Study of light-scattering changes induced in tRNA solutions by a strong optical field of picosecond pulses

Changes in the light-scattering components (λ = 0.53 μm) induced by a strong picosecond optical field (λ = 1.06 μm) applied to macromolecular transfer ribonucleic acid (tRNA) solutions were studied. Two beams were polarized vertically, and the intensity of the vertical and horizontal components of the light (λ = 0.53 μm) scattered at an angle of 90° were measured. The electric field of the strong 30-ps laser pulse was 5.0 × 10³ esu cgs. The experimentally determined changes allowed for calculation of the mean third-order optical polarizability c, and its anisotropy δ_c. The measurements were performed in three different solutions: salt free, with magnesium ions, and without magnesium ions. Changes in tRNA structure reflected in changes of nonlinear light scattering, third-order optical polarizability, and its anisotropy were observed.     

四叔丁基萘酞菁铅化合物的非线性和光限幅特性

合成了四叔丁基萘酞菁铅[(t-Bu)₄NcPb]化合物. 利用元素分析、红外光谱、核磁共振氢谱等方法, 验证了化合物的分子结构. 应用调Q倍频ns/ps Nd:YAG脉冲激光系统, 在波长为532 nm下, 研究了化合物的非线性和光限幅特性. 测得化合物的非线性折射率n₂和三阶非线性极化率χ⁽³⁾分别为2.42×10^－11和7.91×10^－12 esu, 通过计算得到分子极化率γ'为3.4×10^－29 esu. 在透过率69%时限幅阈值为1522 mJ/cm², 箝位值为553 mJ/cm², 有效激发态与基态吸收截面比为3.16.     

Electronic structure of beryllium

The electronic energy bands in beryllium have been recalculated. The earlier work of Terrell [1] was found to contain a systematic error in the form of overlapping muffin tins. The new band structures give a density of states with the Fermi surface lying in the hole like portion, consistent with Hall measurements. All existing calculations misplaced the Fermi surface. As a further check on the new bands, the Hall coefficient A_H was calculated. We obtained A_H = (7.6 ± 0.8) × 10^?24 cgs units for the easy axis or c direction, in excellent agreement with the experimental value of A_H = 8.56 × 10²⁴ cgs units.     

Nonlinear optical properties of systems based on ruthenium(II) tetra-15-crown-5-phthalocyaninate

The third-order nonlinear optical properties of the ruthenium (II) complex with tetra-15-crown-5-phthalocyanine and axially coordinated triethylenediamine molecules (R₄Pc)Ru(TED)₂ were analyzed by means of the z-scanning technique. A solution of (R₄Pc)Ru(TED)₂ in tetrachloroethane was exposed to nanosecond laser pulses at a wavelength of 1064 nm. It was found that the third-order molecular polarizability of the Ru(II) complex is 4.5 × 10^?32 cm⁴/C (esu). The polarizability per molecule increases by a factor of 3.6 when the single molecule occurs in a supramolecular assembly of (R₄Pc)Ru(TED)₂ complexes. The photoelectric and photorefractive properties at 1064 nm of polymer composites, determined by the supramolecular assemblies that exhibits optical absorption and photoelectric sensitivity in the near IR region, are reported.     

Calculation of the nonlinear electric susceptibility of benzene

We calculate the various components of the third-order nonlinear electric susceptibility of the benzene molecule, starting from a CNDO wavefunction. Our theoretical result for the space-fixed nonlinear third-order susceptibility is 6.15 × 10^?36 esu, the corresponding experimental value is 1.58 × 10^?36 esu. We also estimate the contributions from the σ and π electrons to the total susceptibility.     

Spectrophotometric study of the reaction of titanium with bromopyrogallol red in the presence of cetylpyridinium bromide

Optimal conditions were found for the reaction of Ti(IV) with bromopyrogallol red (λ = 625 nm, pH = 2.5, c_DG = 4 × 10^?5M, c_CPB = 5 × 10^?4M) and a new method was developed for the spectrophotometric determination of titanium in the concentration range 0.05–0.5 μg ml^?1. A mechanism was proposed for the studied reaction on the basis of a kinetic study.     

The second and third order non-linear optical properties of liquid crystalline polymers

Abstract

The second and third order non-linear optical susceptibilities of several donoracceptor substituted side chain polymers, some of which exhibit mesophases, will be reported. The susceptibilities were measured by harmonic generation from thin films, typically 0·5 μm thick, at a fundamental wavelength of 1064 nm and 1579 nm. For second harmonic generation, the spin coated films were contact poled on a glass substrate with an interdigited electrode pattern. Typical values obtained were χ⁽²⁾ ₃₁ = 1 × 10^?9 esu and χ⁽²⁾ ₃₃ = 3 × 10^?9 esu, the largest value was χ⁽²⁾ ₃₃ = 6·3 × 10^?9 esu. The difficulty in deriving reliable second order structure-property relations because of the large effect which the contact poling process has on the non-linear optical susceptibility of the films will be highlighted. The highest χ⁽³⁾ value of 5·8 × 10^?12 esu obtained from an amorphous film of a polymer with an asymmetrically substituted azo side group is comparable with the susceptibility of more typical third order non-linear materials such as the main chain polymers polyphenylacetylene and poly-p-phenylenebenzobisthiazole.     

Detection of “memory” effects in polyethylene by magnetic susceptibility

The relevance of diamagnetic susceptibility as a tool for the structure analysis of solid high polymers is stressed in the light of some new examples. The present results complement previous data and offer new aspects on the diamagnetic investigations of longchain hydrocarbons, especially polyethylene (PE). The molecular susceptibility is proportional to the average number of repeat units in the chain. The proportionality factor defines an intermolecular constant μ_k which characterizes different physical states. This was found to be 2.5 × 10^?6 for the liquid and 3.5 × 10^?6 cgs for the crystalline state of paraffins and polyethylene (solution-crystallized). For melt-crystallized material, μ_k, approaches the typical value of the liquid paraffin in agreement with previous results. Such a low μ_k is probably related to the increased disorder of the paracrystalline lattice domains, in contrast to the more ordered microparacrystallites in the so-called “single crystals,” where μ_k = 3.5 × 10^?6. In single crystals of branched PE, μ_k approaches 2.5 × 10^?6 with increasing branching ratio. Like paraffins in the gaseous state, molten PE, with chains longer than 1000 Å, has μ_k = 0. If the solution-crystallized material is molten for 10 min and thereafter cooled, μ_k retains the original value 3.5 × 10^?6 cgs characteristic of the crystalline state. Hence, solution-crystallized polyethylene apparently possesses a kind of “memory.” Such a “memory” can, nevertheless, be partly destroyed when molten PE is stirred for 10 min and then quenched. Aggregates of solution-precipitated crystals with 3% branching concentration give μ_k = 2.9 ± 0.2 × 10^?6 in good agreement with x-ray diffraction data. Finally, experimental details on the magnetic measurements are critically discussed, and various aspects of improvements for further investigations are also described.     

Synthesis,crystal structure and non-linear optical properties of a new cyanide-containing compound

Reaction of K₃[Fe(CN)₆], NiCl₂ and diethylenetriamine (dien) resulted in the formation of a cyanide-containing heterometallic compound [Ni(dien)₂]₂[Fe(CN)₆]·4H₂O 1. The structure consists of two octahedral [Ni(dien)₂]²⁺ cations, one octahedral [Fe(CN)₆]^4? anion and four crystallization water molecules, which are held together by hydrogen-bonding interactions. Its TG curve exhibits two stages of mass loss. Compound 1 in DMF solutions has a very strong third-order non-linear optical (NLO) behavior with an absorption coefficient and refractive index α₂?=?1.10?×?10^?11?m?w^?1, n ₂?=??3.05?×?10^?19?m²?w^?1, respectively, and third-order NLO susceptibility χ⁽³⁾ 4.34?×?10^?13?esu.     

Study of Activation and Inhibition of Certain Metal Ions to Amylase Catalyzed Reaction by Microcalorimetry

IntroductionMostcomplicatedreactionshappenedinlivingcrea tures ,amongthemenzymecatalyzedreactionisanimpor tantclass .Itissignificantinboththeoryandpracticetoinvestigateenzymecatalyzedreaction .Therearemanyex perimentalmethodssuchasspectrophotometry ,titrimetry ,isotopemethod ,microcalorimetryandsoon ,inwhichmi crocalorimetryisanewoneduetoitshighsensitivityandaccuracy .Wecanstudythewholeprocessoftheheatef fectusingamicrocalorimeter .Sincetheabsorptionorpro ductionofheatisanintrinsicpropertyofe…     

Diode effect caused by sequence of benzothiazole on optical properties

In this work, two kinds of benzothiazole derivatives were synthesized. The third-order nonlinear optical properties of the benzothiazole derivatives in minimal curative dose (DCM) were analyzed using the Z-scan measurement at 532 nm with a 120 fs pulse laser. The largest third-order nonlinear susceptibility (χ⁽³⁾) and second-order hyperpolarizability of the complexes (γ) were estimated at 1.4 × 10^?13 esu and 0.86 × 10^?30 esu, respectively. The results showed that the sequence of 2- and 6-position in benzothiazole has served as a “diode,” linking to the other groups that had great influence on the optical properties such as fluorescence and nonlinear optical absorption, and the increase of the polarity and the extension of the conjugate structure had benefits to the third-order nonlinearity. The experimental findings were confirmed with the use of DFT, TDDFT, and ZINDO calculations.     

Thermal lens determination of cytochrome c and its NO complex

Spectrophotometric and thermal lens measurements showed that cw laser beam (450–530 nm, up to 100 mW) does not affect the absorption band of cytochrome c. Therefore, thermal lensing is used for determining cytochrome c (III) (c _min = 1 × 10^?7 mol/L at λ = 488.0 nm; c _min = 3 × 10^?8 mol/L at λ = 514.5 nm) and its active form, cytochrome c (II) (c _min = 1 × 10^?8 mol/L at λ = 514.5 nm). The enhancement of the sensitivity of determination of these species as compared with conventional spectrophotometry is more than two orders of magnitude. The optimal conditions for the formation of the NO complex of cytochrome c for its photometric determination were selected: the molar ratio of dodecyl sulfate (a modifying agent) to cytochrome c is 1: 30 at a working wavelength of 560 nm. When exposed to laser radiation, the nitrosyl complex of cytochrome c dissociates to form cytochrome c (III). The decomposition of this complex can be monitored by thermal lensing (514.5 nm) down to a level of 1 × 10^?7 mol/L.     

Calculation of the electric susceptibilities of the helium atom

We calculated the static and the dynamic dipole polarizabilities and the static quadrupole polarizability of the helium atom. The results are α = 0.2070 × 10^?24 cm³ for the static dipole polarizability and γ₄ = 0.1038 × 10^?40 cm⁵ for the static quadrupole polarizability.     

Elastic moduli of ReO3 by Brillouin scattering

Brillouin light scattering has been used to measure elastic stiffness constants in the metal ReO₃: c₁₁ = (71.7 ± 3.5) × 10¹¹dynes/cm², c₄₄ = (7.11 ± 0.25) × 10¹¹dynes/cm², and c₁₂ = (10.3 ± 3.4) × 10¹¹dynes/cm². These values are significantly higher than those obtained ultrasonically at room temperature by Pearsall and Coldren. Since the Brillouin study employs light which heats the scattering volume, it probes lattice forces at an effectively higher temperature. Additional data taken at lower light intensity confirms the positive acoustic velocity temperature gradient.     

A DFT study on NLO response of push-pull hybrid porphyrin-polyoxometalate complexes

Density functional theory (DFT) calculations were carried out to investigate the second-order nonlinear optical (NLO) properties of a series of proposed porphyrin-polyoxometalate-based complexes related to [5-(3,5-dimethyl-4-hexamolybdate amino-phenyl-ethynyl)-15-(4-nitrophenyl-ethynyl)porphinato]zinc(II) which have donor-π conjugated bridge-acceptor (D-π-A) configurations. Our calculations show that these species possess considerably large molecular total second-order polarizability (β₀), ～2000 × 10^?30 esu. Furthermore, it can be seen that {W₆O₁₈} exhibits stronger electron-donating ability than {Mo₆O₁₈}. And two-dimensional (2D) system with A-π-D-π-A structure might be a promising candidate for NLO materials based on the large β₀ (4583.5 × 10^?30 esu) and in-plane nonlinear anisotropy.     

Study of third-order nonlinear susceptibility of polySchiff base containing triphenylamine

PolySchiff base containing triphenylamine has been synthesized by polycondensation and character-ized by FT-IR,NMR,UV-visible spectrometer. Measurements of the third-order optical nonlinear sus-ceptibility χ(3) by Z-scan technique have shown that the large nonlinearity is dominated by the two-photon absorption in PSB. The sign and size of real part Reχ(3) ,nonlinear refractive index n2 have been measured with the condition of 532 nm,8 ns-duration pulses to be -1.23×10-10 esu,-3.06×10-12 esu;nonlinear absorption index β and size of image part Imχ(3) to be 3.63×10-10 m/W,1.15×10-11 esu,respec-tively,so the third-order nonlinear susceptibility χ(3) is 1.19×10-11 esu. The value is larger than other polymers reported. PSB is self-focusing material and has potential application in nonlinear optic field.     

Non‐Resonant z‐Scan Characterization of the Third‐Order Nonlinear Optical Properties of Conjugated Poly(thiophene azines)

The nonlinear optical properties of a functionalized poly(thiophene azine), namely, poly(3,4‐didodecylthiophene azine), PAZ, at the optical telecommunication wavelength of 1550 nm are investigated by means of the closed‐aperture z‐scan technique in both thin films and solutions. Values of χ⁽³⁾=(2.4±0.4)×10^?13 esu, n₂=(4.0±0.7)×10^?15 cm² W^?1, and γ=(4.5±0.7)×10^?34 esu are estimated for the third‐order (Kerr) susceptibility, the intensity‐dependent refractive index, and the molecular second hyperpolarizability of solution samples, respectively. A very small dependence on the polymer chain length is found. Markedly higher values of (4.4±1.1)×10^?11 esu, (6.6±1.0)×10^?13 cm² W^?1, and (5.0±0.8)×10^?33 esu are measured for the corresponding quantities in thick (up to 20 μm) polymer films cast on quartz plates. The enhancement of the NLO responses on going from solution to solid samples is attributed to a partially ordered structure and to the presence of interchain interactions leading to greater π‐electron delocalization in the cast polymer films. The results are compared with those previously obtained by using third‐harmonic generation (THG), taking into account that those data were measured under conditions of three‐photon resonance, whereas our z‐scan measurements are fully off‐resonance.     

Calculations on the spectra and nonlinear third-order optical susceptibility of c70

The equilibrium geometry and UV-visible spectra of C₇₀ were examined using semiempirical INDO /2 and INDO /CI methods. The results obtained are in good accord with experimental results. On the basis of correct electronic spectra, calculations of the nonlinear third-order optical susceptibility (γijkl) of C₇₀ were performed using the INDO /SDCI method combined with a sum-over-states expression. The calculated value for <γ> (-2 ω, ω, ω, O) is 0.882 × 10^?33 esu (ω = 1.91 μm), which is in good agreement with observation. © 1994 John Wiley & Sons, Inc.     

Synthesis,Crystal Structure and Nonlinear Optical Properties of a new cluster compound: MoS4Cu3(PyPPh2)3Cl

Reaction of [NH₄]₂[MoS₄], CuCl and PyPPh₂ in the solid state produces a cube-like cluster. The cluster crystallizes in the orthorhombic space group P2₁2₁2₁ with four formula units in a cell of dimensions a = 12.8980(10) , b = 17.6820(10), c = 22.665(2) Å. Anisotropic refinement for all nonhydrogen atoms yielded the values R = 0.0397 and R _w = 0.1185 for 8803 observed reflections. The structure is built up from three [Cu(Ph₂PPy)]⁺ units bridged by MoS^2? ₄ to form a tetranuclear symmetrical cube-like molecule. Investigation of the third-order optical nonlinear value showed that it exhibits a considerable nonlinear absorptive and self-defocusing effect with α₂ = 1.3 × 10^?11 m w^?1 and n ₂ = ? 3.2 × 10^?18 m² w^?1 in a 1.5 × 10^?4 M DMF solution.     

The oxidation of methyl radicals at room temperature

Using the technique of molecular modulation spectrometry, we have measured directly the rate constants of several reactions involved in the oxidation of methyl radicals at room temperature: k₁ is in the fall-off pressure regime at our experimental pressures (20–760 torr) where the order lies between second and third and we obtain an estimate for the second-orderlimit of (1.2 ± 0.6) × 10^?12 cm³/molec · sec, together with third-order rate constants of (3.1 ± 0.8) × 10^?31 cm⁶/molec² · sec with N₂ as third body and (1.5 ± 0.8) × 10^?30 with neopentane; we cannot differentiate between k_2a and k_2c and we conclude k_2a + (k_2c) = (3.05 ± 0.8) × 10^?13 cm³/molec · sec and k_2b = (1.6 ± 0.4) × 10^?13 cm³/molec · sec; k₃ = (6.0 ± 1.0) × 10^?11 cm³/molec · sec.