On the dimensionality of superconductivity in cuprate superconductors

The question of the dimensionality of superconductivity is considered within the framework of a model of superconductivity via asymmetric, delocalized “crystalline” π orbitals (analogous to the corresponding molecular orbitals) extending along chains of covalently bonded copper and oxygen ions. It is shown that superconductivity is preceded by a separation of the bonds in the CuO₂ layer into covalent and ionic bonds with ordering of the covalent bonds into chains. Such an ordering facilitates the formation of a crystalline π orbital lowering the crystal energy by the resonance energy of the π bond and is therefore favored. The superconducting current is created by non-dissipative motion of π-electron pairs along the asymmetric, “crystalline” π orbitals extending along chains of covalently bonded copper and oxygen ions, in the presence of an ionic bond between neighboring chains extending through the easily polarizable O²⁻ ions. This ionic bond correlates the motion of the electron pairs along all the π orbitals and stabilizes the superconducting state. Only in this sense is the apparent “onedimensionality” of superconductivity in cuprate superconductors to be understood. Zh. Tekh. Fiz. 68, 82–84 (November 1998)     

Synthesis, Crystal, Absorption and Fluorescence Spectroscopy of Nitro-Stilbene Derivatives with Benzophenones

In this paper, we have presented a range of new nitro-stilbene derivatives with benzophenones via ether or ester bridged bond. These nitro-stilbene derivatives with benzophenones have been conveniently obtained by condensation reaction. The linked benzophenones were efficiently introduced to nitro-stilbene dyes. The structures of these compounds have been characterized with NMR and element analysis. The single crystals of two target compounds (11 and 12) have been obtained, and their X-ray crystallographic data have been determined and discussed. Remarkably different absorption and fluorescence spectroscopy was observed for nitro-stilbene derivatives with benzophenones via different linked bonds. The results show that electron-donating or electron withdrawing bridged bonds have significant influence on the absorption and fluorescence spectroscopy, which makes it possible for the development of ideal nitro-stilbene dyes with benzophenones through chemical strategy.     

Two-Photon Optical Properties of Novel Branched Conjugated Derivatives Carrying Benzophenone Moiety with Various Electron Donor-Acceptor Substituent Groups

This paper presents a range of novel new branched conjugated dyes containing benzophenone moiety. As compared with those of 4-(p-benzoyl-styrene)yl-4'-(styrene)yl-triphenylamine (C1) and 4-(p-benzoyl-styrene)yl-4'-3,4,5-trimethoxyl-styrene)yl-triphenylamine (C2), the maximal linear absorption and emission wavelength of 4-(p-benzoyl-styrene)yl-4'-(p'-nitro-styrene)yl-triphenylamine (C3) displays red-shifted remarkably, While the fluorescence quantum yields of C3 are lower than those of C1 and C2 in various solvents. The fluorescence lifetimes of the derivatives were measured, and radiative and non-radiative transition constants of the derivatives were calculated. Two-photon absorption (TPA) optical data of the derivatives were measured by Ti:sapphire femtosecond laser tuning from 720 to 880 nm at intervals of 20 nm. TPA induced fluorescence emission of C3 is red-shifted with respected to that of C1 and C2. TPA cross sections of C3 are larger than those of C1 and C2 in various excited laser frequencies. TPA cross section of C2 and C3 are much larger than those of 3,4,5-(trimethoxylstyrene)yl-triphenylamine (C4) and 4-(p-nitrostyrene)yl-triphenylamine (C5) respectively under various near-IR Ti:sapphire femtosecond laser wavelength. C1 and C2 show similar one- and two- photon optical nature. Geometry optimization with ab initio method confirms that C3 has different electron density distribution, the energy levels in frontier orbitals, the dipole moment changes, the absorption and emission spectroscopy from those of C1 and C2. The cyclic voltammograms of the derivatives were detected in methylene chloride at various scan rates, and the energy of frontier orbials were estimated further from the redox potentials.     

Spectroscopic properties of DNA-acridine orange biopolymer films

Using electronic absorption, luminescence, and vibrational spectroscopy, we study the properties of DNA-acridine orange biopolymer films. The conformational structure of DNA molecules in the film is examined at different levels of the relative humidity, and the state of dye molecules incorporated into the structure of the biopolymer is estimated. These structures were formed according to the “guest-host” principle and the dye molecule acts as the “guest” and the “host” is the intercalative DNA binding sites. In such system dye molecules demonstrate high luminescence capability and are the uniform optical centers and their fluorescence spectrum doesn’t depend on excitation wavelength.     

A Comprehensive Investigation on the Cooperative Branch Effect on the Optical Properties of Novel Conjugated Compounds

This paper presents a variety of conjugated derivatives with different number of arms (4-styryl-triphenylamine: C1, 4, 4′-di-styryltriphenylamine: C2, 4, 4′, 4″-tri-styryltriphenylamine: C3). The linear absorption and fluorescence maxima and the molar extinction coefficients are in the order of C1<C2<C3 in various solvents. Two-photon absorption (TPA) up-converted emission of the derivatives were determined with Ti:sapphire femtosecond laser. The maximal TPA emission wavelength and the two-photon absorption cross section of the derivatives are also in the order of C1<C2<C3 in various solvents. The dipole moment changes of the derivatives between the excited state and the ground state were estimated from experiment, and they are in the order of C1<C2<C3, which is confirmed further by the molecular geometry optimization of the derivatives. The electron density distribution and the energy levels of the frontier orbital of the derivatives were analyzed. The cyclic voltammograms of the derivatives were performed and discussed.     

Analysis of branched oligophenylene by absorption and fluorescence spectra

A branched oligophenylene has been synthesized based on 1,3,5-tri(4′-bromophenyl)benzene. Absorption and fluorescence spectra were studied and fluorescence quantum yields and lifetimes were measured for the compound in solution. It is demonstrated that the absorption spectrum is a superposition of p-quaterphenyl, p-terphenyl, and biphenyl chromophore absorption bands in a 1:2:1 ratio. The oligomer fluorescence spectrum is found to depend on the excitation wavelength. It is shown that the oligomer fluorescence is determined by two fluorochromic groups, namely fragments with branched p-terphenyl and p-quaterphenyl units. The main fluorescence maxima for these fluorochromic groups coincide with each other and lie in the vicinity of λ = 360 nm. A very weak fluorescence band found in the region 380–440 nm is excited by light with a wavelength lying beyond the oligomer self-absorption region. The reasons for a decrease in fluorescence quantum yields of branched models and the studied oligophenylene as compared with those of linear p-polyphenylene chromophores are discussed.     

Local probing of the surface chemical bond using X-ray emission spectroscopy

2 and CO on Ni(100), benzene on Ni(100) and Cu(110), and glycine adsorbed on Cu(110). New types of molecular states are observed which are directly related to the surface chemical bond. The long-accepted Blyholder model which is based on a frontier orbital concept cannot explain our results for N₂ and CO chemisorption. We find it necessary to offer a new picture where changes in the whole molecular orbital framework have to be considered. We show that both π and σ type interactions are important in describing the bonding in benzene to metal surfaces. The future prospect is illustrated by the adsorption of the simplest amino acid, glycine, on Cu(110). The adsorbate has four different atomic centers where X-ray emission spectra are obtained, providing a unique view of the local electronic structure. Accepted: 6 March 1997     

Acetylene-Substituted Two-Photon Absorbing Molecules With Rigid Elongated Pi-Conjugation: Synthesis,Spectroscopic Properties and Two-Photon Fluorescence Cell Imaging Applications

Two asymmetrical molecules with substituted acetylene as central rigid elongated conjugation are reported as potential chromophores for two-photon microscopic imaging. These molecules consist of a typical D–π–A structure, have different donors (D), the same π-conjugated center (π) and the same acceptor (A). Structural characterization and spectroscopic properties, including single-photon (linear) absorption, quantum yields, single-photon fluorescence, and two-photon absorption spectra, were studied in solvents with different polarity. These acetylene-substituted molecules were found to have high two-photon absorption cross-sections (for example, 690 GM for molecule 1 in toluene), which were determined by a two-photon induced fluorescence method using a femtosecond Ti: sapphire laser as excitation source. Single- and two-photon cellular imaging experiments demonstrate that the substituted acetylene derivatives could be one kind of promising two-photon fluorescence probes for cellular imaging.     

The effect of electron irradiation on the optical properties of the natural armenian zeolite-clinoptilolite

Infrared (IR) absorption and luminescence in chemically and radiation-modified natural Armenian Zeolite (clinoptilolite) samples have been studied. The luminescence was studied in 390–450 nm and 620–710 nm wavelength bands, and the IR measurements were carried out in the 400–5400 cm⁻¹ range. It is shown that the luminescence intensity depends on the content of pure clinoptilolite in the samples and, probably on the distribution of “passive” luminescence centers over Si and Al sites that became “active” under radiation or chemical treatment. The samples of electron irradiated clinoptilolite have higher luminescence intensity than the chemically and thermally treated ones. A decrease in the intensity of IR absorption bands at 3550 cm⁻¹ and 3650 cm⁻¹ was found after irradiation.     

Photophysical properties of substituted intramolecularly hydrogen bonded compounds: A combined experimental and theoretical study

Photophysical properties of prototype excited state intramolecular proton transfer (ESIPT) system 4-methyl-2,6-diformyl phenol (MFOH) and its derivatives were studied by steady state and time-resolved fluorescence spectroscopy as well as by ab-initio quantum chemical calculation. It has been found that nonradiative decay process is the most important deactivation channel in all the cases and the hydrogen bonded enol conformer is stable in the ground state whereas, the proton transferred keto form is energetically favoured in the S₁(ππ^*) state. However, the net gain in stabilization in the process of ESIPT is almost unaffected by the substitution. The reversal of stability in the excited state was explained on the basis of the nature of frontier molecular orbital in all the cases. Intrinsic reaction coordinate analysis showed that drastic change in nonbonded interoxygen distance R(O-O) in the proton transfer pathway causes the switch over from the enol to keto configuration. A close comparison of several properties like molecular geometry, hydrogen bond strength and atomic charge in different derivatives of MFOH were found to be consistent and in good agreement with the experimental results obtained from time-resolved fluorescence experiments.     

Tunable wavelength laser medical system for treating oncological diseases

A new laser medical system (LMS) “LITT-FDT” for treating oncological diseases is presented. The laser system is based on a dye laser pumped by a copper vapor laser. The system features gradual wavelength tuning which allows operation almost with any photosensitizer (PS) when treating oncological diseases by the photodynamic therapy (PDT) method. The results of clinical trials of skin cancer treatment by the PDT method using the “LITT-FDT” laser system are considered.     

光纤化学传感同步吸收-荧光法的建立

建立一种光纤化学传感同步测定吸收光谱和荧光光谱的新方法。自制同步吸收-荧光比色皿,结合光纤化学传感技术,建立同步吸收-荧光光谱法检测仪器,分别测定罗丹明B,维生素B₂,维生素B₆等溶液的同步吸收-荧光光谱,且与传统的紫外-可见吸光光度法和荧光法进行对比。同步吸收-荧光光谱法测得罗丹明B,维生素B₂,维生素B₆与传统吸光光度法和荧光光谱法检测的吸收光谱图和荧光光谱的图谱大体一致。最大荧光强度波长与传统的荧光方法比较准确度高,但最大吸收波长略有偏差。同步吸收-荧光光谱法等同于同步测定荧光物质的吸收光谱和荧光光谱,实现二光谱合二为一,测定最大发射波长时准确度高,但最大吸收波长略有偏差,值得深一步研究。     

母环氨基修饰罗丹明衍生物的结构、热力学性质及其光谱的理论研究

采用DFT/B3LYP方法对3种母环氨基修饰的罗丹明类衍生物的结构进行了全优化,得到此3种化合物的基态和激发态的结构参数、振动光谱、前线分子轨道能量等相关数据,并在基态和激发态几何构型优化的基础上,用TD-DFT方法计算了其气相吸收光谱及发射光谱,全面分析了结构特征对热稳定性、前线分子轨道及光谱性质的影响。结果表明：化合物a末端氨基的扭转运动程度最低,化合物b相对于化合物a,分子共轭及平面程度提高,末端氨基的扭转运动程度增大,气相最大吸收波长及最大发射波长红移,且计算分子中最大发射波长最长,热稳定性最低。化合物c在计算分子中共轭及平面程度、热稳定性、HOMO能量最高,能隙最低,气相最大吸收波长最长。但相对于化合物b末端氨基的扭转运动程度增大,最大发射波长蓝移。     

Chemical bond strain in molecules of polyamide 6 coatings on the steel surface

The structure and stresses of chemical bonds in a 20 μm thick polyamide 6 (PA 6) coating on the steel surface are studied by IR spectroscopy. It is found that PA 6 molecules in the coating are oriented parallel to the metal surface and the content of metastable crystalline (γ) and mesomorphic (β) phases in it is twice as low as in PA 6 films. In the crystalline α phase, the molecular skeleton is compressed and “lateral” (respective to the skeleton) chemical bonds are extended. In the mesomorphic β phase, the concentration of overstressed (extended to a prerupture state) parts in the molecular skeleton is higher than in the film. These effects are explained by a change in the PA 6 low-frequency vibration spectrum at the PA 6-metal interface.     

二苯二硫和二苄二硫润滑性能的量子化学研究

用Gaussian03W程序在B3LYP/631G和HF/631G水平上对二苯二硫(DPDS)和二苄二硫(DBDS)的分子几何构型、电子结构、分子轨道指数及与铁原子簇的相互作用等进行了理论计算.用前线分子轨道理论分析了反应的活性原子和活性键,讨论了DPDS和DBDS与铁原子的作用方式,用前线电子密度,超离域性指数,原子净电荷及化合物与铁原子簇的化学吸附作用能等参数作为判据分析了DPDS和DBDS与铁原子间键合的强弱,反应性的大小.计算结果表明DPDS和DBDS与铁接触时,趋向于S-S键与C-S键断裂,在较为缓和的摩擦条件下,DPDS的抗磨作用优于DBDS,在较为苛刻的摩擦条件下,DBDS的极压作用优于DPDS,与摩擦学试验结果一致.     

Medium effects in the production and π0γ decay of ω-mesons in pA collisions in the GeV region

The ω resonance production and its π⁰γ decay in pA reactions close to threshold is considered within the Intranuclear Cascade (INC) model. The π⁰γ invariant-mass distribution shows two components which correspond to the ω decay “inside” and “outside” the nucleus, respectively. The “inside” component is distorted by medium effects, which introduce a mass shift as well as collisional broadening for the ω-meson and its decaying pion. The relative contribution of the “inside” component is analyzed in detail for different kinematical conditions and nuclear targets. It is demonstrated that a measurement of the correlation in azimuthal angle between the π⁰ and γ momenta allows to separate events related to the “inside”ω decay from different sources of background when uncorrelated π⁰'s and γ's are produced. Received: 2 April 2001 / Accepted: 5 June 2001     

基于密度泛函理论下多肽光谱性质研究

多肽类物质在生物医药等领域是一种重要的生物大分子,而紫外-可见吸收光谱和荧光光谱是研究生物分子精细结构的重要手段。采用密度泛函理论（DFT/RI）计算了生长激素释放肽（GHRP-6）和催产素（Oxytocin）两种多肽的结构模型和分子前线轨道;在含时密度泛函理论（TDDFT）的基础上,引入了TDA等近似,建立了多肽类物质的紫外-可见吸收光谱和荧光光谱的理论模型。结果表明,实验测得到GHRP-6的紫外-可见吸收光谱最大吸收波长为279 nm,计算得到的最大吸收波长为282 nm,误差为3 nm,误差百分比约为1%;Oxytocin紫外-可见吸收光谱的实验值为275 nm,计算值为269 nm,误差百分比约为2%。GHRP-6荧光光谱计算值为368 nm,实验值为360 nm,误差百分比约为2%;Oxytocin荧光光谱计算值为305 nm,实验值为312 nm,误差百分比约为2%。GHRP-6产生荧光的发射波长与色氨酸产生的荧光波长范围相近,说明GHRP-6产生荧光的主要贡献为色氨酸残基上的π→π*轨道跃迁,Oxytocin荧光峰位置与酪氨酸产生的荧光波长范围相近,Oxytocin产生荧光的主要贡献为酪氨酸残基上的π→π*轨道跃迁。根据该模型计算得到的光谱与实验结果吻合度较高,表明该模型能够准确计算多肽类物质紫外-可见吸收光谱和荧光光谱,为实验提供可靠的理论依据。     

Statistical thermodynamics of the formation of an infinite cluster of thermally reversible chemical bonds

A systematic “mean-field” treatment of the thermodynamic equilibrium formation of an infinite cluster of bonds in a system of identical monomers capable of forming from n=0 to n>2 reversible chemical bonds with one another is proposed within the Cayley-tree approximation. For this purpose the difference between the symmetry of the monomers appearing in “point-to-point” and closed bond paths, respectively, is taken into account on the basis of an analysis of the structure of the infinite cluster. Minimization with respect to the distribution of such monomers yields a nontrivial solution corresponding to a lower free energy than the classical solution, which does not allow for the symmetry difference indicated. In addition, it is shown that the classical solution corresponds to the free-energy maximum when the infinite cluster is formed and that the formation of the infinite cluster is a first-order phase transition. The possible form of the phase diagrams of the systems considered is analyzed. Zh. éksp. Teor. Fiz. 115, 979–990 (March 1999)     

Novel motifs for magnetic exchange interactions as exemplified in one dimensional magnets based on the FeCl3-α-di-imine system: Nuclear gamma resonance evidence of slow paramagnetic relaxation and 3D-ordering

The extremes of single ion slow paramagnetic relaxation and cooperative 3D-antiferromagnetic order are exemplified in a series of structurally characterized complexes based on the anhydrous FeCl₃-α-di-imine system. “Soft” Cl−Cl contacts, C−C (π-π) and hydrogen bonding interactions are found to lead to surprisingly strong magnetic exchange among five and six coordinate high-spin iron III monomers. The latter form the building blocks of novel “double chain” polymer magnets held together via the preceding “weak” interactions.     

Water vapor overtones pressure line broadening and shifting measurements

By using a spectrometer having as source a commercial etherostructure Al _x Ga_{1 − x} As diode laser operating in “free-running mode”, line shape parameters of some water vapor ro-vibrational overtones at 820–830 nm have been measured at room temperature. These weak absorption lines have been detected by using the wavelength modulation spectroscopy technique with second-harmonic detection. The broadening and shifting coefficients have been obtained by fitting the collected second-harmonic absorption features while varying the pressure of different foreign gases.