provided by the blue-detuned lattice, the fractional uncertainty due to the hyperpolarizability effects was found to be $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}$ in the relevant clock transition.
TL;DR: In this paper, the FT-IR and FT-Raman spectra of acenocoumarol sodium salt in solid phase have been recorded and analyzed with the help of B3LYP density functional theory (DFT) methods.
Abstract: The FT-IR and FT-Raman spectra of sodium salt of 4-hydroxy-3[1-(4-nitrophenyl)-3-oxobutyl]-2H-1-benzopyran-2-one (acenocoumarol sodium salt) in solid phase have been recorded and analyzed. The optimization geometry, intramolecular hydrogen bonding, and harmonic vibrational wavenumbers of acenocoumarol sodium salt have been investigated with the help of B3LYP density functional theory (DFT) methods. The infrared and Raman spectra were predicted theoretically from the calculated intensities. Natural bond orbital (NBO) analysis indicates the presence of CH···O hydrogen bonding in the molecule. The first static hyperpolarizability of the molecule has been computed. Copyright © 2009 John Wiley & Sons, Ltd.
TL;DR: Comparison of the observed fundamental vibrational frequencies of 2,4-DCA with calculated results by HF and density functional methods indicates that BLYP is superior to other methods for molecular vibrational problems.
TL;DR: In this paper, a combined experimental and theoretical study on molecular structure and vibrational spectra of l -histidinium dihydrogen phosphate-phosphoric acid, with particular emphasize on the correlation between the intermolecular hydrogen bonds and the hyperpolarizability.
TL;DR: Experimental results show that conjugation modulation of the bridge in donor/acceptor molecules simultaneously optimizes the transition moments and the energy-level spacing in the context of quantum limits.
Abstract: A new strategy for optimizing the first hyperpolarizability based on the concept of a modulated conjugated path in linear molecules is investigated. A series of seven novel chromophores with different types of conjugated paths were synthesized and characterized. Hyper-Rayleigh scattering experiments confirmed that modulated conjugation paths that include benzene, thiophene, and/or thiazole rings in combination with azo and/or ethenyl linkages between dihydroxyethylamino donor groups and various acceptor groups result in enhanced intrinsic hyperpolarizabilities that exceed the long-standing apparent limit for two of the chromophores. The experimental results are analyzed and interpreted in the context of quantum limits, which show that conjugation modulation of the bridge in donor/acceptor molecules simultaneously optimizes the transition moments and the energy-level spacing.
TL;DR: In this article, a chalcone co-crystal (C18H19NO4/C17H16NO3Br; 0.972/0.028) has been grown by slow evaporation from solution.
Abstract: Single crystals of a chalcone co-crystal (C18H19NO4/C17H16NO3Br; 0.972/0.028) have been grown by slow evaporation from solution. The powder second harmonic generation (SHG) efficiency of this chalcone co-crystal is 7 times that of urea. The dependence of second harmonic (SH) intensity on particle size revealed the existence of phase matching direction in this crystal. The large SHG efficiency observed is mainly due to the unidirectional alignment of molecular dipoles, in which the dipole moment of each molecule adds to establish a net polarization. The weak N–H⋅⋅⋅O hydrogen-bond interactions help to stabilize the noncentrosymmetric crystal packing and also contribute partly to the SHG. The better thermal stability, transparency and high laser damage resistance (>1.5 GW cm−2 at 532 nm, 8 ns) of this chalcone co-crystal indicate that it is a promising material for frequency doubling of diode lasers down to 470 nm. This molecule also shows a third-order NLO response and good optical limiting property of 8 ns laser pulses at 532 nm. The mechanism for optical limiting in this chalcone was attributed to two-photon induced excited state absorption that leads to reverse saturable absorption. The structure–property relationship in this chalcone and related compounds is discussed based on the experimental results and semiempherical hyperpolarizability calculations.
TL;DR: A new complexant effect onbeta(0), that is, a dependence on the petal number (n) of beta(0) owing to the flexibility of the complexants increasing with the petAL number, is shown.
Abstract: Doping Li atom into higher flexible cyclic polyamines with many amine unit petals (ethyleneimine) forms the n-petal-shaped Li-doped cyclic polyamines (n = 3−5). Three structures, referred to as thr...
TL;DR: In this article, the second-order nonlinear optical response in the dihydroazulene (DHA)-vinylheptafulvene (VHF) equilibrium has been investigated as a function of the nature of the substituent (R) on the phenyl ring by means of quantum chemistry calculations including electron correlation, frequency dispersion, and solvent effects.
Abstract: The contrast of second-order nonlinear optical response in the dihydroazulene (DHA)-vinylheptafulvene (VHF) equilibrium has been investigated as a function of the nature of the substituent (R) on the phenyl ring by means of quantum chemistry calculations including electron correlation, frequency dispersion, and solvent effects. By considering the hyper-Rayleigh scattering (HRS) response, the contrast for R = H and R = CH3 between the DHA and VHF forms is larger than 5 while the contrast between the cis and transVHF forms is close to 1. Adding the NH2 donor group in para position of the phenyl leads to a substantial increase of the HRS first hyperpolarizability of the three forms, which is detrimental to the contrast. Then, in the case of the NO2 acceptor group, a contrast is recovered because the HRS first hyperpolarizability of the DHA form is about 2–3 times larger than for both VHF forms. These variations of first hyperpolarizability as a function of the substituents as well as the associated contrasts have been explained in terms of donor/acceptor strengths and geometrical parameters.
TL;DR: In this article, the second-order nonlinear optical (NLO) properties of a series of transition-metal-trisubstituted polyoxometalates (POMs)−diphosphate clusters were investigated.
Abstract: To date, the most widely used second-order nonlinear optical (NLO) materials are the totally inorganic crystals. However, the small photoelectric coefficients of inorganic NLO materials are the bottleneck in practical applications. The donor−conjugated bridge−acceptor (D−A) model, which is successfully used in the development of organic second-order NLO materials, is still prohibitive in totally inorganic molecules. In the present paper, time-dependent density functional (TDDFT) has been employed to investigate the second-order NLO properties of a series of transition-metal-trisubstituted polyoxometalates (POMs)−diphosphate clusters. We find that these totally inorganic POM clusters possess D−A structure, and the large static first hyperpolarizability can be effectively designed based on this D−A model. The results show that the substituted transition metal centers can be viewed as electron acceptor, and the POM cluster serves as both electron donor and conjugated bridge. The three vanadium atoms derivati...
TL;DR: In this paper, correlated quantum and statistical mechanical calculations are required to understand the dependence of macroscopic electro-optic activity upon chromophore structure and intermolecular electrostatic interactions.
Abstract: Realization of large electro-optic (EO) activity for dipolar organic chromophore-containing materials requires the simultaneous optimization of chromophore first hyperpolarizability (β), acentric order , and number density (N). As these parameters are inter-related, correlated quantum and statistical mechanical calculations are required to understand the dependence of macroscopic electro-optic activity upon chromophore structure and intermolecular electrostatic interactions. Correlated time-dependent density functional theory (TD-DFT) and pseudo-atomistic Monte Carlo (PAMC) calculations are used in an attempt to understand the dependence of linear and nonlinear optical properties on dielectric permittivity, optical frequency, and a variety of spatially-anisotropic interactions that can be nano-engineered into the macroscopic material structure. Structure/function relationships are considered for three classes of organic electro-optic materials: (1) Chromophore/polymer composite materials; (2) chromophores covalently incorporated into passive organic host materials; (3) chromophores incorporated into chromophore-containing host materials—a new class of materials referred to as binary chromophore organic glasses (BCOGs). Issues associated with processing these materials into device structures, including those relevant to the integration with silicon photonics, are discussed. The purpose of this article is to address issues critical to ascertaining the viability of organic electro-optic (OEO) materials for next generation telecommunications, computing, and sensing applications.
TL;DR: The computational modeling, synthesis, and characterization of a series of eight heteroaromatic organic chromophores, designed to self-organize from the vapor phase via directed hydrogen-bond networks, into acentric thin films, are reported.
Abstract: Efficiently organizing molecular nonlinear optical (NLO) chromophores having large first-order hyperpolarizabilities (β) into acentric microstructures for electro-optic (EO) applications represents a significant materials synthesis and processing challenge, in part due to interchromophore dipolar interactions that promote centrosymmetric organization. Here we report the computational modeling, synthesis, and characterization of a series of eight heteroaromatic organic chromophores, designed to self-organize from the vapor phase via directed hydrogen-bond networks, into acentric thin films. Introduction of α,ω-donor−acceptor hydrogen-bonding substituents along the molecular long axes tunes properties such as hyperpolarizability, volatility, thermal stability, film-forming properties, and macroscopic NLO response (χ(2)). DFT-level molecular modeling, INDO/S optical property analysis, and sum-overstates computation indicate that molecular-core fluorination and hydrogen-bond donor incorporation can increase β...
TL;DR: The recently developed long-range corrected Baer-Neuhauser-Livshits (BNL) exchange-correlation functional is implemented and applied and the UV-Vis spectra obtained with the BNL functional are found to be superior compared with other density functional theory (DFT) functionals.
Abstract: We present electronic structure calculations of the ultraviolet/visible (UV-Vis) spectra of highly active push-pull chromophores containing tricyanofuran (TCF) acceptor group. In particular, we have applied the recently developed long-range corrected Baer-Neuhauser-Livshits (BNL) exchange-correlation functional. The performance of this functional compares favorably with other density functional theory (DFT) approaches, including the CAM-B3LYP functional. The accuracy of UV-Vis results for these molecules is best at low values of attenuation parameters (γ) for both BNL and CAM-B3LYP functionals. The optimal value of γ is different for the charge-transfer (CT) and π-π* excitations. The BNL and PBE0 exchange correlation functionals capture the CT states particularly well while the π-π* excitations are less accurate and system dependent. Chromophore conformations, which considerably affect the molecular hyperpolarizability, do not significantly influence the UV-Vis spectra on average. As expected, the color of chromophores is a sensitive function of modifications to its conjugated framework, and is not significantly affected by increasing aliphatic chain length linking a chromophore to a polymer. For selected push-pull aryl-chromophores, we find a significant dependence of absorption spectra on the strength of diphenylaminophenyl donors.
TL;DR: Experimental investigations of optical nonlinearities and nonlinear dynamics in acetone solution of 2,4,5-Trimethoxy-4- nitrochalcone molecule confirmed that fifth-order processes mainly originate from 2PA-induced excited-state non linearities by conducting femtosecond time-resolved degenerate pump-probe measurements.
Abstract: We report experimental investigations of optical nonlinearities and nonlinear dynamics in acetone solution of 2,4,5-Trimethoxy-4′-nitrochalcone. By performing Z-scans with femtosecond laser pulses at low excitation intensity, two-photon absorption (2PA) and third-order nonlinear refraction are measured. As laser excitation intensity exceeds a critical value, however, the interplay between third- and fifth-order nonlinearities is observed. It is also confirmed that fifth-order processes mainly originate from 2PA-induced excited-state nonlinearities by conducting femtosecond time-resolved degenerate pump-probe measurements. All the nonlinear parameters are determined unambiguously in the near infrared region of the 2PA cross-section, second-order hyperpolarizability, excited-state absorption cross-section, excited-state refraction cross-section, lifetime of excited states induced by 2PA, and critical population of the excited states in 2,4,5-Trimethoxy-4′-nitrochalcone molecule.
TL;DR: In this paper, the vibrational wavenumbers of the title compound were computed using the B3LYP/6-31G* basis and compared with the experimental data.
Abstract: Fourier transform (FT)-Raman and Fourier transform infrared (FT-IR) spectra of 3-{[(4-fluorophenyl)methylene]amino}-2-phenylquinazolin-4(3H)-one were recorded and analyzed. The vibrational wavenumbers of the title compound were computed using the B3LYP/6-31G* basis and compared with the experimental data. The prepared compound was identified by NMR and mass spectra. The simultaneous IR and Raman activation of the CO stretching mode shows a charge transfer interaction through a π-conjugated path. The first hyperpolarizability and infrared intensities are reported. The assignments of the normal modes are done by potential energy distribution (PED) calculations. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this paper, the spectral properties of the most prospective electro-optic crystal 4-(N,N-dimethylamino)-N-methyl-4′-toluene sulfonate (DAST) have been comprehensively described with the near infrared Fourier transform (NIR FT) Raman and Fourier Transform Infrared (FT-IR) spectra supported by the density functional theoretical (DFT) computations to elucidate the contribution of vibrational modes to the linear electrooptic (LEO) effect.
Abstract: The optimized geometry and structural features of the most prospective electro-optic crystal 4-(N,N-dimethylamino)-N-methyl-4′-toluene sulfonate (DAST), and the vibrational spectral investigations have been comprehensively described with the near infrared Fourier transform (NIR FT) Raman and Fourier transform infrared (FT-IR) spectra supported by the density functional theoretical (DFT) computations to elucidate the contribution of vibrational modes to the linear electro-optic (LEO) effect. Mulliken population analysis and natural bond orbital (NBO) analysis have also been carried out to analyze the effects of intramolecular charge transfer (ICT), intramolecular hydrogen bonding and hyperconjugative interactions on the geometries. The influence of CT interaction between the phenyl ring and the dimethylamino group of the nonlinear optical (NLO) chromophore on the endocyclic and exocyclic angles, and the electronic effects such as hyperconjugation and back-donation on the methyl hydrogen atoms have been examined. The concurrent intense activation of Raman and IR activities of the effective conjugation vibrational coordinate, which significantly contributes to the LEO effect resulting from the strong electron–phonon (e/ph) coupling, has been analyzed in detail. The effects of frontier orbitals, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), transition of electron density (ED) transfer and the influence of planarity in the stilbazolium ring on the first hyperpolarizability are also discussed. Copyright © 2008 John Wiley & Sons, Ltd.