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Sample records for charge transfer reaction

  1. Computational Approach to Electron Charge Transfer Reactions

    DEFF Research Database (Denmark)

    Jónsson, Elvar Örn

    The step from ab initio atomic and molecular properties to thermodynamic - or macroscopic - properties requires the combination of several theoretical tools. This dissertation presents constant temperature molecular dynamics with bond length constraints, a hybrid quantum mechanics...... show general (or expected) properties. Properties such as in the physical and (semi-)chemical interface between classical and quantum systems and the effects of molecular bond length constraints on the temperature during simulations. As a second step the methodology is applied to the symmetric and...... asymmetric charge transfer reactions between several first-row transition metals in water. The results are compared to experiments and rationalised with classical analytic expressions. Shortcomings of the methods are accounted for with clear steps towards improved accuracy. Later the analysis is extended to...

  2. Charge transfer reaction laser with preionization means

    Science.gov (United States)

    Lauderslager, J. B.; Pacala, T. J. (Inventor)

    1978-01-01

    A helium-nitrogen laser is described in which energy in the visible range is emitted as a result of charge transfer reaction between helium ions and nitrogen molecules. The helium and nitrogen are present in a gas mixture at several atmospheres pressure, with a nitrogen partial pressure on the order of a pair of main discharge electrodes, the gas mixture is preionized to prevent arcing when the discharge pulse is applied. The preionization is achieved by the application of a high voltage across a pair of secondary electrodes which are spaced apart in a direction perpendicular to the spacing direction of the main discharge electrodes and the longitudinal axis of the space in which the gas mixture is contained. Feedback, by means of a pair of appropriately spaced mirrors, is provided, to produce coherent energy pulses at a selected wavelength.

  3. Charge transfer reactions in nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wiederrecht, G.P. [Argonne National Lab., IL (United States). Chemistry Div.; Wasielewski, M.R. [Argonne National Lab., IL (United States). Chemistry Div.]|[Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry; Galili, T.; Levanon, H. [Hebrew Univ. of Jerusalem (Israel). Dept. of Physical Chemistry

    1998-07-01

    Ultrafast transient absorption studies of intramolecular photoinduced charge separation and thermal charge recombination were carried out on a molecule consisting of a 4-(N-pyrrolidino)naphthalene-1,8-imide donor (PNI) covalently attached to a pyromellitimide acceptor (PI) dissolved in the liquid crystal 4{prime}-(n-pentyl)-4-cyanobiphenyl (5CB). The temperature dependencies of the charge separation and recombination rates were obtained at temperatures above the nematic-isotropic phase transition of 5CB, where ordered microdomains exist and scattering of visible light by these domains is absent. The authors show that excited state charge separation is dominated by molecular reorientation of 5CB perpendicular to the director within the liquid crystal microdomains. They also show that charge recombination is adiabatic and is controlled by the comparatively slow collective reorientation of the liquid crystal microdomains relative to the orientation of PNI{sup +}-PI{sup {minus}}. They also report the results of time resolved electron paramagnetic resonance (TREPR) studies of photoinduced charge separation in a series of supramolecular compounds dissolved in oriented liquid crystal solvents. These studies permit the determination of the radical pair energy levels as the solvent reorganization energy increases from the low temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal.

  4. Gaseous charge transfer reactions of multiply charged ions

    International Nuclear Information System (INIS)

    Doubly charged ions produced in electron impact ionization have received relatively little study due to their low abundance and masking from singly charged ions which are detected at the same mass-to-charge ratio by a mass spectrometer. This interference problem was avoided by exploiting a technique in which doubly charged molecular and fragment ions are monitored using a collisional charge-exchange process where only fast singly charged product ions are allowed to reach the detector. Primary research efforts were to determine structures and energetics of multiply charged ions formed in high energy electron impact ionization processes and their reactivities in ion-molecule charge exchange interactions. Doubly charged ion mass distributions for various chemical classes (including acetylenes, alkenes, terpenes and organophosphorus compounds) were recorded and appearance energies of prominent doubly charged ions were measured. Computer molecular orbital calculations (at the MINDO/3 level) of ionic structures, energies and charge distributions were utilized to augment the analysis of experimental results

  5. Deuteron-proton charge exchange reaction at small transfer momentum

    CERN Document Server

    Ladygina, N B

    2004-01-01

    The charge-exchange reaction pd -> npp at 1 GeV projectile proton energy is studied. This reaction is considered in a special kinematics, when the transfer momentum from the beam proton to fast outgoing neutron is close to zero. Our approach is based on the Alt-Grassberger-Sandhas formulation of the multiple-scattering theory for the three-nucleon system. The matrix inversion method has been applied to take account of the final state interaction (FSI) contributions. The differential cross section, tensor analyzing power $C_{0,yy}$, vector-vector $C_{y,y}$ and vector-tensor $C_{y,xz}$ spin correlation parameters of the initial particles are presented. It is shown, that the FSI effects play a very important role under such kinematical conditions. The high sensitivity of the considered observables to the elementary nucleon-nucleon amplitudes has been obtained.

  6. Cross sections for ion-molecular reactions in hydrogen systems and for charge transfer reactions of slow multiply charged ions

    International Nuclear Information System (INIS)

    Cross sections of ion-molecular reactions in hydrogen systems of H+-H2, H2+-H2 and H3+-H2 and charge transfer cross sections of multiply charged ions in atomic and molecular targets are presented in graphs and tables of the part A, B and C. All data presented for 99 collision systems have been measured systematically using an octo-pole ion beam guide (OPIG) technique till now since 1985. The part A is for ion-molecular reactions in hydrogen systems. In the lower energy region below few eV in center-of-mass systems, it is seen obviously at a glance that the ion-molecular reaction in hydrogen systems is dominated by H3+ formation process. In the energy region from few eV to few hundred eV in center-of-mass systems, many reaction channels of decay processes from intermediate molecular states seem to be opened resonantly. Some of cross section data in the part B for charge transfer reactions of low-charged ions produced by a conventional electron impact type (Nier type) ion source should be noted to strongly depend on the electron impact energy due to contamination of low lying metastable states in projectile ions. The part C is for charge transfer reactions of multiply charged ions extracted from a small type of electron beam ion source (Mini-EBIS). In measurements using the mini-EBIS, no evidence of metastable ions existing in the primary ion beam has been found except for doubly charged ion beam. The higher energy end of the present cross sections are connected with previous data in fairly good

  7. Charge transfer reaction of multi-charged oxygen ions with O2

    Science.gov (United States)

    Holzscheiter, H. M.; Church, D. A.

    1981-10-01

    The reaction rates for charge transfer from O2 to doubly and triply charged oxygen atoms are measured in a demonstration of the measurement capabilities of a system at ultrahigh vacuum with low-energy magnetically confined ions. Ions were produced by electron impact ionization of gas within a Penning-type ion trap, with selective removal of unwanted ionization states by radio-frequency resonant excitation. Ion number mass-to-charge ratio spectra obtained at partial pressures of O2 from 9.9 x 10 to the -9th to 1.5 x 10 to the -7th torr yield rate constants of 1.0 x 10 to the -9th cu cm/sec and 2.5 x 10 to the -9th cu cm/sec for the O(2+) and O(3+) reactions, respectively. Measurements made at a 30% increase of the effective axial well depth of the trap demonstrate that the rate constant is essentially energy independent in the energy range studies, implying that the O(2+) cross section for charge transfer has an inverse velocity dependence of the Langevin type, despite a reaction rate lower than the Langevin valve.

  8. Negative ion-uranium hexafluoride charge transfer reactions

    Science.gov (United States)

    Streit, Gerald E.; Newton, T. W.

    1980-10-01

    The flowing afterglow technique has been used to study the process of charge transfer from selected negative ions (F-, Cl-, Br-, I-, SF6-) to UF6. The sole ionic product in all cases was observed to be UF6-. Data analysis was complicated by an unexpected coupling of chemical and diffusive ion loss processes when UF6- product ions were present. The rate coefficients for the charge transfer processes are (k in 10-9 cm3 molecule-1 s-1) F-, 1.3; Cl-, 1.1; Br-, 0.93; I-, 0.77; and SF6-, 0.69. The rate constants agree quite well with the classical Langevin predictions.

  9. Excited state intramolecular charge transfer reaction in 4-(1-azetidinyl)benzonitrile: Solvent isotope effects

    Indian Academy of Sciences (India)

    Tuhin Pradhan; Piue Ghoshal; Ranjit Biswas

    2009-01-01

    Excited state intramolecular charge transfer reaction of 4-(1-azetidinyl) benzonitrile (P4C) in deuterated and normal methanol, ethanol and acetonitrile has been studied in order to investigate the solvent isotope effects on reaction rates and yields. These quantities (reaction rates and yields) along with several other properties such as quantum yield and radiative rates have been found to be insensitive to the solvent isotope substitution in all these solvents. The origin of the solvent isotope insensitivity of the reaction is discussed and correlated with the observed slowing down of the solvation dynamics upon isotope substitution.

  10. Decoupling interfacial reactions between plasmas and liquids: charge transfer vs plasma neutral reactions.

    Science.gov (United States)

    Rumbach, Paul; Witzke, Megan; Sankaran, R Mohan; Go, David B

    2013-11-01

    Plasmas (gas discharges) formed at the surface of liquids can promote a complex mixture of reactions in solution. Here, we decouple two classes of reactions, those initiated by electrons (electrolysis) and those initiated by gaseous neutral species, by examining an atmospheric-pressure microplasma formed in different ambients at the surface of aqueous saline (NaCl) solutions. Electrolytic reactions between plasma electrons and aqueous ions yield an excess of hydroxide ions (OH(-)), making the solution more basic, while reactions between reactive neutral species formed in the plasma phase and the solution lead to nitrous acid (HNO2), nitric acid (HNO3), and hydrogen peroxide (H2O2), making the solution more acidic. The relative importance of either reaction path is quantified by pH measurements, and we find that it depends directly on the composition of the ambient background gas. With a background gas of oxygen or argon, electron transfer reactions yielding excess OH(-) dominate, while HNO2 and HNO3 formed in the plasma and by the dissolution of nitrogen oxide (NOx) species dominate in the case of air and nitrogen. For pure nitrogen (N2) gas, we observe a unique coupling between both reactions, where oxygen (O2) gas formed via water electrolysis reacts in the bulk of the plasma to form NOx, HNO2, and HNO3. PMID:24144120

  11. Effects of acid concentration on intramolecular charge transfer reaction of 4-(azetidinyl) benzonitrile in solution

    Indian Academy of Sciences (India)

    Biswajit Guchhait; Tuhin Pradhan; Ranjit Biswas

    2014-01-01

    Effects of acid concentration on excited state intramolecular charge transfer reaction of 4-(azetidinyl) benzonitrile (P4C) in aprotic (acetonitrile and ethyl acetate) and protic (ethanol) solvents have been studied by means of steady state absorption and fluorescence, and time resolved fluorescence spectroscopic techniques. While absorption and fluorescence bands of P4C have been found to be shifted towards higher energy with increasing acid concentration in acetonitrile and ethyl acetate, no significant dependence has been observed in ethanolic solutions. Reaction rate becomes increasingly slower with acid concentration in acetonitrile and ethyl acetate. In contrast, acid in ethanolic solutions does not produce such an effect on reaction rate. Time-dependent density functional theory calculations have been performed to understand the observed spectroscopic results.

  12. Proton and charge transfer reactions dynamics of a hydroxyflavone derivative in a polar solvent and in a cyclodextrin nanocavity

    International Nuclear Information System (INIS)

    In this work, we report on the observation of ultrafast intramolecular charge- and proton-transfer reactions of 4'-dimethylaminoflavonol (DMAF) in N,N-dimethyl formamide and in γ-cyclodextrin (γ-CD) solution. Upon femtosecond excitation an intramolecular charge transfer (ICT) reaction takes place to produce an ICT structure in ∼200 fs. This structure may undergo a proton transfer reaction to generate a zwitterionic (Z) form in 2-3 ps, or relaxes in its potential energy well, to later equilibrate with that of Z in hundreds of ps. Addition of γ-CD does not significantly affect the fast dynamics of the formed anion. The fs-emission signals of the parent molecule, 3-hydroxyflavone, indicate that the dimethyl amino group in DMAF enhances the rate constant of intermolecular proton-transfer and intramolecular charge-transfer reactions

  13. Charge constrained density functional molecular dynamics for simulation of condensed phase electron transfer reactions

    CERN Document Server

    Oberhofer, H

    2009-01-01

    We present a plane-wave basis set implementation of charge constrained density functional molecular dynamics (CDFT-MD) for simulation of electron transfer reactions in condensed phase systems. Following earlier work of Wu et al. Phys. Rev. A 72, 024502 (2005), the density functional is minimized under the constraint that the charge difference between donor and acceptor is equal to a given value. The classical ion dynamics is propagated on the Born-Oppenheimer surface of the charge constrained state. We investigate the dependence of the constrained energy and of the energy gap on the definition of the charge, and present expressions for the constraint forces. The method is applied to the Ru2+-Ru3+ electron self-exchange reaction in aqueous solution. Sampling the vertical energy gap along CDFT-MD trajectories, and correcting for finite size effects, a reorganization free energy of 1.6 eV is obtained. This is 0.1-0.2 eV lower than a previous estimate based on a continuum model for solvation. smaller value for re...

  14. Charge transfer reactions of Kr2+ and Ne2+ ions with several molecular gases at 300 K

    International Nuclear Information System (INIS)

    Measurements are reported of the rate coefficients and product-ion distributions for the reactions of Kr2+ and Ne2+ ions with H2, N2, O2, CO, CO2 and CH4 at 300 K. The data are obtained with a selected ion flow tube (SIFT). The reaction rates are generally fast, proceeding at or near the gas kinetic limit. In the Kr2+ reactions the only mechanism observed is single charge transfer, whereas for the more energetic Ne2+ ions parallel single and double charge transfer product channels are evident, the double charge transfer channels usually being dominant. The general features of the data are discussed in relation to those previously obtained for the corresponding reactions of Ar2+ and Xe2+ ions. (orig.)

  15. The role of electronic symmetry in charge-transfer-to-solvent reactions: Quantum nonadiabatic computer simulation of photoexcited sodium anions

    OpenAIRE

    Smallwood, C J; Bosma, W B; Larsen, R E; Schwartz, Benjamin J.

    2003-01-01

    Since charge-transfer-to-solvent (CTTS) reactions represent the simplest class of solvent-driven electron transfer reactions, there has been considerable interest in understanding the solvent motions responsible for electron ejection. The major question that we explore in this paper is what role the symmetry of the electronic states plays in determining the solvent motions that account for CTTS. To this end, we have performed a series of one-electron mixed quantum/classical nonadiabatic molec...

  16. Excited state intramolecular charge transfer reaction in nonaqueous electrolyte solutions: Temperature dependence

    International Nuclear Information System (INIS)

    Temperature dependence of the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in ethyl acetate (EA), acetonitrile (ACN), and ethanol at several concentrations of lithium perchlorate (LiClO4) has been investigated by using the steady state and time resolved fluorescence spectroscopic techniques. The temperature range considered is 267-343 K. The temperature dependent spectral peak shifts and reaction driving force (-ΔGr) in electrolyte solutions of these solvents can be explained qualitatively in terms of interaction between the reactant molecule and ion-atmosphere. Time resolved studies indicate that the decay kinetics of P4C is biexponential, regardless of solvents, LiClO4 concentrations, and temperatures considered. Except at higher electrolyte concentrations in EA, reaction rates in solutions follow the Arrhenius-type temperature dependence where the estimated activation energy exhibits substantial electrolyte concentration dependence. The average of the experimentally measured activation energies in these three neat solvents is found to be in very good agreement with the predicted value based on data in room temperature solvents. While the rate constant in EA shows a electrolyte concentration induced parabolic dependence on reaction driving force (-ΔGr), the former in ethanol and ACN increases only linearly with the increase in driving force (-ΔGr). The data presented here also indicate that the step-wise increase in solvent reorganization energy via sequential addition of electrolyte induces the ICT reaction in weakly polar solvents to crossover from the Marcus inverted region to the normal region.

  17. Electron correlation effects in the adiabatic charge transfer reactions at the metal/polar liquid interface

    International Nuclear Information System (INIS)

    New simple expressions for average number of electrons in the valence orbital of a reacting ion and the charge susceptibility are obtained that allow one to calculate adiabatic free energy surfaces (AFES) and corresponding kinetic regime diagrams (KRD) for adiabatic processes of electron transfer from the ion, located in a polar liquid, to a metal within the framework of the exactly solvable (in the limit T→0) model of the metal with the infinitely wide conduction band. This model represents one of limiting cases of the Anderson model that may be applied to s-p metals. Unlike previous studies of the adiabatic reactions in the model of the metal with the infinitely wide conduction band, the present work takes into account the electron-electron correlation effects in an exact manner. General results are illustrated with KRD which determine the regions of the physical parameters of the system corresponding to various types of electron transfer processes. AFES are calculated for some typical parameters sets. The exact AFES are compared with those calculated within the Hartree-Fock approximation. It is shown that the correlation effects are of importance and results not only in a considerable decrease of the activation free energy but also to qualitatively different shapes of AFES in some regions of the system parameters

  18. Study of fluorescence characteristics of the charge-transfer reaction of quinolone agents with bromanil

    Science.gov (United States)

    Li, Wen-Ying; Chen, Xiao-Fang; Xuan, Chun-Sheng

    2009-01-01

    A spectrofluorimetric method was discussed for the determination of three antibacterial quinolone derivatives, ofloxacin (OFL), norfloxacin (NOR) and ciprofloxacin (CIP) through charge-transfer complexation (CTC) with 2,3,5,6-tetrabromo-1,4-benzoquinone (bromanil, TBBQ). The method was based on the reaction of these drugs as n-electron donors with the π-acceptor TBBQ. TBBQ was found to react with these drugs to produce a kind of yellow complexes and the fluorescence intensities of the complexes were enhanced by 29-36 times more than those of the corresponding monomers. UV-vis, 1H NMR and XPS techniques were used to study the complexes formed. The various experimental parameters affecting the fluorescence intensity were studied and optimized. Under optimal reaction conditions, the rectilinear calibration graphs were obtained in the concentration range of 0.021-2.42 μg mL -1, 0.017-2.63 μg mL -1 and 0.019-2.14 μg mL -1 for OFL, NOR and CIP, respectively. The methods developed were applied successfully to the determination of the subject drugs in their pharmaceutical dosage forms with good precision and accuracy compared to official and reported methods as revealed by t- and F-tests.

  19. Sputtered metal source for rate coefficient measurements of asymmetric charge transfer reactions

    International Nuclear Information System (INIS)

    Complete text of publication follows. Asymmetric charge transfer (ACT) reactions between noble gas ions and metal atoms play an important role in numerous glow discharge applications. Due to the sputtering effect of ions impinging on the cathode surface significant metal density can be created in the cathode area of dc noble gas discharges. These metal atoms are then ionized and excited in the negative glow region, which is utilized in glow discharge spectroscopy (GDS) applications. ACT represents an important source of excited metal ions in the negative glow. Numerical modeling of the cathode region of a sputtering discharge requires rate coefficient values of ACT reactions as input data [Bogaerts et al. J. Anal. Atom. Spectrom. 11 (1996) 841]. There are rate coefficient values available in the literature only for volatile metals - in combination with different noble gas ions - that can be evaporated at relatively low temperatures (e.g. Hg, Zn, Cd etc.). However, data for other metals (Cu, Fe, Ag, etc.) have not been measured yet. The aim of this work is to build a metal source that can be applied for rate coefficient measurements of ACT reactions. The new sputtered metal source operates at room temperature creating homogeneous spatial distribution of metal atoms in a 9 cm3 region. Four hollow-cathode discharges - placed symmetrically around the central region - provide the needed metal density in the order of 5 x 1011 cm-3 as determined by atomic absorption spectroscopy. The future work focuses on the ACT rate coefficient measurements. The authors kindly acknowledge the support by the MRTN-CT-035459.

  20. Charge-exchange breakup of the deuteron with the production of two protons and spin structure of the amplitude of the nucleon charge transfer reaction

    International Nuclear Information System (INIS)

    In the framework of the impulse approximation, the relation between the effective cross section of the charge-exchange breakup of a fast deuteron d + a → (pp) + b and the effective cross section of the charge transfer process n + a → p + b is discussed. In doing so, the effects of the proton identity (Fermi-statistics) and of the Coulomb and strong interactions of protons in the final state are taken into account. The distribution over relative momenta of the protons, produced in the charge-exchange process d + p → (pp) + n in the forward direction, is investigated. At the transfer momenta being close to zero the effective cross section of the charge-exchange breakup of a fast deuteron, colliding with the proton target, is determined only by the spin-flip part of the amplitude of the charge transfer reaction n + p → p + n at the zero angle. It is shown that the study of the process d + p → (pp) + n in a beam of the polarized (aligned) deuterons allows one, in principle, to separate two spin-dependent terms in the amplitude of the charge transfer reaction n + p → p + n, one of which does not conserve and the other one conserves the projection of the nucleon spin onto the direction of momentum at the transition of the neutron into the proton

  1. Laser induced fluorescence studies of the charge transfer reactions of N2+ with Ar and N2

    International Nuclear Information System (INIS)

    The charge transfer reactions of N2+ with Ar and N2 have been studied using laser induced fluorescence to monitor N2+. The ions were formed initially within a quadrupole ion trap by electron impact of neutral N2. The experimental conditions were varied such that the trapped N2+ could be examined under collision free conditions or after experiencing a controlled number of collisions with selected background gas. The ion--molecule collisions rapidly altered the internal energy distribution of the trapped N2+ and by monitoring these changes charge transfer cross sections for individual initial vibrational states of the N2+ with Ar and N2 have been estimated. The results show a strong vibrational dependence of the charge transfer cross section in the N2+--N2 system and no measureable dependence in the N2+--Ar system

  2. Excited state intramolecular charge transfer reaction of 4-(morpholenyl) benzonitrile in solution: Effects of hetero atom in the donor moiety

    Indian Academy of Sciences (India)

    Tuhin Pradhan; Harun Al Rasid Gazi; Ranjit Biswas

    2010-07-01

    An intramolecular charge transfer (ICT) molecule with an extra hetero atom in its donor moiety has been synthesized in order to investigate how ICT reaction is affected by hetero atom replacement. Photo-physical and photo-dynamical properties of this molecule, 4-(morpholenyl)benzonitrile (M6C), have been studied in 20 different solvents. The correlation between the reaction driving force (- ) and activation barrier ( #) has been explored in order to understand the solvent effects (static and dynamic) on the photo-excited ICT reaction in this molecule. A Kramer’s model analysis of the experimentally observed reaction rate constants indicates a solvent-averaged activation barrier of ∼ 4 in the absence of solvent dynamical control. The reaction in M6C is therefore not a barrier-less reaction but close to the limit where conventional kinetics might break down.

  3. Theoretical estimation of the rate of photoinduced charge transfer reactions in triphenylamine C60 donor-acceptor conjugate.

    Science.gov (United States)

    Martínez, Juan Pablo; Solà, Miquel; Voityuk, Alexander A

    2016-06-01

    Fullerene-based molecular heterojunctions such as the [6,6]-pyrrolidine-C60 donor-acceptor conjugate containing triphenylamine (TPA) are potential materials for high-efficient dye-sensitized solar cells. In this work, we estimate the rate constants for the photoinduced charge separation and charge recombination processes in TPA-C60 using the unrestricted and time-dependent DFT methods. Different schemes are applied to evaluate excited state properties and electron transfer parameters (reorganization energies, electronic couplings, and Gibbs energies). The use of open-shell singlet or triplet states, several density functionals, and continuum solvation models is discussed. Strengths and limitations of the computational approaches are highlighted. The present benchmark study provides an overview of the expected performance of DFT-based methodologies in the description of photoinduced charge transfer reactions in fullerene heterojunctions. © 2016 Wiley Periodicals, Inc. PMID:26992355

  4. Thermodynamic Integration Networks and Their Application to Charge Transfer Reactions within the AauDyPI Fungal Peroxidase.

    Science.gov (United States)

    Bauß, Anna; Langenmaier, Michael; Strittmatter, Eric; Plattner, Dietmar A; Koslowski, Thorsten

    2016-06-01

    We present a computer simulation study of the thermodynamics and kinetics of charge transfer reactions within the fungal peroxidase AauDyPI from Auricularia auriculae-judae. Driving forces and reorganization energies are obtained from a thermodynamic integration scheme based upon molecular dynamics simulations. To enhance the numerical accuracy, the free energies are analyzed within a least-squares scheme of a closely knit thermodynamic network. We identify Tyr147, Tyr229, and Trp105 as oxidative agents, and find Trp377 to be a long-lived reaction intermediate. The results are compared to recent experimental findings. PMID:27182684

  5. Hydrogen-transfer and charge-transfer in photochemical and radiation induced reactions. Progress report, November 1, 1975--October 31, 1976

    International Nuclear Information System (INIS)

    The relative importance of light absorption, quenching of triplet, and hydrogen transfer repair has been examined in retardation by mercaptans of photoreduction of aromatic ketones by alcohols. In the reduction of benzophenone by 2-propanol, retardation is efficient and, after correction for the first two effects, is due entirely to hydrogen-transfer repair, as indicated by deuterium labeling. In reduction of acetophenone by α-methylbenzyl alcohol, repair by hydrogen transfer is also operative. In reduction of benzophenone by benzhydrol, retardation is less efficient and is due to quenching, as the ketyl radical does not abstract hydrogen from mercaptan rapidly in competition with coupling. Deuterium isotope effects are discussed in terms of competitive reactions. Photoreduction of benzophenone by 2-butylamine and by triethylamine is retarded by aromatic mercaptans and disulfides. Of the retardation not due to light absorption and triplet quenching by the sulfur compounds, half is due to hydrogen-transfer repair, as indicated by racemization and deuterium labeling. The remainder is attributed to quenching by the sulfur compound of the charge-transfer-complex intermediate. Photoreduction by primary and secondary amines, but not by tertiary amines, is accelerated by aliphatic mercaptans. The acceleration is attributed to catalysis of hydrogen transfer by the mercaptan in the charge-transfer complex. The effect is large in hydrocarbon solvent, less in polar organic solvents and absent in water

  6. Excited state charge transfer reaction in (mixed solvent + electrolyte) systems: Role of reactant-solvent and reactant-ion interactions

    Indian Academy of Sciences (India)

    Harun Al Rasid Gazi; Ranjit Biswas

    2011-05-01

    Fluorescence spectroscopic techniques have been used to study the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in two sets of mixed solvents, (1-propanol + ethyl acetate) and (propylene carbonate + acetonitrile), in the absence and presence of a strong electrolyte, lithium perchlorate. These two sets of mixed solvent systems represent binary solvent mixtures of low and high polarities, respectively. Density, sound velocity and viscosity measurements indicate that these two mixed solvent systems are structurally different. Stronger ion-reactant interaction is evidenced in the mole fraction independence of emission frequencies in electrolyte solutions of low polar binary solvent mixtures. For both these mixtures, the reaction driving force (- ) decreases with increase in mole fraction of the relatively less polar solvent component of the mixture. Interestingly, - increases significantly on addition of electrolyte in low polar mixtures and exhibits mixture composition dependence but, in contrast, - in high polar mixtures does not sense variation in mixture composition in presence of electrolyte. This insensitivity to mixture composition for high polar mixtures is also observed for the measured reaction time constant. In addition, the reaction time constant does not sense the presence of electrolyte in the high polar solvent mixtures. The reaction time constant in low polar mixtures, which becomes faster on addition of electrolyte, lengthens on increasing the mole fraction of the relatively less polar solvent component of the mixture. These observations have been qualitatively explained in terms of the measured solvent reorganization energy and reaction driving force by using expressions from the classical theory of electron transfer reaction.

  7. Spectrophotometric determination of quetiapine fumarate in pharmaceuticals and human urine by two charge-transfer complexation reactions

    Directory of Open Access Journals (Sweden)

    Vinay K.B.

    2012-01-01

    Full Text Available Two simple, rapid and accurate spectrophotometric procedures are proposed for the determination of quetiapine fumarate (QTF in pharmaceuticals and in spiked human urine. The methods are based on charge transfer complexation reactions of free base form of the drug (quetiapine, QTP, as n-electron donor (D, with either p-chloranilic acid (p-CAA (method A or 2,3-dichloro-5,6-dicyanoquinone (DDQ (method B as π-acceptors (A. The coloured charge transfer complexes produced exhibit absorption maxima at 520 and 540 nm, in method A and method B, respectively. The experimental conditions such as reagent concentration, reaction solvent and time have been carefully optimized to achieve the maximum sensitivity. Beer’s law is obeyed over the concentration ranges of 8.0 - 160 and 4.0 - 80.0 μg ml-1, for method A and method B, respectively. The calculated molar absorptivity values are 1.77 × 103 and 4.59 × 103 l mol-1cm-1, respectively, for method A and method B. The Sandell sensitivity values, limits of detection (LOD and quantification (LOQ have also been reported. The stoichiometry of the reaction in both cases was accomplished adopting the limiting logarithmic method and was found to be 1: 2 (D: A. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis. The proposed methods were successfully applied for the determination of QTF in pharmaceutical formulations and spiked human urine.

  8. Charge Transfer for Reactions of Sc3+ with N2 and H2 at Electron-volt Energy

    Institute of Scientific and Technical Information of China (English)

    CAO Li; JIANG Yu-Rong; NIE Zong-Xiu; LI Jiao-Mei; GAO Ke-Lin

    2001-01-01

    The charge transfer rate coefficients for reactions of Sc3+ with N2 and H2 have been measured at the meancollision energy of 4.2 Ev. The rate coefficients are derived from the decay rate ofion signals by using ion storagein a radio frequency ion trap. The rate coefficients are 8.18(0.18) × 10-10cm3.s-1 at Tequiv ≈ 1.26 × 104K forSc3+ with N2 and 1.44(0.39) × 10-9 cm3.s-1 at Tequiv ≈ 1.67 × 103 K for Sc3+ with H2, respectively. Both resultsare comparablewith the Langevin rate coefficients.

  9. Non-adiabatic processes in the charge transfer reaction of O2 molecules with potassium surfaces without dissociation

    International Nuclear Information System (INIS)

    Thin potassium films grown on Si(001) substrates are used to measure internal chemicurrents and the external emission of exoelectrons simultaneously during adsorption of molecular oxygen on K surfaces at 120 K. The experiments clarify the dynamics of electronic excitations at a simple metal with a narrow valence band. X-ray photoemission reveals that for exposures below 5 L almost exclusively peroxide K2O2 is formed, i.e., no dissociation of the molecule occurs during interaction. Still a significant chemicurrent and a delayed exoelectron emission are detected due to a rapid injection of unoccupied molecular levels below the Fermi level. Since the valence band width of potassium is approximately equal to the potassium work function (2.4 eV) the underlying mechanism of exoemission is an Auger relaxation whereas chemicurrents are detected after resonant charge transfer from the metal valence band into the injected level. The change of the chemicurrent and exoemission efficiencies with oxygen coverage can be deduced from the kinetics of the reaction and the recorded internal and external emission currents traces. It is shown that the non-adiabaticity of the reaction increases with coverage due to a reduction of the electronic density of states at the surface while the work function does not vary significantly. Therefore, the peroxide formation is one of the first reaction systems which exhibits varying non-adiabaticity and efficiencies during the reaction. Non-adiabatic calculations based on model Hamiltonians and density functional theory support the picture of chemicurrent generation and explain the rapid injection of hot hole states by an intramolecular motion, i.e., the expansion of the oxygen molecule on the timescale of a quarter of a vibrational period

  10. Excited state intramolecular charge transfer reaction in non-aqueous reverse micelles: Effects of solvent confinement and electrolyte concentration

    Indian Academy of Sciences (India)

    Tuhin Pradhan; Harun Al Rasid Gazi; Biswajit Guchhait; Ranjit Biswas

    2012-03-01

    Steady state and time resolved fluorescence emission spectroscopy have been employed to investigate the effects of solvent confinement and electrolyte concentration on excited state intramolecular charge transfer (ICT) reaction in 4-(1-pyrrolidinyl) benzonitrile (P5C), 4-(1-piperidinyl) benzonitrile (P6C), and 4-(1-morpholenyl) benzonitrile (M6C) in AOT/n-heptane/acetonitrile and AOT/n-heptane/methanol reverse micelles. Dramatic confinement effects have been revealed via a huge reduction (factor ranging between 100 and 20) over bulk values of both equilibrium and reaction rate constants. A strong dependence on the size of the confinement () of these quantities has also been observed. dependent average static dielectric constant, viscosity and solvation time-scale have been determined. Estimated dielectric constants for confined methanol and acetonitrile show a decrease from the respective bulk values by a factor of 3-5 and viscosities increased by a factor of 2 at the highest considered. Addition of electrolyte at = 5 for acetonitrile is found to produce a linear increase of confined solvent viscosity but leads to a non-monotonic electrolyte concentration dependence of average solvation time. Reaction rate constant is found to decrease linearly with electrolyte concentration for P5C and P6C but non-monotonically for M6C, the highest decrease for all the molecules being ∼ 20% over the value in the absence of added electrolyte in the solvent pool. The observed huge reduction in reaction rate constant is attributed to the effects of decreased solution polarity, enhanced viscosity and slowed-down solvent reorganization of the solvent under confinement in these non-aqueous reverse micelles.

  11. Non-adiabatic processes in the charge transfer reaction of O2 molecules with potassium surfaces without dissociation

    Science.gov (United States)

    Krix, David; Nienhaus, Hermann

    2014-08-01

    Thin potassium films grown on Si(001) substrates are used to measure internal chemicurrents and the external emission of exoelectrons simultaneously during adsorption of molecular oxygen on K surfaces at 120 K. The experiments clarify the dynamics of electronic excitations at a simple metal with a narrow valence band. X-ray photoemission reveals that for exposures below 5 L almost exclusively peroxide K2O2 is formed, i.e., no dissociation of the molecule occurs during interaction. Still a significant chemicurrent and a delayed exoelectron emission are detected due to a rapid injection of unoccupied molecular levels below the Fermi level. Since the valence band width of potassium is approximately equal to the potassium work function (2.4 eV) the underlying mechanism of exoemission is an Auger relaxation whereas chemicurrents are detected after resonant charge transfer from the metal valence band into the injected level. The change of the chemicurrent and exoemission efficiencies with oxygen coverage can be deduced from the kinetics of the reaction and the recorded internal and external emission currents traces. It is shown that the non-adiabaticity of the reaction increases with coverage due to a reduction of the electronic density of states at the surface while the work function does not vary significantly. Therefore, the peroxide formation is one of the first reaction systems which exhibits varying non-adiabaticity and efficiencies during the reaction. Non-adiabatic calculations based on model Hamiltonians and density functional theory support the picture of chemicurrent generation and explain the rapid injection of hot hole states by an intramolecular motion, i.e., the expansion of the oxygen molecule on the timescale of a quarter of a vibrational period.

  12. Non-adiabatic processes in the charge transfer reaction of O{sub 2} molecules with potassium surfaces without dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Krix, David; Nienhaus, Hermann, E-mail: hermann.nienhaus@uni-due.de [Faculty of Physics, University of Duisburg-Essen and Center of Nanointegration Duisburg-Essen (CENIDE), Lotharstr. 1, D-47048 Duisburg (Germany)

    2014-08-21

    Thin potassium films grown on Si(001) substrates are used to measure internal chemicurrents and the external emission of exoelectrons simultaneously during adsorption of molecular oxygen on K surfaces at 120 K. The experiments clarify the dynamics of electronic excitations at a simple metal with a narrow valence band. X-ray photoemission reveals that for exposures below 5 L almost exclusively peroxide K{sub 2}O{sub 2} is formed, i.e., no dissociation of the molecule occurs during interaction. Still a significant chemicurrent and a delayed exoelectron emission are detected due to a rapid injection of unoccupied molecular levels below the Fermi level. Since the valence band width of potassium is approximately equal to the potassium work function (2.4 eV) the underlying mechanism of exoemission is an Auger relaxation whereas chemicurrents are detected after resonant charge transfer from the metal valence band into the injected level. The change of the chemicurrent and exoemission efficiencies with oxygen coverage can be deduced from the kinetics of the reaction and the recorded internal and external emission currents traces. It is shown that the non-adiabaticity of the reaction increases with coverage due to a reduction of the electronic density of states at the surface while the work function does not vary significantly. Therefore, the peroxide formation is one of the first reaction systems which exhibits varying non-adiabaticity and efficiencies during the reaction. Non-adiabatic calculations based on model Hamiltonians and density functional theory support the picture of chemicurrent generation and explain the rapid injection of hot hole states by an intramolecular motion, i.e., the expansion of the oxygen molecule on the timescale of a quarter of a vibrational period.

  13. Interaction of 2-aminopyrimidine with σ- and π-acceptors involving chemical reactions via initial charge transfer complexation

    Science.gov (United States)

    Rabie, U. M.; Abou-El-Wafa, M. H.; Mohamed, R. A.

    2007-12-01

    Interaction of 2-aminopyrimidine (AP) with iodine as a typical σ-type acceptor and with a typical π-type acceptor, 2,3,5,6-tetrachloro-1,4-benzoquinone, p-chloranil (CHL) have been studied spectrophotometrically. Electronic absorption spectra of the system AP-I 2 in several organic solvents of different polarities have performed clear charge transfer (CT) band(s). Formation constants ( KCT) and molar absorption coefficients ( ɛCT) and thermodynamic properties, Δ H, Δ S, and Δ G, of this system in various organic solvents were determined and discussed. Interaction of AP with the π-acceptor has shown unique behaviors. Chemical reaction has occurred via prior or initial formation of the outer-sphere CT complex followed by formation of the corresponding anion radicals, CHL rad - , as intermediates. UV-vis, 1H NMR, Mass, and FT-IR spectra in addition to the elemental analysis were used to confirm the proposed occurrence of the chemical reaction and to investigate the synthesized solid products.

  14. Electron transfer reactions

    CERN Document Server

    Cannon, R D

    2013-01-01

    Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

  15. Spectrophotometric Determination of Some Fluoroquinolone Antibacterials through Charge-transfer and Ion-pair Complexation Reactions

    Energy Technology Data Exchange (ETDEWEB)

    El-Brashy, Amina Mohamed; El-Sayed Metwally Mohamed; El-Sepai, Fawzi Abdallah [University of Mansoura, Mansoura (Egypt)

    2004-03-15

    Two simple, rapid and sensitive spectrophotometric methods for the determination of three fluoroquinolones, namely levofloxacin, norfloxacin and ciprofloxacin have been performed either in pure form or in their tablets. In the first method, levofloxacin and norfloxacin are directly treated with bromocresol green (BCG) in dichloromethane while ciprofloxacin is allowed to react with the same dye in aqueous acidic buffer. Highly yellow colored complex species were formed instantaneously in case of levofloxacin and norfloxacin or after extraction into dichloromethane for ciprofloxacin. The formed complexes are quantified spectrophotometrically at their absorption maxima at 411 nm for levofloxacin and 412 nm for norfloxacin and ciprofloxacin. The second method involves the reaction of levofloxacin with {rho}-chloranilic acid ({rho}-CA) and norfloxacin with tetracyanoethylene (TCNE) in acetonitrile to give complexes with maximum absorbance at 521 and 333 nm for the two drugs, respectively. Adopting the first procedure, calibration graphs were linear over the range 1- 20 {mu}g mL{sup .1} with mean percentage recoveries of 100.41 {+-} 0.72, 99.99 {+-} 0.54 and 100.23 {+-} 0.91 for the three drugs, respectively. For the second procedure, the concentration ranges were 15-250 {mu}g mL{sup .1} for levofloxacin using {rho}-CA and 0.8-16 {mu}g mL{sup .1} for norfloxacin using TCNE with mean percentage recoveries of 99.88 {+-} 0.45 and 100.26 {+-} 0.68 for the two drugs, respectively. The proposed methods were successfully applied to determine these drugs in their tablet formulations and the results compared favorably to that of reference methods. The proposed methods are recommended for quality control and routine analysis

  16. Spectrophotometric Determination of Some Fluoroquinolone Antibacterials through Charge-transfer and Ion-pair Complexation Reactions

    International Nuclear Information System (INIS)

    Two simple, rapid and sensitive spectrophotometric methods for the determination of three fluoroquinolones, namely levofloxacin, norfloxacin and ciprofloxacin have been performed either in pure form or in their tablets. In the first method, levofloxacin and norfloxacin are directly treated with bromocresol green (BCG) in dichloromethane while ciprofloxacin is allowed to react with the same dye in aqueous acidic buffer. Highly yellow colored complex species were formed instantaneously in case of levofloxacin and norfloxacin or after extraction into dichloromethane for ciprofloxacin. The formed complexes are quantified spectrophotometrically at their absorption maxima at 411 nm for levofloxacin and 412 nm for norfloxacin and ciprofloxacin. The second method involves the reaction of levofloxacin with ρ-chloranilic acid (ρ-CA) and norfloxacin with tetracyanoethylene (TCNE) in acetonitrile to give complexes with maximum absorbance at 521 and 333 nm for the two drugs, respectively. Adopting the first procedure, calibration graphs were linear over the range 1- 20 μg mL.1 with mean percentage recoveries of 100.41 ± 0.72, 99.99 ± 0.54 and 100.23 ± 0.91 for the three drugs, respectively. For the second procedure, the concentration ranges were 15-250 μg mL.1 for levofloxacin using ρ-CA and 0.8-16 μg mL.1 for norfloxacin using TCNE with mean percentage recoveries of 99.88 ± 0.45 and 100.26 ± 0.68 for the two drugs, respectively. The proposed methods were successfully applied to determine these drugs in their tablet formulations and the results compared favorably to that of reference methods. The proposed methods are recommended for quality control and routine analysis

  17. Characterizing reactions to fabricate thin films of charge transfer complexes by synchrotron photoelectron spectroscopy: A case study of DCNQI-Cu

    Science.gov (United States)

    Shimada, Toshihiro; Mochida, Michihiro; Koma, Atsushi

    1997-04-01

    Ultraviolet photoelectron spectroscopy with various photon energies using synchrotron radiation was used to characterize chemical reactions associated with thin film growth of organic charge transfer complex (DMe-DCNQI) 2Cu. Other molecular systems H 2Pc, CuPc and C 60 were also studied to clarify the origin of the systematic relation between the spectra and the incident photon energy. Characteristic photon energy dependence of the photo-ionization cross section of molecular orbitals is useful to analyze the intermolecular reactions.

  18. Ab initio study of the amino group twisting and wagging reaction paths in the intramolecular charge transfer of 4-(N,N-dimethylamino)benzonitrile

    International Nuclear Information System (INIS)

    The behaviour of 4-(N,N-dimethylamino)benzonitrile in its locally-excited and charge-transfer singlet states following the twisting and wagging displacements of the amino group has been investigated theoretically. These reaction paths are expected to play a decisive role in the intramolecular charge transfer observed for this compound in polar solvents. Minimum-energy paths for the lowest excited singlet states have been determined at the CIS level. The corresponding potential-energy profiles have been calculated with the CASSCF and CASPT2 methods. The potential-energy functions depend strongly on the amount of electron correlation included. It can be concluded that, except for large twist angles, wagging leads only to minor changes in the potential-energy curves and dipole moments. The results suggest that the wagging angle can be excluded as a reaction coordinate for the intramolecular charge-transfer process as well as a coupling coordinate of the two lowest excited singlet states. Twisting of the amino group appears to be the relevant reaction coordinate for the intramolecular charge transfer in 4-(N,N-dimethylamino)benzonitrile. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  19. The role of electronic symmetry in charge-transfer-to-solvent reactions: Quantum nonadiabatic computer simulation of photoexcited sodium anions

    International Nuclear Information System (INIS)

    Since charge-transfer-to-solvent (CTTS) reactions represent the simplest class of solvent-driven electron transfer reactions, there has been considerable interest in understanding the solvent motions responsible for electron ejection. The major question that we explore in this paper is what role the symmetry of the electronic states plays in determining the solvent motions that account for CTTS. To this end, we have performed a series of one-electron mixed quantum/classical nonadiabatic molecular dynamics simulations of the CTTS dynamics of sodide, Na-, which has its ground-state electron in an s orbital and solvent-supported CTTS excited states of p-like symmetry. We compare our simulations to previous theoretical work on the CTTS dynamics of the aqueous halides, in which the ground state has the electron in a p orbital and the CTTS excited state has s-like symmetry. We find that the key motions for Na- relaxation involve translations of solvent molecules into the node of the p-like CTTS excited state. This solvation of the electronic node leads to migration of the excited CTTS electron, leaving one of the p-like lobes pinned to the sodium atom core and the other extended into the solvent; this nodal migration causes a breakdown of linear response. Most importantly, for the nonadiabatic transition out of the CTTS excited state and the subsequent return to equilibrium, we find dramatic differences between the relaxation dynamics of sodide and the halides that result directly from differences in electronic symmetry. Since the ground state of the ejected electron is s-like, detachment from the s-like CTTS excited state of the halides occurs directly, but detachment cannot occur from the p-like CTTS excited state of Na- without a nonadiabatic transition to remove the node. Thus, unlike the halides, CTTS electron detachment from sodide occurs only after relaxation to the ground state and is a relatively rare event. In addition, the fact that the electronic symmetry of

  20. High throughput microwell spectrophotometric assay for olmesartan medoxomil in tablets based on its charge-transfer reaction with DDQ

    Directory of Open Access Journals (Sweden)

    Darwish Ibrahim A.

    2014-03-01

    Full Text Available The study describes the development and validation of a new microwell-based spectrophotometric assay for determination of olmesartan medoxomil (OLM in tablets. The formation of a colored charge-transfer (CT complex between OLM as an n-electron donor and 2,3-dichloro- -5,6-dicyano-1,4-benzoquinone (DDQ as a p-electron acceptor was investigated, and employed as the basis for the development of the new assay. The proposed assay was conducted in 96-microwell plates. The absorbance of the colored-CT complex was measured at 460 nm with a microplate reader. Optimum conditions of the reaction and the analytical procedures of the assay were established. Under the optimum conditions, a linear relationship with a good correlation coefficient was found between the absorbance and the concentration of OLM in the range of 2-200 μg per well. The limits of detection and quantitation were 0.53 and 1.61 μg per well, respectively. No interference was observed from the excipients present in OLM tablets or from hydrochlorothiazide and amlodipine besylate that were co-formulated with OLM in some of its formulations. The assay was successfully applied to the analysis of OLM in tablets with good accuracy and precision. The assay described herein has a great practical value in the routine analysis of OLM in quality control laboratories, since it has a high throughput property and consumes low volumes of organic solvent. It thus offers a reduction in the exposure of analysts to the toxic effects of organic solvents, as well as a reduction in the cost of analysis.

  1. Diffusion model for charge transfer from a photosynthetic reaction center to an electrode in a photovoltaic device

    Energy Technology Data Exchange (ETDEWEB)

    Takshi, Arash [Department of Microbiology and Immunology, University of British Columbia (UBC), Vancouver, BC V6T 1Z3 (Canada); Department of Electrical and Computer Engineering and Advanced Materials and Process Engineering Lab, University of British Columbia (UBC), Vancouver, BC V6T 1Z1 (Canada)], E-mail: arasht@ece.ubc.ca; Madden, John D. [Department of Electrical and Computer Engineering and Advanced Materials and Process Engineering Lab, University of British Columbia (UBC), Vancouver, BC V6T 1Z1 (Canada); Beatty, J. Thomas [Department of Microbiology and Immunology, University of British Columbia (UBC), Vancouver, BC V6T 1Z3 (Canada)

    2009-05-30

    In spite of a high quantum efficiency in the bacterial photosynthetic reaction center (RC) the overall efficiency in a RC-based photovoltaic device is very poor partly because of an inefficient collection of charges by electrodes. To explain charge transport between the RC and an electrode a diffusion model is proposed. The numerical solution of the diffusion process describes the measured photocurrent well. An approximation of the initial condition is also made to obtain analytical expressions for the photocurrent. The model suggests that the slow transient response of the photocurrent is due to the diffusion in a biological photovoltaic device.

  2. Diffusion model for charge transfer from a photosynthetic reaction center to an electrode in a photovoltaic device

    International Nuclear Information System (INIS)

    In spite of a high quantum efficiency in the bacterial photosynthetic reaction center (RC) the overall efficiency in a RC-based photovoltaic device is very poor partly because of an inefficient collection of charges by electrodes. To explain charge transport between the RC and an electrode a diffusion model is proposed. The numerical solution of the diffusion process describes the measured photocurrent well. An approximation of the initial condition is also made to obtain analytical expressions for the photocurrent. The model suggests that the slow transient response of the photocurrent is due to the diffusion in a biological photovoltaic device.

  3. Photoinduced intramolecular charge-transfer reactions in 4-amino-3-methyl benzoic acid methyl ester: A fluorescence study in condensedphase and jet-cooled molecular beams

    Indian Academy of Sciences (India)

    Amrita Chakraborty; Samiran Kar; D N Nath; Nikhil Guchhait

    2007-03-01

    Photoinduced intramolecular charge-transfer reactions in 4-amino-3-methyl benzoic acid methyl ester (AMBME) have been investigated spectroscopically. AMBME, with its weak charge donor primary amino group, shows dual emission in polar solvents. Absorption and emission measurements in the condensed phase support the premise that the short wavelength emission band corresponds to local emission and the long wavelength emission band to the charge transfer emission. Laser-induced fluorescence excitation spectra show the presence of two low-energy conformers in jet-cooled molecular beams. Theoretical calculations using density functional theory help to determine structure, vibrational modes, potential energy surface, transition energy and oscillator strength for correlating experimental findings with theoretical results.

  4. Spectroscopic investigation and computational analysis of charge transfer hydrogen bonded reaction between 3-aminoquinoline with chloranilic acid in 1:1 stoichiometric ratio

    Science.gov (United States)

    Al-Ahmary, Khairia M.; Alenezi, Maha S.; Habeeb, Moustafa M.

    2015-10-01

    Charge transfer hydrogen bonded reaction between the electron donor (proton acceptor) 3-aminoquinoline with the electron acceptor (proton donor) chloranilic acid (H2CA) has been investigated experimentally and theoretically. The experimental work included the application of UV-vis spectroscopy to identify the charge transfer band of the formed complex, its molecular composition as well as estimating its formation constants in different solvent included acetonitrile (AN), methanol (MeOH), ethanol (EtOH) and chloroform (CHL). It has been recorded the presence of new absorption bands in the range 500-550 nm attributing to the formed complex. The molecular composition of the HBCT complex was found to be 1:1 (donor:acceptor) in all studied solvents based on continuous variation and photometric titration methods. In addition, the calculated formation constants from Benesi-Hildebrand equation recorded high values, especially in chloroform referring to the formation of stable HBCT complex. Infrared spectroscopy has been applied for the solid complex where formation of charge and proton transfer was proven in it. Moreover, 1H and 13C NMR spectroscopies were used to characterize the formed complex where charge and proton transfers were reconfirmed. Computational analysis included the use of GAMESS computations as a package of ChemBio3D Ultr12 program were applied for energy minimization and estimation of the stabilization energy for the produced complex. Also, geometrical parameters (bond lengths and bond angles) of the formed HBCT complex were computed and analyzed. Furthermore, Mullikan atomic charges, molecular potential energy surface, HOMO and LUMO molecular orbitals as well as assignment of the electronic spectra of the formed complex were presented. A full agreement between experimental and computational analysis has been found especially in the existence of the charge and proton transfers and the assignment of HOMO and LUMO molecular orbitals in the formed complex as

  5. High throughput microwell spectrophotometric assay for olmesartan medoxomil in tablets based on its charge-transfer reaction with DDQ

    OpenAIRE

    Darwish Ibrahim A; Wani Tanveer A; Khalil Nasr Y.; Abdel-Rahman Hamdy M.

    2014-01-01

    The study describes the development and validation of a new microwell-based spectrophotometric assay for determination of olmesartan medoxomil (OLM) in tablets. The formation of a colored charge-transfer (CT) complex between OLM as an n-electron donor and 2,3-dichloro- -5,6-dicyano-1,4-benzoquinone (DDQ) as a p-electron acceptor was investigated, and employed as the basis for the development of the new assay. The proposed assay was conducted in 96-microwell plates. The absorbance of the color...

  6. Symmetric charge transfer cross section of uranium

    International Nuclear Information System (INIS)

    Symmetric charge transfer cross section of uranium was calculated under consideration of reaction paths. In the charge transfer reaction a d3/2 electron in the U atom transfers into the d-electron site of U+(4I9/2) ion. The J value of the U atom produced after the reaction is 6, 5, 4 or 3, at impact energy below several tens eV, only resonant charge transfer in which the product atom is ground state (J=6) takes place. Therefore, the cross section is very small (4-5 x 10-15 cm2) compared with that considered so far. In the energy range of 100-1000eV the cross section increases with the impact energy because near resonant charge transfer in which an s-electron in the U atom transfers into the d-electron site of U+ ion. Charge transfer cross section between U+ in the first excited state (289 cm-1) and U in the ground state was also obtained. (author)

  7. Charge transferred in brush discharges

    Science.gov (United States)

    Talarek, M.; Kacprzyk, R.

    2015-10-01

    Electrostatic discharges from surfaces of plastic materials can be a source of ignition, when appear in explosive atmospheres. Incendivity of electrostatic discharges can be estimated using the transferred charge test. In the case of brush discharges not all the energy stored at the tested sample is released and the effective surface charge density (or surface potential) crater is observed after the discharge. Simplified model, enabling calculation of a charge transferred during electrostatic brush discharge, was presented. Comparison of the results obtained from the simplified model and from direct measurements of transferred charge are presented in the paper.

  8. Vibrational mode and collision energy effects on reaction of H2CO+ with C2H2: Charge state competition and the role of Franck-Condon factors in endoergic charge transfer

    International Nuclear Information System (INIS)

    The effects of collision energy (Ecol) and six different H2CO+ vibrational states on the title reaction have been studied over the center-of-mass Ecol range from 0.1 to 2.6 eV, including measurements of product ion recoil velocity distributions. Ab initio and Rice-Ramsperger-Kassel-Marcus calculations were used to examine the properties of complexes and transition states that might be important in mediating the reaction. Reaction is largely direct, despite the presence of multiple deep wells on the potential surface. Five product channels are observed, with a total reaction cross section at the collision limit. The competition among the major H2+ transfer, hydrogen transfer, and proton transfer channels is strongly affected by Ecol and H2CO+ vibrational excitation, providing insight into the factors that control competition and charge state 'unmixing' during product separation. One of the more interesting results is that endoergic charge transfer appears to be controlled by Franck-Condon factors, implying that it occurs at large inter-reactant separations, contrary to the expectation that endoergic reactions should require intimate collisions to drive the necessary energy conversion

  9. Multinucleon transfer reactions

    International Nuclear Information System (INIS)

    Nuclear reactions induced by complex nuclei are studied. The description of the single neutron transfer is used to show some aspect of the theoretical treatment of transfer reactions and rules concerning the dependence of cross sections on quantum numbers of the initial and final channels are deduced. Strongly excited states of 20Ne, 19F, sup(16,17)0, 15N were studied experimentally by using different projectile-target combinations in the four-particle, eight-particle and ten-particle transfer reactions, leading to the some final nuclei. Obtained results are discussed. In addition, studies of the projectile break-up phenomenon were performed. The dissociation of 6Li and 7Li projectiles was investigated in reactions on Pb, Sn and Ni nuclei. These nuclei were chosen to allow measurements at one incident energy below, above and at the Coulomb barrier. The observed spectra indicate that the process proceeds primarily via the resonance level but the shape deviates from the shape which was calculated assuming isotropic decay of the excited 6Li in its center of mass system. The investigations of the elastic scattering turned out to be more fruitful and allowed to define better the Coulomb barrier for the 6Li-target system. (S.B.)

  10. Charge transfer coefficients for the O+/2D/ + N2 and O+/2D/ + O2 excited ion reactions at thermal energy. [from ionospheric observations

    Science.gov (United States)

    Johnsen, R.; Biondi, M. A.

    1980-01-01

    An investigation of the reactions of metastable O(+) ions and O2 using drift tube-mass spectrometer techniques is presented. It was shown that ordinary charge transfer is the dominant reaction branch in both cases; it occurs with large rate coefficients, k(N2) = (8 + or - 2) x 10 to the -10th cu cm/s and k(O2) = (7 + or - 2) x 10 to the -10th cu cm/s, at an effective ion temperature of about 550 K. The reaction He(+) + O2 is used as a source of metastable O(+) ions, and evidence is presented that the O(+) ions so produced are in the 2D state rather than the 2P state. The results are compared with previous measurements, and inferences drawn from ionospheric observations.

  11. Hydrogen-transfer and charge transfer in photochemical and high energy radiation induced reactions: effects of thiols. Final report, February 1, 1960-january 31, 1979

    International Nuclear Information System (INIS)

    Absorption of ultraviolet or visible light, or high energy radiation, may lead to highly reactive free radicals. Thiols affect the reactions of these radicals in the following ways: (1) transfer of hydrogen from sulfur of the thiol to a substrate radical, converting the radical to a stable molecule, and the thiol to a reactive thiyl radical; and (2) transfer of hydrogen from a substrate radical or molecule to thiyl, regenerating thiol. The thiol is thus used repeatedly and a single molecule may affect the consequences of many quanta. Three effects may ensue, depending upon the system irradiated: (1) the substrate radicals may be converted by thiol-thiyl to the original molecules, and protection against radiation damage is afforded. (2) The radicals may be converted to molecules not identical with the starting materials, and in both cases damage caused by radical combination processes is prevented. (3) Product yields may be increased where the initial radicals might otherwise regenerate starting materials. It was shown that rates of reaction of excited species can be correlated with triplet energies and reduction potentials, and with ionization potentials, that amines are very reactive toward excited carbonyl compounds of all types, and that yields of products from these reactions can be increased by thiols, leading to increased efficiency in utilization of light

  12. Catalysis: Quantifying charge transfer

    Science.gov (United States)

    James, Trevor E.; Campbell, Charles T.

    2016-02-01

    Improving the design of catalytic materials for clean energy production requires a better understanding of their electronic properties, which remains experimentally challenging. Researchers now quantify the number of electrons transferred from metal nanoparticles to an oxide support as a function of particle size.

  13. Biological charge transfer via flickering resonance.

    Science.gov (United States)

    Zhang, Yuqi; Liu, Chaoren; Balaeff, Alexander; Skourtis, Spiros S; Beratan, David N

    2014-07-15

    Biological electron-transfer (ET) reactions are typically described in the framework of coherent two-state electron tunneling or multistep hopping. However, these ET reactions may involve multiple redox cofactors in van der Waals contact with each other and with vibronic broadenings on the same scale as the energy gaps among the species. In this regime, fluctuations of the molecular structures and of the medium can produce transient energy level matching among multiple electronic states. This transient degeneracy, or flickering electronic resonance among states, is found to support coherent (ballistic) charge transfer. Importantly, ET rates arising from a flickering resonance (FR) mechanism will decay exponentially with distance because the probability of energy matching multiple states is multiplicative. The distance dependence of FR transport thus mimics the exponential decay that is usually associated with electron tunneling, although FR transport involves real carrier population on the bridge and is not a tunneling phenomenon. Likely candidates for FR transport are macromolecules with ET groups in van der Waals contact: DNA, bacterial nanowires, multiheme proteins, strongly coupled porphyrin arrays, and proteins with closely packed redox-active residues. The theory developed here is used to analyze DNA charge-transfer kinetics, and we find that charge-transfer distances up to three to four bases may be accounted for with this mechanism. Thus, the observed rapid (exponential) distance dependence of DNA ET rates over distances of ≲ 15 Å does not necessarily prove a tunneling mechanism. PMID:24965367

  14. Velocity Map Imaging Study of Ion-Radical Chemistry: Charge Transfer and Carbon-Carbon Bond Formation in the Reactions of Allyl Radicals with C(.).

    Science.gov (United States)

    Pei, Linsen; Farrar, James M

    2016-08-11

    We present an experimental and computational study of the dynamics of collisions of ground state carbon cations with allyl radicals, C3H5, at a collision energy of 2.2 eV. Charge transfer to produce the allyl cation, C3H5(+), is exoergic by 3.08 eV and proceeds via energy resonance such that the electron transfer occurs without a significant change in nuclear velocities. The products have sufficient energy to undergo the dissociation process C3H5(+) → C3H4(+) + H. Approximately 80% of the reaction products are ascribed to charge transfer, with ∼40% of those products decaying via loss of a hydrogen atom. We also observe products arising from the formation of new carbon-carbon bonds. The experimental velocity space flux distributions for the four-carbon products are symmetric about the centroid of the reactants, providing direct evidence that the products are mediated by formation of a C4H5(+) complex living at least a few rotational periods. The primary four-carbon reaction products are formed by elimination of molecular hydrogen from the C4H5(+) complex. More than 75% of the nascent C4H3(+) products decay by C-H bond cleavage to yield a C4H2(+) species. Quantum chemical calculations at the MP2/6-311+g(d,p) level of theory support the formation of a nonplanar cyclic C4H5(+) adduct that is produced when the p-orbital containing the unpaired electron on C(+) overlaps with the unpaired spin density on the terminal carbon atoms in allyl. Product formation then occurs by 1,2-elimination of molecular hydrogen from the cyclic intermediate to form a planar cyclic C4H3(+) product. The large rearrangement in geometry as the C4H3(+) products are formed is consistent with high vibrational excitation in that product and supports the observation that the majority of those products decay to form the C4H2(+) species. PMID:27434380

  15. Primary charge separation between P* and BA: Electron-transfer pathways in native and mutant GM203L bacterial reaction centers

    International Nuclear Information System (INIS)

    Coherent components in the dynamics of decay of stimulated emission from the primary electron donor excited state P*, and of population of the product charge-separated states P+BA- and P+HA-, were studied in GM203L mutant reaction centers (RCs) of Rhodobacter (Rb.) sphaeroides by measuring oscillations in the kinetics of absorbance changes at 940nm (P* stimulated emission region), 1020nm (BA- absorption region) and 760nm (HA bleaching region). Absorbance changes were induced by excitation of P (870nm) with 18fs pulses at 90K. In the GM203L mutant, replacement of Gly M203 by Leu results in exclusion of the crystallographically defined water molecule (HOH55) located close to the oxygen of the 131-keto carbonyl group of BA and to His M202, which provides the axial ligand to the Mg of the PB bacteriochlorophyll. The results of femtosecond measurements were compared with those obtained with Rb. sphaeroides R-26 RCs containing an intact water HOH55. The main consequences of the GM203L mutation were found to be as follows: (i) a low-frequency oscillation at 32cm-1, which is characteristic of the HOH55-containing RCs, disappears from the kinetics of absorbance changes at 1020 and 760nm in the mutant RC; (ii) electron transfer from P* to BA in the wild type RC was characterized by two time constants of 1.1ps (80%) and 4.3ps (20%), but in the GM203L mutant was characterized by a single time constant of 4.3ps, demonstrating a slowing of primary charge separation. The previously postulated rotation of water HOH55 with a fundamental frequency of 32cm-1, triggered by electron transfer from P* to BA, was confirmed by observation of an isotopic shift of the 32cm-1 oscillation in the kinetics of P+BA- population in deuterated, pheophytin-modified RCs of Rb. sphaeroides R-26, by a factor of 1.6. These data are discussed in terms of the influence of water HOH55 on the energetics of the P*->P+BA- reaction, and protein dynamic events that occur on the time scale of this reaction

  16. Primary charge separation between P* and B{sub A}: Electron-transfer pathways in native and mutant GM203L bacterial reaction centers

    Energy Technology Data Exchange (ETDEWEB)

    Yakovlev, Andrey G. [Department of Photobiophysics, Belozersky Institute of Chemical and Physical Biology, Moscow State University, Moscow 119899 (Russian Federation); Jones, Michael R. [Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD (United Kingdom)], E-mail: m.r.jones@bristol.ac.uk; Potter, Jane A. [Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD (United Kingdom); Fyfe, Paul K. [Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD (United Kingdom); Vasilieva, Lyudmila G. [Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290 (Russian Federation); Shkuropatov, Anatoli Ya. [Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290 (Russian Federation); Shuvalov, Vladimir A. [Department of Photobiophysics, Belozersky Institute of Chemical and Physical Biology, Moscow State University, Moscow 119899 (Russian Federation); Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290 (Russian Federation)], E-mail: shuvalov@issp.serpukhov.su

    2005-12-07

    Coherent components in the dynamics of decay of stimulated emission from the primary electron donor excited state P*, and of population of the product charge-separated states P{sup +}B{sub A}{sup -} and P{sup +}H{sub A}{sup -}, were studied in GM203L mutant reaction centers (RCs) of Rhodobacter (Rb.) sphaeroides by measuring oscillations in the kinetics of absorbance changes at 940nm (P* stimulated emission region), 1020nm (B{sub A}{sup -} absorption region) and 760nm (H{sub A} bleaching region). Absorbance changes were induced by excitation of P (870nm) with 18fs pulses at 90K. In the GM203L mutant, replacement of Gly M203 by Leu results in exclusion of the crystallographically defined water molecule (HOH55) located close to the oxygen of the 13{sup 1}-keto carbonyl group of B{sub A} and to His M202, which provides the axial ligand to the Mg of the P{sub B} bacteriochlorophyll. The results of femtosecond measurements were compared with those obtained with Rb. sphaeroides R-26 RCs containing an intact water HOH55. The main consequences of the GM203L mutation were found to be as follows: (i) a low-frequency oscillation at 32cm{sup -1}, which is characteristic of the HOH55-containing RCs, disappears from the kinetics of absorbance changes at 1020 and 760nm in the mutant RC; (ii) electron transfer from P* to B{sub A} in the wild type RC was characterized by two time constants of 1.1ps (80%) and 4.3ps (20%), but in the GM203L mutant was characterized by a single time constant of 4.3ps, demonstrating a slowing of primary charge separation. The previously postulated rotation of water HOH55 with a fundamental frequency of 32cm{sup -1}, triggered by electron transfer from P* to B{sub A}, was confirmed by observation of an isotopic shift of the 32cm{sup -1} oscillation in the kinetics of P{sup +}B{sub A}{sup -} population in deuterated, pheophytin-modified RCs of Rb. sphaeroides R-26, by a factor of 1.6. These data are discussed in terms of the influence of water HOH55 on

  17. Path integral approach to non-relativistic electron charge transfer

    International Nuclear Information System (INIS)

    A path integral approach has been generalized for the non-relativistic electron charge transfer processes. The charge transfer - the capture of an electron by an ion passing another atom, or more generally the problem of rearrangement collisions - is formulated in terms of influence functionals. It has been shown that the electron charge transfer process can be treated either as an electron transition problem or as ion and atom elastic scattering in the effective potential field. The first-order Born approximation for the electron charge transfer reaction cross section has been reproduced to prove the adequacy of the path integral approach for this problem. (author)

  18. Optimal Control of charge transfer

    OpenAIRE

    Werschnik, J.; Gross, E.K.U.

    2007-01-01

    In this work, we investigate how and to which extent a quantum system can be driven along a prescribed path in space by a suitably tailored laser pulse. The laser field is calculated with the help of quantum optimal control theory employing a time-dependent formulation for the control target. Within a two-dimensional (2D) model system we have successfully optimized laser fields for two distinct charge transfer processes. The resulting laser fields can be understood as a complicated interplay ...

  19. Charge-transfer with graphene and nanotubes

    OpenAIRE

    C.N.R. Rao; Rakesh Voggu

    2010-01-01

    Charge-transfer between electron–donor and –acceptor molecules is a widely studied subject of great chemical interest. Some of the charge-transfer compounds in solid state exhibit novel electronic properties. In the last two to three years, occurrence of molecular charge-transfer involving single-walled carbon nanotubes (SWNTs) and graphene has been demonstrated. This interaction gives rise to significant changes in the electronic properties of these nanocarbons. We examine charge-transfer ph...

  20. Novel Spectrofluorimetric Method for the Determination of Perindopril Erbumine Based on Charge Transfer Reaction with 7-Hydroxycoumarin.

    Science.gov (United States)

    Fael, Hanan; Sakur, Amir Al-Haj

    2015-07-01

    A novel, simple, selective and sensitive spectrofluorimetric method was developed and validated for the determination of perindopril erbumine using 7-hydroxycoumarin. Perindopril erbumine was found to react with 7-hydroxycoumarin in acetonitrile resulting in a new fluorescent product with about 58 nm blue shifted emission. The fluorescence of the complex was measured at 440 nm after excitation at 350 nm in acetonitrile. Under the optimum conditions, the fluorescence intensity was linear over a concentration range of 2.0-16.0 μg/mL (R(2) = 1) with a detection limit of 0.054 μg/mL. The proposed method was fully validated and successfully applied to the analysis of perindopril erbumine in pure form and tablets. Statistical comparison of the results obtained by the proposed and reference method revealed no significant differences in the performance of the two methods regarding the accuracy and precision respectively. The method was shown to be highly specific in the presence of indapamide, a diuretic that is commonly combined with perindopril erbumine. A proposal for the reaction pathway with 7-hydroxycoumarin was postulated. PMID:26149499

  1. Molecular polarizabilities in aqueous proton transfer reactions

    International Nuclear Information System (INIS)

    Dipole polarizabilities of individual ions and molecules are computed from first principles in three condensed-phase systems: pure water, pure hydrofluoric acid, and an equimolar mixture of water and hydrofluoric acid in which HF is mostly ionized. We find that the polarizability of fluorine and oxygen centers varies linearly with the value of the bond order, which measures the local degree of advancement of the ionization reaction F-H+H2O[Fδ-·H·δ+OH2]F-+H3O+. This observation explains the validity of the Lorentz-Lorenz formula for mixtures of acids and water and could have important practical consequences concerning the construction of empirical polarizable reactive force fields. Our results are consistent with the Mulliken charge-transfer picture of proton transfer reactions. The present results also suggest that the average isotropic polarizability of a chemical entity changes substantially only when that entity is involved in charge-transfer processes.

  2. Proceedings of the workshop on 'spin-charge transfer reaction in atomic collision process' for planning of next period of cascade project

    International Nuclear Information System (INIS)

    This workshop was held on February 29, 1992, and was planned to investigate from the theoretical side the spin-charge transfer reaction which is used for a polarized heavy ion source, the development of which has been advanced in the Research Center for Nuclear Physics. In fiscal year 1992, the plan of installing an ECR ion source, Neomafios-10 GHz, as the AVF cyclotron external incident ion source is in progress. This external incidence system can be used also for the research on various atomic physics, in addition to the research on atomic nucleus physics. In this workshop, heated discussion was carried out on what research on atomic physics can be advanced in the Research Center for Nuclear Physics hereafter, through the investigation of the various problems that the atomic physics from low to high energy holds and new technical development. Particularly, the atomic physics using polarized ions seems to become a very unique study in the world. It seems proper to name this polarized heavy ion incidence system Spin factory. This report was edited based on the copies of the transparencies. (K.I.)

  3. Charge transfer complex of some nervous and brain drugs - Part 1: Synthesis, spectroscopic, analytical and biological studies on the reaction between haloperidol antipsychotic drugs with π-acceptors

    Science.gov (United States)

    El-Habeeb, Abeer A.; Al-Saif, Foziah A.; Refat, Moamen S.

    2013-02-01

    Donor-acceptor interactions between the electron donor haloperidol (HPL) and π-acceptors like 7,7,8,8-tetracyanoquinodimethane (TCNQ) and picric acid (PA) have been studied spectrophotometrically in CH3OH solvent. The donor-acceptor (charge transfer complexes) were discussed in terms of formation constant (KCT), molar extinction coefficient (ɛCT), standard free energy (ΔGo), oscillator strength (ƒ), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID). The stoichiometry of these complexes was found to be 1:1 M ratio and having the formulas [(HPL)(TCNQ)] and [(HPL)(PA)], respectively. The charge transfer interaction was successfully applied to determine of HPL drug using mentioned common π-acceptors also, the results obtained herein are satisfactory for estimation of HPL compound in the pharmaceutical form. The formed solid charge-transfer complexes were also isolated and characterized using elemental analysis, conductivity, (infrared, Raman, and 1H NMR) spectra and X-ray powder diffraction (XRD). The experimental data of elemental analyses are in agreement with calculated data. The infrared spectra of both HPL complexes are confirming the participation of sbnd OH of 4-hydroxy-1-piperidyl moiety in the donor-acceptor chelation. The morphological surface of the resulted charge transfer complexes were investigated using scanning electron microscopy (SEM). The thermogravimetric analysis (TG/DTG) and differential scanning calorimetry (DSC) techniques were performed to give knowledge about the thermal stability behavior of the synthesized charge transfer complexes. Thermodynamic parameters were computed from the thermal decomposition data. These complexes were also tested for their antimicrobial activity against six different microorganisms, and the results were compared with the parent drug.

  4. What happens actually in multinucleon transfer reactions?

    International Nuclear Information System (INIS)

    In the 90Zr+208Pb reaction at 560 MeV identical Gaussian isotopic distributions having a width of 2.5 u are observed for products of Z comprised between 40 and 32: Are they really due to a multineutron pick-up process accompanying any proton stripping, as believed today? In fact they are distributions of the neutron number N of the product around its most probable value: This uncertainty in N results from the lifetime of only 0.17 yoctosecond of a new state of nuclear matter, which has been also found in the fission reaction. Interestingly, the new state is characterized by the disappearance of any proton charge and might be triggered, in fission, by a combined shifting of the proton phase against the neutron phase of ordinary matter: It may be asked whether this state is triggered, in transfer reactions, by the crossing of the Coulomb barrier, at which any proton charge should logically disappear.

  5. Long-range charge transfer in biopolymers

    Science.gov (United States)

    Astakhova, T. Yu; Likhachev, V. N.; Vinogradov, G. A.

    2012-11-01

    The results of theoretical and experimental studies on the charge transfer in biopolymers, namely, DNA and peptides, are presented. Conditions that ensure the efficient long-range charge transport (by several tens of nanometres) are considered. The known theoretical models of charge transfer mechanisms are discussed and the scopes of their application are analyzed. Attention is focused on the charge transport by the polaron mechanism. The bibliography includes 262 references.

  6. Transfer reactions in nuclear astrophysics

    Science.gov (United States)

    Bardayan, D. W.

    2016-08-01

    To a high degree many aspects of the large-scale behavior of objects in the Universe are governed by the underlying nuclear physics. In fact the shell structure of nuclear physics is directly imprinted into the chemical abundances of the elements. The tranquility of the night sky is a direct result of the relatively slow rate of nuclear reactions that control and determines a star’s fate. Understanding the nuclear structure and reaction rates between nuclei is vital to understanding our Universe. Nuclear-transfer reactions make accessible a wealth of knowledge from which we can extract much of the required nuclear physics information. A review of transfer reactions for nuclear astrophysics is presented with an emphasis on the experimental challenges and opportunities for future development.

  7. Spectrophotometric determination of repaglinide in tablets based on charge-transfer complexation reaction with chloranilic acid and dichloro-dicyano benzoquinone

    Directory of Open Access Journals (Sweden)

    Cijo Madathil X.

    2011-01-01

    Full Text Available Two simple, accurate, precise, inexpensive, selective and sensitive spectrophotometric methods are described for the determination of repaglinide (RPG in bulk drug and its tablets. The methods were based on the charge- transfer complex reaction between RPG in acetonitrile with p-chloranilic acid (CAA or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ in dioxane and subsequent formation of intensely colored radical anions of the reagents which were measured at 520 nm (CAA or 590 nm (DDQ. Several experimental variables affecting the complex formation, stability of the colored species and sensitivity of the reaction were optimized. Under the optimized conditions, Beer’s law was obeyed over the concentration ranges of 20-400 and 5-80 μg ml-1 RPG for CAA and DDQ methods, respectively, and the corresponding correlation coefficients were 0.9995 and 0.9998. The apparent molar absorptivity values were 1.02x103 and 4.60x103 for CAA and DDQ methods respectively, with corresponding Sandell sensitivity values of 0.4438 and 0.0984 μg cm-2. Limits of detection (LOD were calculated to be 7.07 and 2.42 μg ml-1 and the limits of quantification (LOQ were 21.43 and 7.33 μg ml-1 RPG, for CAA method and DDQ method, respectively. Validation results demonstrated that the inter day and intra day accuracy were up to 97.56%. The precision determined did not exceed 2.5% of RSD. The methods were successfully used for the determination of RPG in tablet form and the results were in good agreement with the label claims as shown by the recoveries which were in the range of 99.22- 102.8% with standard deviation values < 2%. The accuracy of the method was confirmed by recovery studies via standardaddition procedure with excellent recovery 98.24-104.0 ± 1.08-3.35.

  8. Charge Transfer and Catalysis at the Metal Support Interface

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Lawrence Robert [Univ. of California, Berkeley, CA (United States)

    2012-07-31

    Kinetic, electronic, and spectroscopic characterization of model Pt–support systems are used to demonstrate the relationship between charge transfer and catalytic activity and selectivity. The results show that charge flow controls the activity and selectivity of supported metal catalysts. This dissertation builds on extensive existing knowledge of metal–support interactions in heterogeneous catalysis. The results show the prominent role of charge transfer at catalytic interfaces to determine catalytic activity and selectivity. Further, this research demonstrates the possibility of selectively driving catalytic chemistry by controlling charge flow and presents solid-state devices and doped supports as novel methods for obtaining electronic control over catalytic reaction kinetics.

  9. Charge-transfer with graphene and nanotubes

    Directory of Open Access Journals (Sweden)

    C.N.R. Rao

    2010-09-01

    Full Text Available Charge-transfer between electron–donor and –acceptor molecules is a widely studied subject of great chemical interest. Some of the charge-transfer compounds in solid state exhibit novel electronic properties. In the last two to three years, occurrence of molecular charge-transfer involving single-walled carbon nanotubes (SWNTs and graphene has been demonstrated. This interaction gives rise to significant changes in the electronic properties of these nanocarbons. We examine charge-transfer phenomenon in graphene and SWNTs in this article in view of its potential utility in device applications.

  10. Charge transfer induced activity of graphene for oxygen reduction

    Science.gov (United States)

    Shen, Anli; Xia, Weijun; Zhang, Lipeng; Dou, Shuo; Xia, Zhenhai; Wang, Shuangyin

    2016-05-01

    Tetracyanoethylene (TCNE), with its strong electron-accepting ability, was used to dope graphene as a metal-free electrocatalyst for the oxygen reduction reaction (ORR). The charge transfer process was observed from graphene to TCNE by x-ray photoelectron spectroscopy and Raman characterizations. Our density functional theory calculations found that the charge transfer behavior led to an enhancement of the electrocatalytic activity for the ORR.

  11. Charge Transfer and Charge Transport on the Double Helix

    OpenAIRE

    N. P. Armitage; Briman, M.; Gruner, G.

    2003-01-01

    We present a short review of various experiments that measure charge transfer and charge transport in DNA. Some general comments are made on the possible connection between 'chemistry-style' charge transfer experiments that probe fluorescence quenching and remote oxidative damage and 'physics-style' measurements that measure transport properties as defined typically in the solid-state. We then describe measurements performed by our group on the millimeter wave response of DNA. By measuring ov...

  12. Charge transfer and transport in DNA

    OpenAIRE

    Jortner, Joshua; Bixon, Mordechai; Langenbacher, Thomas; Michel-Beyerle, Maria E.

    1998-01-01

    We explore charge migration in DNA, advancing two distinct mechanisms of charge separation in a donor (d)–bridge ({Bj})–acceptor (a) system, where {Bj} = B1,B2, … , BN are the N-specific adjacent bases of B-DNA: (i) two-center unistep superexchange induced charge transfer, d*{Bj}a → d∓{Bj}a±, and (ii) multistep charge transport involves charge injection from d* (or d+) to {Bj}, charge hopping within {Bj}, and charge trapping by a. For off-resonance coupling, mechanism i prevails with the char...

  13. Simulation for signal charge transfer of charge coupled devices

    Institute of Scientific and Technical Information of China (English)

    Wang Zujun; Liu Yinong; Chen Wei; Tang Benqi; Xiao Zhigang; Huang Shaoyan; Liu Minbo; Zhang Yong

    2009-01-01

    Physical device models and numerical processing methods are presented to simulate a linear buried channel charge coupled devices (CCDs). The dynamic transfer process of CCD is carried out by a three-phase clock pulse driver. By using the semiconductor device simulation software MEDICI, dynamic transfer pictures of signal charges cells, electron concentration and electrostatic potential are presented. The key parameters of CCD such as charge transfer efficiency (CTE) and dark electrons are numerically simulated. The simulation results agree with the theoretic and experimental results.

  14. Evidence for excited state intramolecular charge transfer reaction in donor-acceptor molecule 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester: Experimental and quantum chemical approach

    International Nuclear Information System (INIS)

    Intramolecular charge transfer (ICT) reaction has been investigated in 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester (DPDAME) using spectroscopic techniques. The molecule DPDAME shows local emission in non-polar solvent and dual emission in polar solvents. Solvatochromic effects on the Stokes shifted emission band clearly demonstrate the charge transfer character of the excited state. Quantum chemical calculations have been performed at Hartree-Fock (HF) and density functional theoretical (DFT) levels to correlate the experimental findings. Potential energy curves (PECs) for the ICT reaction have been evaluated along the donor twist angle at DFT and time dependent density functional theory (TDDFT) levels for the ground and excited states, respectively, using B3LYP hybrid functional and 6-31G** basis set. The solvent effects on the spectral properties have been explored theoretically at the same level with time dependent density functional theory-polarized continuum model (TDDFT-PCM) and the theoretical results are found to well substantiate the solvent polarity dependent Stokes shifted emission of DPDAME. Huge enhancement of dipole moment (Δμ=16.42 D) of the molecule following photoexcitation dictates the highly polar character of the excited state. Although elucidation of PECs does not exactly predict the operation of ICT according to twisted intramolecular charge transfer (TICT) model in DPDAME, lowering of vertical transition energy as a function of the donor twist coordinate scripts the occurrence of red shifted emission as observed experimentally.

  15. Charge transfer in ionic systems

    International Nuclear Information System (INIS)

    Charge transfer involving multiply charged ions in collision with atomic or molecular targets are determinant processes in controlled thermonuclear fusion research and astrophysical plasma. In such processes, an electron is generally captured in a excited state of the ion, followed by line emission. The observation of line intensities provides important information on the electron temperature, density and spacial distributions in the emitting region of the plasma. From a theoretical point of view, different approaches may be used with regard to the collisional energy range of the process. A semi-classical method is currently used at keV energies, but the description of very low-velocity processes requires a complete quantum mechanical treatment of the dynamics of both electrons and nuclei. The first approach extensively used is the resolution of the stationary close-coupling equations, but we have analyzed recently the efficiency of a time-dependent wave packet method which provides a clear and physical insight into the dynamics of the processes and may be particularly interesting for polyatomic systems since it allows the possibility of developing a fully quantal mechanical treatment for some degrees of freedom, the other ones being treated classically. The keV energy range treatment is presented on two examples pointing out the case of complex ion-atom collision systems, as well as the differences between ion-atom and ion-molecule mechanisms. In connection with translation energy spectroscopy experiments of McLaughlin et al in the 4-28 keV impact energy range, we present a complete ab-initio theoretical approach of the N4+(2s)2S + He system taking into account both single and double electron capture channels. This is an extremely complex collisional system which involves numerous channels with short range interactions and a very intricate interaction region may be observed for interatomic distances around R = 3.5 a.u.. In agreement with experimental data, the

  16. Polarization complex-plane plot of impedance for two-stage charge-transfer reaction complicated with an intermediate adsorption (by example of benzene oxidation at boron-doped diamond electrode)

    International Nuclear Information System (INIS)

    Polarization complex-plane plot of impedance for two-stage anodic reaction with partial charge transfer, complicated with an intermediate adsorption, is theoretically analyzed. The case of linear coverage dependence of the oxidation rate and linear potential dependence of the effective number of electrons involved in each stage, hence, quadratic potential dependence of the activation energies is considered. The result of the modeling agrees qualitatively with experimental data on benzene oxidation at boron-doped diamond electrode. The using of the partial charge transfer concept allowed revealing fine effects of the organics oxidation, which are ascribed to adsorption, in particular, emergence of a loop in the polarization complex-plane plot of impedance

  17. Diffuse charge and Faradaic reactions in porous electrodes

    OpenAIRE

    Biesheuvel, P. M.; Yu, F; Bazant, M.Z.

    2011-01-01

    Porous electrodes instead of flat electrodes are widely used in electrochemical systems to boost storage capacities for ions and electrons, to improve the transport of mass and charge, and to enhance reaction rates. Existing porous electrode theories make a number of simplifying assumptions: (i) The charge-transfer rate is assumed to depend only on the local electrostatic potential difference between the electrode matrix and the pore solution, without considering the structure of ...

  18. Self-affine roughness influence on redox reaction charge admittance

    NARCIS (Netherlands)

    Palasantzas, G

    2005-01-01

    In this work we investigate the influence of self-affine electrode roughness on the admittance of redox reactions during facile charge transfer kinetics. The self-affine roughness is characterized by the rms roughness amplitude w, the correlation length xi and the roughness exponent H (0

  19. Transfer reactions at the neutron dripline with triton target

    CERN Multimedia

    Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.

  20. Interfacial charge transfer in nanoscale polymer transistors

    OpenAIRE

    Worne, J. H.; Giridharagopal, R.; Kelly, K. F.; Natelson, D.

    2008-01-01

    Interfacial charge transfer plays an essential role in establishing the relative alignment of the metal Fermi level and the energy bands of organic semiconductors. While the details remain elusive in many systems, this charge transfer has been inferred in a number of photoemission experiments. We present electronic transport measurements in very short channel ($L < 100$ nm) transistors made from poly(3-hexylthiophene) (P3HT). As channel length is reduced, the evolution of the contact resistan...

  1. Photoinduced intramolecular charge transfer (ICT) reaction in trans-methyl p-(dimethylamino) cinnamate: A combined fluorescence measurement and quantum chemical calculations

    International Nuclear Information System (INIS)

    The photophysical behaviour of trans-methyl p-(dimethylamino) cinnamate (t-MDMAC) donor-acceptor system has been investigated by steady-state absorption and emission spectroscopy and quantum chemical calculations. The molecule t-MDMAC shows an emission from the locally excited state in non-polar solvents. In addition to weak local emission, a strong solvent dependent red shifted fluorescence in polar aprotic solvents is attributed to highly polar intramolecular charge transfer state. However, the formation of hydrogen-bonded clusters with polar protic solvents has been suggested from a linear correlation between the observed red shifted fluorescence band maxima with hydrogen bonding parameters (α). Calculations by ab initio and density functional theory show that the lone pair electron at nitrogen center is out of plane of the benzene ring in the global minimum ground state structure. In the gas phase, a potential energy surface along the twist coordinate at the donor (-NMe2) and acceptor (-CH = CHCOOMe) sites shows stabilization of S1 state and destabilization S2 and S0 states. A similar potential energy calculation along the twist coordinate in acetonitrile solvent using non-equilibrium polarized continuum model also shows more stabilization of S1 state relative to other states and supports solvent dependent red shifted emission properties. In all types of calculations it is found that the nitrogen lone pair is delocalized over the benzene ring in the global minimum ground state and is localized on the nitrogen centre at the 90 deg. twisted configuration. The S1 energy state stabilization along the twist coordinate at the donor site and localized nitrogen lone pair at the perpendicular configuration support well the observed dual fluorescence in terms of proposed twisted intramolecular charge transfer (TICT) model

  2. Activation entropy of electron transfer reactions

    CERN Document Server

    Milischuk, A A; Newton, M D; Milischuk, Anatoli A.; Matyushov, Dmitry V.; Newton, Marshall D.

    2005-01-01

    We report microscopic calculations of free energies and entropies for intramolecular electron transfer reactions. The calculation algorithm combines the atomistic geometry and charge distribution of a molecular solute obtained from quantum calculations with the microscopic polarization response of a polar solvent expressed in terms of its polarization structure factors. The procedure is tested on a donor-acceptor complex in which ruthenium donor and cobalt acceptor sites are linked by a four-proline polypeptide. The reorganization energies and reaction energy gaps are calculated as a function of temperature by using structure factors obtained from our analytical procedure and from computer simulations. Good agreement between two procedures and with direct computer simulations of the reorganization energy is achieved. The microscopic algorithm is compared to the dielectric continuum calculations. We found that the strong dependence of the reorganization energy on the solvent refractive index predicted by conti...

  3. PHOTOINDUCED CHARGE TRANSFER POLYMERIZATION OF STYRENE INITIATED BY ELECTRON ACCEPTOR

    Institute of Scientific and Technical Information of China (English)

    CAO Weixiao; ZHANG Peng; FENG Xinde

    1995-01-01

    Photoinduced charge transfer polymerization of styrene(St) with electron acceptor as initiator was investigated. In case of fumaronitrile (FN) or maleic anhydride (MA) as initiator the polymerization takes place regularly, whereas the tetrachloro-1, 4-benzenequinone (TCQ), 2, 3-dichloro-5, 6-dicyano-1, 4-benzenequinone (DDQ) . or tetracyano ethylene (TCNE) as initiator the polymerization proceeds reluctantly only after the photoaddition reaction. A mechanism was proposed that free radicals would be formed following the charge and proton transfer in the exciplex formed between St and electron acceptors.

  4. Study of nuclei' excitation in the charge exchange reactions (Draft)

    International Nuclear Information System (INIS)

    Carried out experimental and theoretical studies show, that in the nuclear charge exchange reactions there is an unique ability for study both properties and behavior of the delta-isobar in the excited nuclear environment. However for theoretical analysis of these reactions it is necessary have experimental data on nuclei charge exchange on free nucleons. It is offered the experiment of measurement dependence of inclusive cross section of the tritium nuclei charge exchange in 3He nuclei on hydrogen from transferred energy. This reaction is isotopically dependent on 3He nuclei in tritons charge exchange reaction on neutrons. Aim of proposed experiment is checking of a hypothesis believability about the delta-isobar excitation in flying nucleus, and measurement of the process intensity. Peculiarity of this experiment is application of relativistic tritons beams formed from accelerated fragments of 4He nuclei. Experimental facility presents of combination of two one-arm spectrometers: first one - time-flying spectrometer for measurement tritium nuclei impulse in beam to target with accuracy 0.3 % for 6 GeV/s and identification of tritium nuclei, the second one - magnetic spectrometer for identification and measurement of 3He nuclei impulse forming in the result of the charge exchange reaction

  5. Proton transfer reaction - mass spectrometry

    International Nuclear Information System (INIS)

    Proton transfer reaction mass spectrometry (PTR-MS) provides on-line monitoring of volatile organic compounds (VOCs) with a low detection threshold and a fast response time. Commercially available set-ups are usually based on quadrupole analysers but recently new instruments based on time-of-flight (PTR-ToF-MS) analysers have been proposed and commercialized. PTR-MS has been successfully applied to a variety of fields including environmental science, food science and technology, plant physiology and medical science. Many new challenges arise from the newly available PTR-ToF-MS instruments, ranging from mass calibration and absolute VOC concentration determination to data mining and sample classification. This thesis addresses some of these problems in a coherent framework. Moreover, relevant applications in food science and technology are presented. It includes twelve papers published in peer reviewed journals. Some of them address methodological issues regarding PTR-ToF-MS; the others contain applicative studies of PTR-ToF-MS to food science and technology. Among them, there are the first two published applications of PTR-ToF-MS in this field. (author)

  6. Charge Symmetry Breaking and Nuclear Pion Production Reactions

    CERN Document Server

    Bolton, Daniel R

    2011-01-01

    Large momentum transfer reactions such as pion production represent the frontier of Chiral Perturbation Theory and must be understood before more complex reactions can be considered. Pion production is also interesting in its own right, one application being the hadronic extraction of a charge symmetry breaking parameter: the contribution of the down-up quark mass difference to the neutron-proton mass difference. This dissertation reports on two primary projects: (1) a calculation of the charge symmetry breaking forward-backward asymmetry of the differential cross section of the n p -> d pi^0 reaction, and (2) the development of a new theoretical framework addressing the issue of reducibility in the impulse approximation's contribution to pion production. It is shown that the traditional one-body impulse approximation must be replaced by a two-body operator which makes a larger contribution to s-wave pion production.

  7. Transfer of momentum, mass and charge in heavy ion collisions

    International Nuclear Information System (INIS)

    A model for the first two phases of heavy ion collisions based on the transport of single nucleons through the window between the two scattering nuclei is described in some detail. It is pointed out that the model can account simultaneously for a large portion of the energy transfer from relative to intrinsic motion and for the observed variances in mass and charge numbers for reaction times up to the order of 10-21 s. (P.L.)

  8. Multistep processes in charge-exchange reactions

    CERN Document Server

    Demetriou, P; Marianski, B

    2002-01-01

    Cross sections for the charge-exchange sup 6 sup 5 Cu(p, n) sup 6 sup 5 Zn reaction at the incident energy of 27 MeV and the sup 1 sup 0 sup 0 Mo(p, n) sup 1 sup 0 sup 0 Tc reaction at the incident energy of 26 MeV have been calculated using the multistep direct reaction theory of Feshbach, Kerman and Koonin. The theory was modified to include the non-DWBA matrix elements and the isovector collective vibrations according to the prescription of Marcinkowski and Marianski. The results show enhanced contributions from two-, three- and four-step direct reactions in agreement with experiment.

  9. Activation entropy of electron transfer reactions

    International Nuclear Information System (INIS)

    We report microscopic calculations of free energies and entropies for intramolecular electron transfer reactions. The calculation algorithm combines the atomistic geometry and charge distribution of a molecular solute obtained from quantum calculations with the microscopic polarization response of a polar solvent expressed in terms of its polarization structure factors. The procedure is tested on a donor-acceptor complex in which ruthenium donor and cobalt acceptor sites are linked by a four-proline polypeptide. The reorganization energies and reaction energy gaps are calculated as a function of temperature by using structure factors obtained from our analytical procedure and from computer simulations. Good agreement between two procedures and with direct computer simulations of the reorganization energy is achieved. The microscopic algorithm is compared to the dielectric continuum calculations. We found that the strong dependence of the reorganization energy on the solvent refractive index predicted by continuum models is not supported by the microscopic theory. Also, the reorganization and overall solvation entropies are substantially larger in the microscopic theory compared to continuum models

  10. Determinação espectrofotométrica de cefalexina em formulações farmacêuticas explorando a sua reação de transferência de carga com a quinalizarina Spectrophotometric determination of cephalexin in pharmaceutical formulations exploring its charge transfer reaction with quinalizarin

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo R. de Paula

    2010-01-01

    Full Text Available This work proposes a new simple and fast spectrophotometric method for cephalexin determination in pharmaceutical formulations. The method is based on the charge transfer reaction between cephalexin and quinalizarin in dimethylsulfoxide medium. Several analytical parameters related to the system were optimized and the reaction was characterized in terms of stoichiometry. Also, association constant and apparent molar absorptivity of the product were determined. The method presented a limit of detection of 0.46 mg L-1 and a quantification limit of 1.5 mg L-1. It was successfully applied in the determination of cephalexin in two samples of commercial pharmaceutical formulations.

  11. Charge transfer processes of low charge state heavy ions

    International Nuclear Information System (INIS)

    In this paper, some aspects of the collision processes of accelerated heavy ions in very low charge state is reviewed, and the beam loss due to such collisions is estimated. The processes included in ion-atom collisions are electron capture, the electron stripping of ions, and target ionization. The stripping cross sections decrease slowly at high energy, and are much larger than the electron capture cross sections. At low energy, the electron capture is dominant, and this process plays a principal role near ion sources and preacceleration regions. This has not been taken into account properly. In order to keep the beam loss less than 0.1 percent, it is estimated that the average vacuum of about 10-7 to 10-8 Torr is required. An empirical formula to calculate the stripping cross sections of heavy ions in low charge state in collisions is derived. The beam loss due to ion-atom collisions can be estimated. The charge transfer and stripping processes in ion-ion collisions are also discussed. The typical processes in ion-ion collisions are almost same as those in ion-atom collisions. In order to minimize the ion beam loss due to charge-changing processes, it is important to choose the heavy ions with closed shell configurations, which correspond to the slightly more ionized states than the singly ionized state. (Kato, T.)

  12. Charge Injection, Charge Trapping and Charge Transfer in Quantum-Dot Solids

    OpenAIRE

    Boehme, S.C.

    2015-01-01

    This study reports on fundamental processes in Quantum-Dot Solids, after light absorption. Transient Absorption and Time-resolved Photoluminescence spectrocopy reveal the dynamics of charge transfer and charge trapping processes. Typically, both occur on a picosecond time scale and compete with each other. We find that the efficiency of these processes depends on the Fermi level in the Quantum-Dot Solid. The latter can be controlled electrochemically, via charge injection into the Quantum-Dot...

  13. Contribution to very inelastic collisions. Emission mechanism of light charged particles and angular momentum transfer in 40Ar (280 MeV) + 58Ni nuclear reactions

    International Nuclear Information System (INIS)

    This work ends a particularly detailed study on very inelastic collisions in 40A (280 MeV) + 58Ni reaction. The two experiments in coincidence (fragment-fragment and particle-fragment) which are this work basis, essentially experimental, are the following of the very precise inclusive measurements already done on this system. They allowed to precise many important aspects of the reaction mechanism. Conclusions from a precise analysis of the fragment kinematics near the mass symmetry is the new aspect of this study. Information implicitely contained in the two complementary fragment angular correlation width are particularly detailed. Concerning the particle-fragment coincidence experiment, a quantitative analysis method of the invariant cross sections (in the reaction plane) has been developed; it shows clearly what is the origin of the emitted particles. The result of a two-stage mechanism allows to interpret simply the anisotropy out-of-plane of the alpha particle emission. The individual spin has been obtained for the first time for each of the two fragments of very inelastic collisions in nearly all the mass asymmetry domain

  14. Intramolecular charge transfer of 4-(dimethylamino)benzonitrile probed by time-resolved fluorescence and transient absorption: No evidence for two ICT states and a πσ* reaction intermediate

    International Nuclear Information System (INIS)

    For the double exponential fluorescence decays of the locally excited (LE) and intramolecular charge transfer (ICT) states of 4-(dimethylamino)benzonitrile (DMABN) in acetonitrile (MeCN) the same times τ1 and τ2 are observed. This means that the reversible LEICT reaction, starting from the initially excited LE state, can be adequately described by a two state mechanism. The most important factor responsible for the sometimes experimentally observed differences in the nanosecond decay time, with τ1(LE)1(ICT), is photoproduct formation. By employing a global analysis of the LE and ICT fluorescence response functions with a time resolution of 0.5 ps/channel in 1200 channels reliable kinetic and thermodynamic data can be obtained. The arguments presented in the literature in favor of a πσ* state with a bent CN group as an intermediate in the ICT reaction of DMABN are discussed. From the appearance of an excited state absorption (ESA) band in the spectral region between 700 and 800 nm in MeCN for N,N-dimethylanilines with CN, Br, F, CF3, and C(=O)OC2H2 p-substituents, it is concluded that this ESA band cannot be attributed to a πσ* state, as only the C-C≡N group can undergo the required 120 deg. bending.

  15. Coronene-based charge-transfer complexes.

    Science.gov (United States)

    Yoshida, Yukihiro; Isomura, Kazuhide; Kumagai, Yoshihide; Maesato, Mitsuhiko; Kishida, Hideo; Mizuno, Motohiro; Saito, Gunzi

    2016-08-01

    Recent developments in the arena of charge-transfer complexes composed of the D 6h-symmetric polycyclic aromatic hydrocarbon, coronene, are highlighted with emphasis on the structural and physical properties of these complexes. Because of the dual electron-donating and -accepting abilities of coronene, this group involves structurally-defined four cation salts and three anion salts. The Jahn-Teller distortions and in-plane motion of coronene molecules in the solids, both of which are closely associated with the high symmetry of coronene molecules, and syntheses of clathrate-type complexes are also presented. PMID:27294380

  16. Hydrogen-Atom Transfer Reactions.

    Science.gov (United States)

    Wang, Liang; Xiao, Jian

    2016-04-01

    The cascade [1,n]-hydrogen transfer/cyclization, recognized as the tert-amino effect one century ago, has received considerable interest in recent decades, and great achievements have been made. With the aid of this strategy, the inert C(sp(3))-H bonds can be directly functionalized into C-C, C-N, C-O bonds under catalysis of Lewis acids, Brønsted acids, as well as organocatalysts, and even merely under thermal conditions. Hydrogen can be transferred intramolecularly from hydrogen donor to acceptor in the form of hydride, or proton, followed by cyclization to furnish the cyclic products in processes featuring high atom economy. Methylene/methine adjacent to heteroatoms, e.g., nitrogen, oxygen, sulfur, can be exploited as hydride donor as well as methylene/methine without heteroatom assistance. Miscellaneous electrophilic subunits or intermediates, e.g., alkylidene malonate, carbophilic metal activated alkyne or allene, α,β-unsaturated aldehydes/ketone, saturated aldehydes/iminium, ketenimine/carbodiimide, metal carbenoid, electron-withdrawing groups activated allene/alkyne, in situ generated carbocation, can serve as hydride acceptors. This methodology has shown preeminent power to construct 5-, 6-, or 7-membered heterocyclic as well as carbon rings. In this chapter, various hydrogen donors and acceptors are adequately discussed. PMID:27573142

  17. Cell-secreted flavins bound to membrane cytochromes dictate electron transfer reactions to surfaces with diverse charge and pH.

    Science.gov (United States)

    Okamoto, Akihiro; Kalathil, Shafeer; Deng, Xiao; Hashimoto, Kazuhito; Nakamura, Ryuhei; Nealson, Kenneth H

    2014-01-01

    The variety of solid surfaces to and from which microbes can deliver electrons by extracellular electron transport (EET) processes via outer-membrane c-type cytochromes (OM c-Cyts) expands the importance of microbial respiration in natural environments and industrial applications. Here, we demonstrate that the bifurcated EET pathway of OM c-Cyts sustains the diversity of the EET surface in Shewanella oneidensis MR-1 via specific binding with cell-secreted flavin mononucleotide (FMN) and riboflavin (RF). Microbial current production and whole-cell differential pulse voltammetry revealed that RF and FMN enhance EET as bound cofactors in a similar manner. Conversely, FMN and RF were clearly differentiated in the EET enhancement by gene-deletion of OM c-Cyts and the dependency of the electrode potential and pH. These results indicate that RF and FMN have specific binding sites in OM c-Cyts and highlight the potential roles of these flavin-cytochrome complexes in controlling the rate of electron transfer to surfaces with diverse potential and pH. PMID:25012073

  18. Fluctuation spectroscopy in organic charge transfer salts

    International Nuclear Information System (INIS)

    Quasi-twodimensional organic charge-transfer salts show certain analogies to the High-Temperature Cuprate Superconductors (HTSC), e.g., the layered structure where conducting and insulating sheets do alternate as well as the direct proximity of the antiferromagnetic insulating ground state to the superconducting phase. At higher temperatures the formation of a pseudo-gap in the density of states is discussed also. In contrast to the HTSC the electronic properties of the organic charge-transfer salts can be easily influenced by external parameters such as hydrostatic or chemical pressure - in a generalized phase diagram the usage of different anions X can be mapped on the axis W/U as well, see Sec. 4.2 - or moderate temperatures. In the quasi-twodimensional K-(BEDT-TTF)2X salts, e.g., a moderate pressure of p ∝ 250 bar is sufficient to shift the antiferromagnetic-insulating system (X=Cu[N(CN)2]Cl) to the metallic side of the phase diagram showing even superconductivity below a critical temperature of Tc ∝ 12.8 K. Doping as in the HTSC and the undesirable disorder accompanied with it is not necessary to induce a metal-to-insulator transition. Therefore the experimental requirements are more easily met in this class of materials compared to other strongly correlated electron systems. All this makes the organic charge-transfer salts ideal model systems to study fundamental concepts of theoretical solid state physics some of which have been of academical interest only so far. In this work fluctuation spectroscopy has been used for the first time to investigate the low-frequency dynamics of the TT-electron system in the quasi-twodimensional organic charge-transfer salts K-(BEDT-TTF)2X with the aim to gain information about the temperature, pressure and magnetic field dependence of the power spectral density of the resistance noise and therefore about the dynamics of the charge carrier fluctuations. Especially in the vicinity of correlation driven ordering phenomena

  19. Charge density path in cold fusion reactions

    International Nuclear Information System (INIS)

    Cold fusion reactions are very frequently employed to produce compound nuclei with a relatively low excitation energy, which is extremely important for a successful synthesis method, particularly in the region of superheavy nuclei. Usually the charge densities of the projectile, target, and compound nucleus are different. We present a method allowing to take into consideration this difference continuously during the fusion process. Applications are given both in the intermediate mass and the superheavy region. Different cold fusion paths are studied with respect to the change of the charge density within the overlapping region. A transition formula from separated fusion partners up to the compound nucleus is obtained as depending on the geometrical changes. Macroscopic-microscopic approach is used to compute the total deformation energy. Shell corrections are obtained with Strutinsky method, having the new deformed two-center single particle energy levels as an input. Yukawa-plus-exponential model is employed to compute the macroscopic part. Spheroidal deformations are taken into account. By changing the absolute value of semiaxes as well as their ratio, the charge densities of the partners are modified during fusion. As a result of minimization against different paths of the semiaxes ratios from projectile and target values to synthesized nucleus, charge density variation can lower the cold fusion deformation energy. This kind of influence is especially active in the last part of the fusion process, when the projectile is already at least half embedded in the target. For cold fusion of light and intermediate nuclei, the energy variation in the last part of the deformation path reaches 4 MeV for 102 Ru and 3.7 MeV for 152 Dy synthesis. For a possible superheavy production the influence of charge density changes are quantitatively more important. The energy difference in the cold fusion channel barrier of 292 116 reaches about 8 MeV in the last part of the

  20. Radiation reaction for a massless charged particle

    Energy Technology Data Exchange (ETDEWEB)

    Kazinski, P O; Sharapov, A A [Physics Faculty, Tomsk State University, Tomsk, 634050 (Russian Federation)

    2003-07-07

    We derive effective equations of motion for a massless charged particle coupled to the dynamical electromagnetic field with regard to the radiation back reaction. It is shown that unlike the massive case, not all the divergences resulting from the self-action of the particle are Lagrangian, i.e., can be cancelled out by adding appropriate counterterms to the original action. Besides, the order of renormalized differential equations governing the effective dynamics turns out to be greater than the order of the corresponding Lorentz-Dirac equation for a massive particle. For the case of a homogeneous external field, the first radiative correction to the Lorentz equation is explicitly derived via the reduction of order procedure.

  1. Radiation reaction for a massless charged particle

    CERN Document Server

    Kazinski, P O

    2003-01-01

    We derive effective equations of motion for a massless charged particle coupled to the dynamical electromagnetic field having regard to the radiation back reaction. It is shown that unlike the massive case not all the divergences resulting from the self-action of the particle are Lagrangian, i.e. can be canceled out by adding appropriate counterterms to the original action. Besides, the order of renormalized differential equations governing the effective dynamics turns out to be greater than the order of the corresponding Lorentz-Dirac equation for a massive particle. For the case of homogeneous external field the first radiative correction to the Lorentz equation is explicitly derived via the reduction of order procedure.

  2. Radiation reaction for a massless charged particle

    International Nuclear Information System (INIS)

    We derive effective equations of motion for a massless charged particle coupled to the dynamical electromagnetic field with regard to the radiation back reaction. It is shown that unlike the massive case, not all the divergences resulting from the self-action of the particle are Lagrangian, i.e., can be cancelled out by adding appropriate counterterms to the original action. Besides, the order of renormalized differential equations governing the effective dynamics turns out to be greater than the order of the corresponding Lorentz-Dirac equation for a massive particle. For the case of a homogeneous external field, the first radiative correction to the Lorentz equation is explicitly derived via the reduction of order procedure

  3. Radiation reaction for a massless charged particle

    Science.gov (United States)

    Kazinski, P. O.; Sharapov, A. A.

    2003-07-01

    We derive effective equations of motion for a massless charged particle coupled to the dynamical electromagnetic field with regard to the radiation back reaction. It is shown that unlike the massive case, not all the divergences resulting from the self-action of the particle are Lagrangian, i.e., can be cancelled out by adding appropriate counterterms to the original action. Besides, the order of renormalized differential equations governing the effective dynamics turns out to be greater than the order of the corresponding Lorentz-Dirac equation for a massive particle. For the case of a homogeneous external field, the first radiative correction to the Lorentz equation is explicitly derived via the reduction of order procedure.

  4. Communication: Rovibrationally selected study of the N2+(X; v+= 1, N+= 0-8) + Ar charge transfer reaction using the vacuum ultraviolet laser pulsed field ionization-photoion method

    International Nuclear Information System (INIS)

    By employing an electric field pulsing scheme for vacuum ultraviolet laser pulsed field ionization-photoion (PFI-PI) measurements, we have been able to prepare a rovibrationally selected PFI-PI beam of N2+(v+= 1, N+) with not only high intensity and high quantum state purity, but also high kinetic energy resolution, allowing absolute total cross sections [σ(v+= 1, N+)] for the N2+(X; v+= 1, N+) + Ar, N+= 0-8 charge transfer reaction to be measured at center-of-mass collision energies (Ecm) down to thermal energies. The σ(v+= 1, N+= 0-8) values determined at Ecm= 0.04-10.00 eV are in good agreement with the theoretical predictions based on the Landau-Zener-Stueckelberg formulism. Taking into account the experimental uncertainties, the σ(v+= 1, N+), N+= 0-8, measured at Ecm= 1.56 eV are found to be independent of N+.

  5. Dressed Charge of Electron by Radiation Reaction

    Science.gov (United States)

    SETO, Keita; Zhang, Sen; KOGA, James; Moritaka, Toseo; Homma, Kensuke; Nakamiya, Yoshihide; NAGATOMO, Hideo; MIMA, Kunioki

    2016-03-01

    With the progress of ultraintense short pulse laser technologies, the maximum intensity of the lasers has reached the order of 1022W/cm2. Now, several institutes are aiming at higher intensities of over 1024∼W/cm2. It is expected that these lasers can investigate the regime of the ultra-intense field effects like electron-positron pair creation and annihilation, these high-intense laser fields enters into the non-linear QED regime. However, when an electron interacts with lasers with intensities over 1022W/cm2, it has been predicted that the radiation reaction effect becomes significant. The strong radiation field can induce the fluctuation of QED vacuum (vacuum polarization or photon-photon scatterings). Though the propagator for fields is deformed by it, some kind of a polarized charge exists as the dress. In this paper, we will discuss about this dress of an electron generated by radiation in the description of classical physics. It leads to the avoidance of the mathematical difficulty of the radiation reaction problems.

  6. Charge transfer from the n-hexadecane radical cation to cycloalkanes, alkenes and aromatics

    International Nuclear Information System (INIS)

    Charge transfer from n-hexadecane radical cations C16H34+ to solutes as cycloalkanes, alkenes and aromatics was studied by pulse radiolysis. Using ion-pair kinetics the rate constants ksub(s) of the electron transfer reactions C16H34+ + S ->sup(ks) S+ + C16H34 were determined. The electron transfer rate constants ksub(s) increase from low values for slightly exothermic reactions to a limiting value of 9 . 109 dm3 mol-1 s-1 when the electron transfer reaction is more exothermic than -0.4 eV. (orig.)

  7. Resonant charge transfer at dielectric surfaces

    CERN Document Server

    Marbach, Johannes; Fehske, Holger

    2012-01-01

    We report on the theoretical description of secondary electron emission due to resonant charge transfer occurring during the collision of metastable nitrogen molecules with dielectric surfaces. The emission is described as a two step process consisting of electron capture to form an intermediate shape resonance and subsequent electron emission by decay of this ion, either due to its natural life time or its interaction with the surface. The electron capture is modeled using the Keldysh Green's function technique and the negative ion decay is described by a combination of the Keldysh technique and a rate equation approach. We find the resonant capture of electrons to be very efficient and the natural decay to be clearly dominating over the surface-induced decay. Secondary electron emission coefficients are calculated for aluminum oxide, magnesium oxide, silicon oxide, and diamond at several kinetic energies of the projectile. With the exception of magnesium oxide the coefficients turn out to be of the order of...

  8. Resonance effects in fusion and transfer reactions

    International Nuclear Information System (INIS)

    Recent results from fusion and transfer reactions are reviewed together with information they provide for understanding resonance phenomena present in other channels. From present understanding of elastic scattering to a consideration of fusion and the direct reaction channels the discussion covers light nucleus--nucleus systems with targets of A = 10 to 18, reactions of 12C and 16O ions on target nuclei A = 20 to 58, an attempt to characterize the relevant features which have emerged thus far, and parallels with the behaviors observed in the light systems. 69 references

  9. Nucleic Acid Charge Transfer: Black, White and Gray

    OpenAIRE

    Venkatramani, Ravindra; Keinan, Shahar; Balaeff, Alexander; Beratan, David N.

    2011-01-01

    Theoretical studies of charge transport in deoxyribonucleic acid (DNA) and peptide nucleic acid (PNA) indicate that structure and dynamics modulate the charge transfer rates, and that different members of a structural ensemble support different charge transport mechanisms. Here, we review the influences of nucleobase geometry, electronic structure, solvent environment, and thermal conformational fluctuations on the charge transfer mechanism. We describe an emerging framework for understanding...

  10. Transfer reaction code with nonlocal interactions

    CERN Document Server

    Titus, L J; Nunes, F M

    2016-01-01

    We present a suite of codes (NLAT for nonlocal adiabatic transfer) to calculate the transfer cross section for single-nucleon transfer reactions, $(d,N)$ or $(N,d)$, including nonlocal nucleon-target interactions, within the adiabatic distorted wave approximation. For this purpose, we implement an iterative method for solving the second order nonlocal differential equation, for both scattering and bound states. The final observables that can be obtained with NLAT are differential angular distributions for the cross sections of $A(d,N)B$ or $B(N,d)A$. Details on the implementation of the T-matrix to obtain the final cross sections within the adiabatic distorted wave approximation method are also provided. This code is suitable to be applied for deuteron induced reactions in the range of $E_d=10-70$ MeV, and provides cross sections with $4\\%$ accuracy.

  11. Real-time observation of the charge transfer to solvent dynamics

    Science.gov (United States)

    Messina, Fabrizio; Bräm, Olivier; Cannizzo, Andrea; Chergui, Majed

    2013-07-01

    Intermolecular electron-transfer reactions have a crucial role in biology, solution chemistry and electrochemistry. The first step of such reactions is the expulsion of the electron to the solvent, whose mechanism is determined by the structure and dynamical response of the latter. Here we visualize the electron transfer to water using ultrafast fluorescence spectroscopy with polychromatic detection from the ultraviolet to the visible region, upon photo-excitation of the so-called charge transfer to solvent states of aqueous iodide. The initial emission is short lived (~60 fs) and it relaxes to a broad distribution of lower-energy charge transfer to solvent states upon rearrangement of the solvent cage. This distribution reflects the inhomogeneous character of the solvent cage around iodide. Electron ejection occurs from the relaxed charge transfer to solvent states with lifetimes of 100-400 fs that increase with decreasing emission energy.

  12. Charge-transfer excitons in DNA.

    Science.gov (United States)

    Conwell, E M; McLaughlin, P M; Bloch, S M

    2008-02-21

    There have been a number of theoretical treatments of excitons in DNA, most neglecting both the intrachain and interchain wavefunction overlaps of the electron and hole, treating them as Frenkel excitons. Recently, the importance of the intrachain and interchain coupling has been highlighted. Experiments have shown that in (dA)n oligomers and in duplex (dA)n.(dT)n, to be abbreviated (A/T), where A is adenine and T is thymine, the exciton wavefunction is delocalized over several bases. In duplexes it is possible to have charge-transfer (CT) excitons. Theoretical calculations have suggested that CT excitons in DNA may have lower energy than single chain excitons. In all the calculations of excitons in DNA, the polarization of the surrounding water has been neglected. Calculations have shown, however, that polarization of the water by an excess electron or a hole in DNA lowers its energy by approximately 1/2 eV, causing it to become a polaron. It is therefore to be expected that polarization charge induced in the surrounding water has a significant effect on the properties of the exciton. In what follows, we present calculations of some properties CT excitons would have in an A/T duplex taking into account the wavefunction overlaps, the effect of the surrounding water, which results in the electron and hole becoming polarons, and the ions in the water. As expected, the CT exciton has lowest energy when the electron and hole polarons are directly opposite each other. By appropriate choice of the dielectric constant, we can obtain a CT exciton delocalized over the number of sites found in photoinduced absorption experiments. The absorption threshold that we then calculate for CT exciton creation in A/T is in reasonable agreement with the lowest singlet absorption deduced from available data. PMID:18232682

  13. Charge exchange and chemical reactions with trapped Th3+

    International Nuclear Information System (INIS)

    We have measured the reaction rates of trapped, buffer gas cooled Th3+ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th3+ make them more prone to loss. Our results show that reactions of Th3+ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th3+ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th3+ and carbon dioxide. Loss rates of Th3+ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th3+ with nitrogen and argon depend on the internal electronic configuration of the Th3+.

  14. Charge Exchange and Chemical Reactions with Trapped Th$^{3+}$

    CERN Document Server

    Churchill, L R; Chapman, M S

    2010-01-01

    We have measured the reaction rates of trapped, buffer gas cooled Th$^{3+}$ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th$^{3+}$ make them more prone to loss. Our results show that reactions of Th$^{3+}$ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th$^{3+}$ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th$^{3+}$ and carbon dioxide. Loss rates of Th$^{3+}$ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th$^{3+}$ with nitrogen and argon depend on the internal electronic configuration of the Th$^{3+}$.

  15. Second order Born calculation for charge transfer

    International Nuclear Information System (INIS)

    Charge transfer cross sections, from the ground state of the target to the ground state of the projectile, have been computed in a second order Born approximation for protons incident upon hydrogen at energies of 1, 10, and 50 MeV. The exact second order matrix element is evaluated numerically, and the results are compared to a standard peaking approximation (SP), as well as to a new peaking approximation (LP) developed herein. At 50 MeV two distinct second order effects are evident in the differential cross section. For very small (center of mass) scattering angles (THETA approx. = .0320) the second order cross section is smaller than the first order cross section, while at larger angles (THETA approx. = .0540) a second Born peak occurs. This peak can be kinematically associated with a classical two step process which gives rise to the well known dominating v-11 asymptotic velocity dependence of the total cross section. The reduction of the differential cross section at smaller angles serves to decrease the total cross section, as is predicted by the asymptotic expression. At 10 MeV second order effects become less important, and at 1 MeV the kinematic peak has all but disappeared, while the second order cross section has here become larger than the first order cross section. At intermediate energies experimental results indicate that the first order cross section used here is itself too large

  16. Ion momentum and energy transfer rates for charge exchange collisions

    Science.gov (United States)

    Horwitz, J.; Banks, P. M.

    1973-01-01

    The rates of momentum and energy transfer have been obtained for charge exchange collisions between ion and neutral gases having arbitrary Maxwellian temperatures and bulk transport velocities. The results are directly applicable to the F-region of the ionosphere where 0+ - 0 charge is the dominant mechanism affecting ion momentum and energy transfer.

  17. Preparation and characterization of three charge-transfer complexes

    Energy Technology Data Exchange (ETDEWEB)

    Li Yuliang [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Gao Yuanming [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Wu Zi [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Bai Fenglian [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Li Yongfang [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Mo Yiming [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Zhang Bin [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Han Hongxian [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China); Zhu Daoben [Inst. of Chemistry, Chinese Academy of Sciences, Beijing, BJ (China)

    1995-03-15

    We wish to report the preparation and characterization of three new charge transfer complexes of derivatizations of tetrathiafulvalene with buckminsterfullerene. The charge transfer complexes had been characterized by electronic absorption, Fourier transform infrared spectroscopy (FTIR), and elemental analysis and the crystal structure had been analyzed. (orig.)

  18. Symmetric laser-assisted charge transfer: A nonperturbative treatment

    International Nuclear Information System (INIS)

    We present a nonperturbative treatment of laser-assisted charge transfer under conditions of high laser intensity and low collision energy in a specific symmetric charge transfer system: H(1s) + H+ + mhw → H+ + H(n = 1, 2). Previous work in laser-assisted charge transfer has demonstrated that although perturbative treatments are generally valid for lower laser intensities and higher collision energies, nonperturbative treatments are necessary in the present regime where the influence of the laser on the cross sections is more pronounced. The present work is based on the semiclassical impact parameter method, choosing initial conditions appropriate to charge transfer and treating the projectile-target system within a quasimolecular framework. The interaction with the laser is treated semiclassically, in the velocity gauge. We investigate the effect of the laser on both resonant and nonresonant charge transfer processes and provide comparisons with perturbative results. Finally, we shall discuss possibilities for future research

  19. The Charge Form Factor of the Neutron at Low Momentum Transfer from the $^{2}\\vec{\\rm H}(\\vec{\\rm e},{\\rm e}'{\\rm n}){\\rm p}$ Reaction

    CERN Document Server

    Geis, E; Akdogan, T; Arenhövel, H; Alarcon, R; Bertozzi, W; Booth, E; Botto, T; Calarco, J; Clasie, B; Crawford, C B; DeGrush, A; Donnelly, T W; Dow, K; Farkhondeh, M; Fatemi, R; Filoti, O; Franklin, W; Gao, H; Gilad, S; Hasell, D; Karpius, P; Köhl, M; Kolster, H; Lee, T; Maschinot, A; Matthews, J; McIlhany, K; Meitanis, N; Milner, R G; Rapaport, J; Redwine, R P; Seely, J; Shinozaki, A; Sirca, S; Sindile, A; Six, E; Smith, T; Steadman, M; Tonguc, B; Tschalär, C; Tsentalovich, E; Turchinetz, W; Xiao, Y; Xu, W; Zhang, C; Zhou, Z; Zwart, T

    2008-01-01

    We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio $G^{n}_{E}/G^{n}_{M}$ was extracted from the beam-target vector asymmetry $A_{ed}^{V}$ at four-momentum transfers $Q^{2}=0.14$, 0.20, 0.29 and 0.42 (GeV/c)$^{2}$.

  20. Charged particle reaction cross sections and nucleosynthesis

    International Nuclear Information System (INIS)

    The role of proton and α-particle induced reactions in carbon, neon, oxygen and silicon burning in massive stars is surveyed. The problems associated with determining thermonuclear reaction rates for reactions with widely spaced resonances and with closely spaced or overlapping resonances are discussed and the associated experimental approaches are reviewed. Experimental techniques which have been used in the measurement of reaction cross sections are discussed and their strengths and weaknesses are identified. Recent developments in attempts to establish reliable statistical-model codes for calculation of reaction cross sections are presented and discussed. The results of experimental tests of statistical model codes are summarised and evaluated

  1. Electrical double layer effects on ion transfer reactions.

    Science.gov (United States)

    Lin, Chuhong; Laborda, Eduardo; Batchelor-McAuley, Christopher; Compton, Richard G

    2016-04-14

    The potential dependence of the thermodynamics and kinetics of ion transfer reactions as influenced by the electrical double layer are studied via two-dimensional free energy surfaces calculated with an extension of the Anderson-Newns Hamiltonian. The Gibbs energy difference between the reduced and oxidized states, the activation barrier and the resulting current-potential curves are investigated as a function of the potential of zero charge and the Debye length, which are applied to characterize the external electric field. It is found that the current-potential curves of different redox systems are distinctly affected by the electrical double layer depending on the charges of the solution-phase and adsorbed species. For the redox couples sensitive to double layer effects, it is shown that the external electric field can cause a decrease in the driving force for the ion transfer process, which leads to the reversible peak current deviating significantly from the ideal, Nernstian predictions and the effective transfer coefficient being less than 1 even though the ion transfer is kinetically fully reversible. PMID:27001630

  2. Rovibrationally selected ion-molecule collision study using the molecular beam vacuum ultraviolet laser pulsed field ionization-photoion method: charge transfer reaction of N2(+)(X 2Σg+; v+ = 0-2; N+ = 0-9) + Ar.

    Science.gov (United States)

    Chang, Yih Chung; Xu, Yuntao; Lu, Zhou; Xu, Hong; Ng, C Y

    2012-09-14

    We have developed an ion-molecule reaction apparatus for state-selected absolute total cross section measurements by implementing a high-resolution molecular beam vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) ion source to a double-quadrupole double-octopole ion-guide mass spectrometer. Using the total cross section measurement of the state-selected N(2)(+)(v(+), N(+)) + Ar charge transfer (CT) reaction as an example, we describe in detail the design of the VUV laser PFI-PI ion source used, which has made possible the preparation of reactant N(2)(+)(X (2)Σ(g)(+), v(+) = 0-2, N(+) = 0-9) PFI-PIs with high quantum state purity, high intensity, and high kinetic energy resolution. The PFI-PIs and prompt ions produced in the ion source are shown to have different kinetic energies, allowing the clean rejection of prompt ions from the PFI-PI beam by applying a retarding potential barrier upstream of the PFI-PI source. By optimizing the width and amplitude of the pulsed electric fields employed to the VUV-PFI-PI source, we show that the reactant N(2)(+) PFI-PI beam can be formed with a laboratory kinetic energy resolution of ΔE(lab) = ± 50 meV. As a result, the total cross section measurement can be conducted at center-of-mass kinetic energies (E(cm)'s) down to thermal energies. Absolute total rovibrationally selected cross sections σ(v(+) = 0-2, N(+) = 0-9) for the N(2)(+)(X (2)Σ(g)(+); v(+) = 0-2, N(+) = 0-9) + Ar CT reaction have been measured in the E(cm) range of 0.04-10.0 eV, revealing strong vibrational enhancements and E(cm)-dependencies of σ(v(+) = 0-2, N(+) = 0-9). The thermochemical threshold at E(cm) = 0.179 eV for the formation of Ar(+) from N(2)(+)(X; v(+) = 0, N(+)) + Ar was observed by the measured σ(v(+) = 0), confirming the narrow ΔE(cm) spread achieved in the present study. The σ(v(+) = 0-2; N(+)) values obtained here are compared with previous experimental and theoretical results. The theoretical predictions

  3. Rovibrationally selected ion-molecule collision study using the molecular beam vacuum ultraviolet laser pulsed field ionization-photoion method: Charge transfer reaction of N2+(X 2Σg+; v+= 0–2; N+= 0–9) + Ar

    International Nuclear Information System (INIS)

    We have developed an ion-molecule reaction apparatus for state-selected absolute total cross section measurements by implementing a high-resolution molecular beam vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) ion source to a double-quadrupole double-octopole ion-guide mass spectrometer. Using the total cross section measurement of the state-selected N2+(v+, N+) + Ar charge transfer (CT) reaction as an example, we describe in detail the design of the VUV laser PFI-PI ion source used, which has made possible the preparation of reactant N2+(X 2Σg+, v+= 0–2, N+= 0–9) PFI-PIs with high quantum state purity, high intensity, and high kinetic energy resolution. The PFI-PIs and prompt ions produced in the ion source are shown to have different kinetic energies, allowing the clean rejection of prompt ions from the PFI-PI beam by applying a retarding potential barrier upstream of the PFI-PI source. By optimizing the width and amplitude of the pulsed electric fields employed to the VUV-PFI-PI source, we show that the reactant N2+ PFI-PI beam can be formed with a laboratory kinetic energy resolution of ΔElab=± 50 meV. As a result, the total cross section measurement can be conducted at center-of-mass kinetic energies (Ecm’s) down to thermal energies. Absolute total rovibrationally selected cross sections σ(v+= 0–2, N+= 0–9) for the N2+(X 2Σg+; v+= 0–2, N+= 0–9) + Ar CT reaction have been measured in the Ecm range of 0.04–10.0 eV, revealing strong vibrational enhancements and Ecm-dependencies of σ(v+= 0–2, N+= 0–9). The thermochemical threshold at Ecm= 0.179 eV for the formation of Ar+ from N2+(X; v+= 0, N+) + Ar was observed by the measured σ(v+= 0), confirming the narrow ΔEcm spread achieved in the present study. The σ(v+= 0–2; N+) values obtained here are compared with previous experimental and theoretical results. The theoretical predictions calculated based on the Landau-Zener-Stückelberg formulism are found to be

  4. Improved Charge-Transfer Fluorescent Dyes

    Science.gov (United States)

    Meador, Michael

    2005-01-01

    Improved charge-transfer fluorescent dyes have been developed for use as molecular probes. These dyes are based on benzofuran nuclei with attached phenyl groups substituted with, variously, electron donors, electron acceptors, or combinations of donors and acceptors. Optionally, these dyes could be incorporated as parts of polymer backbones or as pendant groups or attached to certain surfaces via self-assembly-based methods. These dyes exhibit high fluorescence quantum yields -- ranging from 0.2 to 0.98, depending upon solvents and chemical structures. The wavelengths, quantum yields, intensities, and lifetimes of the fluorescence emitted by these dyes vary with (and, hence, can be used as indicators of) the polarities of solvents in which they are dissolved: In solvents of increasing polarity, fluorescence spectra shift to longer wavelengths, fluorescence quantum yields decrease, and fluorescence lifetimes increase. The wavelengths, quantum yields, intensities, and lifetimes are also expected to be sensitive to viscosities and/or glass-transition temperatures. Some chemical species -- especially amines, amino acids, and metal ions -- quench the fluorescence of these dyes, with consequent reductions in intensities, quantum yields, and lifetimes. As a result, the dyes can be used to detect these species. Another useful characteristic of these dyes is a capability for both two-photon and one-photon absorption. Typically, these dyes absorb single photons in the ultraviolet region of the spectrum (wavelengths dyes can be excited by two-photon absorption at near-infrared wavelengths (600 to 800 nm) to produce fluorescence spectra identical to those obtained in response to excitation by single photons at half the corresponding wavelengths (300 to 400 nm). While many prior fluorescent dyes exhibit high quantum yields, solvent-polarity- dependent fluorescence behavior, susceptibility to quenching by certain chemical species, and/or two-photon fluorescence, none of them has

  5. On the Possibility of Superfast Charge Transfer in DNA

    OpenAIRE

    Lakhno, V. D.; Sultanov, V. B.

    2013-01-01

    Numerous experiments on charge transfer in DNA yield a contradictory picture of the transfer: on the one hand they suggest that it is a very slow process and the charge is almost completely localized on one Watson-Crick pair, but on the other hand they demonstrate that the charge can travel a very large distance. To explain this contradiction we propose that superfast charge transitions are possible between base pairs on individual DNA fragments resulting in the establishment of a quasi-equil...

  6. Charge Transfer and Support Effects in Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Hervier, Antoine [Univ. of California, Berkeley, CA (United States)

    2011-12-21

    The kinetic, electronic and spectroscopic properties of two-dimensional oxide-supported catalysts were investigated in order to understand the role of charge transfer in catalysis. Pt/TiO2 nanodiodes were fabricated and used as catalysts for hydrogen oxidation. During the reaction, the current through the diode, as well as its I-V curve, were monitored, while gas chromatography was used to measure the reaction rate. The current and the turnover rate were found to have the same temperature dependence, indicating that hydrogen oxidation leads to the non-adiabatic excitation of electrons in Pt. A fraction of these electrons have enough energy to ballistically transport through Pt and overcome the Schottky barrier at the interface with TiO2. The yield for this phenomenon is on the order of 10-4 electrons per product molecule formed, similar to what has been observed for CO oxidation and for the adsorption of many different molecules. The same Pt/TiO2 system was used to compare currents in hydrogen oxidation and deuterium oxidation. The current through the diode under deuterium oxidation was found to be greater than under hydrogen oxidation by a factor of three. Weighted by the difference in turnover frequencies for the two isotopes, this would imply a chemicurrent yield 5 times greater for D2 compared to H2, contrary to what is expected given the higher mass of D2. Reversible changes in the rectification factor of the diode are observed when switching between D2 and H2. These changes are a likely cause for the differences in current between the two isotopes. In the nanodiode experiments, surface chemistry leads to charge flow, suggesting the possibility of creating charge flow to tune surface chemistry. This was done first by exposing a Pt/Si diode to visible light while using it as a catalyst for H2 oxidation. Absorption of the light in the Si, combined with

  7. Controlled transfer of single charge carriers

    International Nuclear Information System (INIS)

    This paper reports on the design and operation of two devices, the turnstile and the pump, that transfer electrons one by one. They are both based on the existence of stable electrostatic configurations in arrays of ultrasmall tunnel junctions. While the turnstile only works in the normal state the pump could in principle achieve the transfer of single Cooper pairs

  8. Effects of Nonlocality on Transfer Reactions

    CERN Document Server

    Titus, Luke J

    2016-01-01

    We solved the nonlocal scattering and bound state equations using the Perey-Buck type interaction, and compared to local equivalent calculations. Using the distorted wave Born approximation we construct the T-matrix for (p,d) transfer on 17O, 41Ca, 49Ca, 127Sn, 133Sn, and 209Pb at 20 and 50 MeV. Additionally we studied (p,d) reactions on 40Ca using the the nonlocal dispersive optical model. We have also included nonlocality consistently into the adiabatic distorted wave approximation and have investigated the effects of nonlocality on on (d,p) transfer reactions for deuterons impinged on 16O, 40Ca, 48Ca, 126Sn, 132Sn, 208Pb at 10, 20, and 50 MeV. We found that for bound states the Perry corrected wave functions resulting from the local equation agreed well with that from the nonlocal equation in the interior region, but discrepancies were found in the surface and peripheral regions. Overall, the Perey correction factor was adequate for scattering states, with the exception for a few partial waves. Nonlocality...

  9. Nuclear data needs in nuclear astrophysics: Charged-particle reactions

    International Nuclear Information System (INIS)

    Progress in understanding a diverse range of astrophysical phenomena - such as the Big Bang, the Sun, the evolution of stars, and stellar explosions - can be significantly aided by improved compilation, evaluation, and dissemination of charged-particle nuclear reaction data. A summary of the charged-particle reaction data needs in these and other astrophysical scenarios is presented, along with recommended future nuclear data projects. (author)

  10. A Monte Carlo study of charge transfer in DNA

    OpenAIRE

    Jakobsson, Mattias; Stafström, Sven

    2008-01-01

    A model describing charge (hole) transport in DNA has been developed. The individual charge transfer steps in the transport process are described by Marcus theory modified to account for electron delocalization over adjacent identical nucleobases. Such a modification, as well as introducing a distance dependence in the reorganization energy, is necessary in order to reach an agreement with the observed transfer rates in well defined model systems to DNA. Using previously published results as ...

  11. Theoretical aspects of electron transfer reactions of complex molecules

    DEFF Research Database (Denmark)

    Kuznetsov, A. M.; Ulstrup, Jens

    2001-01-01

    Features of electron transfer involving complex molecules are discussed. This notion presently refers to molecular reactants where charge transfer is accompanied by large molecular reorganization, and commonly used displaced harmonic oscillator models do not apply. It is shown that comprehensive ...

  12. Charge transfer energies of tetraphenyl-porphyrin-fullerene dyads

    Science.gov (United States)

    Zope, Rajendra; Olguin, Marco; Baruah, Tunna

    2011-03-01

    Porphyrin-fullerene dyads are extensively studied for their photoinduced charge transfer properties. They form a donor-acceptor pair where the fullerene is the acceptor. Accurate theoretical estimate of the charge transfer energies in such systems has proven to be a challenge. In this study we examine the charge transfer energetics for such dyads using our recently developed density functional based excited state method which can yield reliable estimates of charge transfer energetics. In this study the effect of varying both the donor and acceptor components are studied by changing the tetra-phenyl-porphyrin (TPP) to Zn-TPP. Similarly the acceptor component is changed from C60 to C70. The structures were optimized using DFT-D3 theory at the all-electron level. Among the donor-acceptor pairs studied, we find that the ZnTPP-C60 has the lowest charge transfer energy (1.69 eV) and the TPP-C70 (2.13 eV) has the highest charge transfer energy. Supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences of the US Department of Energy through grant DE-SC0002168.

  13. Coherent nuclear wave packet dynamics of laurdan launched by intramolecular charge transfer

    Directory of Open Access Journals (Sweden)

    Kim S. Y.

    2013-03-01

    Full Text Available Coherent nuclear wave packets in the product state launched by the ultrafast intramolecular charge transfer are observed by time-resolved fluorescence with 40 fs time resolution. Direct information on reaction coordinates and structural changes can be obtained.

  14. INTRAMOLECULAR CHARGE AND ENERGY TRANSFER IN MULTICHROMOPHORIC AROMATIC SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Edward C. Lim

    2008-09-09

    A concerted experimental and computational study of energy transfer in nucleic acid bases and charge transfer in dialkylaminobenzonitriles, and related electron donor-acceptor molecules, indicate that the ultrafast photoprocesses occur through three-state conical interactions involving an intermediate state of biradical character.

  15. Theoretical treatment of charge transfer processes of relevance to astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Krstic, P.S.; Stancil, P.C.; Schultz, D.R.

    1997-12-01

    Charge transfer is an important process in many astrophysical and atmospheric environments. While numerous experimental and theoretical studies exist for H and He targets, data on other targets, particularly metals and molecules, are sparse. Using a variety of theoretical methods and computational techniques the authors are developing methods to estimate the cross sections for electron capture (charge transfer) in slow collisions of low charge state ions with heavy (Mg, Ca, Fe, Co, Ni and Zn) neutrals. In this ongoing work particular attention is paid to ascertaining the importance of double electron capture.

  16. Energy and charge transfer in ionized argon coated water clusters

    Czech Academy of Sciences Publication Activity Database

    Kočišek, Jaroslav; Lengyel, Jozef; Fárník, Michal; Slavíček, P.

    2013-01-01

    Roč. 139, č. 21 (2013), s. 214308. ISSN 0021-9606 R&D Projects: GA ČR GAP208/11/0161 EU Projects: European Commission(XE) 238671 - ICONIC Institutional support: RVO:61388955 Keywords : Charged clusters * Charged fragments * Complex reactions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.122, year: 2013

  17. Ultrafast Charge Transfer Visualized by Two-Dimensional Electronic Spectroscopy

    Directory of Open Access Journals (Sweden)

    Mančal T.

    2013-03-01

    Full Text Available Two-dimensional electronic spectroscopy (2D-ES is used to investigate ultrafast excited-state dynamics in a lutetium bisphthalocyanine dimer. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra. The combination of density matrix propagation and quantum chemical calculations results in a molecular view of the charge transfer dynamics and highlights the role of the counter-ion in providing an energetic perturbation which promotes charge transfer across the complex.

  18. Suppression of Electron Transfer to Dioxygen by Charge Transfer and Electron Transfer Complexes in the FAD-dependent Reductase Component of Toluene Dioxygenase*

    Science.gov (United States)

    Lin, Tzong-Yuan; Werther, Tobias; Jeoung, Jae-Hun; Dobbek, Holger

    2012-01-01

    The three-component toluene dioxygenase system consists of an FAD-containing reductase, a Rieske-type [2Fe-2S] ferredoxin, and a Rieske-type dioxygenase. The task of the FAD-containing reductase is to shuttle electrons from NADH to the ferredoxin, a reaction the enzyme has to catalyze in the presence of dioxygen. We investigated the kinetics of the reductase in the reductive and oxidative half-reaction and detected a stable charge transfer complex between the reduced reductase and NAD+ at the end of the reductive half-reaction, which is substantially less reactive toward dioxygen than the reduced reductase in the absence of NAD+. A plausible reason for the low reactivity toward dioxygen is revealed by the crystal structure of the complex between NAD+ and reduced reductase, which shows that the nicotinamide ring and the protein matrix shield the reactive C4a position of the isoalloxazine ring and force the tricycle into an atypical planar conformation, both factors disfavoring the reaction of the reduced flavin with dioxygen. A rapid electron transfer from the charge transfer complex to electron acceptors further reduces the risk of unwanted side reactions, and the crystal structure of a complex between the reductase and its cognate ferredoxin shows a short distance between the electron-donating and -accepting cofactors. Attraction between the two proteins is likely mediated by opposite charges at one large patch of the complex interface. The stability, specificity, and reactivity of the observed charge transfer and electron transfer complexes are thought to prevent the reaction of reductaseTOL with dioxygen and thus present a solution toward conflicting requirements. PMID:22992736

  19. Suppression of electron transfer to dioxygen by charge transfer and electron transfer complexes in the FAD-dependent reductase component of toluene dioxygenase.

    Science.gov (United States)

    Lin, Tzong-Yuan; Werther, Tobias; Jeoung, Jae-Hun; Dobbek, Holger

    2012-11-01

    The three-component toluene dioxygenase system consists of an FAD-containing reductase, a Rieske-type [2Fe-2S] ferredoxin, and a Rieske-type dioxygenase. The task of the FAD-containing reductase is to shuttle electrons from NADH to the ferredoxin, a reaction the enzyme has to catalyze in the presence of dioxygen. We investigated the kinetics of the reductase in the reductive and oxidative half-reaction and detected a stable charge transfer complex between the reduced reductase and NAD(+) at the end of the reductive half-reaction, which is substantially less reactive toward dioxygen than the reduced reductase in the absence of NAD(+). A plausible reason for the low reactivity toward dioxygen is revealed by the crystal structure of the complex between NAD(+) and reduced reductase, which shows that the nicotinamide ring and the protein matrix shield the reactive C4a position of the isoalloxazine ring and force the tricycle into an atypical planar conformation, both factors disfavoring the reaction of the reduced flavin with dioxygen. A rapid electron transfer from the charge transfer complex to electron acceptors further reduces the risk of unwanted side reactions, and the crystal structure of a complex between the reductase and its cognate ferredoxin shows a short distance between the electron-donating and -accepting cofactors. Attraction between the two proteins is likely mediated by opposite charges at one large patch of the complex interface. The stability, specificity, and reactivity of the observed charge transfer and electron transfer complexes are thought to prevent the reaction of reductase(TOL) with dioxygen and thus present a solution toward conflicting requirements. PMID:22992736

  20. Charge Transfer Dynamics from Photoexcited Semiconductor Quantum Dots

    Science.gov (United States)

    Zhu, Haiming; Yang, Ye; Wu, Kaifeng; Lian, Tianquan

    2016-05-01

    Understanding photoinduced charge transfer from nanomaterials is essential to the many applications of these materials. This review summarizes recent progress in understanding charge transfer from quantum dots (QDs), an ideal model system for investigating fundamental charge transfer properties of low-dimensional quantum-confined nanomaterials. We first discuss charge transfer from QDs to weakly coupled acceptors within the framework of Marcus nonadiabatic electron transfer (ET) theory, focusing on the dependence of ET rates on reorganization energy, electronic coupling, and driving force. Because of the strong electron-hole interaction, we show that ET from QDs should be described by the Auger-assisted ET model, which is significantly different from ET between molecules or from bulk semiconductor electrodes. For strongly quantum-confined QDs on semiconductor surfaces, the coupling can fall within the strong coupling limit, in which case the donor-acceptor interaction and ET properties can be described by the Newns-Anderson model of chemisorption. We also briefly discuss recent progress in controlling charge transfer properties in quantum-confined nanoheterostructures through wavefunction engineering and multiple exciton dissociation. Finally, we identify a few key areas for further research.

  1. Dynamics of Charge Transfer in Ordered and Chaotic Nucleotide Sequences

    CERN Document Server

    Fialko, N S

    2013-01-01

    Charge transfer is considered in systems composed of a donor, an acceptor and bridge sites of (AT) nucleotide pairs. For a bridge consisting of 180 (AT) pairs, three cases are dealt with: a uniform case, when all the nucleotides in each strand are identical; an ordered case, when nucleotides in each DNA strand are arranged in an orderly fashion; a chaotic case, when (AT) and (TA) pairs are arranged randomly. It is shown that in all the cases a charge transfer from a donor to an acceptor can take place. All other factors being equal, the transfer is the most efficient in the uniform case, the ordered and chaotic cases are less and the least efficient, accordingly. The results obtained are in agreement with experimental data on long-range charge transfer in DNA.

  2. On the Possibility of Superfast Charge Transfer in DNA

    CERN Document Server

    Lakhno, V D

    2013-01-01

    Numerous experiments on charge transfer in DNA yield a contradictory picture of the transfer: on the one hand they suggest that it is a very slow process and the charge is almost completely localized on one Watson-Crick pair, but on the other hand they demonstrate that the charge can travel a very large distance. To explain this contradiction we propose that superfast charge transitions are possible between base pairs on individual DNA fragments resulting in the establishment of a quasi-equilibrium charge distribution during the time less than that of charge solvation. In other words, we hypothesize these states irrespective of the nature of a mechanism responsible for their establishment, whether it be a hopping mechanism, or a band mechanism, or superexchange, or polaron transport, etc., leaving aside the debates of which one is more advantageous. We discuss qualitative differences between the charge transfer in a dry DNA and that in a solution. In a solution, of great importance is the charge solvation whi...

  3. Light-Induced Charge Separation and Transfer in Bacteriorhodopsin

    Institute of Scientific and Technical Information of China (English)

    HUANG Yu-Hua; LI Qing-Guo; ZHAO You-Yuan; ZHANG Zhong-Bin; OU-YANG Xiao-Ping; GONG Qin-Gan; CHEN Ling-Bing; LI Fu-Ming; LIU Jian; DING Jian-Dong

    2000-01-01

    The photo-voltage signals in bacteriorhodopsin(bR) excited by 1064nm pulse laser are different from those by 532 or 355 nm. It shows that the positive and negative photoelectric signals are produced by the motion of the positive and negative charges, respectively, and more energy is needed for producing the positive charges than the negative. The mechanism of light-induced charge generation and charge transfer in bR was studied and analyzed by measuring the photoelectric signals with different impedance of measuring circuit and different pulse-width of 532 nm laser as pump light.

  4. Competition effects in charged particle induced reactions

    International Nuclear Information System (INIS)

    Absolute cross sections have been measured for 14 reactions: 54Cr(p,γ)55Mn for 0.83 MeV less than or equal to E/sub p/ less than or equal to 3.61 MeV, 54Cr(pn,)54Mn for 2.23 MeV less than or equal to E/sub p/ less than or equal to 3.61 MeV, 51V(p,γ)52Cr for 0.93 MeV less than or equal to E/sub p/ less than or equal to 4.47 MeV, 51V(p,n)51Cr for 1.58 MeV 68Zn(p,γ)69Ga for 1.67 MeV less than or equal to E/sub p/ less than or equal to 4.97 MeV, 68Zn(p,n)68Ga for 3.77 MeV less than or equal to E/sub p/ less than or equal to 5.03 MeV, 68Zn(p,γ)65Cu for 3.36 MeV less than or equal to E/sub p/ less than or equal to 5.48 MeV, 48Ca(p,γ)49Sc for 0.58 MeV less than or equal to E/sub p/ less than or equal to 2.67 MeV, 48Ca(p,n,)48Sc for 0.96 less than or equal to E/sub p/ less than or equal to 2.67 MeV, 37Cl(α,γ)41K for 2.90 MeV less than or equal to E/sub α/ less than or equal to 5.23 MeV, 62Ni(α,γ)66Zn for 5.07 MeV less than or equal to E/sub α/ less than or equal to 8.64 MeV, 62Ni(α,n)65Zn for 6.95 MeV less than or equal to E/sub α/ less than or equal to 8.76 MeV, 64Ni(α,γ)68Zn for 4.50 MeV less than or equal to E/sub α/ less than or equal to 7.45 MeV, and 64Ni(α,n)67Zn for 5.29 less than or equal to E/sub α/ less than or equal to 7.44 MeV. Substantial drops in cross section were observed above the neutron thresholds for all the radiative capture reactions except 48Ca(p,γ). In the 48Ca(p,γ)and 68Zn(p,α) reactions significant though smaller neutron competition effects were observed. These cross sections were compared with cross sections calculated with global Hauser-Feshbach models. Criteria for isospin indexing, width fluctuation corrections, and black nuclues strength functions were established

  5. Charge transfer cross sections for Hg+, Xe+, and Cs+ in collision with various metals and carbon

    International Nuclear Information System (INIS)

    Cross sections for charge transfer between Hg+, Xe+, and Cs+ and the atomic species Fe, Mo, Al, Ti, Ta, and C have been measured in the ion energy range from 1 to 5000 eV. In general, the cross sections for charge transfer were found to be less than 2 x 10-15 cm2 for most processes over the total energy range. The one exception is Hg+ in collision with Ti. The reactants are all open shell atomic species and in most cases where the charge transfer process is exothermic, several resonant pathways exist leading to the products. Some discussion of possible reaction paths is given. The techniques used to form neutral beams of the various species studied is included

  6. Charge transfer cross sections for Hg + , Xe + , and Cs + in collision with various metals and carbon

    Science.gov (United States)

    Rutherford, J. A.; Vroom, D. A.

    1981-01-01

    Cross sections for charge transfer between Hg+, Xe+, and Cs+ and the atomic species Fe, Mo, Al, Ti, Ta, and C have been measured in the ion energy range from 1 to 5000 eV. In general, the cross sections for charge transfer were found to be less than 2×10-15 cm2 for most processes over the total energy range. The one exception is Hg+ in collision with Ti. The reactants are all open shell atomic species and in most cases where the charge transfer process is exothermic, several resonant pathways exist leading to the products. Some discussion of possible reaction paths is given. The techniques used to form neutral beams of the various species studied is included.

  7. Charge-transfer-directed radical substitution enables para-selective C–H functionalization

    Science.gov (United States)

    Boursalian, Gregory B.; Ham, Won Seok; Mazzotti, Anthony R.; Ritter, Tobias

    2016-08-01

    Efficient C–H functionalization requires selectivity for specific C–H bonds. Progress has been made for directed aromatic substitution reactions to achieve ortho and meta selectivity, but a general strategy for para-selective C–H functionalization has remained elusive. Herein we introduce a previously unappreciated concept that enables nearly complete para selectivity. We propose that radicals with high electron affinity elicit arene-to-radical charge transfer in the transition state of radical addition, which is the factor primarily responsible for high positional selectivity. We demonstrate with a simple theoretical tool that the selectivity is predictable and show the utility of the concept through a direct synthesis of aryl piperazines. Our results contradict the notion, widely held by organic chemists, that radical aromatic substitution reactions are inherently unselective. The concept of radical substitution directed by charge transfer could serve as the basis for the development of new, highly selective C–H functionalization reactions.

  8. Ga Nanoparticle/Graphene Platforms: Plasmonic and Charge Transfer Interactions

    Science.gov (United States)

    Yi, Congwen; Kim, Tong-Ho; Yang, Yang; Losurdo, Maria; Brown, April S.

    2013-03-01

    Metal nanoparticle (NP) - graphene multifunctional platforms are of great interest for numerous applications, such as sensing and catalysis, and for fundamental studies on charge transfer and light-matter interactions. To understand platform-photon interactions, it is important to articulate the coupling of photon-based excitations, such as the interaction between plasmons in each of the material components, as well as their charge-based interactions dependent upon the energy alignment at the metal/graphene interface. Herein, we use liquid metal Ga nanoparticles, which can be deposited at 300K on graphene, to explore the surface-enhanced Raman spectroscopy modulation induced by the NPs,. The localized charge transfer between Ga NPs and graphene are investigated, and enhancement of the graphene Raman modes is correlated with metal coverage the transfer of electrons from Ga to graphene creating local regions of enhanced electron concentration which modify the electron-phonon interaction in graphene.

  9. Charge transfer properties of pentacene adsorbed on silver: DFT study

    International Nuclear Information System (INIS)

    Charge transfer properties of pentacene adsorbed on silver is investigated using DFT methods. Optimized geometry of pentacene after adsorption on silver indicates distortion in hexagonal structure of the ring close to the silver cluster and deviations in co-planarity of carbon atoms due to the variations in bond angles and dihedral angles. Theoretically simulated absorption spectrum has a symmetric surface plasmon resonance peak around 486nm corresponding to the transfer of charge from HOMO-2 to LUMO. Theoretical SERS confirms the process of adsorption, tilted orientation of pentacene on silver surface and the charge transfers reported. Localization of electron density arising from redistribution of electrostatic potential together with a reduced bandgap of pentacene after adsorption on silver suggests its utility in the design of electro active organic semiconducting devices

  10. Intramolecular Charge Transfer States in the Condensed Phase

    Science.gov (United States)

    Williams, C. F.; Herbert, J. M.

    2009-06-01

    Time-Dependent Density Functional Theory (TDDFT) with long range corrected functionals can give accurate results for the energies of electronically excited states involving Intramolecular Charge Transfer (ICT) in large molecules. If this is combined with a Molecular Mechanics (MM) representation of the surrounding solvent this technique can be used to interpret the results of condensed phase UV-Vis Spectroscopy. Often the MM region is represented by a set of point charges, however this means that the solvent cannot repolarize to adapt to the new charge distribution as a result of ICT and so the excitation energies to ICT states are overestimated. To solve this problem an algorithm that interfaces TDDFT with the polarizable force-field AMOEBA is presented; the effect of solvation on charge transfer in species such as 4,4'dimethylaminobenzonitrile (DMABN) is discussed. M.A. Rohrdanz, K.M. Martins, and J.M. Herbert, J. Chem. Phys. 130 034107 (2008).

  11. Multiple-charge transfer and trapping in DNA dimers

    Science.gov (United States)

    Tornow, Sabine; Bulla, Ralf; Anders, Frithjof B.; Zwicknagl, Gertrud

    2010-11-01

    We investigate the charge transfer characteristics of one and two excess charges in a DNA base-pair dimer using a model Hamiltonian approach. The electron part comprises diagonal and off-diagonal Coulomb matrix elements such a correlated hopping and the bond-bond interaction, which were recently calculated by Starikov [E. B. Starikov, Philos. Mag. Lett. 83, 699 (2003)10.1080/0950083031000151374] for different DNA dimers. The electronic degrees of freedom are coupled to an ohmic or a superohmic bath serving as dissipative environment. We employ the numerical renormalization group method in the nuclear tunneling regime and compare the results to Marcus theory for the thermal activation regime. For realistic parameters, the rate that at least one charge is transferred from the donor to the acceptor in the subspace of two excess electrons significantly exceeds the rate in the single charge sector. Moreover, the dynamics is strongly influenced by the Coulomb matrix elements. We find sequential and pair transfer as well as a regime where both charges remain self-trapped. The transfer rate reaches its maximum when the difference of the on-site and intersite Coulomb matrix element is equal to the reorganization energy which is the case in a guanine/cytosine (GC)-dimer. Charge transfer is completely suppressed for two excess electrons in adenine/thymine (AT)-dimer in an ohmic bath and replaced by damped coherent electron-pair oscillations in a superohmic bath. A finite bond-bond interaction W alters the transfer rate: it increases as function of W when the effective Coulomb repulsion exceeds the reorganization energy (inverted regime) and decreases for smaller Coulomb repulsion.

  12. Valence Topological Charge-Transfer Indices for Dipole Moments

    Directory of Open Access Journals (Sweden)

    Francisco Torrens

    2003-01-01

    Full Text Available New valence topological charge-transfer indices are applied to the calculation of dipole moments. The algebraic and vector semisum charge-transfer indices are defined. The combination of the charge-transfer indices allows the estimation of the dipole moments. The model is generalized for molecules with heteroatoms. The ability of the indices for the description of the molecular charge distribution is established by comparing them with the dipole moments of a homologous series of phenyl alcohols. Linear and non-linear correlation models are obtained. The new charge-transfer indices improve the multivariable non-linear regression equations for the dipole moment. When comparing with previous results, the variance decreases 92%. No superposition of the corresponding Gk–Jk and GkV – JkV pairs is observed. This diminishes the risk of co-linearity. Inclusion of the oxygen atom in the p-electron system is beneficial for the description of the dipole moment, owing to either the role of the additional p orbitals provided by the heteroatom or the role of steric factors in the p-electron conjugation. Linear and non-linear correlations between the fractal dimension and various descriptors point not only to a homogeneous molecular structure but also to the ability to predict and tailor drug properties.

  13. Bioexcimers as Precursors of Charge Transfer and Reactivity in Photobiology

    Science.gov (United States)

    Serrano-Andrés, Luis; Merchán, Manuela; Roca-Sanjuán, Daniel; Olaso-González, Gloria; Rubio, Mercedes

    2007-11-01

    Accurate CASPT2//CASSCF calculations show that π-stacked interactions in different biochromophores such as DNA nucleobases or porphyrin-quinone pairs yield excimer-like situations which behave as precursors of processes like charge transfer or photoreactivity. Examples are the transfer of charge between a reduced pheophytin and an accepting quinone molecule, process that trigger the sequence of electron transfer phenomena in photosynthetic photosystem II, the electron transfer between adjacent DNA nucleobases in a strand of oligonucleotides, and the photodimerization taking place in cytosine pairs leading to cyclobutanecytosine mutants. These processes take place through nonadiabatic photochemical mechanisms whose evolution is determined by the presence and accessibility of conical intersections and other surface crossings between different electronic states.

  14. Ultrafast Charge Transfer Visualized by Two-Dimensional Electronic Spectroscopy

    OpenAIRE

    Mančal T.; Milota F.; Hauer J; Christensson N.; Bixner O.; Lukeš V.; Kauffmann H. F.

    2013-01-01

    Two-dimensional electronic spectroscopy (2D-ES) is used to investigate ultrafast excited-state dynamics in a lutetium bisphthalocyanine dimer. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra. The combination of density matrix propagation and quantum chemical calculations results in a molecular view of the charge transfer dynamics and highlights the role of the counter-ion in providing an en...

  15. Cross sections for deeply inelastic transfer reactions induced by heavy ions in rare-earth targets

    Science.gov (United States)

    Rivet, M. F.; Bimbot, R.; Gardès, D.; Fleury, A.; Hubert, F.; Llabador, Y.

    1982-04-01

    Cross sections have been measured for deeply inelastic transfer reactions leading to the production of several radio-nuclides. Rare-earth targets were used and the projectiles were Ar, Cr, Fe and Cu ions. The reactions studied corresponded to transfers of two to nine protons and variable numbers of neutrons. The results obtained were used to study the evolution of some characteristics of these reactions, such as integrated cross sections and widths of the isotopic distributions, versus incident mass and transferred mass. These results confirm that mass transfer is driven by the potential energy of the composite system. The decrease of cross sections for increasing charge transfer may be quantitatively explained by assuming thermodynamical equilibrium of the mass asymmetry degree of freedom.

  16. Mechanism of prooxidant reaction of vitamin E. Kinetic, spectroscopic, and ab initio study of proton-transfer reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nagoaka, Shin-ichi; Sawada, Kouhei; Fukumoto, Youji [Ehime Univ., Matsuyama (Japan)] [and others

    1992-08-06

    This paper discusses using kinetic, spectroscopic, and ab initio studies of the prooxidant reaction of vitamin E derivatives to determine second-order rate constants for the reaction of six tocopheroxyl radicals with five alkyl hydroperoxides in benzene along with the first adiabatic ionization potentials of the alkyl hydroperoxides. These results suggest that charge transfer and proton tunneling play important roles in this prooxidant reaction, with proton tunneling taking place below the transition state and allowing the proton to cut a corner on the potential energy surface. 31 refs., 10 figs., 2 tabs.

  17. Two-nucleon transfer reactions with form factor models

    International Nuclear Information System (INIS)

    The theory of two-nucleon transfer reactions is considered. Nuclear reactions are considered with triton or 3He particles which are used as projectiles in stripping reactions and as detected particles in pick-up reactions. In each channel we have a four-particle problem, three of them are nucleons and the fourth is a heavy particle. These transfer reactions are studied on the basis of the generaled R-matrix method. Different channel functions of the sub-clusters in the triton and 3He particles are included. Model form factors are obtained and are used in two-nucleon transfer reactions. Differential cross-sections of different two-nucleon transfer reactions are calculated and are found in good agreement with the experimental data. The correct normalization and spectroscopic factors are obtained. (author)

  18. Charge-Transfer Complex of p-Aminodiphenylamine with Maleic Anhydride: Spectroscopic, Electrochemical, and Physical Properties.

    Science.gov (United States)

    Karaca, Erhan; Kaplan Can, Hatice; Bozkaya, Uğur; Özçiçek Pekmez, Nuran

    2016-07-01

    A new charge-transfer complex and the amide formed by the interaction between the electron donor of the p-aminodiphenylamine and the electron acceptor of maleic anhydride are investigated by spectroscopic methods. The amidation reaction is caused by proton and charge transfer between the maleic anhydride and p-aminodiphenylamine molecules. The Benesi-Hildebrand equation is used to determine the formation constant, the molar extinction coefficient and the standard Gibbs free energy of the complex by using UV/Vis spectroscopy. To reveal the electronic and spectroscopic properties of these molecules, theoretical computations are performed on the structures of maleic anhydride, p-aminodiphenylamine and the conformers of their charge-transfer complex. The charge-transfer complex and amidation reaction mechanism are also confirmed by IR and NMR spectroscopy and HRMS. The nature of the maleic anhydride-p-aminodiphenylamine complex is characterized by cyclic voltammetry, thermogravimetric analysis, XRD and SEM. Solid microribbons of this complex show higher thermal stability than p-aminodiphenylamine. PMID:26990700

  19. Fusion reactivity graphs and tables for charged particle reactions

    International Nuclear Information System (INIS)

    Graphs and tables are presented on 31 light isotope fusion reaction parameters [, n, Q/sub +/, nQ/sub +/ (for n = 1020 fuel ion species/m3 and Q/sub +/ = energy release in charged particles)] in the kinetic temperature range 1 to 1000 keV

  20. Production of neutron-rich isotopes in transfer-type reactions

    International Nuclear Information System (INIS)

    The production yields of new neutron-rich 84,86Zn and 90,92Ge isotopes beyond N=50 and isotopes of nuclei with charge numbers Z=64-80 are estimated for future experiments in the multinucleon transfer reactions at energies close to the Coulomb barrier. (author)

  1. The theoretical study of charge transfer through damaged DNA duplexes

    Czech Academy of Sciences Publication Activity Database

    Šebera, Jakub; Humpolíčková, Jana; Hof, Martin; Kratochvílová, Irena; Páv, Ondřej; Rosenberg, Ivan; Nencka, Radim; Tanaka, Y.; Sychrovský, Vladimír

    Nagybörzsöny : -, 2014. [CESTC 2014. Central European Symposium on Theoretical Chemistry. 21.09.2014-25.09.2014, Nagybörzsöny] R&D Projects: GA ČR GA13-27676S Institutional support: RVO:61388963 ; RVO:61388955 ; RVO:68378271 Keywords : charge transfer * 8-oxoguanine * fluorescence spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry

  2. Enhancing SERS by Means of Supramolecular Charge Transfer

    Science.gov (United States)

    Wong, Eric; Flood, Amar; Morales, Alfredo

    2009-01-01

    In a proposed method of sensing small quantities of molecules of interest, surface enhanced Raman scattering (SERS) spectroscopy would be further enhanced by means of intermolecular or supramolecular charge transfer. There is a very large potential market for sensors based on this method for rapid detection of chemical and biological hazards. In SERS, the Raman signals (vibrational spectra) of target molecules become enhanced by factors of the order of 108 when those molecules are in the vicinities of nanostructured substrate surfaces that have been engineered to have plasmon resonances that enhance local electric fields. SERS, as reported in several prior NASA Tech Briefs articles and elsewhere, has remained a research tool and has not yet been developed into a practical technique for sensing of target molecules: this is because the short range (5 to 20 nm) of the field enhancement necessitates engineering of receptor molecules to attract target molecules to the nanostructured substrate surfaces and to enable reliable identification of the target molecules in the presence of interferants. Intermolecular charge-transfer complexes have been used in fluorescence-, photoluminescence-, and electrochemistry-based techniques for sensing target molecules, but, until now, have not been considered for use in SERS-based sensing. The basic idea of the proposed method is to engineer receptor molecules that would be attached to nanostructured SERS substrates and that would interact with the target molecules to form receptor-target supramolecular charge-transfer complexes wherein the charge transfer could be photoexcited.

  3. CORRELATING ELECTRONIC AND VIBRATIONAL MOTIONS IN CHARGE TRANSFER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, Munira

    2014-06-27

    The goal of this research program was to measure coupled electronic and nuclear motions during photoinduced charge transfer processes in transition metal complexes by developing and using novel femtosecond spectroscopies. The scientific highlights and the resulting scientific publications from the DOE supported work are outlined in the technical report.

  4. Positron Annihilation in Solid Charge-Transfer Complexes

    DEFF Research Database (Denmark)

    Lévay, B.; Jansen, P.

    1979-01-01

    Positron lifetime and angular correlation measurements have been carried out on 1:1 charge-transfer complexes, on their pure donor and acceptor components and on the 1:1 M mechanical mixtures of these components. Complex formation reduced the intensity of the long-lifetime component of the donor ...

  5. Microscopic optical potentials - study of charge-exchange reactions

    International Nuclear Information System (INIS)

    The present thesis is engaged in two different aspects of direct nuclear reactions, namely on the one hand in the microscopic calculation of the imaginary optical potential for the elastic alpha-nucleus scattering as well on the other hand in the microscopic analysis of giant resonance states which are excited by (p,n) and (n,p) charge-exchange reactions. In the first part in the framework of the nuclear structure approximation to the optical potential a microscopic calculation of the imaginary part of the optical potential for α40Ca scattering at Esub(α) = 31 and 100 MeV is performed. In the second part the 208Pb(p,n) and 208Pb(n,p) charge-exchange reactions are studied at low ( E 100 MeV) incident energies. (orig./HS)

  6. A tetrastable naphthalenediimide: anion induced charge transfer, single and double electron transfer for combinational logic gates.

    Science.gov (United States)

    Ajayakumar, M R; Hundal, Geeta; Mukhopadhyay, Pritam

    2013-09-11

    Herein we demonstrate the formation of the first tetrastable naphthalenediimide (NDI, 1a) molecule having multiple distinctly readable outputs. Differential response of 1a to fluoride anions induces intramolecular charge transfer (ICT), single/double electron transfer (SET/DET) leading to a set of combinational logic gates for the first time with a NDI moiety. PMID:23752683

  7. Tight-binding parameters for charge transfer along DNA

    CERN Document Server

    Hawke, L G D; Simserides, C

    2009-01-01

    We systematically examine all the tight-binding parameters pertinent to charge transfer along DNA. The $\\pi$ molecular structure of the four DNA bases (adenine, thymine, cytosine, and guanine) is investigated by using the linear combination of atomic orbitals method with a recently introduced parametrization. The HOMO and LUMO wavefunctions and energies of DNA bases are discussed and then used for calculating the corresponding wavefunctions of the two B-DNA base-pairs (adenine-thymine and guanine-cytosine). The obtained HOMO and LUMO energies of the bases are in good agreement with available experimental values. Our results are then used for estimating the complete set of charge transfer parameters between neighboring bases and also between successive base-pairs, considering all possible combinations between them, for both electrons and holes. The calculated microscopic quantities can be used in mesoscopic theoretical models of electron or hole transfer along the DNA double helix, as they provide the necessar...

  8. Transfer Reactions in Phenyl Carbamate Ethyl Acrylate Polymerizations

    OpenAIRE

    Bennet, Francesca; Roelle, Thomas; Faecke, Thomas; Weiser, Marc-Stephan; Bruder, Friedrich-Karl; Barner-Kowollik, Christopher; Junkers, Thomas

    2013-01-01

    The transfer reactions occurring during polymerization of 2-(phenylcarbamoyloxy)ethyl acrylate (PhCEA) were studied by a detailed product mapping with electrospray ionization mass spectrometry (ESI-MS). Unlike postulated before, PhCEA exhibits the same characteristic transfer reactions as other acrylic monomers at elevated temperatures, resulting in vinyl-terminated and saturated products. Transfer to monomer via abstraction of a hydrogen atom from the ester side chain as suggested before is ...

  9. Measurements of Charge Transfer Efficiency in a Proton-irradiated Swept Charge Device

    CERN Document Server

    YuSa, Wang; XiaoYan, Liu; WeiWei, Cui; YuPeng, Xu; ChengKui, Li; MaoShun, Li; DaWei, Han; TianXiang, Chen; Jia, Huo; Juan, Wang; Wei, Li; Wei, Hu; Yi, Zhang; Bo, Lu; GuoHe, Yin; Yue, Zhu; ZiLiang, Zhang

    2013-01-01

    Charge Coupled Devices (CCDs) have been successfully used in several low energy X-ray astronomical satellite over the past two decades. Their high energy resolution and high spatial resolution make them an perfect tool for low energy astronomy, such as formation of galaxy clusters and environment of black holes. The Low Energy X-ray Telescope (LE) group is developing Swept Charge Device (SCD) for the Hard X-ray Modulation Telescope (HXMT) satellite. SCD is a special low energy X-ray CCD, which could be read out a thousand times faster than traditional CCDs, simultaneously keeping excellent energy resolution. A test method for measuring the charge transfer efficiency (CTE) of a prototype SCD has been set up. Studies of the charge transfer inefficiency (CTI) have been performed at a temperature range of operation, with a proton-irradiated SCD.

  10. Charge separation in synthetic photo-reaction centers

    Energy Technology Data Exchange (ETDEWEB)

    Katz, J.J.

    1978-01-01

    On the basis of electron paramagnetic resonance studies, there is good reason to suppose that the primary electron donor in plant and bacterial photo-reaction centers is a special pair of chlorophyll molecules. The donor--acceptor coordination interactions characteristic of chlorophyll are used to suggest a structure for the chlorophyll special pair. Chlorophyll special pairs with the suggested structure have been prepared in the laboratory. These synthetic reaction centers mimic the essential features of P700 and P865 and provide a useful route to the study of electron transfer from in vivo photo-reaction centers.

  11. Nucleon charge-exchange reactions at intermediate energy

    Energy Technology Data Exchange (ETDEWEB)

    Alford, W.P. [Western Ontario Univ., London, ON (Canada). Dept. of Physics]|[TRIUMF, Vancouver, BC (Canada); Spicer, B.M. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1997-12-31

    An historical review of the development of ideas pertaining to Gamow-Teller giant resonances is given, and a description of the emergence of techniques for the study of charge exchange reactions - particularly the technical advances which yielded the recent volume of new date. The present status of charge exchange reactions is reviewed and assessed. Evidence is presented from the {sup 14}C(p,n) reaction for the dominance of the spin-isospin component of the nucleon-nucleon interaction in intermediate energy reactions. In (p,n) reactions the Gamow-Teller giant resonance dominates the spectra, with higher multipoles contributing. By contrast, in (n,p) reactions in the heavier nuclei, the Gamow-Teller transitions are substantially Pauli-blocked and the spin dipole resonance dominates, with contributions from higher multipoles. Discussions of the multipole decomposition process, used to obtain from the data the contributions of the different multipoles, and the contributions of the multipoles, are given. 226 refs., 19 figs.

  12. Photoinduced charge and energy transfer in molecular wires.

    Science.gov (United States)

    Gilbert, Mélina; Albinsson, Bo

    2015-02-21

    Exploring charge and energy transport in donor-bridge-acceptor systems is an important research field which is essential for the fundamental knowledge necessary to develop future applications. These studies help creating valuable knowledge to respond to today's challenges to develop functionalized molecular systems for artificial photosynthesis, photovoltaics or molecular scale electronics. This tutorial review focuses on photo-induced charge/energy transfer in covalently linked donor-bridge-acceptor (D-B-A) systems. Of utmost importance in such systems is to understand how to control signal transmission, i.e. how fast electrons or excitation energy could be transferred between the donor and acceptor and the role played by the bridge (the "molecular wire"). After a brief description of the electron and energy transfer theory, we aim to give a simple yet accurate picture of the complex role played by the bridge to sustain donor-acceptor electronic communication. Special emphasis is put on understanding bridge energetics and conformational dynamics effects on the distance dependence of the donor-acceptor electronic coupling and transfer rates. Several examples of donor-bridge-acceptor systems from the literature are described as a support to the discussion. Finally, porphyrin-based molecular wires are introduced, and the relationship between their electronic structure and photophysical properties is outlined. In strongly conjugated porphyrin systems, limitations of the existing electron transfer theory to interpret the distance dependence of the transfer rates are also discussed. PMID:25212903

  13. Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles

    Science.gov (United States)

    Liechty, Derek S.; Lewis, Mark J.

    2010-01-01

    Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

  14. Liquid drop effects in subbarrier transfer reactions

    International Nuclear Information System (INIS)

    Reaction products from a multitude of binary channels are observed to emerge at large c.m. angles at subbarrier energies for the 50Ti + 93Nb system. The energy spectra of these products and the distance where they first emerge indicate that these reaction products result from the neck which is formed outside the Coulomb barrier. 9 refs., 5 figs

  15. Heavy ion transfer reactions: Status and perspectives

    Indian Academy of Sciences (India)

    L Corradi

    2010-07-01

    With the large solid angle magnetic spectrometer (PRISMA) coupled to the -array (CLARA), extensive investigations of nuclear structure and reaction dynamics have been carried out. In the present paper aspects of these studies will be presented, focussing more closely on the reaction mechanism, in particular on the properties of quasielastic and deep inelastic processes and on measurements at energies far below the Coulomb barrier.

  16. Localized state and charge transfer in nitrogen-doped graphene

    OpenAIRE

    Joucken, Frederic; Tison, Yann; Lagoute, Jerome; Dumont, Jacques; Cabosart, Damien; Zheng, Bing; Repain, Vincent; Chacon, Cyril; Girard, Yann; Botello-Mendez, Andres Rafael; Rousset, Sylvie; Sporken, Robert; Charlier, Jean-Christophe; Henrard, Luc

    2012-01-01

    Nitrogen-doped epitaxial graphene grown on SiC(000?1) was prepared by exposing the surface to an atomic nitrogen flux. Using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS), supported by Density Functional Theory (DFT) calculations, the simple substitution of carbon by nitrogen atoms has been identifi?ed as the most common doping con?guration. High-resolution images reveal a reduction of local charge density on top of the nitrogen atoms, indicating a charge transfer to the neighbor...

  17. Coupled sensitizer-catalyst dyads: electron-transfer reactions in a perylene-polyoxometalate conjugate.

    Science.gov (United States)

    Odobel, Fabrice; Séverac, Marjorie; Pellegrin, Yann; Blart, Errol; Fosse, Céline; Cannizzo, Caroline; Mayer, Cédric R; Elliott, Kristopher J; Harriman, Anthony

    2009-01-01

    Ultrafast discharge of a single-electron capacitor: A variety of intramolecular electron-transfer reactions are apparent for polyoxometalates functionalized with covalently attached perylene monoimide chromophores, but these are restricted to single-electron events. (et=electron transfer, cr=charge recombination, csr=charge-shift reaction, PER=perylene, POM=polyoxometalate).A new strategy is introduced that permits covalent attachment of an organic chromophore to a polyoxometalate (POM) cluster. Two examples are reported that differ according to the nature of the anchoring group and the flexibility of the linker. Both POMs are functionalized with perylene monoimide units, which function as photon collectors and form a relatively long-lived charge-transfer state under illumination. They are reduced to a stable pi-radical anion by electrolysis or to a protonated dianion under photolysis in the presence of aqueous triethanolamine. The presence of the POM opens up an intramolecular electron-transfer route by which the charge-transfer state reduces the POM. The rate of this process depends on the molecular conformation and appears to involve through-space interactions. Prior reduction of the POM leads to efficient fluorescence quenching, again due to intramolecular electron transfer. In most cases, it is difficult to resolve the electron-transfer products because of relatively fast reverse charge shift that occurs within a closed conformer. Although the POM can store multiple electrons, it has not proved possible to use these systems as molecular-scale capacitors because of efficient electron transfer from the one-electron-reduced POM to the excited singlet state of the perylene monoimide. PMID:19197929

  18. Pion charge-exchange reactions: The analog state transitions

    International Nuclear Information System (INIS)

    The general features of pion charge-exchange reactions leading to nuclear-isobaric-analog states (IAS) and double-isobaric-analog states (DIAS), as they have emerged from studies over the past ten years, are reviewed. The energy range investigated is 20 to 550 MeV for IAS transitions and 20 to 300 MeV for DIAS transitions. These data are seen to play an important role in characterizing the pion optical potential, in determining the Δ-N interaction in nuclei, and in the study of nucleon correlations in nuclei. Recent progress achieved in understanding the role of such correlations in double-charge-exchange reactions is reviewed. 55 refs., 43 figs., 3 tabs

  19. Charged particle induced prompt nuclear reaction and its applications

    International Nuclear Information System (INIS)

    Charged particle induced prompt nuclear reaction analysis (PNR) not only can analyze the content and concentration of elements in sample sensitively and accurately, but also can measure the distributions of elements with depth in surface and near surface layer. And the method is very simple, rapid and nondestructive, and has good depth resolution. So the PNR is very widely used in many modern science and technique field such as solid state physics, surface physics, electrochemistry, metallurgy and material science and so on. This paper deals with the principle, method and the features of the nuclear reaction analysis induced by charged particle. Especially, the distribution analysis of impurities in sample with depth and the improvement of the depth resolution are discussed in detail. Some actual examples of its application are given

  20. Quantifying electron transfer reactions in biological systems

    DEFF Research Database (Denmark)

    Sjulstok, Emil Sjulstok; Olsen, Jógvan Magnus Haugaard; Solov'yov, Ilia A

    2015-01-01

    Various biological processes involve the conversion of energy into forms that are usable for chemical transformations and are quantum mechanical in nature. Such processes involve light absorption, excited electronic states formation, excitation energy transfer, electrons and protons tunnelling...... quantum physics and biology. In this paper we consider electron transfer in biological processes, from a theoretical view-point; namely in terms of quantum mechanical and semi-classical models. We systematically characterize the interactions between the moving electron and its biological environment to...

  1. Charge transfer efficiency improvement of a 4-T pixel by the optimization of electrical potential distribution under the transfer gate

    International Nuclear Information System (INIS)

    The charge transfer efficiency improvement method is introduced by optimizing the electrical potential distribution under the transfer gate along the charge transfer path. A non-uniform doped transfer transistor channel is introduced to provide an ascending electrical potential gradient in the transfer transistor channel. With the adjustments to the overlap length between the R1 region and the transfer gate, the doping dose of the R1 region, and the overlap length between the anti-punch-through (APT) implantations and transfer gate, the potential barrier and potential pocket in the connecting region of transfer transistor channel and the pinned photodiode (PPD) are reduced to improve the electrical potential connection. The simulation results show that the percentage of residual charges to total charges drops from 1/104 to 1/107, and the transfer time is reduced from 500 to 110 ns. This means the charge transfer efficiency is improved. (semiconductor devices)

  2. Promotion of multi-electron transfer for enhanced photocatalysis: A review focused on oxygen reduction reaction

    Science.gov (United States)

    Wang, Changhua; Zhang, Xintong; Liu, Yichun

    2015-12-01

    Semiconductor photocatalysis has attracted significant interest for solar light induced environmental remediation and solar fuel generation. As is well known, photocatalytic performance is determined by three steps: photoexcitation, separation and transport of photogenerated charge carriers, and surface reactions. To achieve higher efficiency, significant efforts have been made on improvement of efficiency of above first two steps, which have been well documented in recent review articles. In contrast, this review intends to focus on strategies moving onto the third step of improvement for enhanced photocatalysis wherein active oxygen species including superoxide radical, hydrogen peroxide, hydroxyl radical are in situ detected. Particularly, surface electron-transfer reduction of oxygen over single component photocatalysts is reviewed and systems enabling multi-electron transfer induced oxygen reduction reaction (ORR) are highlighted. It is expected this review could provide a guideline for readers to better understand the critical role of ORR over photocatalyst in charge carrier separation and transfer and obtain reliable results for enhanced aerobic photocatalysis.

  3. Elastic scattering and charge exchange reactions with exotic beams

    International Nuclear Information System (INIS)

    The elastic scattering of 6He, 10,11Be secondary beams on a (CH2)3 target and the charge exchange reaction p(6He,6Li)n have been measured. Very good agreement was found for the 6He+12C data with a four-body eikonal scattering model. A microscopic optical potential was used to reproduce the proton-nucleus elastic scattering data. (author)

  4. Multidimensional analysis of charged particles from neutron-induced reactions

    International Nuclear Information System (INIS)

    A survey is given of the most recent experimental results obtained using twin gridded ionization chamber constructed at Obninsk, Russia. Peculiarities of (n,α) and (n,f) reactions investigated are discussed. The detailed description ol the method of charge particles spectrometry is presented. Selected results on fission fragment characteristics are discussed more in detail. Present experiments and instrumental developments are focussed on correlations between fragment masses, energies and emission angles and on fine structures in fragment parameter distributions. (author)

  5. Spin transfer coefficients for the (p suprho,n suprho) reaction in the plane wave approximation

    CERN Document Server

    Lee, H S; Kim, B T

    1998-01-01

    The spin transfer coefficients D sub n sub n (theta=0 .deg. ) for the intermediate energy charge exchange reaction (p suprho,n suprho) leading to the giant resonances in the continuum region are investigated. The dependence of the spin transfer coefficients on the nuclear wave function, the reaction Q-value, and the effective two-body interaction are studied using the plane wave approximation. It is shown that both the direct and the exchange parts of the tensor interaction play important roles in determining the D sub n sub n value.

  6. Charge transfer in conjugated oligomers encapsulated into carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Almadori, Y.; Alvarez, L.; Michel, T.; Le Parc, R.; Bantignies, J.L.; Hermet, P.; Sauvajol, J.L. [Laboratoire Charles Coulomb UMR 5521, Universite Montpellier 2, 34095 Montpellier (France); Laboratoire Charles Coulomb UMR 5521, CNRS, 34095 Montpellier (France); Arenal, R. [Laboratoire d' Etude des Microstructures, CNRS-ONERA, 92322 Chatillon (France); Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, U. Zaragoza, 50018 Zaragoza (Spain); Babaa, R. [Laboratoire de Chimie des Surfaces et Interfaces, CEA, IRAMIS, SPCSI, 91191 Gif-sur-Yvette Cedex (France); Chemical Engineering Department, University of Technology PETRONAS, UTP, Ipoh-Perak (Malaysia); Jouselme, B.; Palacin, S. [Laboratoire de Chimie des Surfaces et Interfaces, CEA, IRAMIS, SPCSI, 91191 Gif-sur-Yvette Cedex (France)

    2011-11-15

    This study deals with a hybrid system consisting in quaterthiophene derivative encapsulated inside single-walled and multi-walled carbon nanotubes. Investigations of the encapsulation step are performed by transmission electron microscopy. Raman spectroscopy data point out different behaviors depending on the laser excitation energy with respect to the optical absorption of quaterthiophene. At low excitation energy (far from the oligomer resonance window) there is no significant modification of the Raman spectra before and after encapsulation. By contrast, at high excitation energy (close to the oligomer resonance window), Raman spectra exhibit a G-band shift together with an important RBM intensity loss, suggesting a significant charge transfer between the inserted molecule and the host nanotubes. Those results suggest a photo induced process leading to a significant charge transfer. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Kinematical coincidence method in transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Acosta, L.; Amorini, F. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Auditore, L. [INFN Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina (Italy); Berceanu, I. [Institute for Physics and Nuclear Engineering, Bucharest (Romania); Cardella, G., E-mail: cardella@ct.infn.it [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Chatterjiee, M.B. [Saha Institute for Nuclear Physics, Kolkata (India); De Filippo, E. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Francalanza, L.; Gianì, R. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia, Catania (Italy); Grassi, L. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Rudjer Boskovic Institute, Zagreb (Croatia); Grzeszczuk, A. [Institut of Physics, University of Silesia, Katowice (Poland); La Guidara, E. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania (Italy); Lanzalone, G. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Facoltà di Ingegneria e Architettura, Università Kore, Enna (Italy); Lombardo, I. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Scienze Fisiche, Università Federico II and INFN Sezione di Napoli (Italy); Loria, D.; Minniti, T. [INFN Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina (Italy); Pagano, E.V. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia, Catania (Italy); and others

    2013-07-01

    A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematics is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of {sup 10}Be+p→{sup 9}Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained. The range of applicability of the method is discussed.

  8. Kinematical coincidence method in transfer reactions

    CERN Document Server

    Acosta, L; Auditore, L; Berceanu, I; Cardella, G; Chatterjiee, M B; De Filippo, E; FrancalanzA, L; Gianì, R; Grassi, L; Grzeszczuk, A; La Guidara, E; Lanzalone, G; Lombardo, I; Loria, D; Minniti, T; Pagano, E V; Papa, M; Pirrone, S; Politi, G; Pop, A; Porto, F; Rizzo, F; Rosato, E; Russotto, P; Santoro, S; Trifirò, A; Trimarchi, M; Verde, G; Vigilante, M

    2012-01-01

    A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematic is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of 10Be+p-->9Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained.

  9. Fingerprint of fractional charge transfer at metal/organic interface

    OpenAIRE

    Savu, Sabine-A.; Biddau, Giulio; Pardini, Lorenzo; Bula, Rafael; Bettinger, Holger F; Draxl, Claudia; Chassé, Thomas; Casu, M. Benedetta

    2015-01-01

    Although physisorption is a widely occurring mechanism of bonding at the organic/metal interface, contradictory interpretations of this phenomenon are often reported. Photoemission and X-ray absorption spectroscopy investigations of nanorods of a substituted pentacene, 2,3,9,10-tetrafluoropentacene, deposited on gold single crystals reveal to be fundamental to identify the bonding mechanisms. We find fingerprints of a fractional charge transfer from the clean metal substrate to the physisorbe...

  10. Ultrafast photoinduced intra- und intermolecular charge transfer and solvation

    OpenAIRE

    Bizjak, Tanja

    2004-01-01

    Intra- and intermolecular charge transfer as well as internal conversion processes are studied in various molecular systems. The dynamics of these fundamental photoinduced processes are investigated by pump-probe femtosecond spectroscopy and steady-state fluorescence. Transient spectra are obtained using white light continuum as probe, while time resolved measurements are performed by probing at specific wavelengths with non dispersive detec-tion. Noncollinearly phase matched optical parametr...

  11. Tight-binding parameters for charge transfer along DNA

    OpenAIRE

    Hawke, L. G.D.; Kalosakas, G.; Simserides, C.

    2009-01-01

    We systematically examine all the tight-binding parameters pertinent to charge transfer along DNA. The $\\pi$ molecular structure of the four DNA bases (adenine, thymine, cytosine, and guanine) is investigated by using the linear combination of atomic orbitals method with a recently introduced parametrization. The HOMO and LUMO wavefunctions and energies of DNA bases are discussed and then used for calculating the corresponding wavefunctions of the two B-DNA base-pairs (adenine-thymine and gua...

  12. Femtosecond direct observation of charge transfer between bases in DNA

    OpenAIRE

    Wan, Chaozhi; Fiebig, Torsten; Schiemann, Olav; Barton, Jacqueline K.; Zewail, Ahmed H.

    2000-01-01

    Charge transfer in supramolecular assemblies of DNA is unique because of the notion that the π-stacked bases within the duplex may mediate the transport, possibly leading to damage and/or repair. The phenomenon of transport through π-stacked arrays over a long distance has an analogy to conduction in molecular electronics, but the mechanism still needs to be determined. To decipher the elementary steps and the mechanism, one has to directly measure the dynamics in ...

  13. Interfacial Charge Transfer States in Condensed Phase Systems.

    Science.gov (United States)

    Vandewal, Koen

    2016-05-27

    Intermolecular charge transfer (CT) states at the interface between electron-donating (D) and electron-accepting (A) materials in organic thin films are characterized by absorption and emission bands within the optical gap of the interfacing materials. CT states efficiently generate charge carriers for some D-A combinations, and others show high fluorescence quantum efficiencies. These properties are exploited in organic solar cells, photodetectors, and light-emitting diodes. This review summarizes experimental and theoretical work on the electronic structure and interfacial energy landscape at condensed matter D-A interfaces. Recent findings on photogeneration and recombination of free charge carriers via CT states are discussed, and relations between CT state properties and optoelectronic device parameters are clarified. PMID:26980308

  14. Charge Transfer Excitons at van der Waals Interfaces.

    Science.gov (United States)

    Zhu, Xiaoyang; Monahan, Nicholas R; Gong, Zizhou; Zhu, Haiming; Williams, Kristopher W; Nelson, Cory A

    2015-07-01

    The van der Waals interfaces of molecular donor/acceptor or graphene-like two-dimensional (2D) semiconductors are central to concepts and emerging technologies of light-electricity interconversion. Examples include, among others, solar cells, photodetectors, and light emitting diodes. A salient feature in both types of van der Waals interfaces is the poorly screened Coulomb potential that can give rise to bound electron-hole pairs across the interface, i.e., charge transfer (CT) or interlayer excitons. Here we address common features of CT excitons at both types of interfaces. We emphasize the competition between localization and delocalization in ensuring efficient charge separation. At the molecular donor/acceptor interface, electronic delocalization in real space can dictate charge carrier separation. In contrast, at the 2D semiconductor heterojunction, delocalization in momentum space due to strong exciton binding may assist in parallel momentum conservation in CT exciton formation. PMID:26001297

  15. Probing transitional regions with nuclear transfer reactions

    International Nuclear Information System (INIS)

    Experimental probes which may provide ways to assess differences between presently competing theories for transitional nuclei are of great current interest. In this paper one-neutron transfer data for 52Te nuclei and one-proton transfer data for a long chain of 61Pm nuclei are discussed, with special emphasis on what may be learned from cross sections for weakly excited high- spin states with the parity of the intruding h(sub 11/2) orbitals in these regions. The data for the Pm nuclei covers the full range from the closed N=82 shell to the good rotors (N=92) and exhibits how the proton spectrum responds to increasing the neutron number of the system. The population of the states is discussed within the framework of the coupled-channels-Born-approximation (CCBA), including a critical evaluation of current recipes for calculation of transfer and scattering form factors. (Auth.)

  16. Ultrafast Electron Transfer Kinetics in the LM Dimer of Bacterial Photosynthetic Reaction Center from Rhodobacter sphaeroides.

    Science.gov (United States)

    Sun, Chang; Carey, Anne-Marie; Gao, Bing-Rong; Wraight, Colin A; Woodbury, Neal W; Lin, Su

    2016-06-23

    It has become increasingly clear that dynamics plays a major role in the function of many protein systems. One system that has proven particularly facile for studying the effects of dynamics on protein-mediated chemistry is the bacterial photosynthetic reaction center from Rhodobacter sphaeroides. Previous experimental and computational analysis have suggested that the dynamics of the protein matrix surrounding the primary quinone acceptor, QA, may be particularly important in electron transfer involving this cofactor. One can substantially increase the flexibility of this region by removing one of the reaction center subunits, the H-subunit. Even with this large change in structure, photoinduced electron transfer to the quinone still takes place. To evaluate the effect of H-subunit removal on electron transfer to QA, we have compared the kinetics of electron transfer and associated spectral evolution for the LM dimer with that of the intact reaction center complex on picosecond to millisecond time scales. The transient absorption spectra associated with all measured electron transfer reactions are similar, with the exception of a broadening in the QX transition and a blue-shift in the QY transition bands of the special pair of bacteriochlorophylls (P) in the LM dimer. The kinetics of the electron transfer reactions not involving quinones are unaffected. There is, however, a 4-fold decrease in the electron transfer rate from the reduced bacteriopheophytin to QA in the LM dimer compared to the intact reaction center and a similar decrease in the recombination rate of the resulting charge-separated state (P(+)QA(-)). These results are consistent with the concept that the removal of the H-subunit results in increased flexibility in the region around the quinone and an associated shift in the reorganization energy associated with charge separation and recombination. PMID:27243380

  17. Nucleon transfer reactions in D.W.B.A

    International Nuclear Information System (INIS)

    The DWBA for one nucleon transfer reaction is described as simply and completely as possible to show the possibilities and limits of this method. The extraction of spectroscopic factors is described in the appendix. (authors)

  18. Coherent and semi-coherent neutron transfer reactions

    International Nuclear Information System (INIS)

    Neutron transfer reactions are proposed to account for anomalies reported in Pons-Fleischmann experiments. The prototypical reaction involves the transfer of a neutron (mediated by low frequency electric or magnetic fields) from a donor nucleus to virtual continuum states, followed by the capture of the virtual neutron by an acceptor nucleus. In this work we summarize basic principles, recent results and the ultimate goals of the theoretical effort

  19. INVESTIGATION OF INNER AND OUTER SUBSHELLS VIA TRANSFER REACTIONS

    OpenAIRE

    Gales, S.

    1983-01-01

    Transfer reactions, investigated a high incident energy (from 100 to 300 MeV), have considerably increased our knowledge of the nuclear response function to a particular simple mode of excitation of the nucleus. These reactions are particularly well suited to the study of high spin inner and outer subshells. The advantages of such approach are illustrated using few characteristic examples. a) Strong selectivity in angular momentum transfer, determination of the spin J of the inner hole state ...

  20. Probing nucleon-nucleon correlations via heavy ion transfer reactions

    Directory of Open Access Journals (Sweden)

    Szilner S.

    2015-01-01

    Full Text Available The revival of transfer reaction studies benefited from the construction of the new generation large solid angle spectrometers, coupled to large γ arrays. The recent results of γ-particle coincident measurements demonstrate a strong interplay between single-particle and collective degrees of freedom that is pertinent to the reaction dynamics. By studies of transfer of pairs, valuable information on the component responsible for particle correlations has been derived.

  1. Charge transfer along DNA dimers, trimers and polymers

    CERN Document Server

    Simserides, Constantinos

    2013-01-01

    The transfer of electrons and holes along DNA dimers, trimers and polymers is described at the base-pair level, using the relevant on-site energies of the base-pairs and the hopping parameters between successive base-pairs. The temporal and spatial evolution of carriers along a $N$ base-pair DNA segment is determined, solving a system of $N$ coupled differential equations. Useful physical quantities are calculated including the pure mean carrier transfer rate $k$, the inverse decay length $\\beta$ used for exponential fit ($k = k_0 \\textrm{exp}(-\\beta d)$) of the transfer rate as a function of the charge transfer distance $d = N \\times$ 3.4 {\\AA} and the exponent $\\eta$ used for a power law fit ($k = k_0' N^{-\\eta}$) of the transfer rate as function of the number of monomers $N$. Among others, the electron and hole transfer along the polymers poly(dG)-poly(dC), poly(dA)-poly(dT), GCGCGC..., ATATAT... is studied. $\\beta$ ($\\eta$) falls in the range $\\approx$ 0.2 - 2 {\\AA}$^{-1}$ (1.7 - 17), $k_0$ ($k_0'$) is us...

  2. Nanocontact electrification: patterned surface charges affecting adhesion, transfer, and printing.

    Science.gov (United States)

    Cole, Jesse J; Barry, Chad R; Knuesel, Robert J; Wang, Xinyu; Jacobs, Heiko O

    2011-06-01

    Contact electrification creates an invisible mark, overlooked and often undetected by conventional surface spectroscopic measurements. It impacts our daily lives macroscopically during electrostatic discharge and is equally relevant on the nanoscale in areas such as soft lithography, transfer, and printing. This report describes a new conceptual approach to studying and utilizing contact electrification beyond prior surface force apparatus and point-contact implementations. Instead of a single point contact, our process studies nanocontact electrification that occurs between multiple nanocontacts of different sizes and shapes that can be formed using flexible materials, in particular, surface-functionalized poly(dimethylsiloxane) (PDMS) stamps and other common dielectrics (PMMA, SU-8, PS, PAA, and SiO(2)). Upon the formation of conformal contacts and forced delamination, contacted regions become charged, which is directly observed using Kelvin probe force microscopy revealing images of charge with sub-100-nm lateral resolution. The experiments reveal chemically driven interfacial proton exchange as the dominant charging mechanism for the materials that have been investigated so far. The recorded levels of uncompensated charges approach the theoretical limit that is set by the dielectric breakdown strength of the air gap that forms as the surfaces are delaminated. The macroscopic presence of the charges is recorded using force-distance curve measurements involving a balance and a micromanipulator to control the distance between the delaminated objects. Coulomb attraction between the delaminated surfaces reaches 150 N/m(2). At such a magnitude, the force finds many applications. We demonstrate the utility of printed charges in the fields of (i) nanoxerography and (ii) nanotransfer printing whereby the smallest objects are ∼10 nm in diameter and the largest objects are in the millimeter to centimeter range. The printed charges are also shown to affect the electronic

  3. Efficient charge generation by relaxed charge-transfer states at organic interfaces

    KAUST Repository

    Vandewal, Koen

    2013-11-17

    Interfaces between organic electron-donating (D) and electron-accepting (A) materials have the ability to generate charge carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold via weakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer:fullerene, small-molecule:C60 and polymer:polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90% without the need for excess electronic or vibrational energy. © 2014 Macmillan Publishers Limited.

  4. Two-nucleon transfer reactions uphold supersymmetry in atomic nuclei

    OpenAIRE

    Barea, J.; Bijker, R.; Frank, A.

    2004-01-01

    The spectroscopic strengths of two-nucleon transfer reactions constitute a stringent test for two-nucleon correlations in the nuclear wave functions. A comparison between the recently measured 198Hg(d,alpha)196Au reaction and the predictions from the nuclear quartet supersymmetry lends further support to the validity of supersymmetry in nuclear physics.

  5. Charge and Energy Dependences of Ionization and Transfer for Helium in Collisions with Fast Charged Projectiles

    Institute of Scientific and Technical Information of China (English)

    FU Hong-Bin; WANG Bao-Hong; DING Bao-Wei; LIU Zhao-Yuan

    2009-01-01

    The classical method within the independent electron model is employed to investigate (i) charge dependences of single and double ionization for helium by various charged ions Aq+ (q = 1 - 8) at impact energies of 0.64 and 1.44 MeV/u, respectively, (ii) energy dependences of transfer ionization for helium by 0.5-3 MeV/u A8,9+ ions impact. The Lenz-Jensen model of the atom is applied instead of the Bohr model of the atom, and the impact-parameter dependences are also introduced into the calculations. Satisfactory agreement is found between theoretical and experimental data.

  6. Quantum Coherence as a Witness of Vibronically Hot Energy Transfer in Bacterial Reaction Centre

    CERN Document Server

    Paleček, David; Westenhoff, Sebastian; Zigmantas, Donatas

    2016-01-01

    Photosynthetic proteins have evolved over billions of years so as to undergo optimal energy transfer to the sites of charge separation. Based on spectroscopically detected quantum coherences, it has been suggested that this energy transfer is partially wavelike. This conclusion critically depends on assignment of the coherences to the evolution of excitonic superpositions. Here we demonstrate for a bacterial reaction centre protein that long-lived coherent spectroscopic oscillations, which bear canonical signatures of excitonic superpositions, are essentially vibrational excited state coherences shifted to the ground state of the chromophores . We show that appearance of these coherences is brought about by release of electronic energy during the energy transfer. Our results establish how energy migrates on vibrationally hot chromophores in the reaction centre and they call for a re-examination of claims of quantum energy transfer in photosynthesis.

  7. Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization

    Science.gov (United States)

    Vaikkinen, Anu; Kauppila, Tiina J.; Kostiainen, Risto

    2016-04-01

    The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M+. decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques.

  8. Isotope effect in charge-transfer collisions of H with He{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Loreau, J.; Dalgarno, A. [Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Ryabchenko, S. [Northern (Arctic) Federal University, 17 Severnaya Dvina Emb., 163002 Arkhangelsk (Russian Federation); Laboratoire de Chimie Quantique et Photophysique, Universite Libre de Bruxelles (ULB), CP160/09, 1050 Bruxelles (Belgium); Vaeck, N. [Laboratoire de Chimie Quantique et Photophysique, Universite Libre de Bruxelles (ULB), CP160/09, 1050 Bruxelles (Belgium)

    2011-11-15

    We present a theoretical study of the isotope effect arising from the replacement of H by T in the charge-transfer collision H(n=2) + He{sup +}(1s) at low energy. Using a quasimolecular approach and a time-dependent wave-packet method, we compute the cross sections for the reaction including the effects of the nonadiabatic radial and rotational couplings. For H(2s) + He{sup +}(1s) collisions, we find a strong isotope effect at energies below 1 eV/amu for both singlet and triplet states. We find a much smaller isotopic dependence of the cross section for H(2p) + He{sup +}(1s) collisions in triplet states, and no isotope effect in singlet states. We explain the isotope effect on the basis of the potential energy curves and the nonadiabatic couplings, and we evaluate the importance of the isotope effect on the charge-transfer rate coefficients.

  9. Cross sections for charge transfer between mercury ions and other metals

    Science.gov (United States)

    Vroom, D. A.; Rutherford, J. A.

    1977-01-01

    Cross sections for charge transfer between several ions and metals of interest to the NASA electro propulsion program have been measured. Specifically, the ions considered were Hg(+), Xe(+) and Cs(+) and the metals Mo, Fe, Al, Ti, Ta, and C. Measurements were made in the energy regime from 1 to 5,000 eV. In general, the cross sections for charge transfer were found to be less than 10 to the minus 15 power sq cm for most processes over the total energy range. Exceptions are Hg(+) in collision with Ti and Ta. The results obtained for each reaction are given in both graphical and numerical form in the text. For quick reference, the data at several ion velocities are condensed into one table given in the summary.

  10. Coupled electron-nuclear dynamics: Charge migration and charge transfer initiated near a conical intersection

    Science.gov (United States)

    Mendive-Tapia, David; Vacher, Morgane; Bearpark, Michael J.; Robb, Michael A.

    2013-07-01

    Coupled electron-nuclear dynamics, implemented using the Ehrenfest method, has been used to study charge migration with fixed nuclei, together with charge transfer when nuclei are allowed to move. Simulations were initiated at reference geometries of neutral benzene and 2-phenylethylamine (PEA), and at geometries close to potential energy surface crossings in the cations. Cationic eigenstates, and the so-called sudden approximation, involving removal of an electron from a correlated ground-state wavefunction for the neutral species, were used as initial conditions. Charge migration without coupled nuclear motion could be observed if the Ehrenfest simulation, using the sudden approximation, was started near a conical intersection where the states were both strongly coupled and quasi-degenerate. Further, the main features associated with charge migration were still recognizable when the nuclear motion was allowed to couple. In the benzene radical cation, starting from the reference neutral geometry with the sudden approximation, one could observe sub-femtosecond charge migration with a small amplitude, which results from weak interaction with higher electronic states. However, we were able to engineer large amplitude charge migration, with a period between 10 and 100 fs, corresponding to oscillation of the electronic structure between the quinoid and anti-quinoid cationic electronic configurations, by distorting the geometry along the derivative coupling vector from the D6h Jahn-Teller crossing to lower symmetry where the states are not degenerate. When the nuclear motion becomes coupled, the period changes only slightly. In PEA, in an Ehrenfest trajectory starting from the D2 eigenstate and reference geometry, a partial charge transfer occurs after about 12 fs near the first crossing between D1, D2 (N+-Phenyl, N-Phenyl+). If the Ehrenfest propagation is started near this point, using the sudden approximation without coupled nuclear motion, one observes an

  11. Charge-exchange and charge-conserving reactions on Mg, Ar, Zr, and Sn isotopes

    International Nuclear Information System (INIS)

    We investigate charge-exchange reactions (CEXRs) and charge-conserving reactions (CCORs) on Mg, Ar, Zr, and Sn isotopes by comparing our theoretical results to relevant experimental data on stable nuclei. As for CEXRs, first, we discuss nuclear beta decay because it may give more convincing input data on the network calculations for successive capture reactions by protons and neutrons. Second, we address the importance of the Gamow Teller (GT) states that are low-lying excited states well known in the conventional nuclear physics while high-lying excited states still remain to be studied. The third topic, which is viable through the CCORs, is the symmetry energy associated with the equation of state of nuclear matter. By using the CCORs, we can study the isoscalar giant dipole resonance (ISGDR) and the pigmy dipole resonance (PDR). We discuss theoretical results regarding these CEXRs and CCORs on 26Mg, 40Ar, 90,92Zr, and 112∼124Sn and compare them with available experimental data. Our calculations are carried out by using the proton-neutron quasi-particle random phase approximation (pnQRPA), the QRPA, the deformed QRPA (DQRPA), the shell model and a hybrid model. Our results are shown to agree with the data available. These nuclear reactions considered in this report will complement capture reactions by protons and neutrons which are of vital importance for understanding the element abundances in the cosmos.

  12. Golden rule kinetics of transfer reactions in condensed phase: The microscopic model of electron transfer reactions in disordered solid matrices

    Energy Technology Data Exchange (ETDEWEB)

    Basilevsky, M. V.; Mitina, E. A. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); Odinokov, A. V. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); National Research Nuclear University “MEPhI,” 31, Kashirskoye shosse, Moscow (Russian Federation); Titov, S. V. [Karpov Institute of Physical Chemistry, 3-1/12, Building 6, Obuha pereulok, Moscow (Russian Federation)

    2013-12-21

    kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.

  13. Variation of kinetic isotope effect in multiple proton transfer reactions

    Indian Academy of Sciences (India)

    B Saritha; M Durga Prasad

    2012-01-01

    Recently, we had suggested that the motion along the promoter mode in the first part of the IRC of proton transfer reaction enhances the delocalization of electrons on the acceptor atom into the * orbital of the donor-hydrogen covalent bond, and as a consequence weakens it. This leads to a reduction of the barrier to the proton transfer as well as the stretching frequency of donor-hydrogen bond. An extension of this to the concerted multiple proton transfer reactions implies that the kinetic isotope effect in such reaction depends exponentially on the number of protons that are being transferred. Computational evidence on three systems, (HF)3, formic acid dimer, and (H2O) clusters is provided to support this assertion.

  14. Impact of speciation on the electron charge transfer properties of nanodiamond drug carriers

    Science.gov (United States)

    Sun, Baichuan; Barnard, Amanda S.

    2016-07-01

    Unpassivated diamond nanoparticles (bucky-diamonds) exhibit a unique surface reconstruction involving graphitization of certain crystal facets, giving rise to hybrid core-shell particles containing both aromatic and aliphatic carbon. Considerable effort is directed toward eliminating the aromatic shell, but persistent graphitization of subsequent subsurface-layers makes perdurable purification a challenge. In this study we use some simple statistical methods, in combination with electronic structure simulations, to predict the impact of different fractions of aromatic and aliphatic carbon on the charge transfer properties of the ensembles of bucky-diamonds. By predicting quality factors for a variety of cases, we find that perfect purification is not necessary to preserve selectivity, and there is a clear motivation for purifying samples to improve the sensitivity of charge transfer reactions. This may prove useful in designing drug delivery systems where the release of (selected) drugs needs to be sensitive to specific conditions at the point of delivery.Unpassivated diamond nanoparticles (bucky-diamonds) exhibit a unique surface reconstruction involving graphitization of certain crystal facets, giving rise to hybrid core-shell particles containing both aromatic and aliphatic carbon. Considerable effort is directed toward eliminating the aromatic shell, but persistent graphitization of subsequent subsurface-layers makes perdurable purification a challenge. In this study we use some simple statistical methods, in combination with electronic structure simulations, to predict the impact of different fractions of aromatic and aliphatic carbon on the charge transfer properties of the ensembles of bucky-diamonds. By predicting quality factors for a variety of cases, we find that perfect purification is not necessary to preserve selectivity, and there is a clear motivation for purifying samples to improve the sensitivity of charge transfer reactions. This may prove

  15. Geometric rearrangement of adsorbate driven by the charge transfer

    Energy Technology Data Exchange (ETDEWEB)

    Pavlyukh, Yaroslav; Berakdar, Jamal [Institut fuer Physik, Martin-Luther-Universitaet Halle-Wittenberg, Halle (Germany); Huebner, Wolfgang [Department of Physics and Research Center OPTIMAS, Kaiserslautern University of Technology (Germany)

    2010-05-15

    Adsorption of alkali atoms induces a significant charge redistribution in the region around the adatom. Such charge displacement is associated with a large dipole moment responsible for the interaction of adatoms and a reduction of the surface work function. In addition to these well-known effects our first principles simulations for the Na{sub 9}{sup +} cluster on the Cu(001) surface demonstrate how the charge transfer (CT) from the adsorbate to the substrate can drastically change the geometric structure of the cluster. We report on a detailed study of the adsorption process using quantum chemistry. A representation of the substrate by a cluster of 54 Cu atoms allows us to treat quantum mechanically the electronic structure of both systems, the adsorbate and the surface, on equal footing. Subsequently, we analyze the charge distribution in the composite system. Convergence of the results is verified by considering a much larger substrate cluster containing 126 Cu atoms. The role of the CT is further elucidated by the geometry optimization of the bare cluster with and without an electron deficit. It is shown that the CT drives the system to a meta-stable state which thereafter relaxes to a new configuration. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  16. Delta excitation in nuclei: the lesson of charge exchange reactions

    International Nuclear Information System (INIS)

    We present an attempt of theoretical interpretation of charge exchange reactions on nuclei in the region of the delta resonance. Special care is taken to insure consistency with the constraints from pion and photon excitation channels. Good agreement with measured spectra can be obtained for all types of targets and incident ions except for polarized deuterons data which appear hardly reconcilable with the others within our interpretation. Despite the peripheral character of these reactions, a sizeable part of the observed downward shift of the resonance is possibly ascribable to a yet undetected collective mode of the nucleus at high excitation, the pionic branch. Our limited commitment is due to uncomplete knowledge of the NN → N Δ interaction and the transition form factors of the probing ions which has been palliated by some phenomenology

  17. Coherent pion production in heavy ion charge exchange reactions

    International Nuclear Information System (INIS)

    We report the first observation of coherent pion production induced by a heavy ion charge exchange reaction. The (12C,12N) reaction [D. Bachelier et al., Phys. Lett. B 172 (1986) 23; M. Roy-Stephan et al., Nucl. Phys. A 488 (1988) 178] at 1.1 GeV/nucleon has been used to shine negative (off-shell) pions on nuclei and observe (on-shell) pions, leaving the target nucleus in its ground state. The experiment was performed at the Laboratoire National Saturne with the SPES4-π setup [Laurent Farhi PHD thesis IPNO-T97-12, Universite d'Orsay, 1997; Rasmus Dahl Ph.D., Niels Bohr Institutet, Copenhagen (1999)

  18. Tunable charge transfer properties in metal-phthalocyanine heterojunctions

    Science.gov (United States)

    Siles, P. F.; Hahn, T.; Salvan, G.; Knupfer, M.; Zhu, F.; Zahn, D. R. T.; Schmidt, O. G.

    2016-04-01

    Organic materials such as phthalocyanine-based systems present a great potential for organic device applications due to the possibility of integrating films of different organic materials to create organic heterostructures which combine the electrical capabilities of each material. This opens the possibility to precisely engineer and tune new electrical properties. In particular, similar transition metal phthalocyanines demonstrate hybridization and charge transfer properties which could lead to interesting physical phenomena. Although, when considering device dimensions, a better understanding and control of the tuning of the transport properties still remain in the focus of research. Here, by employing conductive atomic force microscopy techniques, we provide an insight about the nanoscale electrical properties and transport mechanisms of MnPc and fluorinated phthalocyanines such as F16CuPc and F16CoPc. We report a transition from typical diode-like transport mechanisms for pure MnPc thin films to space-charge-limited current transport regime (SCLC) for Pc-based heterostructures. The controlled addition of fluorinated phthalocyanine also provides highly uniform and symmetric-polarized transport characteristics with conductance enhancements up to two orders of magnitude depending on the polarization. We present a method to spatially map the mobility of the MnPc/F16CuPc structures with a nanoscale resolution and provide theoretical calculations to support our experimental findings. This well-controlled nanoscale tuning of the electrical properties for metal transition phthalocyanine junctions stands as key step for future phthalocyanine-based electronic devices, where the low dimension charge transfer, mediated by transition metal atoms could be intrinsically linked to a transfer of magnetic moment or spin.Organic materials such as phthalocyanine-based systems present a great potential for organic device applications due to the possibility of integrating films of

  19. Polarization and charge transfer in the hydration of chloride ions

    International Nuclear Information System (INIS)

    A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation and MP2-level calculations are performed to examine the electronic structure properties of the ions and surrounding waters in the external field of more distant waters. The ChelpG method is employed to explore the effective charges and dipoles on the chloride ions and first-shell waters. The quantum theory of atoms in molecules (QTAIM) is further utilized to examine charge transfer from the anion to surrounding water molecules. The clusters extracted from the AMOEBA simulations exhibit high probabilities of anisotropic solvation for chloride ions in bulk water. From the QTAIM analysis, 0.2 elementary charges are transferred from the ion to the first-shell water molecules. The default AMOEBA model overestimates the average dipole moment magnitude of the ion compared to the quantum mechanical value. The average magnitude of the dipole moment of the water molecules in the first shell treated at the MP2-level, with the more distant waters handled with an AMOEBA effective charge model, is 2.67 D. This value is close to the AMOEBA result for first-shell waters (2.72 D) and is slightly reduced from the bulk AMOEBA value (2.78 D). The magnitude of the dipole moment of the water molecules in the first solvation shell is most strongly affected by the local water-water interactions and hydrogen bonds with the second solvation shell, rather than by interactions with the ion.

  20. Polarization and charge transfer in the hydration of chloride ions

    Science.gov (United States)

    Zhao, Zhen; Rogers, David M.; Beck, Thomas L.

    2010-01-01

    A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation and MP2-level calculations are performed to examine the electronic structure properties of the ions and surrounding waters in the external field of more distant waters. The ChelpG method is employed to explore the effective charges and dipoles on the chloride ions and first-shell waters. The quantum theory of atoms in molecules (QTAIM) is further utilized to examine charge transfer from the anion to surrounding water molecules. The clusters extracted from the AMOEBA simulations exhibit high probabilities of anisotropic solvation for chloride ions in bulk water. From the QTAIM analysis, 0.2 elementary charges are transferred from the ion to the first-shell water molecules. The default AMOEBA model overestimates the average dipole moment magnitude of the ion compared to the quantum mechanical value. The average magnitude of the dipole moment of the water molecules in the first shell treated at the MP2-level, with the more distant waters handled with an AMOEBA effective charge model, is 2.67 D. This value is close to the AMOEBA result for first-shell waters (2.72 D) and is slightly reduced from the bulk AMOEBA value (2.78 D). The magnitude of the dipole moment of the water molecules in the first solvation shell is most strongly affected by the local water-water interactions and hydrogen bonds with the second solvation shell, rather than by interactions with the ion.

  1. Excitons with charge transfer in sncl2-phthalocyanine films

    OpenAIRE

    Vertsimakha, Ya. I.; Lutsyk, P. M.

    2014-01-01

    The absorption, modulated photoreflectance, and photovoltage spectra of dichlorotin phthalocyanine (SnCl2Pc) films have been measured. These films are thermally deposited in vacuum at different substrate temperatures. The energies of charge-transfer-states (CT-states) in SnCl2Pc films (1.35, 1.52, and 2.05 eV) and the diffusion length of Frenkel excitons (130+/-30 nm) have been determined. The photosensitivity of SnCl2Pc films is comparable to that of n-type perylene derivative (MPP) layers a...

  2. Charge transfer between epitaxial graphene and silicon carbide

    OpenAIRE

    Kopylov, S; A. Tzalenchuk; Kubatkin, Sergey; Fal'ko, V. I.

    2010-01-01

    We analyze doping of graphene grown on SiC in two models which differ by the source of charge transferred to graphene, namely, from SiC surface and from bulk donors. For each of the two models, we find the maximum electron density induced in monolayer and bilayer graphene, which is determined by the difference between the work function for electrons in pristine graphene and donor states on/in SiC, and analyze the responsivity of graphene to the density variation by means of electrostatic gate...

  3. Optics of Chromites and Charge-Transfer Transitions

    OpenAIRE

    Andrei V. Zenkov

    2008-01-01

    Specific features of the charge-transfer (CT) states and O2p→Cr3d transitions in the octahedral (CrO6)9− complex are considered in the cluster approach. The reduced matrix elements of the electric-dipole transition operator are calculated on many-electron wave functions of the complex corresponding to the initial and final states of a CT transition. Modeling the optic spectrum of chromites has yielded a complicated CT band. The model spectrum is in satisfactory agreement with experi...

  4. Photoinduced charge-transfer materials for nonlinear optical applications

    Science.gov (United States)

    McBranch, Duncan W.

    2006-10-24

    A method using polyelectrolyte self-assembly for preparing multi-layered organic molecular materials having individual layers which exhibit ultrafast electron and/or energy transfer in a controlled direction occurring over the entire structure. Using a high molecular weight, water-soluble, anionic form of poly-phenylene vinylene, self-assembled films can be formed which show high photoluminescence quantum efficiency (QE). The highest emission QE is achieved using poly(propylene-imine) (PPI) dendrimers as cationic binders. Self-quenching of the luminescence is observed as the solid polymer film thickness is increased and can be reversed by inserting additional spacer layers of transparent polyelectrolytes between each active conjugated layer, such that the QE grows with thickness. A red shift of the luminescence is also observed as additional PPV layers are added. This effect persists as self-quenching is eliminated. Charge transfer superlattices can be formed by additionally incorporating C.sub.60 acceptor layers.

  5. Three-particle Coulomb on-shell vertex functions. Behaviour of amplitude of simultaneous transfer reaction of two charged particles in the vicinity of the nearest singularity in cos0

    International Nuclear Information System (INIS)

    The connection of the on-shell function with the asymptotical coefficient of the three-particle wave functtion of the bound system in a configuration space is found. The expression for the leading singularity term of the exact amplitude of sub-Coulomb reactions is found in the vicinity of the nearest singularity

  6. Progress on the evaluation of charged particle nuclear reaction data in Sichuan University

    International Nuclear Information System (INIS)

    The evaluations of excitation function of 9 reactions induced by charged particles (p, α, d) have been fulfilled. The evaluated nuclear reactions and the experimental works are presented. The recommended data for each reaction were remarked

  7. Dynamical Theory of Charge Transfer Between Complex Atoms and Surfaces

    Science.gov (United States)

    Chaudhuri, Basudev; Marston, Brad

    2000-03-01

    An existing dynamical quantum many-body theory of charge transfer(A. V. Onufriev and J. B. Marston, Phys. Rev. B 53), 13340 (1996); J. Merino and J. B. Marston, Phys. Rev. B 58, 6982 (1998). describes atoms with simple s-orbitals, such as alkalis and alkaline-earths, interacting with metal surfaces. The many-body equations of motion (EOM) are developed systematically as an expansion in the number of surface particle-hole excitations. Here we generalize this theory to describe atoms with richer orbital structures, such as atomic oxygen. In the simplest version of the model, only the single-particle p_z-orbitals of the atom, the ones oriented perpendicular to the surface, participate directly in resonant charge transfer as they have the largest overlap with the metallic wavefunctions. However, as the several-electron Russell-Saunders eigenstates, labeled by total angular momenta quantum numbers J, L, and S, are built out of products of single-particle orbitals, non-trivial matrix elements must be incorporated into the many-body EOM's. Comparison to recent experimental results(A. C. Lavery, C. E. Sosolik, and B. H. Cooper, Nucl. Instrum. Meth. B 157), 42 (1999); A. C. Lavery et al. to appear in Phys. Rev. B. on the scattering of low-energy oxygen ions off Cu(001) surfaces is made.

  8. Charge Transfer Based Colorimetric Detection of Silver Ion

    International Nuclear Information System (INIS)

    We have demonstrated the colorimetric chemosensor for detection of Ag+ via formation of nanoparticles which is based on the intramolecular CT interaction between the electron-rich (2,6-dialkoxynaphthalene; Np) moiety and the electron-deficient (methyl viologen; MV2+) moiety of a single sensor molecule. Under irradiation of light, Ag+ was reduced to very small silver nanoparticle by CT interaction in the presence of OEGs as flexible recognition moiety of Ag+ and stabilizer for Ag nanoparticles, thus Ag nanoparticles resulted to reddish brown in the color change of sensor solution, gradually. Therefore, the charge-transfer interaction between an electron-deficient and an electron-rich units existing at a sensor molecule can be regarded as a new and efficient method to construct various colorimetric chemosensors. Donor.acceptor interactions or charge transfer (CT) interactions are an important class of non-covalent interactions and have been widely exploited in self-assembling systems. Beyond molecular chemistry, supramolecular chemistry aims at constituting highly complex, functional chemical systems from components held together by intermolecular forces. Chemosensors are the molecules of abiotic origin that bind selectively and reversibly with the analyte with concomitant change in one or more properties of the system. The recognition and signaling of ionic and neutral species of varying complexity is one of the most intensively studied areas of contemporary supramolecular chemistry

  9. Excited State Structural Dynamics of Carotenoids and Charge Transfer Systems

    International Nuclear Information System (INIS)

    This dissertation describes the development and implementation of a visible/near infrared pump/mid-infrared probe apparatus. Chapter 1 describes the background and motivation of investigating optically induced structural dynamics, paying specific attention to solvation and the excitation selection rules of highly symmetric molecules such as carotenoids. Chapter 2 describes the development and construction of the experimental apparatus used throughout the remainder of this dissertation. Chapter 3 will discuss the investigation of DCM, a laser dye with a fluorescence signal resulting from a charge transfer state. By studying the dynamics of DCM and of its methyl deuterated isotopomer (an otherwise identical molecule), we are able to investigate the origins of the charge transfer state and provide evidence that it is of the controversial twisted intramolecular (TICT) type. Chapter 4 introduces the use of two-photon excitation to the S1 state, combined with one-photon excitation to the S2 state of the carotenoid beta-apo-8'-carotenal. These 2 investigations show evidence for the formation of solitons, previously unobserved in molecular systems and found only in conducting polymers Chapter 5 presents an investigation of the excited state dynamics of peridinin, the carotenoid responsible for the light harvesting of dinoflagellates. This investigation allows for a more detailed understanding of the importance of structural dynamics of carotenoids in light harvesting

  10. Heavy-ion transfer reactions at large internuclear distances using the PRISMA magnetic spectrometer

    Directory of Open Access Journals (Sweden)

    Montanari D. J.

    2013-12-01

    Full Text Available We measured excitation functions for the main transfer channels in the 116Sn+60Ni reaction at different bombarding energies from above to well below the Coulomb barrier. The experiment has been performed in inverse kinematics, detecting the lighter (target-like ions with the magnetic spectrometer PRISMA at very forward angles. Good mass, nuclear charge and kinetic energy resolutions have been achieved. The comparison between the data and microscopic calculations for the present case and for the previously measured 96Zr+40Ca system, namely superfluid and near closed shells nuclei, should significantly improve our understanding of nucleon-nucleon correlation properties in multinucleon transfer processes.

  11. The Coulomb integrals and the diffraction model of transfer reactions

    International Nuclear Information System (INIS)

    New asymptotic expressions for the Coulomb integrals are derived and compared with numerical results, the Watson asymptotics and the WKB approximations. The analytical expressions for the Coulomb integrals are used in cross section calculations for single-nucleon transfer reactions in the framework of the diffraction model. The case of the zero orbital angular momentum transfer is considered. The interference of the Fresnel and Fraunhofer parts of the reaction amplitude are discused in detail. The undertaken treatment can be useful for the interpretation of the associated experimental data and the results of DWBA calculations. (orig.)

  12. Mass transfer with complex reversible chemical reactions. II: Parallel reversible chemical reactions

    NARCIS (Netherlands)

    Versteeg, G.F.; Kuipers, J.A.M.; Beckum, van F.P.H.; Swaaij, van W.P.M.

    1990-01-01

    An absorption model has been developed which can be used to calculate rapidly absorption rates for the phenomenon mass transfer accompanied by multiple complex parallel reversible chemical reactions. This model can be applied for the calculation of the mass transfer rates, enhancement factors and co

  13. Solid State Rechargeable Organic Batteries Based on Polymer Composites of Charge-transfer Materials

    Directory of Open Access Journals (Sweden)

    R.K. Gupta

    2004-01-01

    Full Text Available Solid-state galvanic cells based on charge-transfer complexes have been extensively used. However, the low mechanical strengths of these materials have restricted their applications. To overcome this problem, the polymer composite of these materials have been prepared and used in fabrication of solid-state batteries. The pressed pellet of these materials has been used as cathode in contact with zinc as anode metal. The electrochemical characterization of these cells such as open-circuit voltages, short-circuit currents, their time and temperature dependence and rechargeability of these cells have been studied. The impedance analyses have been done to understand the nature of the electrode reaction.

  14. Integer charge transfer at the tetrakis(dimethylamino)ethylene/Au interface

    DEFF Research Database (Denmark)

    Lindell, L.; Unge, Mikael; Osikowicz, W.; Stafstrom, S.; Salaneck, W.R.; Crispin, X.; de Jong, M.P.

    2008-01-01

    conditions, where direct overlap of the organic pi system from the metal bands is prevented due to presence of oxides and/or hydrocarbons. We present direct experimental and theoretical evidence showing that the interface energetic for such systems is governed by exchange of an integer amount of electrons.......In organic-based electronics, interfacial properties have a profound impact on device performance. The lineup of energy levels is usually dependent on interface dipoles, which may arise from charge transfer reactions. In many applications, metal-organic junctions are prepared under ambient...

  15. Two-dimensional femtosecond optical spectroscopy of trapping dynamics in a charge-transfer process

    Science.gov (United States)

    Keß, Martin; Engel, Volker

    2016-04-01

    We study charge-transfer dynamics monitored by two-dimensional (2D) optical spectroscopy. The often used model consisting of two coupled diabatic electronic states in a single reaction coordinate is used to demonstrate the relation between the vibronic dynamics and the 2D-spectra. Within the employed wave-function approach, dissipation is included via a quantum-jump algorithm with explicit treatment of dephasing. States with long lifetimes which decay slowly due to the interaction with the environment are identified. Using filtered Fourier transforms, energy and time resolved information about the dissipative system dynamics can be obtained.

  16. Oxidation and metal-insertion in molybdenite surfaces: evaluation of charge-transfer mechanisms and dynamics

    Directory of Open Access Journals (Sweden)

    Shutthanandan V

    2008-06-01

    Full Text Available Abstract Molybdenum disulfide (MoS2, a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS2 is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia. The present work was performed to understand thermal oxidation and metal-insertion processes of molybdenite surfaces. The analysis was performed using atomic force microscopy (AFM, scanning electron microscopy (SEM, transmission electron microscopy (TEM, Rutherford backscattering spectrometry (RBS, and nuclear reaction analysis (NRA. Structural studies using SEM and TEM indicate the local-disordering of the structure as a result of charge-transfer process between the inserted lithium and the molybdenite layer. Selected area electron diffraction measurements indicate the large variations in the diffusivity of lithium confirming that the charge-transfer is different along and perpendicular to the layers in molybdenite. Thermal heating of molybenite surface in air at 400°C induces surface oxidation, which is slow during the first hour of heating and then increases significantly. The SEM results indicate that the crystals formed on the molybdenite surface as a result of thermal oxidation exhibit regular thin-elongated shape. The average size and density of the crystals on the surface is dependent on the time of annealing; smaller size and high density during the first one-hour and

  17. Oxidation and metal-insertion in molybdenite surfaces: evaluation of charge-transfer mechanisms and dynamics.

    Science.gov (United States)

    Ramana, C V; Becker, U; Shutthanandan, V; Julien, C M

    2008-01-01

    Molybdenum disulfide (MoS2), a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS2 is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia.The present work was performed to understand thermal oxidation and metal-insertion processes of molybdenite surfaces. The analysis was performed using atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA).Structural studies using SEM and TEM indicate the local-disordering of the structure as a result of charge-transfer process between the inserted lithium and the molybdenite layer. Selected area electron diffraction measurements indicate the large variations in the diffusivity of lithium confirming that the charge-transfer is different along and perpendicular to the layers in molybdenite. Thermal heating of molybenite surface in air at 400 degrees C induces surface oxidation, which is slow during the first hour of heating and then increases significantly. The SEM results indicate that the crystals formed on the molybdenite surface as a result of thermal oxidation exhibit regular thin-elongated shape. The average size and density of the crystals on the surface is dependent on the time of annealing; smaller size and high density during the first one-hour and significant

  18. Charge-changing reactions and their influence on the ion motion in a Penning trap

    International Nuclear Information System (INIS)

    Charge-changing reactions can lead to a significant change of the ion motion which may result in the loss of the ions from the trap. For the present experiments singly charged gold clusters from an external laser vaporization source have been transferred into a Penning trap and transformed into dianions by use of an electron bath of simultaneously stored electrons. The dianions have been investigated by collisional activation and laser excitation where electron emission has been observed as a cooling mechanism. Electron emission doubles the value of the cyclotron radius and in addition, the ions acquire a finite magnetron radius. This leads to an extension of the radial distance of the ion motion from the trap's axis by a factor of about three

  19. Electrical conduction in organic charge transfer complexes under pressure: A theoretical view

    Science.gov (United States)

    Singh, Yadunath

    2016-05-01

    We propose a theoretical view of temperature dependent electrical conductivity in organic charge transfer complexes and radical ion salts. Understanding of the basic conduction mechanism under high pressure in these systems is our aim. The mechanism is discussed mainly on the basis of molecular orbital overlap theory, role of charge transfer forces and charge density waves etc.

  20. Japan Charged-Particle Nuclear Reaction Data Group (JCPRG)

    International Nuclear Information System (INIS)

    This it the progress report of the Executive Committee of the Japan Charged-Particle Nuclear Reaction Data Group (JCPRG). Since the last NRDC meeting in June 2003, the group has carried out the following activities: Compilation of CPND for NRDF and EXFOR; Compilation of CPND bibliographies for CINDA; Improvement of Web-based data input system HENDEL; Improvement of NRDF retrieval system DARPE; Development of utilization system for EXFOR and evaluated libraries; Data services for Japanese users. The regular JCPRG budget has ended at March 2001. They are applying a competitive budget for our further activity. The Executive Committee is organized by 7 researchers and 1 secretary. 6 postdoctoral researchers in Meme Media Lab. of Hokkaido Univ., 6 graduated students in Nuclear Physics Laboratory of Hokkaido Univ. and 1 technical staff work part-time. 1.5 equivalent man year is dedicated to NRDC Network activities

  1. Heat, Mass and Charge Transport, and Chemical Reactions at Surfaces

    Directory of Open Access Journals (Sweden)

    Signe Kjelstrup

    2005-03-01

    Full Text Available In this work we derive the excess entropy production rate for heat, mass and charge transport into, out of and across a surface, using as basic variables the excess densities proposed by Gibbs. With the help of these variables we define the surface as an autonomous system (i.e. a surface in local equilibrium and find its excess entropy production rate. This then determines the conjugate fluxes and forces. Equivalent forms of the entropy production rate are given. The forms contain finite differences of intensive variables into and across the surface as driving forces. The general form of the force-flux relations is given. The expressions for the fluxes serve as boundary conditions for integration across heterogeneous systems. Two examples are discussed in more detail. The first example is the practically important coupled transport of heat and mass into and through a liquid-vapor surface. The second example concerns phenomena at electrode surfaces: the coupled transport of heat, mass and charge and a chemical reaction. By assuming that the two sides of the surface can be described as resistances in series, we are able to reduce the number of unknown transport coefficients considerably. For both examples it is shown that the coupling coefficients for heat and mass flow are large at the surface, when the homogeneous phases have a large enthalpy difference. As a consequence it is not sufficient to use, for instance, Fourier’s law for transport of heat across surfaces.

  2. Single proton transfer reactions on odd-even nuclei

    International Nuclear Information System (INIS)

    This thesis is devoted to the study of one proton transfer reactions, performed with the use of the magnetic spectrograph QMG/2 of the KVI, in two regions of the mass table. Stripping and pickup reactions on the odd-A target nuclei 193Ir and 197Au are described in the first part. The experimental spectroscopic factors obtained are used to test several collective models that are based on coupling between bosons (phonons) and fermions. In the second part, the proton stripping reactions on 113In and 115In are studied. Shell model calculations are performed and applied to the experimental results. (Auth.)

  3. Population of isomeric states in fusion and transfer reactions in beams of loosely bound nuclei near the Coulomb barrier

    International Nuclear Information System (INIS)

    The influence of the mechanisms of nuclear reactions on the population of 195mHg and 197mHg(7/2−), 198mTl and 196mTl(7+), and 196mAu and 198mAu(12−) isomeric nuclear states obtained in reactions induced by beams of 3He, 6Li, and 6He weakly bound nuclei is studied. The behavior of excitation functions and high values of isomeric ratios (δm/δg) for products of nuclear reactions proceeding through a compound nucleus and involving neutron evaporation are explained within statistical models. Reactions in which the emission of charged particles occurs have various isomeric ratios depending on the reaction type. The isomeric ratio is lower in direct transfer reactions involving charged-particle emission than in reactions where the evaporation of charged particles occurs. Reactions accompanied by neutron transfer usually have a lower isomeric ratio, which behaves differently for different direct-reaction types (stripping versus pickup reactions)

  4. Electron transfer reactions involving porphyrins and chlorophyll a

    International Nuclear Information System (INIS)

    Electron transfer reactions involving porphyrins (P) and quinones (Q) have been studied by pulse radiolysis. The porphyrins used were tetraphenylporphyrin (H2TPP), its tetracarboxy derivative (H2TCPP), the sodium and zinc compounds (Na2TPP and ZnTPP), and chlorophyll a (Chl a). These compounds were found to be rapidly reduced by electron transfer from (CH3)2CO-. Reduction by (CH3)2COH was rapid in aqueous solutions but relatively slow in i-PrOH solutions. Transient spectra of the anion radicals were determined and, in the case of H2TCPP-., a pK = 9.7 was derived for its protonation. Electron-transfer reactions from the anion radical of H2TCPP to benzoquinone, duroquinone, 9,10-anthraquinone 2-sulfonate, and methylviologen occur in aqueous solutions with rate constants approx. 107-109 M-1 s-1 which depend on the pH and the quinone reduction potential. Reactions of Na2TPP-., ZnTPP-., and Chl a-. with anthraquinone in basic i-PrOH solutions occur with rate constants approx. 109 M-1 s-1. The spectral changes associated with these electron-transfer reactions as observed over a period of approx. 1 ms indicated, in some cases, the formation of an intermediate complex [P...Q-.]. 8 figures, 2 tables

  5. Modelling of mass transfer in combination with radical reactions

    NARCIS (Netherlands)

    Hoorn, J. A. A.; Versteeg, G. F.

    2006-01-01

    The diffusion-reaction equations for different model versions have been solved using a finite-differencing technique. In all models a reactant A is transferred from the gas to the liquid phase and reacts in the liquid with B to form P. The calculations comprised a simple stoichiometric model, a syst

  6. Towards neutron drip line via transfer-type reactions

    International Nuclear Information System (INIS)

    Possibilities of production of light neutron-rich isotopes 24,26O, 32Ne, 36,38Mg, 42Si and 56,58,60Ca in transfer-type reactions are analyzed. The optimal conditions for their production are suggested. The measurement of the excitation function can allow us to estimate the binding energy of exotic nuclei

  7. Dual Fluorescence in GFP Chromophore Analogues: Chemical Modulation of Charge Transfer and Proton Transfer Bands.

    Science.gov (United States)

    Chatterjee, Tanmay; Mandal, Mrinal; Das, Ananya; Bhattacharyya, Kalishankar; Datta, Ayan; Mandal, Prasun K

    2016-04-14

    Dual fluorescence of GFP chromophore analogues has been observed for the first time. OHIM (o-hydroxy imidazolidinone) shows only a charge transfer (CT) band, CHBDI (p-cyclicamino o-hydroxy benzimidazolidinone) shows a comparable intensity CT and PT (proton transfer) band, and MHBDI (p-methoxy o-hydroxy benzimidazolidinone) shows a higher intensity PT band. It could be shown that the differential optical behavior is not due to conformational variation in the solid or solution phase. Rather, control of the excited state electronic energy level and excited state acidity constant by functional group modification could be shown to be responsible for the differential optical behavior. Chemical modification-induced electronic control over the relative intensity of the charge transfer and proton transfer bands could thus be evidenced. Support from single-crystal X-ray structure, NMR, femtosecond to nanosecond fluorescence decay analysis, and TDDFT-based calculation provided important information and thus helped us understand the photophysics better. PMID:26998908

  8. Optics of Chromites and Charge-Transfer Transitions

    Directory of Open Access Journals (Sweden)

    Andrei V. Zenkov

    2008-08-01

    Full Text Available Specific features of the charge-transfer (CT states and O2p→Cr3d transitions in the octahedral (CrO69− complex are considered in the cluster approach. The reduced matrix elements of the electric-dipole transition operator are calculated on many-electron wave functions of the complex corresponding to the initial and final states of a CT transition. Modeling the optic spectrum of chromites has yielded a complicated CT band. The model spectrum is in satisfactory agreement with experimental data which demonstrates the limited validity of the generally accepted concept of a simple structure of CT spectra.

  9. Magnetic ordering in fullerene charge-transfer complexes

    Science.gov (United States)

    Sato, Tohru; Yamabe, Tokio; Tanaka, Kazuyoshi

    1997-07-01

    We have determined the ground states of the charge-transfer (CT) complexes in which the energy levels of the highest occupied molecular orbital (HOMO) of donors and the lowest unoccupied MO (LUMO) of acceptors are closely located, and examined some fullerene complexes consisting of C60, C70, tetrakis(dimethylamino)ethylene (TDAE), and 1,1',3,3'-tetramethyl-Δ2,2'-bi(imidazolidine) (TMBI). The observed magnetic properties of TDAE-C60, TMBI-C60, and TDAE-C70 can be accounted for by employing realistic parameters. The effective Hamiltonian including up to the fourth-order perturbation has also been derived in the fourfold degenerate model space. The effective Hamiltonian can plausibly reproduce the magnetic phase diagram obtained by the variational treatment of TDAE-C60. It has been shown that the third and the fourth processes contribute to the stabilization of the antiferromagnetic state.

  10. Self-interaction effects on charge-transfer collisions

    CERN Document Server

    Quashie, Edwin E; Andrade, Xavier; Correa, Alfredo A

    2016-01-01

    In this article, we investigate the role of the self-interaction error in the simulation of collisions using time-dependent density functional theory (TDDFT) and Ehrenfest dynamics. We compare many different approximations of the exchange and correlation potential, using as a test system the collision of $\\mathrm{H^+ + CH_4}$ at $30~\\mathrm{eV}$. We find that semi-local approximations, like PBE, and even hybrid functionals, like B3LYP, produce qualitatively incorrect predictions for the scattering of the proton. This discrepancy appears because the self-interaction error allows the electrons to jump too easily to the proton, leading to radically different forces with respect to the non-self-interacting case. From our results, we conclude that using a functional that is self-interaction free is essential to properly describe charge-transfer collisions between ions and molecules in TDDFT.

  11. Positron annihilation studies of some charge transfer molecular complexes

    CERN Document Server

    El-Sayed, A; Boraei, A A A

    2000-01-01

    Positron annihilation lifetimes were measured for some solid charge transfer (CT) molecular complexes of quinoline compounds (2,6-dimethylquinoline, 6-methoxyquinoline, quinoline, 6-methylquinoline, 3-bromoquinoline and 2-chloro-4-methylquinoline) as electron donor and picric acid as an electron acceptor. The infrared spectra (IR) of the solid complexes clearly indicated the formation of the hydrogen-bonding CT-complexes. The annihilation spectra were analyzed into two lifetime components using PATFIT program. The values of the average and bulk lifetimes divide the complexes into two groups according to the non-bonding ionization potential of the donor (electron donating power) and the molecular weight of the complexes. Also, it is found that the ionization potential of the donors and molecular weight of the complexes have a conspicuous effect on the average and bulk lifetime values. The bulk lifetime values of the complexes are consistent with the formation of stable hydrogen-bonding CT-complexes as inferred...

  12. Pairing interaction and two-nucleon transfer reactions

    CERN Document Server

    Potel, Gregory; Barranco, Francisco; Vigezzi, Enrico; Broglia, Ricardo A

    2014-01-01

    Making use of the fact that the collective modes associated with the spontaneous (static and dynamic) violation of gauge invariance in atomic nuclei (pairing rotations and pairing vibrations) are amenable to a simple, quite accurate nuclear structure description (BCS and QRPA respectively), it is possible to quantitatively test the reaction mechanism which is at the basis of two-nucleon transfer reactions, specific probe of pairing in nuclei. With the help of the static and dynamic mean field spectroscopic amplitudes, taking into account successive and simultaneous transfer channels properly corrected because of non-orthogonality effects, as well as describing the associated elastic channels in terms of experimentally determined optical potentials, one obtains absolute, two-particle transfer differential cross sections which provide an overall account of the data within experimental errors. One of the first results connected with such quantitative studies of pairing correlations in nuclei is the observation o...

  13. Neutron transfer reactions in the fp-shell region

    International Nuclear Information System (INIS)

    Neutron transfer reactions were used to study the stability of the magic number N=28 near 56Ni. On one hand the one-neutron pickup (d,p) reaction was used for precision spectroscopy of single-particle levels in 55Fe. On the other hand we investigated the two-neutron transfer mechanism into 56Ni using the pickup reaction 58Ni(vectorp,t)56Ni. In addition the reliability of inverse kinematics reactions at low energy to study exotic nuclei was tested by the neutron transfer reactions t(40Ar,p)42Ar and d(54Fe,p)55Fe using tritium and deuterium targets, respectively, and by comparing the results with those of the normal kinematics reactions. The experimental data, differential cross-section and analyzing powers, are compared to DWBA and coupled channel calculations utilizing the code CHUCK3. By performing the single-neutron stripping reaction (vectord,p) on 54Fe the 1f7/2 shell in the ground state configuration was found to be partly broken. The instability of the 1f7/2 shell and the magic number N=28 was confirmed once by observing a number of levels with Jπ = 7/2- at low excitation energies, which should not be populated if 54Fe has a closed 1f7/2 shell, and also by comparing our high precision experimental data with a large scale shell model calculation using the ANTOINE code [5]. Calculations including a partly broken 1f7/2 shell show better agreement with the experiment. The instability of the 1f7/2 shell was confirmed also by performing the two-neutron pick-up reaction (vectorp,t) on 58Ni to study 56Ni, where a considerable improvement in the DWBA calculation was observed after considering 1f7/2 as a broken shell. To prove the reliability of inverse kinematics transfer reactions at low energies (∝ 2 AMeV), the aforementioned single-neutron transfer reaction (d,p) was repeated using a beam of 54Fe ions and a deuteron target. From this inverse kinematics experiment we were able to reproduce the absolute cross-section and angular distributions for a number of 55Fe

  14. Neutrino and antineutrino charge-exchange reactions on 12C

    International Nuclear Information System (INIS)

    We extend the formalism of weak interaction processes, obtaining new expressions for the transition rates, which greatly facilitate numerical calculations, for both neutrino-nucleus reactions and muon capture. Explicit violation of the conserved vector current hypothesis by the Coulomb field, as well as development of a sum-rule approach for inclusive cross sections, has been worked out. We have done a thorough study of exclusive (ground-state) properties of 12B and 12N within the projected quasiparticle random phase approximation (PQRPA). Good agreement with experimental data achieved in this way put into evidence the limitations of the standard RPA and QRPA models, which come from the inability of the RPA to open the p3/2 shell and from the nonconservation of the number of particles in the QRPA. The inclusive neutrino/antineutrino (ν/ν-tilde) reactions 12C(ν,e-)12N and 12C(ν-tilde,e+)12B are calculated within both the PQRPA and the relativistic QRPA. It is found that (i) the magnitudes of the resulting cross sections are close to the sum-rule limit at low energy, but significantly smaller than this limit at high energies, for both ν and ν-tilde; (ii) they increase steadily when the size of the configuration space is augmented, particularly for ν/ν-tilde energies >200 MeV; and (iii) they converge for sufficiently large configuration space and final-state spin. The quasi-elastic 12C(ν,μ-)12N cross section recently measured in the MiniBooNE experiment is briefly discussed. We study the decomposition of the inclusive cross section based on the degree of forbiddenness of different multipoles. A few words are dedicated to the ν/ν-tilde-12C charge-exchange reactions related to astrophysical applications.

  15. Metal-Organic Coordination Number Determined Charge Transfer Magnitude

    Science.gov (United States)

    Yang, Hung-Hsiang; Chu, Yu-Hsun; Lu, Chun-I.; Yang, Tsung-Han; Yang, Kai-Jheng; Kaun, Chao-Cheng; Hoffmann, Germar; Lin, Minn-Tsong

    2014-03-01

    By the appropriate choice of head groups and molecular ligands, various metal-organic coordination geometries can be engineered. Such metal-organic structures provide different chemical environments for molecules and give us templates to study the charge redistribution within the metal-organic interface. We created various metal-organic bonding environment by growing self-assembly nanostructures of Fe-PTCDA (3,4,9,10-perylene tetracarboxylic dianhydride) chains and networks on a Au(111) surface. Bonding environment dependent frontier molecular orbital energies are acquired by low temperature scanning tunneling microscopy and scanning tunneling spectroscopy. By comparing the frontier energies with the molecular coordination environments, we conclude that the specific coordination affects the magnitude of charge transfer onto each PTCDA in the Fe-PTCDA hybridization system. H.-H. Yang, Y.-H. Chu, C.-I Lu, T.-H. Yang, K.-J. Yang, C.-C. Kaun, G. Hoffmann, and M.-T. Lin, ACS Nano 7, 2814 (2013).

  16. Doping graphene films via chemically mediated charge transfer

    Directory of Open Access Journals (Sweden)

    Ishikawa Ryousuke

    2011-01-01

    Full Text Available Abstract Transparent conductive films (TCFs are critical components of a myriad of technologies including flat panel displays, light-emitting diodes, and solar cells. Graphene-based TCFs have attracted a lot of attention because of their high electrical conductivity, transparency, and low cost. Carrier doping of graphene would potentially improve the properties of graphene-based TCFs for practical industrial applications. However, controlling the carrier type and concentration of dopants in graphene films is challenging, especially for the synthesis of p-type films. In this article, a new method for doping graphene using the conjugated organic molecule, tetracyanoquinodimethane (TCNQ, is described. Notably, TCNQ is well known as a powerful electron accepter and is expected to favor electron transfer from graphene into TCNQ molecules, thereby leading to p-type doping of graphene films. Small amounts of TCNQ drastically improved the resistivity without degradation of optical transparency. Our carrier doping method based on charge transfer has a huge potential for graphene-based TCFs.

  17. Charge Transfer Characteristics and Initiation Mechanisms of Long Delayed Sprites

    Science.gov (United States)

    Li, J.; Cummer, S. A.; Lyons, W. A.; Nelson, T. E.

    2007-12-01

    Simultaneous measurements of high altitude optical emissions and the magnetic field produced by sprite-associated lightning discharges enable a close examination of the link between low altitude lightning process and high altitude sprite process. In this work, we report results of the coordinated analysis of high speed (1000--10000 frames per second) sprite video and wideband (0.1 Hz to 30 kHz) magnetic field measurements made simultaneously at the Yucca Ridge Field Station and Duke University during the June through August 2005 campaign period. During the observation period, the high speed camera detected 83 sprite events in 67 TLE sequences, which are caused by the same number of +CGs. 46% of these sprite events are delayed more than 10 ms after the lightning return stroke. With the estimated lightning source current moment waveform, we computed the continuing current amplitude and total charge transfer characteristics of the long delayed sprites (>10 ms delay). Our calculation shows the total charge moment change of the long delayed sprites can vary from several hundred C km to more than ten thousand C km. All the long delayed sprites are related with intense continuing current bigger than 2 kA. This continuing current provides about 50% to 90% of the total charge transfer. However, a bigger continuing current does not necessarily mean a shorter time delay. This indicates that other processes also involved in the sprite initiation for long delayed sprites. In our observations, the sferic burst, a high frequency noise caused by intra-cloud activity, is always accompanied by a slow intensification in the lightning source current before the time of sprite initiation. Thus we used the lightning source current as an input and employed a 2-D FDTD model to numerically simulate the electric field at different altitudes and compare it with the breakdown field. Including the effect of the electron mobility dependence on electric field, the simulation results showed that

  18. Charge transfer inefficiency in the pre- and post-irradiated Swept Charge Device CCD236

    International Nuclear Information System (INIS)

    This paper describes the mapping of spectral response of an e2v technologies Swept Charge Device (SCD) CCD236 pre and post irradiation with a 10 MeV equivalent proton fluence of 5.0 × 108 protons cm−2. The CCD236 is a large area (4.4 cm2) X-ray detector which will be used in India's Chandrayaan-2 Large Soft X-ray Spectrometer (CLASS) and China's Hard X-ray Modulation Telescope (HXMT). To enable the suppression of surface dark current, clocking is performed continuously resulting in a linear readout. As such the flat field illumination used to measure any change in spectral response over a conventional Charge-Coupled Devices (CCDs) is not possible. An alternative masking technique has been used to expose pinpoint regions of the device to Mn-Kα and Mn-Kβ X-rays, enabling a local map of spectral response to be built up over the device. This novel approach allows for an estimation of the Charge Transfer Inefficiency (CTI) of the device to be made by allowing the creation of a CTI scatter plot similar to that typically observed in conventional CCDs

  19. Modeling molecular conduction in DNA wires: Charge transfer theories and dissipative quantum transport

    OpenAIRE

    Bulla, R; Gutierrez, R.; Cuniberti, G.

    2006-01-01

    Measurements of electron transfer rates as well as of charge transport characteristics in DNA produced a number of seemingly contradictory results, ranging from insulating behaviour to the suggestion that DNA is an efficient medium for charge transport. Among other factors, environmental effects appear to play a crucial role in determining the effectivity of charge propagation along the double helix. This chapter gives an overview over charge transfer theories and their implication for addres...

  20. Proton-Coupled Electron Transfer Reactions with Photometric Bases Reveal Free Energy Relationships for Proton Transfer.

    Science.gov (United States)

    Eisenhart, Thomas T; Howland, William C; Dempsey, Jillian L

    2016-08-18

    The proton-coupled electron transfer (PCET) oxidation of p-aminophenol in acetonitrile was initiated via stopped-flow rapid-mixing and spectroscopically monitored. For oxidation by ferrocenium in the presence of 7-(dimethylamino)quinoline proton acceptors, both the electron transfer and proton transfer components could be optically monitored in the visible region; the decay of the ferrocenium absorbance is readily monitored (λmax = 620 nm), and the absorbance of the 2,4-substituted 7-(dimethylamino)quinoline derivatives (λmax = 370-392 nm) red-shifts substantially (ca. 70 nm) upon protonation. Spectral analysis revealed the reaction proceeds via a stepwise electron transfer-proton transfer process, and modeling of the kinetics traces monitoring the ferrocenium and quinolinium signals provided rate constants for elementary proton and electron transfer steps. As the pKa values of the conjugate acids of the 2,4-R-7-(dimethylamino)quinoline derivatives employed were readily tuned by varying the substituents at the 2- and 4-positions of the quinoline backbone, the driving force for proton transfer was systematically varied. Proton transfer rate constants (kPT,2 = (1.5-7.5) × 10(8) M(-1) s(-1), kPT,4 = (0.55-3.0) × 10(7) M(-1) s(-1)) were found to correlate with the pKa of the conjugate acid of the proton acceptor, in agreement with anticipated free energy relationships for proton transfer processes in PCET reactions. PMID:27500804

  1. Conformational Dependence of a Protein Kinase Phosphate Transfer Reaction

    CERN Document Server

    Henkelman, Graeme; Tung, Chang-Shung; Fenimore,, P W; McMahon, Benjamin H

    2004-01-01

    Atomic motions and energetics for a phosphate transfer reaction catalyzed by the cAMP-dependent protein kinase (PKA) are calculated by plane-wave density functional theory, starting from structures of proteins crystallized in both the reactant conformation (RC) and the transition-state conformation (TC). In the TC, we calculate that the reactants and products are nearly isoenergetic with a 0.2 eV barrier; while phosphate transfer is unfavorable by over 1.2 eV in the RC, with an even higher barrier. With the protein in the TC, the motions involved in reaction are small, with only P$_\\gamma$ and the catalytic proton moving more than 0.5 \\AA. Examination of the structures reveals that in the RC the active site cleft is not completely closed and there is insufficient space for the phosphorylated serine residue in the product state. Together, these observations imply that the phosphate transfer reaction occurs rapidly and reversibly in a particular conformation of the protein, and that the reaction can be gated by...

  2. Mass transfer model for two-layer TBP oxidation reactions

    International Nuclear Information System (INIS)

    To prove that two-layer, TBP-nitric acid mixtures can be safely stored in the canyon evaporators, it must be demonstrated that a runaway reaction between TBP and nitric acid will not occur. Previous bench-scale experiments showed that, at typical evaporator temperatures, this reaction is endothermic and therefore cannot run away, due to the loss of heat from evaporation of water in the organic layer. However, the reaction would be exothermic and could run away if the small amount of water in the organic layer evaporates before the nitric acid in this layer is consumed by the reaction. Provided that there is enough water in the aqueous layer, this would occur if the organic layer is sufficiently thick so that the rate of loss of water by evaporation exceeds the rate of replenishment due to mixing with the aqueous layer. This report presents measurements of mass transfer rates for the mixing of water and butanol in two-layer, TBP-aqueous mixtures, where the top layer is primarily TBP and the bottom layer is comprised of water or aqueous salt solution. Mass transfer coefficients are derived for use in the modeling of two-layer TBP-nitric acid oxidation experiments. Three cases were investigated: (1) transfer of water into the TBP layer with sparging of both the aqueous and TBP layers, (2) transfer of water into the TBP layer with sparging of just the TBP layer, and (3) transfer of butanol into the aqueous layer with sparging of both layers. The TBP layer was comprised of 99% pure TBP (spiked with butanol for the butanol transfer experiments), and the aqueous layer was comprised of either water or an aluminum nitrate solution. The liquid layers were air sparged to simulate the mixing due to the evolution of gases generated by oxidation reactions. A plastic tube and a glass frit sparger were used to provide different size bubbles. Rates of mass transfer were measured using infrared spectrophotometers provided by SRTC/Analytical Development

  3. Isotopic resolution of fission fragments from 238U + 12C transfer and fusion reactions

    International Nuclear Information System (INIS)

    Recent results from an experiment at GANIL, performed to investigate the main properties of fission-fragment yields and energy distributions in different fissioning nuclei as a function of the excitation energy, in a neutron-rich region of actinides, are presented. Transfer reactions in inverse kinematics between a 238U beam and a 12C target produced different actinides, within a range of excitation energy below 30 MeV. These fissioning nuclei are identified by detecting the target-like recoil, and their kinetic and excitation energy are determined from the reconstruction of the transfer reaction. The large-acceptance spectrometer VAMOS was used to identify the mass, atomic number and charge state of the fission fragments in flight. As a result, the characteristics of the fission-fragment isotopic distributions of a variety of neutron-rich actinides are observed for the first time over the complete range of fission fragments. (authors)

  4. Charge-transfer complex versus σ-complex formed between TiO2 and bis(dicyanomethylene) electron acceptors.

    Science.gov (United States)

    Fujisawa, Jun-ichi; Nagata, Morio; Hanaya, Minoru

    2015-11-01

    A novel group of organic-inorganic hybrid materials is created by the combination of titanium dioxide (TiO2) nanoparticles with bis(dicyanomethylene) (TCNX) electron acceptors. The TiO2-TCNX complex is produced by the nucleophilic addition reaction between a hydroxy group on the TiO2 surface and TCNX, with the formation of a σ-bond between them. The nucleophilic addition reaction generates a negatively-charged diamagnetic TCNX adsorbate that serves as an electron donor. The σ-bonded complex characteristically shows visible-light absorption due to interfacial charge-transfer (ICT) transitions. In this paper, we report on another kind of complex formation between TiO2 and TCNX. We have systematically studied the structures and visible-light absorption properties of the TiO2-TCNX complexes, with changing the electron affinity of TCNX. We found that TCNX acceptors with lower electron affinities form charge-transfer complexes with TiO2 without the σ-bond formation. The charge-transfer complexes show strong visible-light absorption due to interfacial electronic transitions with little charge-transfer nature, which are different from the ICT transitions in the σ-bond complexes. The charge-transfer complexes induce efficient light-to-current conversions due to the interfacial electronic transitions, revealing the high potential for applications to light-energy conversions. Furthermore, we demonstrate that the formation of the two kinds of complexes is selectively controlled by the electron affinity of TCNX. PMID:26418266

  5. Charge transport in columnar stacked triphenylenes: Effects of conformational fluctuations on charge transfer integrals and site energies

    NARCIS (Netherlands)

    Senthilkumar, K.; Grozema, F.C.; Bickelhaupt, F.M.; Siebbeles, L.D.A.

    2003-01-01

    Values of charge transfer integrals, spatial overlap integrals and site energies involved in transport of positive charges along columnar stacked triphenylene derivatives are provided. These parameters were calculated directly as the matrix elements of the Kohn–Sham Hamiltonian, defined in terms of

  6. Light induced electron transfer reactions of metal complexes

    International Nuclear Information System (INIS)

    Properties of the excited states of tris(2,2'-bipyridine) and tris(1,10-phenanthroline) complexes of chromium(III), iron(II), ruthenium(II), osmium(II), rhodium(III), and iridium(III) are described. The electron transfer reactions of the ground and excited states are discussed and interpreted in terms of the driving force for the reaction and the distortions of the excited states relative to the corresponding ground states. General considerations relevant to the conversion of light into chemical energy are presented and progress in the use of polypyridine complexes to effect the light decomposition of water into hydrogen and oxygen is reviewed

  7. Understanding quark flow in high momentum transfer exclusive reactions

    International Nuclear Information System (INIS)

    This paper reports on a 5.9 GeV/c secondary beam of pions, kaons, and protons directed into a liquid hydrogen target that has been used to study high momentum transfer exclusive reactions of the form A + B → C + D. The high sensitivity of this experiment has allowed the differential cross section for 19 two body exclusive reactions to be measured around 90 degrees in the center of mass frame. These high statistic measurements confirm the conclusion of an earlier 10 GeV/c experiment which found that the relative magnitudes of the cross sections are consistent with the dominance of the quark interchange diagram

  8. Understanding quark flow in high momentum transfer exclusive reactions

    International Nuclear Information System (INIS)

    A 5.9 GeV/c secondary beam of pions, kaons, and protons directed into a liquid hydrogen target has been used to study high momentum transfer exclusive reactions of the form A + B → C + D. The high sensitivity of this experiment has allowed the differential cross section for 19 two body exclusive reactions to be measured around 90 degrees in the center of mass frame. These high statistic measurements confirm the conclusion of an earlier 10 GeV/c experiment which found that the relative magnitudes of the cross sections are consistent with the dominance of the quark interchange diagram. 6 refs., 4 fig., 1 tab

  9. KRATTA, a versatile triple telescope array for charged reaction products

    CERN Document Server

    Łukasik, J; Budzanowski, A; Czech, B; Skwirczyńska, I; Brzychczyk, J; Adamczyk, M; Kupny, S; Lasko, P; Sosin, Z; Wieloch, A; Kiš, M; Leifels, Y; Trautmann, W

    2013-01-01

    A new detection system KRATTA, Krak\\'ow Triple Telescope Array, is presented. This versatile, low threshold, broad energy range system has been built to measure the energy, emission angle, and isotopic composition of light charged reaction products. It consists of 38 independent modules which can be arranged in an arbitrary configuration. A single module, covering actively about 4.5 msr of the solid angle at the optimal distance of 40 cm from the target, consists of three identical, 0.500 mm thick, large area photodiodes, used also for direct detection, and of two CsI(1500 ppm Tl) crystals of 2.5 and 12.5 cm length, respectively. All the signals are digitally processed. The lower identification threshold, due to the thickness of the first photodiode, has been reduced to about 2.5 MeV for protons (~0.065 mm of Si equivalent) by applying a pulse shape analysis. The pulse shape analysis allowed also to decompose the complex signals from the middle photodiode into their ionization and scintillation components and...

  10. A schematic model for energy and charge transfer in the chlorophyll complex

    DEFF Research Database (Denmark)

    Bohr, Henrik; Malik, F.B.

    2011-01-01

    A theory for simultaneous charge and energy transfer in the carotenoid-chlorophyll-a complex is presented here and discussed. The observed charge transfer process in these chloroplast complexes is reasonably explained in terms of this theory. In addition, the process leads to a mechanism to drive...... are in the range of pico-seconds and less. The change in electronic charge distribution in internuclear space as the system undergoes an electronic transition to a higher-energy state could, under appropriate physical conditions, lead to oscillating dipoles capable of transmitting energy from the...... ground state by fluorescence with no electron being transferred. In the process proposed herein, charge and energy both are transferred from donor to acceptor which can further de-excite by fluorescence. The charge transfer time scale involving an actual transfer of electron is in the pico-second range....

  11. Energy and Charge Transfer from Guest to Host in Doped Organic Electroluminescent Devices

    Institute of Scientific and Technical Information of China (English)

    李宏建; 彭景翠; 许雪梅; 瞿述; 罗小华; 赵楚军

    2002-01-01

    The luminescence properties of doped organic electroluminescent devices are explained by means off Hamiltonian model. The results show that there is a corresponding relation between the amount of transferred charge and the change of the energy originating from charge transfer, and the relation can be influenced by dopant concentration.As the amount of transferred charge increases, the total energy decreases and the luminescence intensity increases.Therefore, we deduce that the energy transfer from guest to host may be derived from the charge transfer. For a given organic electroluminescent device, the maximum value of the conductivity can be observed in a specific dopant concentration. The calculated results show that the greater the transferred charges, the higher the conductivities in doped organic electroluminescent devices. The results agree basically with experimental results.

  12. A new state of nuclear matter observed in transfer reactions

    International Nuclear Information System (INIS)

    The cross section curves for the formation, at the barrier, of trans-target isotopes of a heavy element by bombardment of a heavy target with various heavy ions, and those for the formation of isotopes of a superheavy element by complete fusion projectile and target, both are similar to the distribution of the neutron number N of a fission fragment around its most probable value. This situation suggests that nucleons are transferred according to one and the same law in the fission reaction and in the transfer reactions: This law results from the creation of a new state of nuclear matter, having a lifetime of only 0.17 yoctosecond, and causing uncertainties in the neutron number N of the product amounting to 2.54 atomic mass unit, as measured by J. Terrell in his study of the prompt neutron emission.

  13. Export or recombination of charges in reaction centers in intact cells of photosynthetic bacteria.

    Science.gov (United States)

    Asztalos, Emese; Maróti, Péter

    2009-12-01

    The kinetics and thermodynamics of forward and reverse electron transfer around the reaction center of purple bacterium Rhodobacter sphaeroides were studied in vivo by flash-excited delayed fluorescence, prompt fluorescence (induction) and kinetic difference absorption. By protection of the photomultiplier from intense bacteriochlorophyll prompt fluorescence evoked by laser excitation, the time resolution of the fluorometer was reduced typically 10 micros. Two precursor states of the delayed fluorescence were identified: P(+)Q(A)(-) and cyt c(2)(3+)Q(A)(-) whose enthalpy levels were 340 meV and 1020 meV below A, respectively. The free energy of the P(+)Q(A)(-) state relative to A* was -870 meV in whole cells. Similar values were obtained earlier for isolated reaction center and chromatophore. The free energies of cyt c(2)(3+)Q(A)(-) and P(+)Q(A)(-) states showed no or very weak (-6 meV/pH unit) pH-dependence, respectively, supporting the concept of pH-independent redox midpoint potential of Q(A)/Q(A)(-) in intact cells. In accordance with the multiphasic kinetics of delayed fluorescence, the kinetics of re-opening of the closed reaction center is also complex (it extends up to 1 s) as a consequence of acceptor and donor-side reactions. The control of charge export from the reaction center by light regime, redox agents and inhibitors is investigated. The complex kinetics may arise from the distribution of quinones in different redox states on the acceptor side (Q(B) binding site and pool) and from organization of electron transfer components in supercomplexes. PMID:19555655

  14. Coherent production of pions in nuclei with (3He,t) charge exchange reaction at 2. GeV

    International Nuclear Information System (INIS)

    The (3He,t) charge exchange reaction at 2. GeV incident energy with the new setup SPES IV-π has been realized in order to study the coherent production process of pions. This setup allows to isolate the ground state of the target nucleus, and to sign this process without ambiguity. Some preliminary results in target excitation energy and transferred energy are given. (author)

  15. Electron transfer reactions in chemistry. Theory and experiment

    OpenAIRE

    Marcus, Rudolph A.

    1997-01-01

    Since the late 1940s, the field of electron transfer processes has grown enormously, both in chemistry and biology. The development of the field, experimentally and theoretically, as well as its relation to the study of other kinds of chemical reactions, represents to us an intriguing history, one in which many threads have been brought together. In this lecture, some history, recent trends, and my own involvement in this research are described.

  16. Study of transfer reactions in inverse kinematics with the TIARA array

    International Nuclear Information System (INIS)

    The newly commissioned TIARA array has been coupled for the first time to the VAMOS spectrometer and the EXOGAM germanium array to study nucleon transfer reactions in inverse kinematics and using beams of low intensity, which are typical of radioactive beam experiments. This set-up offers a high geometrical efficiency for the charged particle detection, a high efficiency for γ-ray detection and a final energy resolution only limited by the Doppler broadening. This report demonstrates the potential of such an apparatus to study single-nucleon transfer reactions with radioactive nuclear beams. A beam of 14N at 10.6 MeV/nucleon with an intensity of 105 s-1 was directed onto a CD2 target of 1 mg cm-2. Proton angular distributions have been measured for the population of 15N in the ground state and in excited states at 7.15 and 7.56 MeV. Transferred l-values deduced from comparison to DWBA calculations are in very good agreement with the well-known shell structure of 15N. We have therefore demonstrated the effectiveness of this set-up in studying nucleon transfer reactions in inverse kinematics and with low-intensity beams

  17. One or two step processes in one or two proton transfer reactions induced by heavy ions

    International Nuclear Information System (INIS)

    The one-proton and two-proton transfer reactions induced by 12C and 16O ion beams in the respective 5+ and 6+ charge states (at 48MeV and 56MeV respectively) were experimentally studied with 62Ni targets. A simultaneous analysis of elastic and inelastic scattering gave the precise characteristics of the optical potential (surface transparency). The DWBA formalism reproduces well the general shapes of angular distributions when the optical potential range is increased in the exit channel (decrease in the Coulomb barrier forward shift of the angular distribution). As for one-proton transfer, the DWBA calculation gives spectroscopic factors in good agreement with the light ion experimental data, in condition that an exact calculation is effected with a finite range potential (recoil). As for two-proton transfer, a DWBA calculation subestimates the experimental cross sections. A more complete calculation of the form factor including the relative motions of both protons and sequential transfers is more valuable. The angular distributions at forward angles are imperfectly reproduced by a DWBA calculation, two-step processes involving a core excitation must be taken into account: projectile excitation in the reaction 62Ni(12C,11B)63Cu or target excitation and residual nucleus excitation in the reaction 62Ni(16O,14C)64Zn

  18. Energy transfer followed by electron transfer in a supramolecular triad composed of boron dipyrrin, zinc porphyrin, and fullerene: a model for the photosynthetic antenna-reaction center complex.

    Science.gov (United States)

    D'Souza, Francis; Smith, Phillip M; Zandler, Melvin E; McCarty, Amy L; Itou, Mitsunari; Araki, Yasuyuki; Ito, Osamu

    2004-06-30

    The first example of a working model of the photosynthetic antenna-reaction center complex, constructed via self-assembled supramolecular methodology, is reported. For this, a supramolecular triad is assembled by axially coordinating imidazole-appended fulleropyrrolidine to the zinc center of a covalently linked zinc porphyrin-boron dipyrrin dyad. Selective excitation of the boron dipyrrin moiety in the boron dipyrrin-zinc porphyrin dyad resulted in efficient energy transfer (k(ENT)(singlet) = 9.2 x 10(9) s(-)(1); Phi(ENT)(singlet) = 0.83) creating singlet excited zinc porphyrin. Upon forming the supramolecular triad, the excited zinc porphyrin resulted in efficient electron transfer to the coordinated fullerenes, resulting in a charge-separated state (k(cs)(singlet) = 4.7 x 10(9) s(-)(1); Phi(CS)(singlet) = 0.9). The observed energy transfer followed by electron transfer in the present supramolecular triad mimics the events of natural photosynthesis. Here, the boron dipyrrin acts as antenna chlorophyll that absorbs light energy and transports spatially to the photosynthetic reaction center, while the electron transfer from the excited zinc porphyrin to fullerene mimics the primary events of the reaction center where conversion of the electronic excitation energy to chemical energy in the form of charge separation takes place. The important feature of the present model system is its relative "simplicity" because of the utilized supramolecular approach to mimic rather complex "combined antenna-reaction center" events of photosynthesis. PMID:15212538

  19. Constraints on Parton Charge Symmetry and Implications for Neutrino Reactions

    Energy Technology Data Exchange (ETDEWEB)

    J.T. Londergan; Anthony Thomas

    2004-07-01

    For the first time, charge symmetry breaking terms in parton distribution functions have been included in a global fit to high energy data. We review the results obtained for both valence and sea quark charge symmetry violation, and we compare these results with the most stringent experimental upper limits on charge symmetry violation for parton distribution functions, and with theoretical estimates of charge symmetry violation. The limits allowed in the global fit would tolerate a rather large violation of charge symmetry. We discuss the implications of this for the extraction of the Weinberg angle in neutrino DIS by the NuTeV collaboration.

  20. Minor actinide fission induced by multi-nucleon transfer reaction in inverse kinematics

    Directory of Open Access Journals (Sweden)

    Taieb J.

    2010-03-01

    Full Text Available In the framework of nuclear waste incineration and design of new generation nuclear reactors, experimental data on fission probabilities and on fission fragment yields of minor actinides are crucial to design prototypes. Transfer-induced fission has proven to be an efficient method to study fission probabilities of actinides which cannot be investigated with standard techniques due to their high radioactivity. We report on the preliminary results of an experiment performed at GANIL that investigates fission probabilities with multi-nucleon transfer reactions in inverse kinematics between a 238U beam on a 12C target. Actinides from U to Cm were produced with an excitation energy range from 0 to 30 MeV. In addition, inverse kinematics allowed to characterize the fission fragments in mass and charge. A key point of the analysis resides in the identification of the actinides produced in the different transfer channels. The new annular telescope SPIDER was used to tag the target-like recoil nucleus of the transfer reaction and to determine the excitation energy of the actinide. The fission probability for each transfer channel is accessible and the preliminary results for 238U are promising.

  1. Dynamic Peptide Library for the Discovery of Charge Transfer Hydrogels.

    Science.gov (United States)

    Berdugo, Cristina; Nalluri, Siva Krishna Mohan; Javid, Nadeem; Escuder, Beatriu; Miravet, Juan F; Ulijn, Rein V

    2015-11-25

    Coupling of peptide self-assembly to dynamic sequence exchange provides a useful approach for the discovery of self-assembling materials. In here, we demonstrate the discovery and optimization of aqueous, gel-phase nanostructures based on dynamically exchanging peptide sequences that self-select to maximize charge transfer of n-type semiconducting naphthalenediimide (NDI)-dipeptide bioconjugates with various π-electron-rich donors (dialkoxy/hydroxy/amino-naphthalene or pyrene derivatives). These gel-phase peptide libraries are characterized by spectroscopy (UV-vis and fluorescence), microscopy (TEM), HPLC, and oscillatory rheology and it is found that, of the various peptide sequences explored (tyrosine Y-NDI with tyrosine Y, phenylalanine F, leucine L, valine V, alanine A or glycine G-NH2), the optimum sequence is tyrosine-phenylalanine in each case; however, both its absolute and relative yield amplification is dictated by the properties of the donor component, indicating cooperativity of peptide sequence and donor/acceptor pairs in assembly. The methodology provides an in situ discovery tool for nanostructures that enable dynamic interfacing of supramolecular electronics with aqueous (biological) systems. PMID:26540455

  2. Charge transfer and in-cloud structure of large-charge-moment positive lightning strokes in a mesoscale convective system

    Science.gov (United States)

    Lu, Gaopeng; Cummer, Steven A.; Li, Jingbo; Han, Feng; Blakeslee, Richard J.; Christian, Hugh J.

    2009-08-01

    Lightning observations in the very high frequency band and measurements of ultra low frequency magnetic fields are analyzed to investigate the charge transfer and in-cloud structure of eight positive cloud-to-ground (+CG) strokes in a mesoscale convective system. Although no high altitude images were recorded, these strokes contained large charge moment changes (1500-3200 C·km) capable of producing nighttime sprites. Even though the convective region of the storm was where the flashes originated and where the CG strokes could occur, the charge transferred to ground was mainly from the stratiform region. The post-stroke long continuing currents were connected to highly branched negative leader extension into the stratiform region. While the storm dissipated, the altitude of negative leader propagation in the stratiform area dropped gradually from 8 to 5 km, indicating that in some and perhaps all of these strokes, it was the upper positive charge in the stratiform region that was transferred.

  3. Analysis of transfer reactions: determination of spectroscopic factors

    International Nuclear Information System (INIS)

    An overview of the most popular models used for the analysis of direct reaction data is given, concentrating on practical aspects. The 4 following models (in order of increasing sophistication): the distorted wave born approximation (DWBA), the adiabatic model, the coupled channels born approximation, and the coupled reaction channels are briefly described. As a concrete example, the C12(d,p)C13 reaction at an incident deuteron energy of 30 MeV is analysed with progressively more physically sophisticated models. The effect of the choice of the reaction model on the spectroscopic information extracted from the data is investigated and other sources of uncertainty in the derived spectroscopic factors are discussed. We have showed that the choice of the reaction model can significantly influence the nuclear structure information, particularly the spectroscopic factors or amplitudes but occasionally also the spin-parity, that we wish to extract from direct reaction data. We have also demonstrated that the DWBA can fail to give a satisfactory description of transfer data but when the tenets of the theory are fulfilled DWBA can work very well and will yield the same results as most sophisticated models. The use of global rather than fitted optical potentials can also lead to important differences in the extracted spectroscopic factors

  4. Single nucleon heavy ion transfer reactions on argon isotopes

    International Nuclear Information System (INIS)

    Single nucleon transfer reactions, both pickup and stripping, on all three stable isotopes of argon - 36Ar, 38Ar and 40Ar - have been studied using a 11B projectile at a laboratory energy of 116 MeV. Using a gas target, the forward angle reaction cross-sections were measured with a telescope of silicon surface barrier detectors. The shape of the differential cross-section is discussed in terms of a semiclassical reaction analysis. An exact finite range DWBA code has been used to extract the spectroscopic factors of the strongly populated states and the spectroscopic factors are compared with those obtained using light ion transfer reactions. The excitation energies and spectroscopic factors of levels in nuclei in the mass range A=35-41 are modelled using various effective shell model interactions. Both a complete sd shell space and a space incorporating parts of the sd and fp shells have been used. The results of a phenomenological modified surface delta interaction are compared with those of interactions based on the realistic interaction matrix elements of Kuo. (author)

  5. Study of photo-activated electron transfer reactions in the first excited singlet state by picosecond and nanosecond laser spectroscopy

    International Nuclear Information System (INIS)

    Picosecond laser spectroscopy has been used to study two photo-activated electron transfer reactions: - a bimolecular electron transfer reaction between a sensitizer, DODCI, and an electron acceptor, methylviologen. The two radical ions created with an electron transfer efficiency γ ≅ 0.07 have been identified in picosecond and nanosecond laser absorption spectroscopy by adding selective solutes such as para-benzoquinone (an electron acceptor) or L(+) ascorbic acid (an electron donor). - an intramolecular electron transfer reaction in a triad molecule consisting of a tetra-aryl-porphyrin covalently linked to both a carotenoid and a quinone. The photoinduced charge separation occurs within 30 ps and leads, with a yield of 25 pc, to the formation of a zwitterion whose half-life is 2.5 μs. The experimental results obtained in these two studies show an effective decrease in the recombination rate of the two radical ions created in the encounter pair. (author)

  6. Electron Transfer Reactions: Generalized Spin-Boson Approach

    CERN Document Server

    Merkli, Marco

    2012-01-01

    We introduce a mathematically rigorous analysis of a generalized spin-boson system for the treatment of a donor-acceptor (reactant-product) quantum system coupled to a thermal quantum noise. The donor/acceptor probability dynamics describes transport reactions in chemical processes in presence of a noisy environment -- such as the electron transfer in a photosynthetic reaction center. Besides being rigorous, our analysis has the advantages over previous ones that (1) we include a general, non energy-conserving system-environment interaction, and that (2) we allow for the donor or acceptor to consist of multiple energy levels lying closely together. We establish explicit expressions for the rates and the efficiency (final donor-acceptor population difference) of the reaction. In particular, we show that the rate increases for a multi-level acceptor, but the efficiency does not.

  7. Mechanism of Charge Transfer from Plasmonic Nanostructures to Chemically Attached Materials.

    Science.gov (United States)

    Boerigter, Calvin; Aslam, Umar; Linic, Suljo

    2016-06-28

    Plasmonic metal nanoparticles can efficiently convert the energy of visible photons into the energy of hot charge carriers within the nanoparticles. These energetic charge carriers can transfer to molecules or semiconductors, chemically attached to the nanoparticles, where they can induce photochemical transformations. Classical models of photoinduced charge excitation and transfer in metals suggest that the majority of the energetic charge carriers rapidly decay within the metal nanostructure before they are transferred into the neighboring molecule or semiconductor, and therefore, the efficiency of charge transfer is low. Herein, we present experimental evidence that calls into question this conventional picture. We demonstrate a system where the presence of a molecule, adsorbed on the surface of a plasmonic nanoparticle, significantly changes the flow of charge within the excited plasmonic system. The nanoparticle-adsorbate system experiences high rates of direct, resonant flow of charge from the nanoparticle to the molecule, bypassing the conventional charge excitation and thermalization process taking place in the nanoparticle. This picture of charge transfer suggests that the yield of extracted hot electrons (or holes) from plasmonic nanoparticles can be significantly higher than the yields expected based on conventional models. We discuss a conceptual physical framework that allows us to explain our experimental observations. This analysis points us in a direction toward molecular control of the charge transfer process using interface and local field engineering strategies. PMID:27268233

  8. Analytical study for the charge-transfer complexes of losartan potassium

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Ibrahim A. [Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University, Assiut 71526 (Egypt)]. E-mail: iadarwish@yahoo.com

    2005-09-06

    Studies were carried out, for the first time, to investigate the charge-transfer reactions of losartan potassium (LOS-K) as n-electron donor with the {sigma}-acceptor iodine and various {pi}-acceptors: 7,7,8,8-tetracyanoquinodimethane, 1,3,5-trinitrobenzene, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, p-chloranilic acid, tetracyanoethylene, 2,3,5,6-tetrabromo-1,4-benzoquinone, 2,3,5,6-tetrachloro-1,4-benzoquinone, and 2,4,7-trinitro-9-fluorenone. Different colored charge-transfer complexes and radical anions were obtained. Different variables affecting the reactions were studied and optimized. The formed complexes and the site of interaction were examined by UV-vis, IR, and {sup 1}H NMR techniques, and computational molecular modeling. The formation of the colored complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis of LOS-K in pure form as well as in its pharmaceutical tablets. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9985-0.9998) were found between the absorbances and the concentrations of LOS-K in the range of 2-200 {mu}g ml{sup -1}. The limits of assays detection ranged from 0.61 to 19.65 {mu}g ml{sup -1}. No interference could be observed from the co-formulated hydrochlorothiazide (HCTZ), as well as from the additives commonly present in the tablets. The methods were successfully applied to the analysis of tablets from different manufacturers that contain LOS-K, alone or combined with HCTZ, with good accuracy and precision; the recovery percentages ranged from 98.96 {+-} 1.62% to 101.58 {+-} 1.29%. The results were compared favourably with the reported method.

  9. Theory of chemical kinetics and charge transfer based on nonequilibrium thermodynamics.

    Science.gov (United States)

    Bazant, Martin Z

    2013-05-21

    Advances in the fields of catalysis and electrochemical energy conversion often involve nanoparticles, which can have kinetics surprisingly different from the bulk material. Classical theories of chemical kinetics assume independent reactions in dilute solutions, whose rates are determined by mean concentrations. In condensed matter, strong interactions alter chemical activities and create variations that can dramatically affect the reaction rate. The extreme case is that of a reaction coupled to a phase transformation, whose kinetics must depend not only on the order parameter but also on its gradients at phase boundaries. Reaction-driven phase transformations are common in electrochemistry, when charge transfer is accompanied by ion intercalation or deposition in a solid phase. Examples abound in Li-ion, metal-air, and lead-acid batteries, as well as metal electrodeposition-dissolution. Despite complex thermodynamics, however, the standard kinetic model is the Butler-Volmer equation, based on a dilute solution approximation. The Marcus theory of charge transfer likewise considers isolated reactants and neglects elastic stress, configurational entropy, and other nonidealities in condensed phases. The limitations of existing theories recently became apparent for the Li-ion battery material LixFePO4 (LFP). It has a strong tendency to separate into Li-rich and Li-poor solid phases, which scientists believe limits its performance. Chemists first modeled phase separation in LFP as an isotropic "shrinking core" within each particle, but experiments later revealed striped phase boundaries on the active crystal facet. This raised the question: What is the reaction rate at a surface undergoing a phase transformation? Meanwhile, dramatic rate enhancement was attained with LFP nanoparticles, and classical battery models could not predict the roles of phase separation and surface modification. In this Account, I present a general theory of chemical kinetics, developed over

  10. Quantum State Transfer between Charge and Flux Qubits in Circuit-QED

    Institute of Scientific and Technical Information of China (English)

    WU Qin-Qin; LIAO Jie-Qiao; KUANG Le-Man

    2008-01-01

    @@ We propose a scheme to implement quantum state transfer in a hybrid circuit quantum electrodynamics (QED)system which consists of a superconducting charge qubit, a flux qubit, and a transmission line resonator (TLR).It is shown that quantum state transfer between the charge qubit and the flux qubit can be realized by using the TLR as the data bus.

  11. Electron-Wavepacket Reaction Dynamics in Proton Transfer of Formamide

    Science.gov (United States)

    Nagashima, Kengo; Takatsuka, Kazuo

    2009-10-01

    We apply the semiclassical Ehrenfest theory, which provides electron wavepacket dynamics coupled to nuclear motion, to a study of water-assisted proton relay in formamide compared with a forced proton transfer in gas phase, both of which are associated with the tautomerization. We start with the enol (imidic acid) form HO-CH═NH and track its proton transfer process to the keto (amide) form O═CH-NH2. Identifying the fact that this is indeed a "proton transfer process" rather than hydrogen-atom migration in terms of radical character on the proton, we show a collective quantum flux of electrons, which flows backward against the proton motion. This backward flux compensates the electrons tightly covering the proton, as represented in the Mulliken charge. The enol form formamide is one of the simplest species in the group O═CR1-NHR2, which is a unit of polypeptide. In the gas phase, the nitrogen atom may have a pyramidal structure as in the ammonium molecule; therefore, the C-N bond may allow low barrier rotation along it. This rotation is strongly prohibited by the formation of the double bond C═N induced by the proton transfer. Not only the dynamical process of proton transfer itself but also the electronic structures left behind are greatly affected by the presence of water molecule(s) and polar solvents. In discussing the relative stability of the formamide after the proton transfer, the following resonance structures are frequently mentioned, O--CH═N+H2 ↔ O═CH-NH2. Here we address the dynamical manifestation of the resonance structures in terms of our dynamical electron theory.

  12. Multinucleon transfer reactions studied with the new generation spectrometers

    International Nuclear Information System (INIS)

    With the advent of large solid angle magnetic spectrometers new possibilities are opened for different kind of studies in low energy heavy ion reactions. In the field of transfer reactions, in particular, one of the most interesting item is how single particle and more complex degrees of freedom, namely pair or cluster ones, or deep inelastic components, act in the transfer process. This, in inclusive studies, can be probed by looking at the behaviour of the differential and total cross sections and total kinetic energy loss distributions of multi-neutron and multi-proton transfer channels. Even more detailed studies can be performed via gamma-particle coincidences. With the new magnetic spectrometer PRISMA coupled to the gamma array CLARA, it is now experimentally possible to measure the transfer strength to specific final states with high efficiency. Valuable information about the structure of those states can be derived from the study of their decay modes. With this kind of set-up the lowest excited levels of neutron rich nuclei moderately far from stability can be investigated, addressing key topics in nuclear spectroscopy, namely shell quenching, nuclear symmetries, clustering aspects in light and heavy nuclei. Similar combination of magnetic spectrometers and gamma arrays installed at radioactive ion beam facilities allow to push these reaction mechanism and spectroscopy studies further away from the stability, both in the neutron rich and proton rich regions. In this talk a selection of recent results in the field will be presented and hints will be given on interesting new experiments to be done next

  13. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures.

    Science.gov (United States)

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Liangbo; West, Damien; Meunier, Vincent; Zhang, Shengbai

    2016-01-01

    The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs. PMID:27160484

  14. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

    Science.gov (United States)

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Liangbo; West, Damien; Meunier, Vincent; Zhang, Shengbai

    2016-05-01

    The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.

  15. ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Graham; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K.; Bassi, Roberto; Fleming, Graham R.

    2008-04-02

    Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

  16. Crystal Growth of new charge-transfer salts based on $\\pi$-conjugated molecules

    CERN Document Server

    Morherr, Antonia; Chernenkaya, Alisa; Bäcker, Jan-Peter; Schönhense, Gerd; Bolte, Michael; Krellner, Cornelius

    2016-01-01

    New charge transfer crystals of $\\pi$-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure is reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-F$_x$, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with $\\pi$-conjug...

  17. Crystal growth of new charge-transfer salts based on π-conjugated donor molecules

    Science.gov (United States)

    Morherr, Antonia; Witt, Sebastian; Chernenkaya, Alisa; Bäcker, Jan-Peter; Schönhense, Gerd; Bolte, Michael; Krellner, Cornelius

    2016-09-01

    New charge transfer crystals of π-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure are reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-Fx, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with π-conjugated donor molecules.

  18. Inelastic process observed in charge-exchange reactions of 56Fe at 500 MeV/u

    Directory of Open Access Journals (Sweden)

    Momota S.

    2014-03-01

    Full Text Available The inelastic (IE component of the reaction product, which is produced through charge-exchange reactions at relativistic energies of E ~ 1 GeV/u, is one of the hopeful probes used to study the nuclear medium effect on Δ excitation. In the present study, the longitudinal-momentum (PL distribution of 56Co, produced by bombarding C-and CH2-target with a primary beam of 56Fe at E=500 MeV/u, was observed by means of the spectrometer at HIMAC facility. The IE peak of 56Co, produced from H and C targets, was successfully observed in energy transfer spectrum. The behaviors of the IE peaks are consistent with those observed in previous experiments. A remarkable reduction of the energy transfer for the IE process was also observed with C target compared with H target. The present results have shown the feasibility to investigate the energy transfer in charge-exchange reactions for heavy reaction system at the energy down to 500 MeV/u.

  19. Modulation of the charge transfer and photophysical properties in non-fused tetrathiafulvalene-benzothiadiazole derivatives.

    Science.gov (United States)

    Pop, Flavia; Seifert, Sabine; Hankache, Jihane; Ding, Jie; Hauser, Andreas; Avarvari, Narcis

    2015-01-28

    Bis(thiomethyl)- and bis(thiohexyl)-tetrathiafulvalene-bromo-benzothiadiazoles, containing electron donor tetrathiafulvalene (TTF) and electron acceptor benzothiadiazole (BTD) units, have been prepared by Stille coupling reactions between the TTF-SnMe3 precursors and BTD-Br2. In another series of experiments, TTF-acetylene-BTD compounds have been synthesized by Sonogashira coupling between either TTF-acetylenes and BTD-Br2 in low yields, or TTF-iodine and BTD-acetylene in moderate yields. In the compound TTF-C≡C-BTD the TTF and BTD units are coplanar in the solid state, as shown by the single crystal X-ray structure, and there is segregation in the packing between the donor and acceptor units. All the derivatives have good electron donor properties, as determined by cyclic voltammetry measurements, and they can also be reversibly reduced thanks to the presence of the BTD moiety. UV-visible spectroscopy and photophysical investigations show the presence of an intramolecular charge transfer (ICT) band and an emission band originating from the charge transfer. Both the absorption and the emission are modulated by the substitution scheme and the insertion of the acetylenic bridge. PMID:25410315

  20. Endoergic and resonant charge transfer excitation in He-Cu discharge

    Science.gov (United States)

    Mezei, P.; Rózsa, K.; Jánossy, M.; Apai, P.

    1987-09-01

    The intensity of Cu-II lines with upper level energies near and above those of the He ion was measured as a function of He pressure in a Cu hollow cathode tube. In this tube at low pressures the negative glow could expand above the cathode. The maximum intensity of the Cu-II 493.1 nm line was found in the low voltage, high pressure hollow cathode discharge region in accordance with a resonant charge transfer excitation process. Enhancement of the intensity of the Cu-II 436.5 nm and 417.9 nm lines was observed in the cathode glow at low pressures. Excitation of these lines is attributed to endoergic charge transfer collisions between He ions accelerated by the 2 kV tube voltage and ground state Cu atoms. The cross-section for this reaction exciting the 436.5 nm line was estimated to be of the order of 10-17 cm2.

  1. The calibration of sub-Coulomb heavy ion proton transfer reactions

    International Nuclear Information System (INIS)

    Measurements were made of the cross sections for the 27Al(16O,15N)28Si, 89Y(15N,16O)88Sr and 89Y(27Al,28Si)88Sr reactions at energies near and below the Coulomb barrier. The first reaction required separate measurements of the transfer to elastic cross section ratio for particular charge states, the charge state distribution for 27Al and 28Si ions, and the absolute elastic scattering cross section for the 27Al + 16O system. The ratio measurement required the combined use of two relatively new scientific instruments: the momentum filter and the Bragg curve spectrometer. The latter two transfer measurements were performed using the same setup involving surface barrier detectors at backward angles. Additional elastic scattering data for the 15N + 28Si, 89Y + 15N, 89Sr + 27Al, and 88Sr + 28Si systems was collected to provide entrance and exit channel parameters needed for the theoretical calculations of the transfer reaction cross sections. The calculations were made using the DWBA code, LOLA, which assumes a one-step direct reaction mechanism. A correction was made to the code to properly include the effects of the spin-orbit force in the proton binding potentials. The original goal of these measurements was to combine the three normalization factors to determine the ground state proton spectroscopic factors for 16O, 28Si and 89Y. Such an analysis was found to yield a spectroscopic factor which significantly exceeded the shell model limit in the case of 16O. It is possible that the inclusion of multi-step processes may resolve this disagreement. 36 refs., 109 figs., 21 tabs

  2. Probing the temperature dependence of proton transfer to charged platinum electrodes by reactive molecular dynamics trajectory studies

    International Nuclear Information System (INIS)

    We have performed reactive trajectory calculations of proton discharge on charged platinum surfaces as a function of temperature and charge. A recently developed 9-state empirical valence bond model has been employed. The temperature dependence follows an Arrhenius law with activation energies in the range of 0.1 eV. The activation energy for the discharge reaction decreases significantly with increasing driving force as modeled by an increasingly negative surface charge on the electrode. The analysis shows that the average orientation of molecules in the adsorbed water layer reacts to the approaching proton. Within increasing temperature, configurations become more prevalent which facilitate fast proton transfer by Grotthuss style proton hops from the second to the first layer. This effect becomes more pronounced near more negatively charged surfaces and leads to the computed reduction of the activation energy

  3. Carotenoid charge transfer states and their role in energy transfer processes in LH1-RC complexes from aerobic anoxygenic phototrophs.

    Science.gov (United States)

    Šlouf, Václav; Fuciman, Marcel; Dulebo, Alexander; Kaftan, David; Koblížek, Michal; Frank, Harry A; Polívka, Tomáš

    2013-09-26

    Light-harvesting complexes ensure necessary flow of excitation energy into photosynthetic reaction centers. In the present work, transient absorption measurements were performed on LH1-RC complexes isolated from two aerobic anoxygenic phototrophs (AAPs), Roseobacter sp. COL2P containing the carotenoid spheroidenone, and Erythrobacter sp. NAP1 which contains the carotenoids zeaxanthin and bacteriorubixanthinal. We show that the spectroscopic data from the LH1-RC complex of Roseobacter sp. COL2P are very similar to those previously reported for Rhodobacter sphaeroides, including the transient absorption spectrum originating from the intramolecular charge-transfer (ICT) state of spheroidenone. Although the ICT state is also populated in LH1-RC complexes of Erythrobacter sp. NAP1, its appearance is probably related to the polarity of the bacteriorubixanthinal environment rather than to the specific configuration of the carotenoid, which we hypothesize is responsible for populating the ICT state of spheroidenone in LH1-RC of Roseobacter sp. COL2P. The population of the ICT state enables efficient S1/ICT-to-bacteriochlorophyll (BChl) energy transfer which would otherwise be largely inhibited for spheroidenone and bacteriorubixanthinal due to their low energy S1 states. In addition, the triplet states of these carotenoids appear well-tuned for efficient quenching of singlet oxygen or BChl-a triplets, which is of vital importance for oxygen-dependent organisms such as AAPs. PMID:23130956

  4. Dynamics of the excited state intramolecular charge transfer

    International Nuclear Information System (INIS)

    The 6-dodecanoyl-2-dimethylaminonaphtalene (laurdan), a derivative of 6-propanoyl- 2-dimethylaminonaphthalene (prodan), has been used as a fluorescent probe in cell imaging, especially in visualizing the lipid rafts by the generalized polarization (GP) images, where GP=(I440-I490)/(I440+I490) with I being the fluorescence intensity. The fluorescence spectrum of laurdan is sensitive to its dipolar environment due to the intramolecular charge transfer (ICT) process in S1 state, which results in a dual emission from the locally excited (LE) and the ICT states. The ICT process and the solvation of the ICT state are very sensitive to the dipolar nature of the environment. In this work, the ICT of laurdan in ethanol has been studied by femtosecond time resolved fluorescence (TRF), especially TRF spectra measurement without the conventional spectral reconstruction method. TRF probes the excited states exclusively, a unique advantage over the pump/probe transient absorption technique, although time resolution of the TRF is generally lower than transient absorption and the TRF spectra measurement was possible only though the spectral reconstruction. Over the years, critical advances in TRF technique have been made in our group to achieve <50 fs time resolution with direct full spectra measurement capability. Detailed ICT and the subsequent solvation processes can be visualized unambiguously from the TRF spectra. Fig. 1 shows the TRF spectra of laurdan in ethanol at several time delays. Surprisingly, two bands at 433 and 476 nm are clearly visible in the TRF spectra of laurdan even at T = 0 fs. As time increases, the band at 476 nm shifts to the red while its intensity increases. The band at 433 nm also shifts slightly to the red, but loses intensity as time increases. The intensity of the 476 nm band reaches maximum at around 5 ps, where it is roughly twice as intense as that at 0 fs, and stays constant until lifetime decay is noticeable. The spectra were fit by two log

  5. Explicit inclusion of nonlocality in (d,p) transfer reactions

    CERN Document Server

    Titus, L J; Potel, G

    2016-01-01

    Background: Traditionally, nucleon-nucleus optical potentials are made local for convenience. In recent work we studied the effects of including nonlocal interactions explicitly in the final state for (d,p) reactions, within the distorted wave Born approximation. Purpose: Our goal in this work is to develop an improved formalism for nonlocal interactions that includes deuteron breakup and to use it to study the effects of including nonlocal interactions in transfer (d,p) reactions, in both the deuteron and the proton channel. Method: We extend the finite-range adiabatic distorted wave approximation to include nonlocal nucleon optical potentials. We apply our method to (d,p) reactions on 16O, 40Ca, 48Ca, 126Sn, 132Sn, and 208Pb at 10, 20 and 50 MeV. Results: We find that nonlocality in the deuteron scattering state reduces the amplitude of the wave function in the nuclear interior, and shifts the wave function outward. In many cases, this has the effect of increasing the transfer cross section at the first pea...

  6. Self-interaction and charge transfer in organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Koerzdoerfer, Thomas

    2009-12-18

    This work concentrates on the problem of self-interaction, which is one of the most serious problems of commonly used approximative density functionals. As a major result of this work, it is demonstrated that self-interaction plays a decisive role for the performance of different approximative functionals in predicting accurate electronic properties of organic molecular semiconductors. In search for a solution to the self-interaction problem, a new concept for correcting commonly used density functionals for self-interaction is introduced and applied to a variety of systems, spanning small molecules, extended molecular chains, and organic molecular semiconductors. It is further shown that the performance of functionals that are not free from self-interaction can vary strongly for different systems and observables of interest, thus entailing the danger of misinterpretation of the results obtained from those functionals. The underlying reasons for the varying performance of commonly used density functionals are discussed thoroughly in this work. Finally, this thesis provides strategies that allow to analyze the reliability of commonly used approximations to the exchange-correlation functional for particular systems of interest. This cumulative dissertation is divided into three parts. Part I gives a short introduction into DFT and its time-dependent extension (TDDFT). Part II provides further insights into the self-interaction problem, presents a newly developed concept for the correction of self-interaction, gives an introduction into the publications, and discusses their basic results. Finally, the four publications on self-interaction and charge-transfer in extended molecular systems and organic molecular semiconductors are collected in Part III. (orig.)

  7. Development of a utility system for charged particle nuclear reaction data by using intelligentPad

    Energy Technology Data Exchange (ETDEWEB)

    Aoyama, Shigeyoshi; Ohbayashi, Yoshihide [Information Processing Center, Kitami Institute of Technology, Kitami, Hokkaido (Japan); Masui, Hiroshi [Meme Media Laboratory, Hokkaido University, Sapporo, Hokkaido (Japan); Kato, Kiyoshi [Hokkaido University, Graduate School of Science, Sapporo, Hokkaido (Japan); Chiba, Masaki [Faculty of Social Information, Sapporo Gakuin Univ., Ebetsu, Hokkaido (Japan)

    2000-03-01

    We have developed a utility system, WinNRDF2, for a nuclear charged particle reaction data of NRDF (Nuclear Reaction Data File) on the IntelligentPad architecture. By using the system, we can search the experimental data of a charged particle reaction of NRDF. Furthermore, we also see the experimental data by using graphic pads which was made through the CONTIP project. (author)

  8. Reactions of charged and neutral recoil particles following nuclear transformations

    International Nuclear Information System (INIS)

    The status of the following programs is reported: study of the stereochemistry of halogen atom or ion reactions produced via (eta,γ) or (IT) nuclear reactions with diastereomeric molecules; study of nuclear decay induced reactions of halogen species with organic compounds in the gas phase; decay-induced labelling of compounds of biochemical interest; energetics and mechanisms involved in the reactions of highly energetic carbon-11 atoms with simple organic molecules; and chemistry of the positronium. (LK)

  9. Mechanisms for charge-transfer processes at electrode/solid-electrolyte interfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Chueh, William; El Gabaly Marquez, Farid; Whaley, Josh A.; McCarty, Kevin F.; McDaniel, Anthony H.; Farrow, Roger L.

    2011-11-01

    This report summarizes the accomplishments of a Laboratory-Directed Research and Development (LDRD) project focused on developing and applying new x-ray spectroscopies to understand and improve electric charge transfer in electrochemical devices. Our approach studies the device materials as they function at elevated temperature and in the presence of sufficient gas to generate meaningful currents through the device. We developed hardware and methods to allow x-ray photoelectron spectroscopy to be applied under these conditions. We then showed that the approach can measure the local electric potentials of the materials, identify the chemical nature of the electrochemical intermediate reaction species and determine the chemical state of the active materials. When performed simultaneous to traditional impedance-based analysis, the approach provides an unprecedented characterization of an operating electrochemical system.

  10. Pentanidium-catalyzed enantioselective phase-transfer conjugate addition reactions

    KAUST Repository

    Ma, Ting

    2011-03-09

    A new chiral entity, pentanidium, has been shown to be an excellent chiral phase-transfer catalyst. The enantioselective Michael addition reactions of tert-butyl glycinate-benzophenone Schiff base with various α,β- unsaturated acceptors provide adducts with high enantioselectivities. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications of this methodology. Phosphoglycine ester analogues can also be utilized as the Michael donor, affording enantioenriched α-aminophosphonic acid derivatives and phosphonic analogues of (S)-proline. © 2011 American Chemical Society.

  11. Electron transfer pathway analysis in bacterial photosynthetic reaction center

    CERN Document Server

    Kitoh-Nishioka, Hirotaka

    2016-01-01

    A new computational scheme to analyze electron transfer (ET) pathways in large biomolecules is presented with applications to ETs in bacterial photosynthetic reaction center. It consists of a linear combination of fragment molecular orbitals and an electron tunneling current analysis, which enables an efficient first-principles analysis of ET pathways in large biomolecules. The scheme has been applied to the ET from menaquinone to ubiquinone via nonheme iron complex in bacterial photosynthetic reaction center. It has revealed that not only the central Fe$^{2+}$ ion but also particular histidine ligands are involved in the ET pathways in such a way to mitigate perturbations that can be caused by metal ion substitution and depletion, which elucidates the experimentally observed insensitivity of the ET rate to these perturbations.

  12. CHARGE-TRANSFER AND ENERGY-TRANSFER IN THE PHOTO-INDUCED COPOLYMERIZATION OF 2-VINYLNAPHTHALENE WITH MALEIC ANHYDRIDE

    Institute of Scientific and Technical Information of China (English)

    LI Tong; LUO Bin; LI Shanjun; CHU Guobei

    1990-01-01

    The initiation mechanism of the copolymerization of 2-vinylnaphthalene with maleic anhydride was studied under irradiation of 365 nm. The excited complex was formed from ( 1 ) the local excitation of 2-vinylnaphthalene followed by the charge-transfer interaction with maleic anhydride and ( 2 ) the excitation of the ground state charge-transfer complex, and then it collapsed to 1,4-tetramethylene biradical for initiation. A 1:1 alternating copolymer was formed in different monomer feeds. Addition of benzophenone could greatly enhance the rate of copolymerization through energy-transfer mechanism.

  13. Proton transfers in the Strecker reaction revealed by DFT calculations

    Directory of Open Access Journals (Sweden)

    Shinichi Yamabe

    2014-08-01

    Full Text Available The Strecker reaction of acetaldehyde, NH3, and HCN to afford alanine was studied by DFT calculations for the first time, which involves two reaction stages. In the first reaction stage, the aminonitrile was formed. The rate-determining step is the deprotonation of the NH3+ group in MeCH(OH-NH3+ to form 1-aminoethanol, which occurs with an activation energy barrier (ΔE≠ of 9.6 kcal/mol. The stereochemistry (R or S of the aminonitrile product is determined at the NH3 addition step to the carbonyl carbon of the aldehyde. While the addition of CN− to the carbon atom of the protonated imine 7 appears to scramble the stereochemistry, the water cluster above the imine plane reinforces the CN− to attack the imine group below the plane. The enforcement hinders the scrambling. In the second stage, the aminonitrile transforms to alanine, where an amide Me-CH(NH2-C(=O-NH2 is the key intermediate. The rate-determining step is the hydrolysis of the cyano group of N(amino-protonated aminonitrile which occurs with an ΔE≠ value of 34.7 kcal/mol. In the Strecker reaction, the proton transfer along the hydrogen bonds plays a crucial role.

  14. Catalytic Transfer Hydogenation Reactions for Undergraduate Practical Programs

    Science.gov (United States)

    Hanson, R. W.

    1997-04-01

    A brief review of catalytic transfer hydrogenation (CTH) reactions is given. Attention is drawn, particularly, to the utility of ammonium formate as the hydrogen donor in this type of reaction. The reduction of aryl carbonyl compounds to the corresponding methylene derivatives by ammonium formate in the presence of 10% Pd/C at 110°C is compared to their reductive ammonation which occurs at higher temperatures in the absence of the catalyst (the Leuckart reaction). It is suggested that the low cost and simplicity of CTH reactions using ammonium formate as the hydrogen donor, together with the high yields obtained in many cases, make them excellent candidates for inclusion in undergraduate practical programmes. Laboratory instructions are given for the reduction of nitrobenzene to aniline (isolated as benzanilide), benzophenone to diphenylmethanol and fluorenone to fluorene, in all cases using ammonium formate as the hydrogen donor and 10% Pd/C as the catalyst. Thin layer chromatography shows that in each case the product is homogeneous; the yields are essentially quantitative.

  15. Charge transport in columnar stacked triphenylenes: Effects of conformational fluctuations on charge transfer integrals and site energies

    OpenAIRE

    K. Senthilkumar; Grozema, F.C.; Bickelhaupt, F.M.; Siebbeles, L.D.A.

    2003-01-01

    Values of charge transfer integrals, spatial overlap integrals and site energies involved in transport of positive charges along columnar stacked triphenylene derivatives are provided. These parameters were calculated directly as the matrix elements of the Kohn–Sham Hamiltonian, defined in terms of the molecular orbitals on individual triphenylene molecules. This was realized by exploiting the unique feature of the Amsterdam density functional theory program that allows one to use molecular o...

  16. Isovector spin observables in nuclear charge reactions at LAMPF

    International Nuclear Information System (INIS)

    LAMPF has undertaken a major development program to upgrade facilities for nuclear charge-exchange studies at intermediate energies. The major components of this upgrade are a medium-resolution spectrometer and neutron time-of-flight system for good resolution (δ E < 1 MeV) charge-exchange perograms in (n,p) and (p,n) respectively. Major emphasis is placed on polarization phenomena using polarized beams and analyzing the polarization of the outgoing particle

  17. Radiation reaction from electromagnetic fields in the neighborhood of a point charge

    CERN Document Server

    Singal, Ashok K

    2015-01-01

    From the electromagnetic field in the neighborhood of a "point charge" in arbitrary motion, it is shown that the Poynting flux across a spherical surface of vanishingly small radius, surrounding the charge in its instantaneous rest-frame, is nil. The absence of the Poynting flux in the neighborhood of such a charge explicitly shows that there are no radiative losses from an instantly stationary point charge. While this might appear to contradict Larmor's formula for radiation, nevertheless, it is in complete conformity with energy conservation. After all a charge stationary, even if for an instant, possesses no kinetic energy at the moment that could be lost into radiation. Further, from the rate of electromagnetic momentum flow, calculated using the Maxwell stress tensor, across a surface surrounding the charge, the radiation reaction is determined which turns out to be proportional to the first time derivative of the acceleration of the charge. The power loss due to radiation reaction, hitherto derived in t...

  18. 179Ta and 180Ta structure by transfer reactions

    International Nuclear Information System (INIS)

    Transfer reactions (α,t); (3He,d); (p,t) and (p,d) have been used to study the nuclear spectroscopy of 179Ta and 180Ta. In 179Ta, 5/2- and 9/2- states of the 1/2(541) configuration have been identified. The core-quasiproton interaction has to be taken into account in order to explain the two-nucleon transfer intensities in the 181Ta(p,t)179Ta reaction. A level scheme has been proposed for 180Ta for the first time. Especially the ground state is identified with the (1+,1) level of the [7/2+(404)sub(p), 9/2+(624)sub(n)] configuration and spin (9-,9) of the configuration [9/2-(514)sub(p), 9/2+(624)sub(n)] has been assigned to the long-lived isomer. From the observed configurations in 180Ta, the matrix elements of the effective residual interaction vsub(np) have been deduced and compared to theoretical predictions

  19. Single-nucleon transfer reactions on 18F

    International Nuclear Information System (INIS)

    Simultaneous measurement of the proton-transfer 18F(d, n)19Ne and neutron-transfer 18F(d, p)19F reactions were performed with a 18F radioactive beam at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The experiments clarify the nuclear structure of 19Ne near the proton threshold, which is relevant for understanding the rates of proton-induced reactions on 18F in novae. Analogs for several states in the mirror nucleus 19F have not yet been identified in 19Ne, indicating that the level structure of 19Ne in this region is incomplete. We observed 15 levels in 19Ne from the 18F(d, n)19Ne measurement and 18 levels in 19F from the 18F(d, p)19F measurement. Angular distributions were extracted for all strongly populated states and compared to distorted-wave Born approximation calculations. The angular distributions for all the known states in the two nuclei determined in this work are consistent with their previously assigned spins and parities. The spectroscopic factors determined for these levels in the two nuclei are reported.

  20. Exceptional photosensitivity of a polyoxometalate-based charge-transfer hybrid material.

    Science.gov (United States)

    Liao, Jian-Zhen; Wu, Chen; Wu, Xiao-Yuan; Deng, Shui-Quan; Lu, Can-Zhong

    2016-05-31

    An unusual room-temperature light sensitivity was realized in a polyoxometalate-based hybrid material due to cooperative multicomponent molecular charge-transfer interactions taking place in this material, mainly among POMs, NDIs, and other molecules. The functional π-acidic NDI linkers and POM clusters in the discussed hybrid material were individually designed as photosensors and electron reservoirs. To propose a photo-induced charge-transfer mechanism, EPR, XPS, UV-Vis and computational studies were carried out, and indicated the presence of active charge-transfer interactions among several of the components. PMID:27192943

  1. Single-collision studies of energy transfer and chemical reaction

    Energy Technology Data Exchange (ETDEWEB)

    Valentini, J.J. [Columbia Univ., New York, NY (United States)

    1993-12-01

    The research focus in this group is state-to-state dynamics of reaction and energy transfer in collisions of free radicals such as H, OH, and CH{sub 3} with H{sub 2}, alkanes, alcohols and other hydrogen-containing molecules. The motivation for the work is the desire to provide a detailed understanding of the chemical dynamics of prototype reactions that are important in the production and utilization of energy sources, most importantly in combustion. The work is primarily experimental, but with an important and growing theoretical/computational component. The focus of this research program is now on reactions in which at least one of the reactants and one of the products is polyatomic. The objective is to determine how the high dimensionality of the reactants and products differentiates such reactions from atom + diatom reactions of the same kinematics and energetics. The experiments use highly time-resolved laser spectroscopic methods to prepare reactant states and analyze the states of the products on a single-collision time scale. The primary spectroscopic tool for product state analysis is coherent anti-Stokes Raman scattering (CARS) spectroscopy. CARS is used because of its generality and because the extraction of quantum state populations from CARS spectra is straightforward. The combination of the generality and easy analysis of CARS makes possible absolute cross section measurements (both state-to-state and total), a particularly valuable capability for characterizing reactive and inelastic collisions. Reactant free radicals are produced by laser photolysis of appropriate precursors. For reactant vibrational excitation stimulated Raman techniques are being developed and implemented.

  2. Requirements for charged particle light isotopes reaction data for advanced fuel cycles including two step reaction mechanism

    International Nuclear Information System (INIS)

    Requirements for light charged isotopes nuclear reaction data for advanced fusion fuel cycles are identified. This is performed in the frame of the compilation of charged particle nuclear reaction data. Those reactions are considered which determine the nuclear energy production, burn kinetics, neutron- and radionuclide production among fuel and ash isotopes. Emphasis is put on the fuel p-11B for which a review of the status of existing data is given. Other exotic fuel candidates (e.g. p-6Li) and some exotic reactions occurring in D-3He based fuels are also considered, however in less detail. We conclude that there is a lack of experimental and evaluated data for several important reactions. It is recommended that evaluations be performed, existing ones reexamined, and that they are made easily accessible for the increasing number of researchers studying advanced fuels. (author). 52 refs, 10 figs, 6 tabs

  3. Probing the pairing interaction through two-neutron transfer reactions

    Directory of Open Access Journals (Sweden)

    Margueron J.

    2012-12-01

    Full Text Available The treatment of the pairing interaction in mean-field-based models is addressed. In particular, the possibility to use pair transfers as A tool to better constrain this interaction is discussed. First, pairing inter-actions with various density dependencies (surface/volume mixing are used in the microscopic Hartree-Fock-Bogoliubov + quasiparticle random-phase approximation model to generate the form factors to be used in reaction calculations. Cross sections for (p,t two-neutron transfer reactions are calculated in the one-step zero-range distorted-wave Born approximation for some Tin isotopes and for incident proton energies from 15 to 35 MeV. Three different surface/volume mixings of A zero-range density-dependent pairing interaction are employed in the microscopic calculations and the sensitivity of the cross sections to the different mixings is analyzed. Differences among the three different theoretical predictions are found espacially for the nucleus 136Sn and they are more important at the incident proton energy of 15 MeV. We thus indicate (p,t two-neutron transfer reactions with very neutron-rich Sn isotopes and at proton energies around 15 MeV as good experimental cases where the surface/volume mixing of the pairing interaction may be probed. In the second part of the manuscript, ground-state to ground-state transitions are investigated. Approximations made to estimate two-nucleon transfer probabilities in ground-state to ground-state transitions and the physical interpretation of these probabilities are discussed. Probabilities are often calculated by approximating both ground states of the initial nucleus A and of the final nucleus A±2 by the same quasiparticle vacuum. We analyze two improvements of this approach. First, the effect of using two different ground states with average numbers of particles A and A±2 is quantified. Second, by using projection techniques, the role of particle number restoration is analyzed. Our analysis

  4. Detergent effects on primary charge separation in wild-type and mutant Rhodobacter capsulatus reaction centers

    International Nuclear Information System (INIS)

    The primary electron-transfer processes in reaction centers (RCs) from wild-type and several mutants of Rhodobacter capsulatus have been investigated as a function of the detergent used to extract the RC protein from the membrane. Wild-type and L(M212)H mutant RCs that have been isolated using the detergent Deriphat 160-C both display somewhat slower initial charge separation (longer P* lifetimes) than the same RCs isolated using the detergent LDAO. For the F(L181)Y/Y(M208)F/L(M212)H triple mutant, the differences in the initial charge separation events for Deriphat-versus LDAO-isolated RCs are more significant. In all cases, use of Deriphat 160-C to extract the protein from the membrane yields RCs in which the QY band of P is retained at its native position near 865 nm, whereas LDAO extraction yields RCs that have the P band near 850 nm. Origins of the differences in both the ground state spectrum and the photochemistry, including possible RC-lipid associations, are considered

  5. Skeletal Isomerization and Inter-molecular Hydrogen Transfer Reactions in Catalytic Cracking

    Institute of Scientific and Technical Information of China (English)

    Gao Yongcan; Zhang Jiushun; Xie Chaogang; Long Jun

    2002-01-01

    Bimolecular hydrogen transfer and skeletal isomerization are the important secondary reac tions among catalytic cracking reactions, which affect product yield distribution and product quality.Catalyst properties and operating parameters have great impact on bimolecular hydrogen transfer and skeletal isomerization reactions. Bimolecular hydrogen transfer activity and skeletal isomerization activity of USY-containing catalysts are higher than that of ZSM-5-containing catalyst. Coke deposition on the active sites of catalyst may suppress bimolecular hydrogen transfer activity and skeletal isomerization activity of catalyst in different degrees. Short reaction time causes a decrease of hydrogen trans fer reaction, but an increase of skeletal isomerization reaction compared to cracking reaction in catalytic cracking process.

  6. A charge transfer complex of cadmium with TCNQ (7, 7', 8, 8') (tetracyanoquinodimethane) and 1, 10 phenanthroline: optical, electronic and electrical characterization

    International Nuclear Information System (INIS)

    A new charge-transfer complex involving cadmium as the electric donor, TCNQ as the electron-acceptor and the 1, 10 phenanthroline (phen) as the hetero-aromatic ligand, has been synthesized by means of an electrochemical reaction. The average charge of TCNQ, the transition metal oxidation state and the charge-transfer degree of Cd-phen-TCNQ are obtained using spectrophotometric measurements and photoelectron spectroscopy. The results are compared with those determined for Cd-TCNQ, in order to obtain insight into the effect of the 1, 10 phenanthroline on the electron-transfer reaction. The behavior of the electrical d.c. conductivity vs. the temperature shows that Cd-phen-TCNQ has a room temperature conductivity of about 0.1 OMEGA -1 cm-1, which is more than one order of magnitude higher than that of the Cd-TCNQ species, and an energy gap of the order 0.09 eV

  7. Cross sections for charge transfer between mercury ions and other metals. Final report, June 1973--April 1977

    International Nuclear Information System (INIS)

    Cross sections for charge transfer between several ions and metals of interest to the NASA electro propulsion program have been measured. Specifically, the ions considered were Hg+, Xe+ and Cs+ and the metals Mo, Fe, Al, Ti, Ta, and C. Measurements were made in the energy regime from 1 to 5,000 eV. In general, the cross sections for charge transfer were found to be less than 10-15 cm2 for most processes over the total energy range. Exceptions are Hg+ in collision with Ti and Ta. The results obtained for each reaction are given in both graphical and numerical form in the text. For quick reference, the data at several ion velocities are condensed into one table given in the summary

  8. Thermodynamic, kinetic and electronic structure aspects of a charge-transfer active bichromophoric organofullerene

    Indian Academy of Sciences (India)

    K Senthil Kumar; Archita Patnaik

    2013-03-01

    Our recent work on charge transfer in the electronically push-pull dimethylaminoazobenzene-fullerene C60 donor-bridge-acceptor dyad through orbital picture revealed charge displacement from the n(N=N) (non-bonding) and (N=N) type orbitals centred on the donor part to the purely fullerene centred LUMOs and (LUMO+n) orbitals, delocalized over the entire molecule. Consequently, this investigation centres around the kinetic and thermodynamic parameters involved in the solvent polarity dependent intramolecular photo-induced electron transfer processes in the dyad, indispensable for artificial photosynthetic systems. A quasi-reversible electron transfer pathway was elucidated with electrode-specific heterogeneous electron transfer rate constants.

  9. Optimizing multi-step B-side charge separation in photosynthetic reaction centers from Rhodobacter capsulatus

    Energy Technology Data Exchange (ETDEWEB)

    Faries, Kaitlyn M. [Washington Univ., St. Louis, MO (United States); Kressel, Lucas L. [Argonne National Lab. (ANL), Argonne, IL (United States); Dylla, Nicholas P. [Argonne National Lab. (ANL), Argonne, IL (United States); Wander, Marc J. [Argonne National Lab. (ANL), Argonne, IL (United States); Hanson, Deborah K. [Argonne National Lab. (ANL), Argonne, IL (United States); Holten, Dewey [Washington Univ., St. Louis, MO (United States); Laible, Philip D. [Argonne National Lab. (ANL), Argonne, IL (United States); Kirmaier, Christine [Washington Univ., St. Louis, MO (United States)

    2016-02-01

    Using high-throughput methods for mutagenesis, protein isolation and charge-separation functionality, we have assayed 40 Rhodobacter capsulatus reaction center (RC) mutants for their P+ QB- yield (P is a dimer of bacteriochlorophylls and Q is a ubiquinone) as produced using the normally inactive B-side cofactors BB and HB (where B is a bacteriochlorophyll and H is a bacteriopheophytin). Two sets of mutants explore all possible residues at M131 (M polypeptide, native residue Val near HB) in tandem with either a fixed His or a fixed Asn at L181 (L polypeptide, native residue Phe near BB). A third set of mutants explores all possible residues at L181 with a fixed Glu at M131 that can form a hydrogen bond to HB. For each set of mutants, the results of a rapid millisecond screening assay that probes the yield of P+ QB- are compared among that set and to the other mutants reported here or previously. For a subset of eight mutants, the rate constants and yields of the individual B-side electron transfer processes are determined via transient absorption measurements spanning 100 fs to 50 μs. The resulting ranking of mutants for their yield of P+ QB- from ultrafast experiments is in good agreement with that obtained from the millisecond screening assay, further validating the efficient, high-throughput screen for B-side transmembrane charge separation. Results from mutants that individually show progress toward optimization of P+ HB- → P+ QB- electron transfer or initial P* → P+ HB- conversion highlight unmet challenges of optimizing both processes simultaneously.

  10. Topological effects of charge transfer in telomere G-quadruplex: Mechanism on telomerase activation and inhibition

    CERN Document Server

    Wang, Xin

    2015-01-01

    We explore charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of charge transport in TG4 DNA. The consecutive TG4(CTG4) is semiconducting with 0.2 ~ 0.3eV energy gap. Charges transfers favorably in the consecutive TG4, but are trapped in the non-consecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly ~ 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

  11. Topological Effects of Charge Transfer in Telomere G-Quadruplex Mechanism on Telomerase Activation and Inhibition

    Science.gov (United States)

    Wang, Xin; Liang, Shi-Dong

    2013-02-01

    We explore the charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of the charge transport in TG4 DNA. The consecutive TG4 (CTG4) is semiconducting with 0.2 0.3 eV energy gap. Charges transfer favorably in the CTG4, but are trapped in the nonconsecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

  12. A fast calculation algorithm for the charge transfer loss in CCDs

    International Nuclear Information System (INIS)

    Charge transfer loss due to deep level traps in CCDs is a common phenomenon. In single-photon counting CCDs for X-ray detection, the charge loss results in a degradation of spectroscopic resolution. The transfer loss of a signal depends on various parameters like temperature, number of transferred charges, number of charges in the preceding signals and the elapsed time between these signals. Each signal has to be corrected individually with respect to these parameters. An algorithm based on first principles of capture and emission, that allows a fast determination of the transfer loss is presented. The model was tested on calibration data of an X-ray pn-CCD of the EPIC consortium for XMM. The model describes the experimental data very well

  13. Electrical resistivity study of some organic charge transfer complexes under pressure

    International Nuclear Information System (INIS)

    Electrical resistivity study of the organic charge transfer complexes tetramethyl benzidine - TCNQ and tetramethyl p-phenylene diamine - TCNQ has been carried out up to pressure 80 kilobar. Using the structural aspect, a conduction mechanism under pressure is suggested. (author)

  14. Effects of Electron-Transfer Coupled with Collision-Induced Dissociation (ET/CID) on Doubly Charged Peptides and Phosphopeptides

    Science.gov (United States)

    Liu, Chih-Wei; Lai, Chien-Chen

    2011-01-01

    Electron-transfer dissociation (ETD) is a useful peptide fragmentation technique that can be applied to investigate post-translational modifications (PTMs), the sequencing of highly hydrophilic peptides, and the identification of large peptides and even intact proteins. In contrast to traditional fragmentation methods, such as collision-induced dissociation (CID), ETD produces c- and z·-type product ions by randomly cleaving the N-Cα bonds. The disappointing fragmentation efficiency of ETD for doubly charged peptides and phosphopeptide ions has been improved by ETcaD (supplemental activation). However, the ETD data derived from most database search algorithms yield low confidence scores due to the presence of unreacted precursors and charge-reduced ions within MS/MS spectra. In this work, we demonstrate that eight out of ten standard doubly charged peptides and phosphopeptides can be effortlessly identified by electron-transfer coupled with collision-induced dissociation (ET/CID) using the SEQUEST algorithm without further spectral processing. ET/CID was performed with the further dissociation of the charge-reduced ions isolated from ETD ion/ion reactions. ET/CID had high fragmentation efficiency, which elevated the confidence scores of doubly charged peptide and phosphospeptide sequencing. ET/CID was found to be an effective fragmentation strategy in "bottom-up" proteomic analysis.

  15. Excitation of thermonuclear reaction in the focus of a precise spherical charge of an exploding sudstance

    International Nuclear Information System (INIS)

    The paper briefly describes the history of gasodynamic thermonuclear fusion development and presents certain results of experiments on excitation of thermonuclear reaction in the focus of a spherical charge of a liquid explosive

  16. The neutron-proton charge-exchange amplitudes measured in the dp -> ppn reaction

    CERN Document Server

    Mchedlishvili, D; Carbonell, J; Chiladze, D; Dymov, S; Dzyuba, A; Engels, R; Gebel, R; Glagolev, V; Grigoryev, K; Goslawski, P; Hartmann, M; Kacharava, A; Kamerdzhiev, V; Keshelashvili, I; Khoukaz, A; Komarov, V; Kulessa, P; Kulikov, A; Lehrach, A; Lomidze, N; Lorentz, B; Macharashvili, G; Maier, R; Merzliakov, S; Mielke, M; Mikirtychyants, M; Mikirtychyants, S; Nioradze, M; Ohm, H; Papenbrock, M; Prasuhn, D; Rathmann, F; Serdyuk, V; Seyfarth, H; Stein, H J; Steffens, E; Stockhorst, H; Stroeher, H; Tabidze, M; Trusov, S; Uzikov, Yu; Valdau, Yu; Wilkin, C

    2012-01-01

    The unpolarised differential cross section and the two deuteron tensor analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were obtained for small momentum transfers to a (pp) system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The values obtained for the proton analysing power also suggest th...

  17. Charged-Particle Thermonuclear Reaction Rates: III. Nuclear Physics Input

    OpenAIRE

    Iliadis, Christian; Longland, Richard; Champagne, Art; Coc, Alain

    2010-01-01

    The nuclear physics input used to compute the Monte Carlo reaction rates and probability density functions that are tabulated in the second paper of this series (Paper II) is presented. Specifically, we publish the input files to the Monte Carlo reaction rate code RatesMC, which is based on the formalism presented in the first paper of this series (Paper I). This data base contains overwhelmingly experimental nuclear physics information. The survey of literature for this review was concluded ...

  18. The neutron-proton charge-exchange amplitudes measured in the dp {yields} ppn reaction

    Energy Technology Data Exchange (ETDEWEB)

    Mchedlishvili, D.; Chiladze, D. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); Barsov, S.; Dzyuba, A. [Petersburg Nuclear Physics Institute, High Energy Physics Department, Gatchina (Russian Federation); Carbonell, J. [Universite Paris-Sud, IN2P3-CNRS, Institut de Physique Nucleaire, Orsay Cedex (France); Dymov, S. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Universitaet Erlangen-Nuernberg, Physikalisches Institut II, Erlangen (Germany); Engels, R.; Gebel, R.; Hartmann, M.; Kacharava, A.; Kamerdzhiev, V.; Lehrach, A.; Lorentz, B.; Maier, R.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Seyfarth, H.; Stein, H.J.; Stockhorst, H.; Stroeher, H. [Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); Glagolev, V. [JINR, Laboratory of High Energies, Dubna (Russian Federation); Grigoryev, K.; Mikirtychyants, M.; Mikirtychyants, S.; Valdau, Yu. [Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); Petersburg Nuclear Physics Institute, High Energy Physics Department, Gatchina (Russian Federation); Goslawski, P.; Khoukaz, A.; Mielke, M.; Papenbrock, M. [Universitaet Muenster, Institut fuer Kernphysik, Muenster (Germany); Keshelashvili, I. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); University of Basel, Department of Physics, Basel (Switzerland); Komarov, V.; Kulikov, A. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Kulessa, P. [H. Niewodniczanski Institute of Nuclear Physics PAN, Krakow (Poland); Lomidze, N.; Nioradze, M.; Tabidze, M. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); Macharashvili, G. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Merzliakov, S. [Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Steffens, E. [Universitaet Erlangen-Nuernberg, Physikalisches Institut II, Erlangen (Germany); Trusov, S. [Forschungszentrum Rossendorf, Institut fuer Kern- und Hadronenphysik, Dresden (Germany); Uzikov, Yu. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); M. V. Lomonosov Moscow State University, Department of Physics, Moscow (Russian Federation); Wilkin, C. [UCL, Physics and Astronomy Department, London (United Kingdom)

    2013-04-15

    The unpolarised differential cross section and the two deuteron tensor analysing powers A{sub xx} and A{sub yy} of the vector dp {yields} {l_brace}pp{r_brace}{sub s}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27GeV, data were obtained for small momentum transfers to a {l_brace}pp{r_brace}{sub s} system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters C{sub x,x} and C{sub y,y} that were carried out in the vector dvector p {yields} {l_brace}pp{r_brace}{sub s}n reaction at 1.2 and 2.27GeV. The values obtained for the proton analysing power A{sub y}{sup p} also suggest the need for a radical re-evaluation of the neutron-proton elastic scattering amplitudes at the higher energy. It is therefore clear that such measurements can provide a valuable addition to the neutron-proton database in the charge-exchange region. (orig.)

  19. Metal-organic charge transfer can produce biradical states and is mediated by conical intersections

    OpenAIRE

    Tishchenko, Oksana; Li, Ruifang; Truhlar, Donald G.

    2010-01-01

    The present paper illustrates key features of charge transfer between calcium atoms and prototype conjugated hydrocarbons (ethylene, benzene, and coronene) as elucidated by electronic structure calculations. One- and two-electron charge transfer is controlled by two sequential conical intersections. The two lowest electronic states that undergo a conical intersection have closed-shell and open-shell dominant configurations correlating with the 4s2 and 4s13d1 states of Ca, respectively. Unlike...

  20. Oxidation and metal-insertion in molybdenite surfaces: evaluation of charge-transfer mechanisms and dynamics

    OpenAIRE

    Shutthanandan V; Becker U; Ramana CV; Julien CM

    2008-01-01

    Abstract Molybdenum disulfide (MoS2), a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS2 is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer me...

  1. Quantum Plasmonics: Optical Monitoring of DNA-Mediated Charge Transfer in Plasmon Rulers.

    Science.gov (United States)

    Lerch, Sarah; Reinhard, Björn M

    2016-03-01

    Plasmon coupling between DNA-tethered gold nanoparticles is investigated by correlated single-particle spectroscopy and transmission electron microscopy for interparticle separations between 0.5 and 41 nm. Spectral characterization reveals a weakening of the plasmon coupling due to DNA-mediated charge transfer for separations up to 2.8 nm. Electromagnetic simulations indicate a coherent charge transfer across the DNA. PMID:26789736

  2. Light charged particle emission in heavy-ion reactions – What have we learnt?

    Indian Academy of Sciences (India)

    S Kailas

    2001-07-01

    Light charged particles emitted in heavy-ion induced reactions, their spectra and angular distributions measured over a range of energies, carry the signature of the underlying reaction mechanisms. Analysis of data of light charged particles, both inclusive and exclusive measured in coincidence with gamma rays, fission products, evaporation residues have yielded interesting results which bring out the influence of nuclear structure, nuclear mean field and dynamics on the emission of these particles.

  3. Charge transfer along DNA molecule within Peyrard-Bishop-Holstein model

    Science.gov (United States)

    Edirisinghe, Neranjan; Apalkov, Vadym

    2010-03-01

    Charge transport through DNA molecule is important in many areas ranging from DNA damage repair to molecular nanowires. It is now widely accepted that a phonon mediated hopping of a charge carrier plays a major role in charge transport through DNA. In the present study we investigate system dynamics within Peyrard-Bishop-Holstein model for the charge transfer between donor and acceptor sites. We found that an escape time of a charge, trapped at the donor state of the DNA strand, is very sensitive to the initial value of H-bond stretching. This suggests importance of ensemble averaging. Moreover sharp phase transitions were observed for escape time in parameter space of transfer integrals and phonon-charge coupling constant.

  4. Mass transfer in porous media with heterogeneous chemical reaction

    Directory of Open Access Journals (Sweden)

    Souza S.M.A.G.Ulson de

    2003-01-01

    Full Text Available In this paper, the modeling of the mass transfer process in packed-bed reactors is presented and takes into account dispersion in the main fluid phase, internal diffusion of the reactant in the pores of the catalyst, and surface reaction inside the catalyst. The method of volume averaging is applied to obtain the governing equation for use on a small scale. The local mass equilibrium is assumed for obtaining the one-equation model for use on a large scale. The closure problems are developed subject to the length-scale constraints and the model of a spatially periodic porous medium. The expressions for effective diffusivity, hydrodynamic dispersion, total dispersion and the Darcy's law permeability tensors are presented. Solution of the set of final equations permits the variations of velocity and concentration of the chemical species along the packed-bed reactors to be obtained.

  5. Fermi level alignment in molecular nanojunctions and its relation to charge transfer

    DEFF Research Database (Denmark)

    Stadler, Robert; Jacobsen, Karsten Wedel

    2006-01-01

    by orders of magnitude. We present a quantitative analysis of the relation between this level alignment (which can be estimated from charging free molecules) and charge transfer for bipyridine and biphenyl dithiolate (BPDT) molecules attached to gold leads based on density functional theory...... energetically higher end of the gap in the transmission function for bipyridine and at its lower end for BPDT....

  6. Evaluation of charged-particle reactions for fusion applications

    International Nuclear Information System (INIS)

    New evaluations of the total reaction cross sections for 2H(d,n)3He, 2H(d,p)3H, 3H(t,2n)4He,3H(d,n)4He, and 3He(d,p)4He have been completed. These evaluations are based on all known published data from 1946 to 1990 and include over 1150 measured data points from 67 references. The purpose of this work is to provide a consistent and well-documented set of cross sections for use in calculations relating to fusion energy research. A new thermonuclear data file, TDF, and a library of FORTRAN subprograms to read the file have been developed. Calculated from the new evaluations, the TDF file contains information on the Maxwellian-averaged reaction rates as a function of reaction and plasma temperature and the Maxwellian-averaged average energy of the interacting particles and reaction products. Routines are included that provide thermally-broadened spectral information for the secondary reaction products. 67 refs., 18 figs

  7. Integer versus Fractional Charge Transfer at Metal(/Insulator)/Organic Interfaces: Cu(/NaCl)/TCNE

    OpenAIRE

    Hofmann, O.; Rinke, P.; Scheffler, M.; Heimel, G.

    2015-01-01

    Semilocal and hybrid density functional theory was used to study the charge transfer and the energy-level alignment at a representative interface between an extended metal substrate and an organic adsorbate layer. Upon suppressing electronic coupling between the adsorbate and the substrate by inserting thin, insulating layers of NaCl, the hybrid functional localizes charge. The laterally inhomogeneous charge distribution resulting from this spontaneous breaking of translational symmetry is re...

  8. Electrostatic sensors applied to the measurement of electric charge transfer in gas-solids pipelines

    OpenAIRE

    Woodhead, Stephen; Denham, John; Armour-Chelu, David

    2005-01-01

    This paper describes the development of a number of electric charge sensors. The sensors have been developed specifically to investigate triboelectric charge transfer which takes place between particles and the pipeline wall, when powdered materials are conveyed through a pipeline using air. A number of industrial applications exist for such gas-solids pipelines, including pneumatic conveyors, vacuum cleaners and dust extraction systems. The build-up of electric charge on pipelines and powder...

  9. Conformationally Gated Charge Transfer in DNA Three-Way Junctions.

    Science.gov (United States)

    Zhang, Yuqi; Young, Ryan M; Thazhathveetil, Arun K; Singh, Arunoday P N; Liu, Chaoren; Berlin, Yuri A; Grozema, Ferdinand C; Lewis, Frederick D; Ratner, Mark A; Renaud, Nicolas; Siriwong, Khatcharin; Voityuk, Alexander A; Wasielewski, Michael R; Beratan, David N

    2015-07-01

    Molecular structures that direct charge transport in two or three dimensions possess some of the essential functionality of electrical switches and gates. We use theory, modeling, and simulation to explore the conformational dynamics of DNA three-way junctions (TWJs) that may control the flow of charge through these structures. Molecular dynamics simulations and quantum calculations indicate that DNA TWJs undergo dynamic interconversion among "well stacked" conformations on the time scale of nanoseconds, a feature that makes the junctions very different from linear DNA duplexes. The studies further indicate that this conformational gating would control charge flow through these TWJs, distinguishing them from conventional (larger size scale) gated devices. Simulations also find that structures with polyethylene glycol linking groups ("extenders") lock conformations that favor CT for 25 ns or more. The simulations explain the kinetics observed experimentally in TWJs and rationalize their transport properties compared with double-stranded DNA. PMID:26266714

  10. Spectroscopic characterization of charge transfer complexes of 2,3-diaminopyridine with chloranilic acid and dihydroxy-p-benzoquinone in polar solvent

    Science.gov (United States)

    Al-Ahmary, Khairia M.

    2014-01-01

    Charge transfer (CT) complexes formed between 2,3-aminopyridine (2,3-DAP) as electron donor with the π-electron acceptors chloranilic acid (CHA) and dihydroxy-p-benzoquinone (DHBQ) were investigated spectrophotometrically in ethanol. Minimum-maximum absorbance method has been used for estimating the formation constants of the charge transfer reactions (KCT). Job's method of continuous variation and photometric titration studies were used to detect the stoichiometric ratios of the formed complexes and they showed that 1:1 complexes were produced. The molar extinction coefficient (ε), oscillator strength (f), dipole moment (μ), charge transfer energy (ECT), ionization potential (IP) and the dissociation energy (W) of the formed complexes were estimated, they reached acceptable values suggesting the stability of the formed CT-complexes. The solid CT-complexes were synthesized and characterized by elemental analyses, 1H NMR and FTIR spectroscopies where the formed complexes included proton and electron transfer.

  11. Electron transfer and decay processes of highly charged iodine ions

    International Nuclear Information System (INIS)

    In the present experimental work we have investigated multi-electron transfer processes in Iq+ (q=10, 15, 20 and 25) + Ne, Ar, Kr and Xe collisions at 1.5q keV energy. The branching ratios between Auger and radiative decay channels have been measured in decay processes of multiply excited states formed by multi-electron transfer collisions. It has been shown that, in all the multi-electron transfer processes investigated, the Auger decays are far dominant over the radiative decay processes and the branching ratios are clearly characterized by the average principal quantum number of the initial excited states of projectile ions. We could express the branching ratios in high Rydberg states formed in multi-electron transfer processes by using the decay probability of one Auger electron emission. (author)

  12. Energy and charge transfer between quasi-zero-dimensional nanostructures

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Menšík, Miroslav

    Washington, DC : TechConnect, 2015, s. 71-74. ISBN 978-1-4987-4727-1. [TechConnect World Innovation . Washington, DC (US), 14.06.2015-17.06.2015] R&D Projects: GA MŠk(CZ) LD14011; GA MŠk LH12236 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : exciton transfer * electron transfer * electron-phonon interaction * quantum dots * irreversible quantum transport Subject RIV: BM - Solid Matter Physics ; Magnetism

  13. Humidity independent mass spectrometry for gas phase chemical analysis via ambient proton transfer reaction

    International Nuclear Information System (INIS)

    Graphical abstract: Direct and humidity independent mass spectrometry analysis of gas phase chemicals could be achieved via ambient proton transfer ionization, ion intensity was found to be stable with humidity ranged from ∼10% to ∼100%. - Highlights: • A humidity independent mass spectrometric method for gas phase samples analysis. • A universal and good sensitivity method. • The method can real time identify plant released raw chemicals. - Abstract: In this work, a humidity independent mass spectrometric method was developed for rapid analysis of gas phase chemicals. This method is based upon ambient proton transfer reaction between gas phase chemicals and charged water droplets, in a reaction chamber with nearly saturate humidity under atmospheric pressure. The humidity independent nature enables direct and rapid analysis of raw gas phase samples, avoiding time- and sample-consuming sample pretreatments in conventional mass spectrometry methods to control sample humidity. Acetone, benzene, toluene, ethylbenzene and meta-xylene were used to evaluate the analytical performance of present method. The limits of detection for benzene, toluene, ethylbenzene and meta-xylene are in the range of ∼0.1 to ∼0.3 ppbV; that of benzene is well below the present European Union permissible exposure limit for benzene vapor (5 μg m−3, ∼1.44 ppbV), with linear ranges of approximately two orders of magnitude. The majority of the homemade device contains a stainless steel tube as reaction chamber and an ultrasonic humidifier as the source of charged water droplets, which makes this cheap device easy to assemble and facile to operate. In addition, potential application of this method was illustrated by the real time identification of raw gas phase chemicals released from plants at different physiological stages

  14. Spectrophotometric study of the charge transfer complexation of some porphyrin derivatives as electron donors with tetracyanoethylene

    Science.gov (United States)

    El-Zaria, Mohamed E.

    2008-01-01

    Charge transfer complexes (CTC) of 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetra(4-tolyl)porphyrin (TTP), 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMP), Zn-5,10,15,20-tetraphenylporphyrin (Zn-TPP), and Zn-5,10,15,20-tetra(4-tolyl)porphyrin (Zn-TTP) with tetracyanoethylene (TCNE) have been studied at various temperatures in CH 2Cl 2 and CCl 4. The data are discussed in terms of equilibrium constant ( KCT), molar extinction coefficient ( ɛCT), thermodynamic standard reaction quantities (Δ G°, Δ H° and Δ S°), oscillator strength ( f), and transition dipole moment ( μ). The spectrum obtained for TPP/TCNE, TTP/TCNE, and TMP/TCNE systems shows two main absorption bands at 475 and 690 nm, which are not due to the absorption of any of the reactants. These bands are characteristic of an intermolecular charge transfer involving the overlap of the lowest unoccupied molecular orbital (LUMO) of the acceptor with the highest occupied molecular orbital (HOMO) of the donor. The results reveal that the interaction between the donors and acceptor is due to π-π * transitions by the formation of radical ion pairs. The stoichiometry of the complexes was found to be 1:1 ratio by the Job and straight line methods between donors and acceptor with the maximum absorption bands at wavelengths of 475 and 690 nm. The observed data show salvation effects on the spectral and thermodynamics properties of CTC. The ionization potential of the donors and the dissociation energy of the CTC were also determined and are found to be constant.

  15. Multinucleon transfer in O,1816,19F+208Pb reactions at energies near the fusion barrier

    Science.gov (United States)

    Rafferty, D. C.; Dasgupta, M.; Hinde, D. J.; Simenel, C.; Simpson, E. C.; Williams, E.; Carter, I. P.; Cook, K. J.; Luong, D. H.; McNeil, S. D.; Ramachandran, K.; Vo-Phuoc, K.; Wakhle, A.

    2016-08-01

    Background: Nuclear reactions are complex, involving collisions between composite systems where many-body dynamics determines outcomes. Successful models have been developed to explain particular reaction outcomes in distinct energy and mass regimes, but a unifying picture remains elusive. The irreversible transfer of kinetic energy from the relative motion of the collision partners to their internal states, as is known to occur in deep inelastic collisions, has yet to be successfully incorporated explicitly into fully quantal reaction models. The influence of these processes on fusion is not yet quantitatively understood. Purpose: To investigate the population of high excitation energies in transfer reactions at sub-barrier energies, which are precursors to deep inelastic processes, and their dependence on the internuclear separation. Methods: Transfer probabilities and excitation energy spectra have been measured in collisions of O,1816,19F+208Pb , at various energies below and around the fusion barrier, by detecting the backscattered projectile-like fragments in a Δ E -E telescope. Results: The relative yields of different transfer outcomes are strongly driven by Q values, but change with the internuclear separation. In 16O+208Pb , single nucleon transfer dominates, with a strong contribution from -2 p transfer close to the Coulomb barrier, though this channel becomes less significant in relation to the -2 p 2 n transfer channel at larger separations. For 18O+208Pb , the -2 p 2 n channel is the dominant charge transfer mode at all separations. In the reactions with 19F,-3 p 2 n transfer is significant close to the barrier, but falls off rapidly with energy. Multinucleon transfer processes are shown to lead to high excitation energies (up to ˜15 MeV), which is distinct from single nucleon transfer modes which predominantly populate states at low excitation energy. Conclusions: Kinetic energy is transferred into internal excitations following transfer, with this

  16. Spectroscopy and dynamics of charge transfer excitons in type-II band aligned quantum confined heterostructures

    International Nuclear Information System (INIS)

    We illustrate effect of charge transfer (CT) in type-II quantum confined heterostructure by comparing CdSe quantum dots (QDs), CdSe/CdTe heterostructure quantum dots (HQDs) and CdSe/CdTe/CdSe quantum well-quantum dots (QWQDs) heterostructures. CdSe core QDs were synthesized using a kinetic growth method where QD size depends on reaction time. For shell coating we used modified version of successive ionic layer adsorption and reaction (SILAR). Size of different QDs ∼5 to 7 nm were measured by transmission electron microscopy (TEM). Strong red shift from ∼597 to ∼746 nm in photoluminescence (PL) spectra from QDs to QWQDs shows high tunability which is not possible with single constituent semiconductor QDs. PL spectra have been recorded at different temperatures (10K-300K). Room temperature time correlated single photon counting (TCSPC) measurements for QDs to QWQDs show three exponential radiative decay. The slowest component decay constant in QWQDs comes around eight fold to ∼51 ns as compared to ∼6.5 ns in HQD suggesting new opportunities to tailor the radiative carrier recombination rate of CT excitons

  17. The TIARA Array for the Study of Nucleon Transfer Reactions

    International Nuclear Information System (INIS)

    The TIARA array is designed for the study of nucleon transfer reactions in inverse kinematics, using radioactive beams. Crucially, the energies of coincident gamma-rays will be used to give better energy resolution for final excited states than can be achieved by measuring the energies of particles alone. Thus, an extremely compact array of position sensitive silicon strips will fit inside an array of four segmented clover EXOGAM Ge detectors which can each be mounted as close as 50mm from the target. Approximately 90% of 4π is covered by 400μm silicon detectors manufactured using 6-inch technology. Particle ID is by the kinematical correlation between the angle and the deposited energy, measured in coincidence with the beam-like particle recorded near zero degrees. Construction will be complete early in 2003 and the array will be deployed initially at GANIL, in front of the VAMOS spectrometer. An early application will be the reaction d(56Ni,55Ni)t

  18. Multinucleon transfer in the 136Xe+208Pb reaction

    Science.gov (United States)

    Li, Cheng; Zhang, Fan; Li, Jingjing; Zhu, Long; Tian, Junlong; Wang, Ning; Zhang, Feng-Shou

    2016-01-01

    The dynamic mechanics in the multinucleon transfer reaction 136Xe+208Pb at an incident energy of Ec .m .=450 MeV is investigated by using the improved quantum molecular dynamics model (ImQMD). The lifetime of the neck directly influences the nucleon exchange and energy dissipation between the projectile and the target. The total-kinetic-energy-mass distributions and excitation energy division of primary binary fragments and the mass distributions of primary fragments at different impact parameters are calculated. The thermal equilibrium between two reaction partners has been observed at the lifetime of a neck larger than 480 fm /c . By using the statistical decay code gemini to describe the de-excitation process of the primary fragments, the isotope production cross sections from Pt to At are compared with the prediction by the dinuclear system and GRAZING model. The calculations indicate that the GRAZING model is suitable for estimating the isotope production cross sections only for Δ Z =-1 to +2; the DNS + gemini calculations underestimate the cross sections in the neutron-rich and neutron-deficient regions; and the ImQMD + gemini calculations give reasonable predictions of the isotope production cross sections for Δ Z =-3 to 0.

  19. Charge Transfer in FeO: A combined Molecular-Dynamics and Ab Initio Study

    International Nuclear Information System (INIS)

    Molecular dynamics simulations and ab initio electronic structure calculations were carried out to determine the rate of charge transfer in stoichiometric w-stite (FeO). The charge transfer of interest occurs by II/III valence interchange between nearest-neighbor Fe atoms, with the Fe(III) constituting a ''hole'' electronic defect. There are two possible nearest-neighbor charge transfers in the FeO lattice, which occur between edge-sharing or corner-sharing FeO6 octahedra. Molecular dynamics simulations predict charge transfer rates of 3.7x1011 and 1.9x109 s-1 for the edge and corner transfers, respectively, in good agreement with those calculated using an ab initio cluster approach (1.6x1011 and 8.0x108 s-1, respectively). The calculated rates are also similar to those along basal and c-axis directions in hematite (?-Fe2O3) determined previously. Therefore, as is the case for hematite, w-stite is predicted to show anisotropic electrical conductivity. Our findings indicate that a rigid ion model does not give acceptable results, thus showing the need to account for the change in polarizability of the system upon charge transfer. Our model achieves this by using a simple mechanical shell model. By calculating the electronic coupling matrix elements for many transition state configurations obtained from the molecular dynamics simulations, we found evidence that the position of the bridging oxygen atoms can greatly affect the amount electronic coupling between the donor and acceptor states. Finally, we address the effect of oxygen vacancies on the charge transfer. It was found that an oxygen vacancy not only creates a driving force for holes to transport away from the vacancy (or equivalently for electrons to diffuse toward the vacancy) but also lowers the free energy barriers for charge transfer. In addition, the reorganization energy significantly differed from the non-defective case in a small radius around the defect

  20. On the HSAB based estimate of charge transfer between adsorbates and metal surfaces

    International Nuclear Information System (INIS)

    Graphical abstract: Left: molecule-to-metal electron charge transfer (ΔN) is proportional to the difference between the metal’s work function and molecular electronegativity. Right: correlation between the work function and explicitly DFT calculated ΔN. Highlights: ► HSAB based electron transfer parameter, ΔN, is analyzed for adsorbates on metal surfaces. ► ΔN gives reasonably estimated trends of charge transfer for atomic and molecular adsorbates. ► Adatom-metal bond strength is linearly proportional to metal-to-adatom charge transfer. ► DFT calculated adsorption energies of the N, O, and Cl adatoms on 11 different metals. ► DFT calculated work functions of low Miller index surfaces for 11 different metals. - Abstract: The applicability of the HSAB based electron charge transfer parameter, ΔN, is analyzed for molecular and atomic adsorbates on metal surfaces by means of explicit DFT calculations. For molecular adsorbates ΔN gives reasonable trends of charge transfer if work function is used for electronegativity of metal surface. For this reason, calculated work functions of low Miller index surfaces for 11 different metals are reported. As for reactive atomic adsorbates, e.g., N, O, and Cl, the charge transfer is proportional to the adatom valence times the electronegativity difference between the metal surface and the adatom, where the electronegativity of metal is represented by a linear combination of atomic Mulliken electronegativity and the work function of metal surface. It is further shown that the adatom-metal bond strength is linearly proportional to the metal-to-adatom charge transfer thus making the ΔN parameter a useful indicator to anticipate the corresponding adsorption energy trends.

  1. Parasitic components from charge transfer in neutral beams for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, O.A.

    1978-02-01

    Charge exchange within accelerating grids in neutral beam systems produces parasitic beam components which degrade the performance of the systems. These components also change the plasma confinement properties at the target. This note discusses parasitic beams produced in three types of grid systems: (1) TFTR/MFTF sources, (2) accel-decel grids for low energy beams, and (3) the JSC negative ion system.

  2. Intermolecula transfer and elimination of molecular hydrogen in thermal reactions of unsaturated organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Suria, S.

    1995-02-10

    Two reactions which are important to coal liquefaction include intermolecular transfer and the elimination of two hydrogen atoms. We have designed several model reactions to probe the viability of several hydrogen transfer and elimination pathways. This report described studies on these reactions using organic model compounds.

  3. Integral cross section measurements and product recoil velocity distributions of Xe2+ + N2 hyperthermal charge-transfer collisions

    Science.gov (United States)

    Hause, Michael L.; Prince, Benjamin D.; Bemish, Raymond J.

    2016-07-01

    Charge exchange from doubly charged rare gas cations to simple diatomics proceeds with a large cross section and results in populations of many vibrational and electronic product states. The charge exchange between Xe2+ and N2, in particular, is known to create N2 + in both the A and B electronic states. In this work, we present integral charge exchange cross section measurements of the Xe2+ + N2 reaction as well as axial recoil velocity distributions of the Xe+ and N2 + product ions for collision energies between 0.3 and 100 eV in the center-of-mass (COM) frame. Total charge-exchange cross sections decrease from 70 Å2 to about 40 Å2 with increasing collision energy through this range. Analysis of the axial velocity distributions indicates that a Xe2+ - N2 complex exists at low collision energies but is absent by 17.6 eV COM. Analysis of the axial velocity distributions reveals evidence for complexes with lifetimes comparable to the rotational period at low collision energies. The velocity distributions are consistent with quasi-resonant single charge transfer at high collision energies.

  4. Integral cross section measurements and product recoil velocity distributions of Xe(2+) + N2 hyperthermal charge-transfer collisions.

    Science.gov (United States)

    Hause, Michael L; Prince, Benjamin D; Bemish, Raymond J

    2016-07-28

    Charge exchange from doubly charged rare gas cations to simple diatomics proceeds with a large cross section and results in populations of many vibrational and electronic product states. The charge exchange between Xe(2+) and N2, in particular, is known to create N2 (+) in both the A and B electronic states. In this work, we present integral charge exchange cross section measurements of the Xe(2+) + N2 reaction as well as axial recoil velocity distributions of the Xe(+) and N2 (+) product ions for collision energies between 0.3 and 100 eV in the center-of-mass (COM) frame. Total charge-exchange cross sections decrease from 70 Å(2) to about 40 Å(2) with increasing collision energy through this range. Analysis of the axial velocity distributions indicates that a Xe(2+) - N2 complex exists at low collision energies but is absent by 17.6 eV COM. Analysis of the axial velocity distributions reveals evidence for complexes with lifetimes comparable to the rotational period at low collision energies. The velocity distributions are consistent with quasi-resonant single charge transfer at high collision energies. PMID:27475363

  5. Giant quantum Hall plateaus generated by charge transfer in epitaxial graphene.

    Science.gov (United States)

    Alexander-Webber, J A; Huang, J; Maude, D K; Janssen, T J B M; Tzalenchuk, A; Antonov, V; Yager, T; Lara-Avila, S; Kubatkin, S; Yakimova, R; Nicholas, R J

    2016-01-01

    Epitaxial graphene has proven itself to be the best candidate for quantum electrical resistance standards due to its wide quantum Hall plateaus with exceptionally high breakdown currents. However one key underlying mechanism, a magnetic field dependent charge transfer process, is yet to be fully understood. Here we report measurements of the quantum Hall effect in epitaxial graphene showing the widest quantum Hall plateau observed to date extending over 50 T, attributed to an almost linear increase in carrier density with magnetic field. This behaviour is strong evidence for field dependent charge transfer from charge reservoirs with exceptionally high densities of states in close proximity to the graphene. Using a realistic framework of broadened Landau levels we model the densities of donor states and predict the field dependence of charge transfer in excellent agreement with experimental results, thus providing a guide towards engineering epitaxial graphene for applications such as quantum metrology. PMID:27456765

  6. Giant quantum Hall plateaus generated by charge transfer in epitaxial graphene

    Science.gov (United States)

    Alexander-Webber, J. A.; Huang, J.; Maude, D. K.; Janssen, T. J. B. M.; Tzalenchuk, A.; Antonov, V.; Yager, T.; Lara-Avila, S.; Kubatkin, S.; Yakimova, R.; Nicholas, R. J.

    2016-07-01

    Epitaxial graphene has proven itself to be the best candidate for quantum electrical resistance standards due to its wide quantum Hall plateaus with exceptionally high breakdown currents. However one key underlying mechanism, a magnetic field dependent charge transfer process, is yet to be fully understood. Here we report measurements of the quantum Hall effect in epitaxial graphene showing the widest quantum Hall plateau observed to date extending over 50 T, attributed to an almost linear increase in carrier density with magnetic field. This behaviour is strong evidence for field dependent charge transfer from charge reservoirs with exceptionally high densities of states in close proximity to the graphene. Using a realistic framework of broadened Landau levels we model the densities of donor states and predict the field dependence of charge transfer in excellent agreement with experimental results, thus providing a guide towards engineering epitaxial graphene for applications such as quantum metrology.

  7. Integer Charge Transfer and Hybridization at an Organic Semiconductor/Conductive Oxide Interface

    KAUST Repository

    Gruenewald, Marco

    2015-02-11

    We investigate the prototypical hybrid interface formed between PTCDA and conductive n-doped ZnO films by means of complementary optical and electronic spectroscopic techniques. We demonstrate that shallow donors in the vicinity of the ZnO surface cause an integer charge transfer to PTCDA, which is clearly restricted to the first monolayer. By means of DFT calculations, we show that the experimental signatures of the anionic PTCDA species can be understood in terms of strong hybridization with localized states (the shallow donors) in the substrate and charge back-donation, resulting in an effectively integer charge transfer across the interface. Charge transfer is thus not merely a question of locating the Fermi level above the PTCDA electron-transport level but requires rather an atomistic understanding of the interfacial interactions. The study reveals that defect sites and dopants can have a significant influence on the specifics of interfacial coupling and thus on carrier injection or extraction.

  8. Inductive Power Transfer with Resonance for Wireless Charging of Batteries in Electric Vehicles

    OpenAIRE

    Roaldset, Johanna Ruud

    2010-01-01

    This report investigates inductive power transfer with resonance for wireless charging of electric vehicle (EV) batteries. The inspiration for the topic came from the paper Basic experimental study on helical antennas of wireless power transfer for Electric Vehicles by using magnetic resonant couplings by T. Imura, H. Okabe and Y. Hory [7]. The paper presents laboratory results of more than 97% power transfer efficiency at a distance between the coils of up to 20 cm. The coils used are air ...

  9. Transfer ionization cross-sections measured in collisions of highly charged argon ions with neon target

    Institute of Scientific and Technical Information of China (English)

    MA; Xinwen(马新文); LIU; Huiping; (刘惠萍); CHEN; Ximeng; (陈熙萌); YANG; Zhihu; (杨治虎); SHEN; Ziyong; (申自勇); WANG; Youde; (王友德); YU; Deyang; (于得洋); CAI; Xiaohong; (蔡晓红); LIU; Zhaoyuan; (刘兆远)

    2003-01-01

    Multiple electron transfer processes are studied for Arq+ + Ne (q = 8, 9, 11, 12) collisions by using multi-parameter coincidence techniques. Various electron transfer processes are identified experimentally and the related cross-sections are measured. The dependence of transfer ionization cross-sections on the recoil charge states is compared with the results from the modified molecular classical overbarrier model. It is found that the modified model described the experimental results reasonably.

  10. Elucidation of charge storage characteristics of conducting polymer film using redox reaction

    CERN Document Server

    Contractor, Asfiya Q

    2013-01-01

    A general technique to investigate charge storage characteristics of conducting polymer films has been developed. A redox reaction is conducted on a polymer film on a rotating disk electrode under potentiostatic condition so that the rate of charging of the film equals the rate of removal of the charge by the reaction. In an experiment on polyaniline film deposited on platinum substrate, using Fe2+/Fe3+ in HCl as the redox system, the voltammogram shows five distinct linear segments (bands) with discontinuity in the slope at specific transition potentials. These bands are the same as those indicated by ESR/Raman spectroscopy with comparable transition potentials. From the dependence of the slopes of the bands on concentration of ferrous and ferric ions, it was possible to estimate the energies of the charge carrier in different bands. It is shown that the charge storage in the film is capacitive.

  11. Study of charged current reactions induced by muon antineutrinos

    International Nuclear Information System (INIS)

    We present in this work a study of antineutrino reactions on light targets. We have used the Gargamelle cloud chamber with a propane-freon mix. In the 2 first chapters we give a brief description of the experimental setting and we present the selection criteria of the events. In the third chapter we analyse the data for the reaction anti-ν + p → μ+ + n that preserves strangeness. We have deduced the values of the axial (MA) and vector (MV) form factors: MA = (O.92 ± 0.08) GeV and MV = (0.86 ± 0.04) GeV. In the fourth chapter we study reactions in which strange particles appear (ΔS = 1) and we have determined their production cross-sections. The elastic reaction: anti-ν + p → μ+ + Λ is studied in a more accurate manner thanks to a 3-constraint adjustment that enables the selection of events occurring on free protons. We have deduced from our data the longitudinal, orthogonal and transverse polarization of Λ, we have got respectively Pl = -0.06 ± 0.44; Pp = 0.29 ± 0.41; Pt 1.05 ± 0.30. We have also deduced the values of the total cross-section as a function of the incident antineutrino energy E: σ (0.27 ± 0.02)*E*10-38 cm-2. E has been assessed from the energy deposited in the cloud chamber and we have adjusted the cross-section with a straight line as it is expected under the assumption of scale invariance. (A.C.)

  12. Photophysics of charge transfer in a polyfluorene/violanthrone blend

    Science.gov (United States)

    Cabanillas-Gonzalez, J.; Virgili, T.; Lanzani, G.; Yeates, S.; Ariu, M.; Nelson, J.; Bradley, D. D. C.

    2005-01-01

    We present a study of the photophysical and photovoltaic properties of blends of violanthrone in poly[9, 9-bis (2-ethylhexyl)-fluorene-2, 7-diyl ] (PF2/6) . Photoluminescence quenching and photocurrent measurements show moderate efficiencies for charge generation, characteristic of such polymer/dye blends. Pump-probe measurements on blend films suggest that while ˜47% of the total exciton population dissociates within 4ps of photoexcitation, only ˜32% subsequently results in the formation of dye anions. We attribute the discrepancy to the likely formation of complex species with long lifetimes, such as stabilized interface charge pairs or exciplexes. This conclusion is supported by the appearance of a long lifetime component of 2.4ns in the dynamics of the photoinduced absorption signal associated to polarons in photoinduced absorption bands centered at 560nm .

  13. Charge transfer in the presence of a radiation field

    International Nuclear Information System (INIS)

    In the first Borm approximation, the dressing modification in laser-assisted charge exchange collision is investigated. The cross sections for electron capture by a proton from dressed atomic hydrogen and dressed helium targets are calculated within a wide energy range. Theoretical results show that with impact energy increasing, the dressing effect leads to increasingly significant cross-section modifications. The modified capture cross sections are increasing functions of the ratio of laser strength to frequency. (author)

  14. Analysis of incomplete charge transfer effects in a CMOS image sensor

    Institute of Scientific and Technical Information of China (English)

    Han Liqiang; Yao Suying; Xu Jiangtao; Xu Chao; Gao Zhiyuan

    2013-01-01

    A method to judge complete charger transfer is proposed for a four-transistor CMOS image sensor with a large pixel size.Based on the emission current theory,a qualitative photoresponse model is established to the preliminary prediction.Further analysis of noise for incomplete charge transfer predicts the noise variation.The test pixels were fabricated in a specialized 0.18μm CMOS image sensor process and two different processes of buried N layer implantation are compared.The trend prediction corresponds with the test results,especially as it can distinguish an unobvious incomplete charge transfer.The method helps us judge whether the charge transfer time satisfies the requirements of the readout circuit for the given process especially for pixels of a large size.

  15. Charge transfer excitations from excited state Hartree-Fock subsequent minimization scheme

    CERN Document Server

    Theophilou, Iris; Thanos, S

    2014-01-01

    Photoinduced charge transfer processes play a key role for novel photovoltaic phenomena and devices. Thus, the development of ab initio methods that allow for accurate and computationally inexpensive treatment of charge transfer excitations is a topic that attracts nowadays a lot of scientific attention. In this paper we extend an approach recently introduced for the description of single and double excitations (M. Tassi, I. Theophilou and S. Thanos, Int. J. Quantum Chem., {113}, 690 (2013), M. Tassi, I. Theophilou and S. Thanos, J. Chem. Phys. {138}, 124107 (2013)) to allow for the description of intermolecular charge transfer excitations. For the description of an excitation where an electron is transferred from a donor system to an acceptor one, it is necessary to keep the excited state orthogonal to the ground sate in order to avoid variational collapse. These conditions are achieved by decomposing the subspace spanned by the Hartree-Fock (HF) ground state orbitals to four subspaces: The subspace spanned ...

  16. Reduction of charge transfer resistance at the lithium phosphorus oxynitride/lithium cobalt oxide interface by thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Iriyama, Yasutoshi; Kako, Tomonori; Yada, Chihiro; Abe, Takeshi; Ogumi, Zempachi [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)

    2005-08-26

    An all-solid-state thin-film battery consisting of a c-axis-oriented LiCoO{sub 2} thin-film and a lithium phosphorus oxynitride (LiPON) glass electrolyte was fabricated. Thermal treatment at 473K after fabrication of the LiPON/LiCoO{sub 2} interface decreased the charge transfer resistance at the interface, and the resistance was further reduced by prolonging the thermal treatment time. The charge transfer resistance per unit electrode area (interfacial resistivity) of a film battery thermal-treated for 60min decreased down to 125{omega}cm{sup 2}, which is ca. five times larger than that in the case of an organic electrolyte (1moldm{sup -3} LiClO{sub 4} dissolved in propylene carbonate)/LiCoO{sub 2} interface (25{omega}cm{sup 2}). Due to the reduction of the charge transfer resistance at the LiPON/LiCoO{sub 2} interface, the reaction current of the film battery was greatly increased by the thermal treatment. Also, thermally treated film batteries showed stable electrochemical lithium insertion/extraction properties compared with the batteries using conventional organic electrolytes. Both the voltammograms and the impedance spectra of the film battery maintained their initial shape for over 100 cycles, and the capacity retention ratio per cycle was calculated to be 99.9%. (author)

  17. Reduction of charge transfer resistance at the lithium phosphorus oxynitride/lithium cobalt oxide interface by thermal treatment

    Science.gov (United States)

    Iriyama, Yasutoshi; Kako, Tomonori; Yada, Chihiro; Abe, Takeshi; Ogumi, Zempachi

    An all-solid-state thin-film battery consisting of a c-axis-oriented LiCoO 2 thin-film and a lithium phosphorus oxynitride (LiPON) glass electrolyte was fabricated. Thermal treatment at 473 K after fabrication of the LiPON/LiCoO 2 interface decreased the charge transfer resistance at the interface, and the resistance was further reduced by prolonging the thermal treatment time. The charge transfer resistance per unit electrode area (interfacial resistivity) of a film battery thermal-treated for 60 min decreased down to 125 Ω cm 2, which is ca. five times larger than that in the case of an organic electrolyte (1 mol dm -3 LiClO 4 dissolved in propylene carbonate)/LiCoO 2 interface (25 Ω cm 2). Due to the reduction of the charge transfer resistance at the LiPON/LiCoO 2 interface, the reaction current of the film battery was greatly increased by the thermal treatment. Also, thermally treated film batteries showed stable electrochemical lithium insertion/extraction properties compared with the batteries using conventional organic electrolytes. Both the voltammograms and the impedance spectra of the film battery maintained their initial shape for over 100 cycles, and the capacity retention ratio per cycle was calculated to be 99.9%.

  18. Charge separation reaction in clusters of polar molecules. MD simulations

    International Nuclear Information System (INIS)

    Rate constant of intermolecular electron transfer (ET) in a photoexcited donor-acceptor model system solvated by a cluster of polar molecules has been expressed in terms of the statistical distribution of the electrostatic potential energy difference between the reacting sites. This distribution has been calculated for a particular case of acetonitrile clusters at ∼ 120 K by MD computer simulation. The MD values of the cluster reorganization energy and the ET rate constant have been compared with the corresponding MD results for the donor-acceptor pair solvated in bulk acetonitrile and with theoretical predictions based on the continuum model. (author)

  19. Charge transfer dynamics of 3,4,9,10-perylene-tetracarboxylic-dianhydride molecules on Au(111) probed by resonant photoemission spectroscopy.

    Science.gov (United States)

    Cao, Liang; Wang, Yu-Zhan; Chen, Tie-Xin; Zhang, Wen-Hua; Yu, Xiao-Jiang; Ibrahim, Kurash; Wang, Jia-Ou; Qian, Hai-Jie; Xu, Fa-Qiang; Qi, Dong-Chen; Wee, Andrew T S

    2011-11-01

    Charge transfer dynamics across the lying-down 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) organic semiconductor molecules on Au(111) interface has been investigated using the core-hole clock implementation of resonant photoemission spectroscopy. It is found that the charge transfer time scale at the PTCDA∕Au(111) interface is much larger than the C 1s core-hole lifetime of 6 fs, indicating weak electronic coupling between PTCDA and the gold substrate due to the absence of chemical reaction and∕or bonding. PMID:22070311

  20. The lowest-energy charge-transfer state and its role in charge separation in organic photovoltaics.

    Science.gov (United States)

    Nan, Guangjun; Zhang, Xu; Lu, Gang

    2016-06-29

    Energy independent, yet higher than 90% internal quantum efficiency (IQE), has been observed in many organic photovoltaics (OPVs). However, its physical origin remains largely unknown and controversial. The hypothesis that the lowest charge-transfer (CT) state may be weakly bound at the interface has been proposed to rationalize the experimental observations. In this paper, we study the nature of the lowest-energy CT (CT1) state, and show conclusively that the CT1 state is localized in typical OPVs. The electronic couplings in the donor and acceptor are found to determine the localization of the CT1 state. We examine the geminate recombination of the CT1 state and estimate its lifetime from first principles. We identify the vibrational modes that contribute to the geminate recombination. Using material parameters determined from first principles and experiments, we carry out kinetic Monte Carlo simulations to examine the charge separation of the localized CT1 state. We find that the localized CT1 state can indeed yield efficient charge separation with IQE higher than 90%. Dynamic disorder and configuration entropy can provide the energetic and entropy driving force for charge separation. Charge separation efficiency depends more sensitively on the dimension and crystallinity of the acceptor parallel to the interface than that normal to the interface. Reorganization energy is found to be the most important material parameter for charge separation, and lowering the reorganization energy of the donor should be pursued in the materials design. PMID:27306609

  1. Charge versus Energy Transfer Effects in High-Performance Perylene Diimide Photovoltaic Blend Films.

    Science.gov (United States)

    Singh, Ranbir; Shivanna, Ravichandran; Iosifidis, Agathaggelos; Butt, Hans-Jürgen; Floudas, George; Narayan, K S; Keivanidis, Panagiotis E

    2015-11-11

    Perylene diimide (PDI)-based organic photovoltaic devices can potentially deliver high power conversion efficiency values provided the photon energy absorbed is utilized efficiently in charge transfer (CT) reactions instead of being consumed in nonradiative energy transfer (ET) steps. Hitherto, it remains unclear whether ET or CT primarily drives the photoluminescence (PL) quenching of the PDI excimer state in PDI-based blend films. Here, we affirm the key role of the thermally assisted PDI excimer diffusion and subsequent CT reaction in the process of PDI excimer PL deactivation. For our study we perform PL quenching experiments in the model PDI-based composite made of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene)-2-6-diyl] (PBDTTT-CT) polymeric donor mixed with the N,N'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) acceptor. Despite the strong spectral overlap between the PDI excimer PL emission and UV-vis absorption of PBDTTT-CT, two main observations indicate that no significant ET component operates in the overall PL quenching: the PL intensity of the PDI excimer (i) increases with decreasing temperature and (ii) remains unaffected even in the presence of 10 wt % content of the PBDTTT-CT quencher. Temperature-dependent wide-angle X-ray scattering experiments further indicate that nonradiative resonance ET is highly improbable due to the large size of PDI domains. The dominance of the CT over the ET process is verified by the high performance of devices with an optimum composition of 30:70 PBDTTT-CT:PDI. By adding 0.4 vol % of 1,8-diiodooctane we verify the plasticization of the polymer side chains that balances the charge transport properties of the PBDTTT-CT:PDI composite and results in additional improvement in the device efficiency. The temperature-dependent spectral width of the PDI excimer PL band suggests the presence of energetic disorder in the

  2. Charge Transfer Properties Through Graphene Layers in Gas Detectors

    CERN Document Server

    Thuiner, P; Jackman, R.B.; Müller, H.; Nguyen, T.T.; Oliveri, E.; Pfeiffer, D.; Resnati, F.; Ropelewski, L.; Smith, J.A.; van Stenis, M.; Veenhof, R.

    2015-01-01

    Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical, electrical and optical properties. For the first time graphene layers suspended on copper meshes were installed into a gas detector equipped with a gaseous electron multiplier. Measurements of low energy electron and ion transfer through graphene were conducted. In this paper we describe the sample preparation for suspended graphene layers, the testing procedures and we discuss the preliminary results followed by a prospect of further applications.

  3. Fullerene-Based Photoactive Layers for Heterojunction Solar Cells: Structure, Absorption Spectra and Charge Transfer Process

    Directory of Open Access Journals (Sweden)

    Yuanzuo Li

    2014-12-01

    Full Text Available The electronic structure and optical absorption spectra of polymer APFO3, [70]PCBM/APFO3 and [60]PCBM/APFO3, were studied with density functional theory (DFT, and the vertical excitation energies were calculated within the framework of the time-dependent DFT (TD-DFT. Visualized charge difference density analysis can be used to label the charge density redistribution for individual fullerene and fullerene/polymer complexes. The results of current work indicate that there is a difference between [60]PCBM and [70]PCBM, and a new charge transfer process is observed. Meanwhile, for the fullerene/polymer complex, all calculations of the twenty excited states were analyzed to reveal all possible charge transfer processes in depth. We also estimated the electronic coupling matrix, reorganization and Gibbs free energy to further calculate the rates of the charge transfer and the recombination. Our results give a clear picture of the structure, absorption spectra, charge transfer (CT process and its influencing factors, and provide a theoretical guideline for designing further photoactive layers of solar cells.

  4. Non-Markovian reduced dynamics of ultrafast charge transfer at an oligothiophene–fullerene heterojunction

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Keith H., E-mail: keith.hughes@bangor.ac.uk [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Cahier, Benjamin [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Martinazzo, Rocco [Dipartimento di Chimica Università degli Studi di Milano, v. Golgi 19, 20133 Milano (Italy); Tamura, Hiroyuki [WPI-Advanced Institute for Material Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Burghardt, Irene [Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main (Germany)

    2014-10-17

    Highlights: • Quantum dynamical study of exciton dissociation at a heterojunction interface. • The non-Markovian quantum dynamics involves a highly structured spectral density. • Spectral density is reconstructed from an effective mode transformation of the Hamiltonian. • The dynamics is studied using the hierarchical equations of motion approach. • It was found that the temperature has little effect on the charge transfer. - Abstract: We extend our recent quantum dynamical study of the exciton dissociation and charge transfer at an oligothiophene–fullerene heterojunction interface (Tamura et al., 2012) [6] by investigating the process using the non-perturbative hierarchical equations of motion (HEOM) approach. Based upon an effective mode reconstruction of the spectral density the effect of temperature on the charge transfer is studied using reduced density matrices. It was found that the temperature had little effect on the charge transfer and a coherent dynamics persists over the first few tens of femtoseconds, indicating that the primary charge transfer step proceeds by an activationless pathway.

  5. Process techniques of charge transfer time reduction for high speed CMOS image sensors

    International Nuclear Information System (INIS)

    This paper proposes pixel process techniques to reduce the charge transfer time in high speed CMOS image sensors. These techniques increase the lateral conductivity of the photo-generated carriers in a pinned photodiode (PPD) and the voltage difference between the PPD and the floating diffusion (FD) node by controlling and optimizing the N doping concentration in the PPD and the threshold voltage of the reset transistor, respectively. The techniques shorten the charge transfer time from the PPD diode to the FD node effectively. The proposed process techniques do not need extra masks and do not cause harm to the fill factor. A sub array of 32 × 64 pixels was designed and implemented in the 0.18 μm CIS process with five implantation conditions splitting the N region in the PPD. The simulation and measured results demonstrate that the charge transfer time can be decreased by using the proposed techniques. Comparing the charge transfer time of the pixel with the different implantation conditions of the N region, the charge transfer time of 0.32 μs is achieved and 31% of image lag was reduced by using the proposed process techniques. (semiconductor devices)

  6. Charge transfer and charge conversion of K and N defect centers in Si3N4

    Science.gov (United States)

    Pacchioni, Gianfranco; Erbetta, Davide

    2000-06-01

    Charge traps in silicon nitride and their interaction have been studied by first principle density functional theory (DFT) calculations. The K0 (N3≡Si•) and N0 (Si2=N•) Si and N dangling bond centers, respectively, are electrically active paramagnetic point defects. They show an amphoteric behavior and convert into the more stable diamagnetic charged centers K- (N3≡Si-), K+ (N3≡Si+), N- (Si2=N-), and N+ (Si2=N+). The overcoordination of K+ and N+ and the electrostatic interaction with the K- or N- counterparts are important contributions to the negative-U character of the defects.

  7. High resolution parallel reaction monitoring with electron transfer dissociation for middle-down proteomics.

    Science.gov (United States)

    Sweredoski, Michael J; Moradian, Annie; Raedle, Matthias; Franco, Catarina; Hess, Sonja

    2015-08-18

    In recent years, middle-down proteomics has emerged as a popular technique for the characterization and quantification of proteins not readily amenable to typical bottom-up approaches. So far, all high resolution middle-down approaches are done in data-dependent acquisition mode, using both collision-induced dissociation or electron capture/transfer dissociation techniques. Here, we explore middle-down proteomics with electron transfer dissociation using a targeted acquisition mode, parallel reaction monitoring (PRM), on an Orbitrap Fusion. As an example of a highly modified protein, we used histone H3 fractions from untreated and DMSO-treated Murine ErythroLeukemia (MEL) cells. We first determined optimized instrument parameters to obtain high sequence coverage using a synthetic standard peptide. We then setup a combined method of both MS1 scans and PRM scans of the 20 most abundant combinations of methylation and acetylation of the +10 charge state of the N-terminal tail of H3. Weak cation exchange hydrophilic interaction chromatography was used to separate the N-terminal H3 tail, primarily, by its acetylation and, to a secondary degree, by its methylation status, which aided in the interpretation of the results. After deconvolution of the highly charged ions, peaks were annotated to a minimum set of 254 H3 proteoforms in the untreated and treated samples. Upon DMSO treatment, global quantitation changes from the MS1 level show a relative decrease of 2, 3, 4, and 5 acetylations and an increase of 0 and 1 acetylations. A fragment ion map was developed to visualize specific differences between treated and untreated samples. Taken together, the data presented here show that middle-down proteomics with electron transfer dissociation using PRM is a novel, attractive method for the effective analysis and quantification of large and highly modified peptides. PMID:26176279

  8. Charge transfer cross sections for Hg/sup +/, Xe/sup +/, and Cs/sup +/ in collision with various metals and carbon

    Energy Technology Data Exchange (ETDEWEB)

    Rutherford, J.A.; Vroom, D.A.

    1981-01-01

    Cross sections for charge transfer between Hg/sup +/, Xe/sup +/, and Cs/sup +/ and the atomic species Fe, Mo, Al, Ti, Ta, and C have been measured in the ion energy range from 1 to 5000 eV. In general, the cross sections for charge transfer were found to be less than 2 x 10/sup -15/ cm/sup 2/ for most processes over the total energy range. The one exception is Hg/sup +/ in collision with Ti. The reactants are all open shell atomic species and in most cases where the charge transfer process is exothermic, several resonant pathways exist leading to the products. Some discussion of possible reaction paths is given. The techniques used to form neutral beams of the various species studied is included.

  9. DNA in a Dissipative Environment: A Charge Transfer Approach

    Science.gov (United States)

    Behnia, Sohrab; Fathizadeh, Samira; Akhshani, Afshin

    2015-08-01

    Conductivity properties of DNA molecule is investigated in a simple, chemically specific approach, that is intimately related to the Su-Schrieffer-Heeger (SSH) model. In the SSH model, the non-diagonal matrix element dependent on intersite displacements is considered and there is a coupling between the charge and lattice deformation along DNA helix. In order to study the evolution of the electrical current flowing through DNA in the presence of external electrical field, the electrical current is directly extracted from the dynamical equations. Ranges of electrical field and hopping constant value are estimated using MLE approach. The model is studied by means of I-V characteristic diagrams and the environmental effects is conducted through a phonon bath using different lengths of DNA. The NDR and quasi-Ohmic regions are observed.

  10. Evaluation of Bulk Charging in Geostationary Transfer Orbit and Earth Escape Trajectories Using the Numit 1-D Charging Model

    Science.gov (United States)

    Minow, Joseph I.; Coffey, Victoria N.; Parker, Linda N.; Blackwell, William C., Jr.; Jun, Insoo; Garrett, Henry B.

    2007-01-01

    The NUMIT 1-dimensional bulk charging model is used as a screening to ol for evaluating time-dependent bulk internal or deep dielectric) ch arging of dielectrics exposed to penetrating electron environments. T he code is modified to accept time dependent electron flux time serie s along satellite orbits for the electron environment inputs instead of using the static electron flux environment input originally used b y the code and widely adopted in bulk charging models. Application of the screening technique ts demonstrated for three cases of spacecraf t exposure within the Earth's radiation belts including a geostationa ry transfer orbit and an Earth-Moon transit trajectory for a range of orbit inclinations. Electric fields and charge densities are compute d for dielectric materials with varying electrical properties exposed to relativistic electron environments along the orbits. Our objectiv e is to demonstrate a preliminary application of the time-dependent e nvironments input to the NUMIT code for evaluating charging risks to exposed dielectrics used on spacecraft when exposed to the Earth's ra diation belts. The results demonstrate that the NUMIT electric field values in GTO orbits with multiple encounters with the Earth's radiat ion belts are consistent with previous studies of charging in GTO orb its and that potential threat conditions for electrostatic discharge exist on lunar transit trajectories depending on the electrical proper ties of the materials exposed to the radiation environment.

  11. Charge transfer in collisions of Beq+ (q=2-4) and Bq+ (q=3-5) ions with H

    International Nuclear Information System (INIS)

    The charge transfer reactions in collisions of Beq+(q=2-3) and Bq+(q=3-4) ions and atomic hydrogen are investigated by using the quantal molecular orbital close-coupling (QMOCC) and the two-center atomic-orbital close-coupling (TC-AOCC) methods. Total and sub-shells state-selective cross sections are calculated for low and intermediate energy region and compared with other data available. Sets of recommended cross sections, based on the QMOCC and TC-AOCC calculations, are deduced and tabulated for Be2,3+ + H and B3,4+ + H collisions, which provide important atomic data needed in the charge-exchange-recombination spectroscopy diagnostics in magnetic fusion plasmas investigation

  12. Engineering the Charge Transfer in all 2D Graphene-Nanoplatelets Heterostructure Photodetectors

    Science.gov (United States)

    Robin, A.; Lhuillier, E.; Xu, X. Z.; Ithurria, S.; Aubin, H.; Ouerghi, A.; Dubertret, B.

    2016-05-01

    Two dimensional layered (i.e. van der Waals) heterostructures open up great prospects, especially in photodetector applications. In this context, the control of the charge transfer between the constituting layers is of crucial importance. Compared to bulk or 0D system, 2D materials are characterized by a large exciton binding energy (0.1–1 eV) which considerably affects the magnitude of the charge transfer. Here we investigate a model system made from colloidal 2D CdSe nanoplatelets and epitaxial graphene in a phototransistor configuration. We demonstrate that using a heterostructured layered material, we can tune the magnitude and the direction (i.e. electron or hole) of the charge transfer. We further evidence that graphene functionalization by nanocrystals only leads to a limited change in the magnitude of the 1/f noise. These results draw some new directions to design van der Waals heterostructures with enhanced optoelectronic properties.

  13. Engineering the Charge Transfer in all 2D Graphene-Nanoplatelets Heterostructure Photodetectors.

    Science.gov (United States)

    Robin, A; Lhuillier, E; Xu, X Z; Ithurria, S; Aubin, H; Ouerghi, A; Dubertret, B

    2016-01-01

    Two dimensional layered (i.e. van der Waals) heterostructures open up great prospects, especially in photodetector applications. In this context, the control of the charge transfer between the constituting layers is of crucial importance. Compared to bulk or 0D system, 2D materials are characterized by a large exciton binding energy (0.1-1 eV) which considerably affects the magnitude of the charge transfer. Here we investigate a model system made from colloidal 2D CdSe nanoplatelets and epitaxial graphene in a phototransistor configuration. We demonstrate that using a heterostructured layered material, we can tune the magnitude and the direction (i.e. electron or hole) of the charge transfer. We further evidence that graphene functionalization by nanocrystals only leads to a limited change in the magnitude of the 1/f noise. These results draw some new directions to design van der Waals heterostructures with enhanced optoelectronic properties. PMID:27143413

  14. Heat transfer from the evaporator outlet to the charge of thermostatic expansion valves

    DEFF Research Database (Denmark)

    Langmaack, Lasse Nicolai; Knudsen, Hans-Jørgen Høgaard

    2006-01-01

    outlet with a special mounting strap. The heat transfer is quite complex because it takes place both directly through the contact points between bulb and pipe and indirectly through the mounting strap The TXV has to react to temperature changes at the evaporator outlet. Therefore, the dynamic behavior of...... the valve (and thereby the whole refrigeration system) depends greatly on the heat transfer between the evaporator outlet tube and the charge in the bulb. In this paper a model for the overall heat transfer between the pipe and the charge is presented. Geometrical data and material properties have......The bulb of a thermostatic expansion valve (TXV) is basically a temperature-pressure converter. It senses the temperature at the outlet of the evaporator, and the substance in the bulb (charge) generates the corresponding saturation pressure inside the bulb. The bulb is mounted on the evaporator...

  15. Examination of charge transfer in Au/YSZ for high-temperature optical gas sensing

    International Nuclear Information System (INIS)

    Highlights: • A sensing mechanism for Au/YSZ high-temperature optical gas sensing films is proposed. • XPS yields potential evidence for a charge transfer based plasmonic sensing mechanism. • The mechanism involves a change in free carrier density of Au due to charge transfer. - Abstract: Au-nanoparticle incorporated oxide thin film materials demonstrate significant promise as functional sensor materials for high temperature optical gas sensing in severe environments relevant for fossil and nuclear based power generation. The Au/yttria-stabilized zirconia (YSZ) system has been extensively studied in the literature and serves as a model system for fundamental investigations that seek to better understand the mechanistic origin of the plasmonic gas sensing response. In this work, X-ray photoelectron spectroscopy techniques are applied to Au/YSZ films in an attempt to provide further experimental evidence for a proposed sensing mechanism involving a change in free carrier density of Au nanoparticles due to charge transfer

  16. Oxidized Fatty Acid Analysis by Charge Switch Derivatization, Selected Reaction Monitoring and Accurate Mass Quantification

    OpenAIRE

    Liu, Xinping; Moon, Sung Ho; Mancuso, David J.; Jenkins, Christopher M.; Guan, Shaoping; Sims, Harold F.; Gross, Richard W.

    2013-01-01

    A highly sensitive, specific and robust method for the analysis of oxidized metabolites of linoleic, acid (LA), arachidonic acid (AA) and docosahexaenoic acid (DHA) was developed using charge-switch derivatization, LC-ESI MS/MS with selected reaction monitoring (SRM) and quantitation by high mass accuracy analysis of product ions thereby minimizing interferences from contaminating ions. Charge-switch derivatization of LA, AA and DHA metabolites with N-(4-aminomethylphenyl)-pyridinium resulted...

  17. An Accurate and Linear Scaling Method to Calculate Charge-Transfer Excitation Energies and Diabatic Couplings

    CERN Document Server

    Pavanello, Michele; Visscher, Lucas; Neugebauer, Johannes

    2012-01-01

    Quantum--Mechanical methods that are both computationally fast and accurate are not yet available for electronic excitations having charge transfer character. In this work, we present a significant step forward towards this goal for those charge transfer excitations that take place between non-covalently bound molecules. In particular, we present a method that scales linearly with the number of non-covalently bound molecules in the system and is based on a two-pronged approach: The molecular electronic structure of broken-symmetry charge-localized states is obtained with the Frozen Density Embedding formulation of subsystem Density-Functional Theory; subsequently, in a post-SCF calculation, the full-electron Hamiltonian and overlap matrix elements among the charge-localized states are evaluated with an algorithm which takes full advantage of the subsystem DFT density partitioning technique. The method is benchmarked against Coupled-Cluster calculations and achieves chemical accuracy for the systems considered...

  18. Quantum mechanical investigations on the role of neutral and negatively charged enamine intermediates in organocatalyzed reactions

    International Nuclear Information System (INIS)

    Highlights: • M06-2X functional is suitable to model key steps of proline-catalyzed reactions. • Investigation of the proline-catalyzed aldol reaction mechanism. • Influence of water molecules on the C–C bond formation step. • Mechanism for the reaction of proline-derived enamines with benzhydrylium cations. - Abstract: The proline-catalyzed aldol reaction is the seminal example of asymmetric organocatalysis. Previous theoretical and experimental studies aimed at identifying its mechanism in order to rationalize the outcome of this reaction. Here, we focus on key steps with modern first principle methods, i.e. the M06-2X hybrid exchange–correlation functional combined to the solvation density model to account for environmental effects. In particular, different pathways leading to the formation of neutral and negatively charged enamine intermediates are investigated, and their reactivity towards two electrophiles, i.e. an aldehyde and a benzhydrylium cation, are compared. Regarding the self-aldol reaction, our calculations confirm that the neutral enamine intermediate is more reactive than the negatively charged one. For the reaction with benzhydrylium cations however, the negatively charged enamine intermediate is more reactive

  19. Quantum mechanical investigations on the role of neutral and negatively charged enamine intermediates in organocatalyzed reactions

    Energy Technology Data Exchange (ETDEWEB)

    Hubin, Pierre O., E-mail: pierre.hubin@unamur.be [Laboratoire de Physico-Chimie Informatique (PCI), Unité de Chimie Physique Théorique et Structurale, University of Namur, 61 rue de Bruxelles, 5000 Namur (Belgium); Jacquemin, Denis [Laboratoire CEISAM – UMR CNRS 6230, Université de Nantes, 2 rue de la Houssinière, BP92208, 44322 Nantes Cedex 3 (France); Institut Universitaire de France 103, Boulevard St Michel, 75005 Paris Cedex 5 (France); Leherte, Laurence; Vercauteren, Daniel P. [Laboratoire de Physico-Chimie Informatique (PCI), Unité de Chimie Physique Théorique et Structurale, University of Namur, 61 rue de Bruxelles, 5000 Namur (Belgium)

    2014-04-15

    Highlights: • M06-2X functional is suitable to model key steps of proline-catalyzed reactions. • Investigation of the proline-catalyzed aldol reaction mechanism. • Influence of water molecules on the C–C bond formation step. • Mechanism for the reaction of proline-derived enamines with benzhydrylium cations. - Abstract: The proline-catalyzed aldol reaction is the seminal example of asymmetric organocatalysis. Previous theoretical and experimental studies aimed at identifying its mechanism in order to rationalize the outcome of this reaction. Here, we focus on key steps with modern first principle methods, i.e. the M06-2X hybrid exchange–correlation functional combined to the solvation density model to account for environmental effects. In particular, different pathways leading to the formation of neutral and negatively charged enamine intermediates are investigated, and their reactivity towards two electrophiles, i.e. an aldehyde and a benzhydrylium cation, are compared. Regarding the self-aldol reaction, our calculations confirm that the neutral enamine intermediate is more reactive than the negatively charged one. For the reaction with benzhydrylium cations however, the negatively charged enamine intermediate is more reactive.

  20. Study of the pd→→n{pp}s charge-exchange reaction using a polarised deuterium target

    Directory of Open Access Journals (Sweden)

    B. Gou

    2015-02-01

    Full Text Available The vector and tensor analysing powers, Ay and Ayy, of the pd→→n{pp}s charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the S01 state, here denoted by {pp}s. The polarisation of the deuterium gas was established through measurements in parallel of proton–deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers q≥160 MeV/c. These data provide a good continuation of the earlier results at q≤140 MeV/c obtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings. These successful results confirm that the ANKE deuteron charge-exchange programme can be extended to much higher energies with a polarised deuterium target than can be achieved with a polarised deuteron beam.

  1. Charge transfer properties through graphene for applications in gaseous detectors

    Science.gov (United States)

    Franchino, S.; Gonzalez-Diaz, D.; Hall-Wilton, R.; Jackman, R. B.; Muller, H.; Nguyen, T. T.; de Oliveira, R.; Oliveri, E.; Pfeiffer, D.; Resnati, F.; Ropelewski, L.; Smith, J.; van Stenis, M.; Streli, C.; Thuiner, P.; Veenhof, R.

    2016-07-01

    Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical and electrical properties. Regarded as the thinnest and narrowest conductive mesh, it has drastically different transmission behaviours when bombarded with electrons and ions in vacuum. This property, if confirmed in gas, may be a definitive solution for the ion back-flow problem in gaseous detectors. In order to ascertain this aspect, graphene layers of dimensions of about 2×2 cm2, grown on a copper substrate, are transferred onto a flat metal surface with holes, so that the graphene layer is freely suspended. The graphene and the support are installed into a gaseous detector equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency properties to electrons and ions are studied in gas as a function of the electric fields. The techniques to produce the graphene samples are described, and we report on preliminary tests of graphene-coated GEMs.

  2. Charge Transfer Properties Through Graphene for Applications in Gaseous Detectors

    CERN Document Server

    Franchino, S; Hall-Wilton, R.; Jackman, R.B.; Muller, H.; Nguyen, T.T.; de Oliveira, R.; Oliveri, E.; Pfeiffer, D.; Resnati, F.; Ropelewski, L.; Smith, J.; van Stenis, M.; Streli, C.; Thuiner, P.; Veenhof, R.

    2015-01-01

    Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical and electrical properties. Regarded as the thinnest and narrowest conductive mesh, it has drastically different transmission behaviours when bombarded with electrons and ions in vacuum. This property, if confirmed in gas, may be a definitive solution for the ion back-flow problem in gaseous detectors. In order to ascertain this aspect, graphene layers of dimensions of about 2x2cm$^2$, grown on a copper substrate, are transferred onto a flat metal surface with holes, so that the graphene layer is freely suspended. The graphene and the support are installed into a gaseous detector equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency properties to electrons and ions are studied in gas as a function of the electric fields. The techniques to produce the graphene samples are described, and we report on preliminary tests of graphene-coated GEMs.

  3. Assessing the importance of proton transfer reactions in DNA.

    Science.gov (United States)

    Jacquemin, Denis; Zúñiga, José; Requena, Alberto; Céron-Carrasco, José Pedro

    2014-08-19

    Although engineered by millions of years of evolution, the cellular machinery is not flawless, and errors regularly appear during DNA replication. The subsequent alteration of the stored genetic message results in a mutation and might be the starting point of important health disorders. The question therefore is what causes DNA mutations? All living organisms are constantly exposed to a number of external agents such as free radicals and to radiation, which may lead to induced mutations. There are also mutations happening without invoking the action of any exogenous element, the so-called spontaneous mutations. The former can be partially controlled by avoiding exposure to high-risk environments, while the latter are more intriguing because their origin is unclear and difficult to determine. As noted by Watson and Crick when they first discovered the DNA structure, the correct replication of DNA rests on the assumption that the base pairs remain in their most stable, canonical form. However, protons along the interbase hydrogen-bond network are not static entities. They can in fact interchange their positions in DNA bases through proton transfer (PT) reactions before strands unwind, giving rise to noncanonical structures defined as rare tautomers. The importance of these rare tautomers was also cleverly anticipated by Watson and Crick and some years later claimed by Löwdin to be a source of spontaneous mutations. In Watson and Crick's words: "It would be of interest to know the precise difference in free energy between the various tautomeric forms under physiological conditions." Unfortunately, rare tautomeric forms are very difficult to detect, so no direct and accurate free energy measure has been discerned. In contrast, theoretical chemistry is making good progress toward the quantification of PT reactions in DNA and their biological consequences. This Account touches upon the theoretical studies devoted to appraising the importance of rare tautomers as

  4. Photochemical charge transfer observed in nanoscale hydrogen evolving photocatalysts using surface photovoltage spectroscopy

    OpenAIRE

    Wang, J.; Zhao, J; Osterloh, FE

    2015-01-01

    © The Royal Society of Chemistry. The application of inorganic nanostructures for solar water splitting is currently limited by our understanding of photochemical charge transfer on the nanoscale, where space charge layers are less effective for carrier separation. Here we employ surface photovoltage spectroscopy to measure the internal photovoltages in single crystalline platinum/ruthenium-modified Rh-doped SrTiO3 nanocrystals for the first time. Voltages of -0.88 V and -1.13 V are found bet...

  5. Influence of Complex Stabilities on Electron-Transfer Reactions

    International Nuclear Information System (INIS)

    The rate of exchange in solutions containing sulphate ions was measured in the system FeII/FeIII at different temperatures with 5'9Fe as a tracer. At 25°C and an ionic strength of 1 the rate constants are: k1[FeSO+4/Fe2+] =295 litres mole-1 sec-1, k2[Fe(SO4)2-/Fe2+] =17 500 litres mole-1 sec-1. The activation energies are E1 =13.8 kcal/mole, E2 = 15kcal/mole. For the rate constants of the electron exchange between different complexes of FeIII and Fe2+ ions the following relation was found: log10k = 1.1 + 0. 5 |Δlog10K|, where Δ log10K is the difference between the logarithms of the stability constants of the FeIII and FeII complexes with the same ligands. All rate constants for electron exchange between FeIII complexes and Fe2+ ions follow this relation (as far as stability constants are known). In the system CeIII/ CeIV a first-order reaction with respect to CeIII contributes to the exchange reaction. This is explained by the formation of excited CeIII ions. The rate constant is k5 = 4.45 x 10-4 sec-1 (0°C). At 0°C the rate constants for the second-order reactions are: k1[CeSO+24/Ce3+] = 0.10 litres mole-1 sec-1, k2[Ce(SO4)2/Ce3+] = 0.11 litres mole-1 sec-1; k3[Ce(SO4)2-3/Ce3+] = 0.17 litres mole-1 sec-1, k4 [Ce4+/Ce3+] = 5.05 x 10-3 litres mole-1 sec-1. The electron exchange is accelerated by sulphate ions, but not to the same extent as in the system FeII/FeIII. The fact that the rate constants k, k2 and k3 are nearly equal shows that the charge of the complexes has no influence. The rate constants in the system CeIII/CeIV also follow a relation of the form log k = a + bΔlog K. The constants a and b were found to be: a = -2.3, b = 0.4. In the system UIV/UVI - in the absence of light - the rate of the electron exchange in solutions containing sulphate ions is proportional to the concentrations of UIV and UVI and inversely proportional to the third power of the H+ concentration. The rate determining step is the disproportionation of UV which is present in

  6. Contribution of decay products of transfer reactions to heavy ion inelastic and transfer spectra

    International Nuclear Information System (INIS)

    A study of decay product contributions to inclusive ejectile kinetic energy spectra is presented. Analytical formulae for the positions and widths of these contributions are derived from kinematical considerations. A formal integral expression for the double differential cross section dsub(σ)sup(2)/dΩdE is given in the case of one particle emission from an excited state of the ejectile. The effects of anisotropic angular distributions are studied. The differential cross sections are then computed by a Monte Carlo method and compared to experimental spectra over a large range of measured systems. The transfer-evaporation mechanism is shown to contribute strongly to the background of the spectra but not to be responsible for the narrow structure observed in some reactions

  7. What's new in the proton transfer reaction from pyranine to water? A femtosecond study of the proton transfer dynamics

    International Nuclear Information System (INIS)

    The proton transfer from excited pyranine to water is studied by the femtosecond fluorescence upconversion technique. It is shown for the first time that the proton transfer reaction in water proceeds by three successive steps: the solvent cage relaxation, the specific solute-solvent hydrogen-bond formation and finally the ion pair dissociation/diffusion

  8. New charge exchange model of GEANT4 for 9Be(p,n)9B reaction

    International Nuclear Information System (INIS)

    A new data-based charge exchange model of GEANT4 dedicated to the 9Be(p,n)9B reaction is developed by taking the ENDF/B-VII.1 differential cross-section data as input. Our model yields results that are in good agreement with the experimental neutron yield spectrum data obtained for proton beams of energy (20–35) MeV. In particular, in contrast to all the considered GEANT4 hadronic models, the peak structure resulting from the discrete neutrons generated by the charge-exchange reaction is observed to be accurately reproduced in our model

  9. Online exhaled gas measurements for radiotherapy patients by proton transfer reaction mass spectrometry.

    Science.gov (United States)

    Zou, Xue; Zhou, Wenzhao; Shen, Chengyin; Wang, Hongmei; Lu, Yan; Wang, Hongzhi; Chu, Yannan

    2016-08-01

    The present study assessed whether exhaled breath analysis using proton transfer reaction mass spectrometry (PTR-MS) could screen for radiation exposure. As the intensity of proton transfer reaction reagent ion H3(16)O(+) can be calculated with the intensity of H3(18)O(+), the intensity of H3(18)O(+) was monitored to observe the stability of the PTR-MS instrument during the experiment. The PTR-MS was applied for detecting the volatile organic compounds (VOCs) in the exhaled breath from 42 radiotherapy patients and other 61 patients who had not received radiotherapy. All patients were enrolled in the local cancer hospital. In the experiment, the subjects breathe slowly to the PTR-MS through a direct inlet system without any sampling bag or tube. The breath mass spectrometric data was statistically analyzed using Mann-Whitney U test and stepwise discriminant analysis to find the characteristic ions of radiation exposure. Receiver operating characteristics (ROC) analysis was applied for a combination of the characteristic ions. The PTR-MS instrument was stable as the intensity of reaction ion H3(16)O(+) was maintained in 1.1%. Through statistically analysis, we found 6 kinds of characteristic ions of radiation exposure, specifically mass-to-charge ratio (m/z) 93, m/z 41, m/z 102, m/z 79, m/z 131, and m/z 143. The sensitivity (true positive rate) and specificity (true negative rate) were 78.6% and 82.0% respectively. The integrated area under the ROC curve (AUC) was 0.869. The results in our study demonstrated the potential of the online breath tester PTR-MS as a non-invasive screening for radiation exposure. PMID:27209162

  10. Satellite structure in laser-assisted charge-transfer cross sections

    International Nuclear Information System (INIS)

    A six-state coupled-channel calculation has been performed on the laser-assisted charge-transfer collision H++Na+hω. A greatly enhanced charge-transfer cross section is observed for low-energy collisions if the photon energy is matched to the classical satellite frequency. This frequency is determined by the location of an extremum in the difference of potential energies between the laser-pumped initial and final molecular states. The stationary-phase method has been used to reproduce the general features and the magnitude of the cross-section structure

  11. Polarization dependence of charge-transfer excitations in La2CuO4

    Science.gov (United States)

    Lu, Li; Chabot-Couture, Guillaume; Hancock, Jason; Vajk, Owen; Yu, Guichuan; Ishii, Kenji; Mizuki, Jun'ichiro; Casa, Diego; Gog, Thomas; Greven, Martin

    2006-03-01

    We have carried out an extensive resonant inelastic x-ray scattering (RIXS) study of La2CuO4 at the Cu K-edge. Multiple charge-transfer excitations have been identified using the incident photon energy dependence of the cross section and studied carefully with polarizations E//c and E //ab. An analysis of the incident photon energy dependence, the polarization dependence, as well as the K-edge absorption spectra, indicates that the RIXS spectra reveal rich physics about the K-edge absorption process and momentum-dependent charge-transfer excitations in cuprates.

  12. Laser-plasma ion sources: application to charge-transfer X-ray lasers

    International Nuclear Information System (INIS)

    Preliminary experiments directed towards the application of laser-produced plasmas in a charge-transfer X-ray laser are described. The motivation for these is the potential of the charge-transfer process to become a highly efficient pump process due to its large cross-section and state selective nature. The experiments show bright emission of ionic lines in the soft X-ray region when a beam of ions from a laser-plasma hits a secondary target a few millimeters away. (orig.)

  13. Fluorescence behavior of intramolecular charge transfer state in trans-ethyl p-(dimethylamino)cinamate

    International Nuclear Information System (INIS)

    Steady-state and time-resolved emission studies have been performed to investigate the intramolecular charge transfer (ICT) behavior of trans-ethyl p-(dimethylamino)cinamate (EDAC) in various solvents. Large fluorescence spectral shift in more polar solvents indicates an efficient charge transfer from the donor site to the acceptor moiety in the excited state compared to the ground state. The excited state properties in hydrogen-bonding solvents are markedly different from other solvents indicating the possible competition of intermolecular hydrogen bond formation with the electron donor site and ICT

  14. 36-MeV-triton-induced charge exchange: Mass measurements and energy levels of neutron-rich nuclei and the charge exchange reaction mechanism

    International Nuclear Information System (INIS)

    Energy spectra and differential cross sections have been obtained for the charge exchange reaction (3H,3He) on targets of /sup 30,28/Si and /sup 26/Mg at an incident energy of 36 MeV. Previously unobserved energy levels of /sup 30/Al and /sup 26/Na are reported and compared to shell model predictions. Microscopic form factors based on the M3Y effective nucleon-nucleon interaction are used in distorted-wave Born approximation codes to fit the data. The sensitivity of the model to input parameters is discussed and some spin assignments made. Coupled channels calculations are performed to fit the two-step contributions to the data via sequential one-nucleon transfers

  15. Measurements of selected charge transfer processes at low energies. Final report, November 1977-November 1978

    Energy Technology Data Exchange (ETDEWEB)

    Rutherford, J.A.; Neynaber, R.H.; Vroom, D.A.

    1978-11-01

    Measurement of the charge transfer cross section for the process N/sup +/ + O yields N + O/sup +/ was completed during the contract year. The experiment was conducted using a crossed beam apparatus. The O atoms were formed in a microwave or rf discharge using pure O/sub 2/ with traces of H/sub 2/O present. Varying the amount of H/sub 2/O present allowed the dissocation fraction in the O/sub 2/ to the varied. This variation was needed to allow determination of the effects of other competing processes. The cross section for the above reaction was determined in the energy range from 0.5 eV to 12 eV in the center-of-mass system. The signals obtained indicated that this process does not vary rapidly with energy. The cross section was determined to be 1.2 x 10/sup -17/ cm/sup 2/ at the lowest energies studied and increases to approximately 2.5 x 10/sup -17/ cm/sup 2/ at 12 eV in the center-of-mass. Cross sections for the reactions Al/sup +/ + O/sub 2/ yields AlO/sup +/ + O and Al + O/sub 2//sup +/ and Al/sup +/ + N/sub 2/ yields AlN/sup +/ + N and Al + N/sub 2//sup +/ were measured during the contract period. The values determined for these processes were essentially the same as those measured previously. In addition, the upper limits determined at energies where these processes have very small probabilities were pushed to lower values. The measurements were undertaken to resolve a conflict between our data and cross section values postulated to explain results obtained in another experiment.

  16. Core polarization phenomena in pion-nucleus charge-exchange reactions above the delta resonance

    International Nuclear Information System (INIS)

    We study pion-induced single- and double-charge exchange reactions in nuclei at energies above the Δ(3/2,3/2) resonance using a microscopic, parameter-free Glauber approach. We introduce corrections in the amplitudes due to the medium polarization from an isospin-flip spin-nonflip source which dominates the reaction in the transitions studied and which has not previously been identified. Using an effective force derived from the study of electromagnetic transitions we obtain sizable reductions of the cross sections in both single- and double-charge exchanges, which bring the results of both reactions into close agreement with experiment. Predictions for angular distributions for both reactions on 14C, 18O, and 42Ca targets are made which should serve as guidelines for experiments planned in this region and as further tests of the proposed isovector renormalization

  17. Neutrino nuclear responses for double beta decays and astro neutrinos by charge exchange reactions

    Science.gov (United States)

    Ejiri, Hiroyasu

    2014-09-01

    Neutrino nuclear responses are crucial for neutrino studies in nuclei. Charge exchange reactions (CER) are shown to be used to study charged current neutrino nuclear responses associated with double beta decays(DBD)and astro neutrino interactions. CERs to be used are high energy-resolution (He3 ,t) reactions at RCNP, photonuclear reactions via IAR at NewSUBARU and muon capture reactions at MUSIC RCNP and MLF J-PARC. The Gamow Teller (GT) strengths studied by CERs reproduce the observed 2 neutrino DBD matrix elements. The GT and spin dipole (SD) matrix elements are found to be reduced much due to the nucleon spin isospin correlations and the non-nucleonic (delta isobar) nuclear medium effects. Impacts of the reductions on the DBD matrix elements and astro neutrino interactions are discussed.

  18. Charged-particle thermonuclear reaction rates: II. Tables and graphs of reaction rates and probability density functions

    International Nuclear Information System (INIS)

    Numerical values of charged-particle thermonuclear reaction rates for nuclei in the A=14 to 40 region are tabulated. The results are obtained using a method, based on Monte Carlo techniques, that has been described in the preceding paper of this issue (Paper I). We present a low rate, median rate and high rate which correspond to the 0.16, 0.50 and 0.84 quantiles, respectively, of the cumulative reaction rate distribution. The meaning of these quantities is in general different from the commonly reported, but statistically meaningless expressions, 'lower limit', 'nominal value' and 'upper limit' of the total reaction rate. In addition, we approximate the Monte Carlo probability density function of the total reaction rate by a lognormal distribution and tabulate the lognormal parameters μ and σ at each temperature. We also provide a quantitative measure (Anderson-Darling test statistic) for the reliability of the lognormal approximation. The user can implement the approximate lognormal reaction rate probability density functions directly in a stellar model code for studies of stellar energy generation and nucleosynthesis. For each reaction, the Monte Carlo reaction rate probability density functions, together with their lognormal approximations, are displayed graphically for selected temperatures in order to provide a visual impression. Our new reaction rates are appropriate for bare nuclei in the laboratory. The nuclear physics input used to derive our reaction rates is presented in the subsequent paper of this issue (Paper III). In the fourth paper of this issue (Paper IV) we compare our new reaction rates to previous results.

  19. Effects of the difference between the charge and matter deformations on fusion reactions of unstable nuclei

    CERN Document Server

    Rumin, T; Rumin, Tamanna; Takigawa, Noboru

    2002-01-01

    Relativistic mean field calculations suggest that the charge and matter deformations significantly differ in some of the unstable neutron and proton rich nuclei. We discuss the effects of the difference on the fusion reactions induced by them at energies near and below the Coulomb barrier by taking the $^{19,25,37}$Na + $^{208}$Pb reactions as examples. We also discuss whether one can probe the difference by the so called fusion barrier distribution analysis.

  20. High efficiency charged-particle spectrometer using gridded ionization chamber for fast-neutron induced reactions

    International Nuclear Information System (INIS)

    A high efficiency charged particle spectrometer for fast neutron induced reactions has been developed using a gridded-ionization chamber taking advantage of its large solid angle and capability of energy-angle determination. It is characterized by high stopping-power and low background to be applicable for alpha-particles emitted by 15 MeV neutrons and protons for MeV incident neutrons. The spectrometer has been applied successfully for (n, alpha) and (n, p) reactions. (orig.)

  1. What can we learn from A(π+, η)B charge exchange reaction?

    International Nuclear Information System (INIS)

    Within DWIA formalism, the η production cross sections from nuclear target by charge exchange reaction A(π+, η)B are calculated. For 13C target the cross sections at forward angles are of the order of 10 μb/sr at Tπ = 660 MeV, which can be measured experimentally. The high momentum component of the wave function of single particle bound state is essential for describing this reaction

  2. Locomotion of Electrocatalytic Nanomotors due to Reaction Induced Charge Auto-Electrophoresis

    CERN Document Server

    Moran, J L; Posner, J D

    2010-01-01

    Bimetallic rod-shaped nanomotors swim autonomously in hydrogen peroxide solutions. Here we present a scaling analysis, computational simulations, and experimental data that show that the nanomotor locomotion is driven by fluid slip around the nanomotor surface due to electrical body forces. The body forces are generated by a coupling of charge density and electric fields induced by electrochemical reactions occurring on the nanomotor surface. We describe the dependence of nanomotor motion on the nanomotor surface potential and reaction-driven flux.

  3. Computing intramolecular charge and energy transfer rates using optimal modes

    International Nuclear Information System (INIS)

    In our recent work [X. Yang and E. R. Bittner, J. Phys. Chem. A 118, 5196 (2014)], we showed how to construct a reduced set of nuclear motions that capture the coupling between electronic and nuclear degrees of freedom over the course of an electronic transition. We construct these modes, referred to as “Lanczos modes,” by applying a search algorithm to find linear combinations of vibrational normal modes that optimize the electronic/nuclear coupling operator. Here, we analyze the irreducible representations of the dominant contributions of these modes and find that for the cases considered here, these belong to totally symmetric irreducible representations of the donor and acceptor moieties. Upon investigating the molecular geometry changes following the transition, we propose that the electronic transition process can be broken into two steps, in the agreement of Born-Oppenheimer approximation: a fast excitation transfer occurs, facilitated by the “primary Lanczos mode,” followed by slow nuclear relaxation on the final electronic diabatic surface

  4. Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

    International Nuclear Information System (INIS)

    A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

  5. Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

    Energy Technology Data Exchange (ETDEWEB)

    Paret, Stefan

    2010-02-22

    A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

  6. Pre-equilibrium dipole strength in charge asymmetric peripheral heavy-ion reactions

    International Nuclear Information System (INIS)

    We report on the results obtained from the study of the 32S+64Ni and 32S+58Ni peripheral reactions at incident energies Elab=288 MeV and Elab=320 MeV, respectively. High-energy γ-rays were detected in an array of 8 seven-pack BaF2 clusters. Coincidence with complex fragments detected in 12 three-stage telescopes ensured the selection of peripheral reaction events. All of the relevant reaction parameters were kept constant with the exception of the different initial dipole moment caused by the different entrance channel charge asymmetry. While for quasi-elastic events no N/Z effect was observed in the differential γ-ray multiplicities of the two reactions, for deep-inelastic events a larger dipole γ-ray emission occurs during the more N/Z asymmetric reaction. A theoretical interpretation based on a collective Bremsstrahlung analysis of the reaction dynamics is presented. (orig.)

  7. High spin levels populated in multinucleon transfer reaction with 480 MeV 12C

    International Nuclear Information System (INIS)

    Two- and three-nucleon stripping reactions induced by 480 MeV 12C have been studied on 12C, 16O, 28Si, 40Ca and 54Fe target nuclei. Discrete levels are fed with cross sections up to 1 mb/sr for d-transfer reactions and one order and two orders of magnitude less for 2p- and 3He-transfer reactions, respectively. These reactions preferentially populate high spin states with stretched configurations. Several spin assignments were known from transfer reactions induced by lighter projectiles at incident energies well above the Coulomb barrier. In the case of two-nucleon transfer reactions, the energy of these states is well reproduced by crude shell model calculations. Such estimates are of use in proposing spins of newly observed states especially as the shapes of the measured angular distributions are independent of the final spin of the residual nucleus

  8. Role of transfer reactions in heavy-ion collisions at the Coulomb barrier

    Directory of Open Access Journals (Sweden)

    Pollarolo Giovanni

    2011-10-01

    Full Text Available One and two neutron transfer reactions are discussed in the semiclassical formalism. The twoneutrons transfer cross sections are calculated in the successive approximation. Comparisons with new experimental data below the Coulomb barrier are discussed in term of transfer probabilities as a function of the distance of closest approach for Coulomb scattering.

  9. Studies of high-spin cluster states induced by multiparticle transfer reactions

    International Nuclear Information System (INIS)

    The characteristic selectivity due to the reaction dynamics and clustering structure among transferred nucleons is first described. Using such an advantageous selectivity, high-spin cluster states can be sorted out. Examples involving either one-, two-, three- or four-nucleon transfer reactions are mentioned with emphazing spectroscopic problems. It is clear that a lack in reaction mechanism theory hinders quantitative arguments at present time

  10. Fragmentation and direct transfer reactions for 40Ar incident beam on 27Al target at 1760 MeV

    International Nuclear Information System (INIS)

    Peripheral collision studies performed with 40Ar projectiles at 44 MeV/A and 27Al target show that both fragmentation and transfer reactions can be discerned in this type of interaction. The experimental observation of fragments with masses charges and velocities close to those of the incident beam are the signature of transfer reactions and a detailed analysis of the energy spectra of such fragments has been carried out and interpreted in terms of a direct diffraction transfer model. On the other hand, for large mass transfer reactions, abrasion is the suitable mechanism. Inclusive fragment measurement together with the appropriate residual nuclei-fragment coincidence results then provides experimental data in good agreement with the theoretical predictions obtained from a participant spectator model. These investigations also indicate that the separation energies of the participant from the spectator nucleus, at least within the framework of the above model, can be interpreted in terms of a friction force which becomes more efficient as the projectile energy decreases. (author)

  11. Enhancement of visible-light-driven photoresponse of Mn/ZnO system: photogenerated charge transfer properties and photocatalytic activity

    Science.gov (United States)

    Lu, Yongchun; Lin, Yanhong; Xie, Tengfeng; Shi, Shoulei; Fan, Haimei; Wang, Dejun

    2012-09-01

    A visible-light-active ZnO photocatalyst system in the presence of manganese ions (Mn/ZnO) was prepared via a simple and rapid approach. XRD, XPS, Raman scattering and UV-Vis DRS confirmed the manganese exists in multivalent forms (Mn3+/Mn2+) in the ZnO lattice, furthermore, ZnO light absorption is extended to the visible region. The photocatalytic activities of the catalysts were evaluated by measuring the photodegrading efficiency of 2,4-dichlorophenol (DCP) under visible light irradiation. With an optimal molar ratio of 5% in Mn/ZnO the highest rate photodegradation was achieved under the experimental conditions. We have characterized the separation and transfer behavior of the photogenerated charges in the visible region by means of surface photovoltage (SPV), surface photocurrent (SPC) and transient photovoltage (TPV) techniques. Based on the comprehensive investigation of the photovoltaic properties of Mn/ZnO photocatalyst, we illustrate the behavior of photogenerated charges have distinct effects on the photocatalytic activity. It is demonstrated that the incorporation of multivalent Mn in ZnO promoted the separation of photogenerated charges, inhibited the recombination of photogenerated carriers, and thus prolonged the charges lifetime to participate in the photocatalytic reaction, resulting in highly efficient photocatalytic activity, which is attributed to the formation of a strong electronic interaction between the multivalent Mn and ZnO.

  12. [Time-resolved optical studies of charge relaxation and charge transfer at electrode interfaces

    Energy Technology Data Exchange (ETDEWEB)

    1992-12-31

    Key components were identified in a quantitative model of carrier relaxation in semiconductor electrodes: nonlinear aspects of nonradiative and radiative recombination, effect of space charge field on carrier dynamics, self-absorption effects in direct gas semiconductors, and influence of surface state population kinetics on charge carrier recombination. For CdSe, the first three are operative (no direct proof of the last one). A realistic kinetic model for carrier recombination in the bulk of CdSe was used which includes important nonlinear effects, both radiative and nonradiative. The change in interfacial recombination velocity with the chemical nature of the sinterface was studied (n-CdSe/silane interfaces). Temperature effect (278 to 328 K) on fluorescence decay of n-CdSe in contact with 0.5 M KOH was found to be weak. An analytical solution was obtained for time-resolved fluoresence from electrodes under potential bias, and is being tested. Fluorescence work on a different material, CdS, indicate different recombination kinetics; this material was used to directly pump an optical transition of a surface state.

  13. Dynamics of chemical reactions of multiply-charged cations: Information from beam scattering experiments

    Czech Academy of Sciences Publication Activity Database

    Herman, Zdeněk

    2015-01-01

    Roč. 378, FEB 2015 (2015), s. 113-126. ISSN 1387-3806 Institutional support: RVO:61388955 Keywords : Multiply-charged ions * Dynamics of chemical reactions * Beam scattering Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.972, year: 2014

  14. CsI based charged particle array for reaction studies at IUAC

    International Nuclear Information System (INIS)

    Developmental activities in charge particle detector array for investigating reaction dynamics has been initiated at IUAC. The array will consist of CsI(TI) detectors coupled to photo-diode and is being developed to study fusion-fission dynamics and will also serve as an ancillary detector system for National Array of Neutron Detectors (NAND)

  15. Charge-transfer energy in closed-shell ion-atom interactions. [for H and Li ions in He

    Science.gov (United States)

    Alvarez-Rizzatti, M.; Mason, E. A.

    1975-01-01

    The importance of charge-transfer energy in the interactions between closed-shell ions and atoms is investigated. Ab initio calculations on H(plus)-He and Li(plus)-He are used as a guide for the construction of approximate methods for the estimation of the charge-transfer energy for more complicated systems. For many alkali ion-rate gas systems the charge-transfer energy is comparable to the induction energy in the region of the potential minimum, although for doubly charged alkaline-earth ions in rare gases the induction energy always dominates. Surprisingly, an empirical combination of repulsion energy plus asymptotic induction energy plus asymptotic dispersion energy seems to give a fair representation of the total interaction, especially if the repulsion energy is parameterized, despite the omission of any explicit charge-transfer contribution. More refined interaction models should consider the charge-transfer energy contribution.

  16. Charge transfer in a sharply nonuniform electric field mediated by swirling liquid flow with minimal hydraulic resistance

    Science.gov (United States)

    Nagorny, V. S.; Smirnovsky, A. A.; Chernyshev, A. S.; Kolodyazhny, D. Yu.

    2015-09-01

    A scheme of a fuel nozzle with "needle-plane" electrode system, the location of which enables one to minimize the imparted hydraulic resistance, is proposed. We consider the processes of charge transfer in a sharply inhomogeneous electric field in order to estimate the amount of charge coming out of the channel. For this purpose, we used the OpenFOAM software package, modified to account for the electrohydrodynamic effects. By using the k-ω SST turbulence model within an axial-symmetrical RANS problem, the vortex liquid flow and charge transfer are calculated. The impact of vorticity degree on the processes of charge transfer is studied. It is found that the charge flowing out of the calculation domain is about 80% of the injected charge. The vorticity degree in the above range of values has little effect on the process of charge transfer.

  17. Anomalous charge and negative-charge-transfer insulating state in cuprate chain-compound KCuO_2

    OpenAIRE

    Choudhury, D.; Rivero, P.; Meyers, D.; Liu, X.; Cao, Y; Middey, S.; Whitaker, M. J.; Barraza-Lopez, S.; Freeland, J. W.; Greenblatt, M.; Chakhalian, J.

    2015-01-01

    Using a combination of X-ray absorption spectroscopy experiments with first principle calculations, we demonstrate that insulating KCuO_2 contains Cu in an unusually-high formal-3+ valence state, the ligand-to-metal (O to Cu) charge transfer energy is intriguingly negative (Delta~ -1.5 eV) and has a dominant (~60%) ligand-hole character in the ground state akin to the high Tc cuprate Zhang-Rice state. Unlike most other formal Cu^{3+} compounds, the Cu 2p XAS spectra of KCuO_2 exhibits pronoun...

  18. Changes in wetting and contact charge transfer by femtosecond laser-ablation of polyimide

    International Nuclear Information System (INIS)

    Highlights: • Laser ablation significantly reduced the triboelectric charging of polyimide films. • Hierarchical micro/nanostructures formed on the surface of the sample. • Structural anisotropy leads to spatially varying contact angles of water droplets. • Raman spectroscopy revealed a carbonization of the polyimide sample. • The corresponding loss of insulation may explain the reduction of charge transfer. - Abstract: In this study it is demonstrated that the triboelectric charging of polyimide thin films is significantly reduced by using a femtosecond laser to nanostructure its. It is found that the contact charge transfer between laser-ablated Kapton and aluminum is almost negligible, and even much lower than the significant current occurring when non-treated Kapton touches the metal. Scanning electron microscopy demonstrates that laser ablation produces a hierarchical micro and nanostructure, and it is found that the structural anisotropy leads to spatially varying contact angles of water droplets residing on the surface. Raman spectra suggest that the centers of the laser-ablated tracks are carbonized; therefore, the loss of insulation can be responsible for the reduction of charge transfer

  19. Changes in wetting and contact charge transfer by femtosecond laser-ablation of polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Guo, X.D., E-mail: xiaodong.guo@uib.no [Department of Physics and Technology, Allegaten 55, 5020 Bergen, University of Bergen (Norway); Dai, Y.; Gong, M. [Department of Physics, Shanghai 200444, Shanghai University (China); Qu, Y.G. [Center for Geobiology, Allegaten 41, 5020 Bergen, University of Bergen (Norway); Helseth, L.E. [Department of Physics and Technology, Allegaten 55, 5020 Bergen, University of Bergen (Norway)

    2015-09-15

    Highlights: • Laser ablation significantly reduced the triboelectric charging of polyimide films. • Hierarchical micro/nanostructures formed on the surface of the sample. • Structural anisotropy leads to spatially varying contact angles of water droplets. • Raman spectroscopy revealed a carbonization of the polyimide sample. • The corresponding loss of insulation may explain the reduction of charge transfer. - Abstract: In this study it is demonstrated that the triboelectric charging of polyimide thin films is significantly reduced by using a femtosecond laser to nanostructure its. It is found that the contact charge transfer between laser-ablated Kapton and aluminum is almost negligible, and even much lower than the significant current occurring when non-treated Kapton touches the metal. Scanning electron microscopy demonstrates that laser ablation produces a hierarchical micro and nanostructure, and it is found that the structural anisotropy leads to spatially varying contact angles of water droplets residing on the surface. Raman spectra suggest that the centers of the laser-ablated tracks are carbonized; therefore, the loss of insulation can be responsible for the reduction of charge transfer.

  20. Hybridization-controlled charge transfer and induced magnetism at correlated oxide interfaces

    Science.gov (United States)

    Grisolia, M. N.; Varignon, J.; Sanchez-Santolino, G.; Arora, A.; Valencia, S.; Varela, M.; Abrudan, R.; Weschke, E.; Schierle, E.; Rault, J. E.; Rueff, J.-P.; Barthélémy, A.; Santamaria, J.; Bibes, M.

    2016-05-01

    At interfaces between conventional materials, band bending and alignment are classically controlled by differences in electrochemical potential. Applying this concept to oxides in which interfaces can be polar and cations may adopt a mixed valence has led to the discovery of novel two-dimensional states between simple band insulators such as LaAlO3 and SrTiO3. However, many oxides have a more complex electronic structure, with charge, orbital and/or spin orders arising from strong Coulomb interactions at and between transition metal and oxygen ions. Such electronic correlations offer a rich playground to engineer functional interfaces but their compatibility with the classical band alignment picture remains an open question. Here we show that beyond differences in electron affinities and polar effects, a key parameter determining charge transfer at correlated oxide interfaces is the energy required to alter the covalence of the metal-oxygen bond. Using the perovskite nickelate (RNiO3) family as a template, we probe charge reconstruction at interfaces with gadolinium titanate GdTiO3. X-ray absorption spectroscopy shows that the charge transfer is thwarted by hybridization effects tuned by the rare-earth (R) size. Charge transfer results in an induced ferromagnetic-like state in the nickelate, exemplifying the potential of correlated interfaces to design novel phases. Further, our work clarifies strategies to engineer two-dimensional systems through the control of both doping and covalence.

  1. Quantum-Classical Path Integral Simulation of Ferrocene-Ferrocenium Charge Transfer in Liquid Hexane.

    Science.gov (United States)

    Walters, Peter L; Makri, Nancy

    2015-12-17

    We employ the quantum-classical path integral methodology to simulate the outer sphere charge-transfer process of the ferrocene-ferrocenium pair in liquid hexane with unprecedented accuracy. Comparison of the simulation results to those obtained by mapping the solvent on an effective harmonic bath demonstrates the accuracy of linear response theory in this system. PMID:26673195

  2. Surface characterization and surface electronic structure of organic quasi-one-dimensional charge transfer salts

    DEFF Research Database (Denmark)

    Sing, M.; Schwingenschlögl, U.; Claessen, R.;

    2003-01-01

    We have thoroughly characterized the surfaces of the organic charge-transfer salts TTF-TCNQ and (TMTSF)(2)PF6 which are generally acknowledged as prototypical examples of one-dimensional conductors. In particular x-ray-induced photoemission spectroscopy turns out to be a valuable nondestructive d...

  3. Determination of Interfacial Charge-Transfer Rate Constants in Perovskite Solar Cells.

    Science.gov (United States)

    Pydzińska, Katarzyna; Karolczak, Jerzy; Kosta, Ivet; Tena-Zaera, Ramon; Todinova, Anna; Idígoras, Jesus; Anta, Juan A; Ziółek, Marcin

    2016-07-01

    A simple protocol to study the dynamics of charge transfer to selective contacts in perovskite solar cells, based on time-resolved laser spectroscopy studies, in which the effect of bimolecular electron-hole recombination has been eliminated, is proposed. Through the proposed procedure, the interfacial charge-transfer rate constants from methylammonium lead iodide perovskite to different contact materials can be determined. Hole transfer is faster for CuSCN (rate constant 0.20 ns(-1) ) than that for 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD; 0.06 ns(-1) ), and electron transfer is faster for mesoporous (0.11 ns(-1) ) than that for compact (0.02 ns(-1) ) TiO2 layers. Despite more rapid charge separation, the photovoltaic performance of CuSCN cells is worse than that of spiro-OMeTAD cells; this is explained by faster charge recombination in CuSCN cells, as revealed by impedance spectroscopy. The proposed direction of studies should be one of the key strategies to explore efficient hole-selective contacts as an alternative to spiro-OMeTAD. PMID:27253726

  4. NiO: correlated band structure of a charge-transfer insulator

    Czech Academy of Sciences Publication Activity Database

    Kuneš, Jan; Anisimov, V.I.; Skornyakov, S.L.; Lukoyanov, A.V.; Vollhardt, D.

    2007-01-01

    Roč. 99, č. 15 (2007), 156404/1-156404/4. ISSN 0031-9007 Institutional research plan: CEZ:AV0Z10100521 Keywords : band structure * dynamical mean field * charge transfer insulators Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.944, year: 2007

  5. Elastic, excitation, ionization and charge transfer cross sections of current interest in fusion energy research

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, D.R.; Krstic, P.S. [Oak Ridge National Lab. TN (United States). Physics Div.

    1997-01-01

    Due to the present interest in modeling and diagnosing the edge and divertor plasma regions in magnetically confined fusion devices, we have sought to provide new calculations regarding the elastic, excitation, ionization, and charge transfer cross sections in collisions among relevant ions, neutrals, and isotopes in the low-to intermediate-energy regime. We summarize here some of our recent work. (author)

  6. On the relation between local and charge-transfer exciton bindingenergies in organic photovoltaic materials

    NARCIS (Netherlands)

    de Gier, Hilde Dorothea; Braam, Henderika; Havenith, Remco

    2015-01-01

    In organic photovoltaic devices two types of excitons can be generated for which different binding energies can be defined: the binding energy of the local exciton generated immediately after light absorption on the polymer and the binding energy of the charge-transfer exciton generated through the

  7. Molecular orbital (SCF-Xα-SW) theory of metal-metal charge transfer processes in minerals

    Science.gov (United States)

    Sherman, David M.

    1987-01-01

    A number of mixed valence iron oxides and silicates (e.g., magnetite, ilvaite) exhibit thermally induced electron delocalization between adjacent Fe2+ and Fe3+ ions and optically induced electronic transitions which are assigned to Fe2+→Fe3+ intervalence charge transfer.

  8. Solvent-induced reversible solid-state colour change of an intramolecular charge-transfer complex.

    Science.gov (United States)

    Li, Ping; Maier, Josef M; Hwang, Jungwun; Smith, Mark D; Krause, Jeanette A; Mullis, Brian T; Strickland, Sharon M S; Shimizu, Ken D

    2015-10-11

    A dynamic intramolecular charge-transfer (CT) complex was designed that displayed reversible colour changes in the solid-state when treated with different organic solvents. The origins of the dichromatism were shown to be due to solvent-inclusion, which induced changes in the relative orientations of the donor pyrene and acceptor naphthalenediimide units. PMID:26299357

  9. Symmetry-breaking intramolecular charge transfer in the excited state of meso-linked BODIPY dyads

    KAUST Repository

    Whited, Matthew T.

    2012-01-01

    We report the synthesis and characterization of symmetric BODIPY dyads where the chromophores are attached at the meso position, using either a phenylene bridge or direct linkage. Both molecules undergo symmetry-breaking intramolecular charge transfer in the excited state, and the directly linked dyad serves as a visible-light-absorbing analogue of 9,9′-bianthryl.

  10. Behavior of charge-transfer absorption upon passing through the neutral-ionic phase transition

    DEFF Research Database (Denmark)

    Jacobsen, Claus Schelde; Torrance, J. B.

    1983-01-01

    The charge-transfer band is determined from reflectance measurements on single crystals of TTF-chloranil from 300 to 45 K, passing through the neutral-ionic phase transition at 84 K. As the temperature is decreased from 300 K toward the transition, hnuCT decreases slowly from 0.66 to 0.55 e...

  11. Mechanism and Dynamics of Charge Transfer in Donor-Bridge-Acceptor Systems

    NARCIS (Netherlands)

    Gorczak-Vos, N.

    2016-01-01

    Photoinduced charge transfer in organic materials is a fundamental process in various biological and technological areas. Donor-bridge-acceptor (DBA) molecules are used as model systems in numerous theoretical and experimental work to systematically study and unravel the underlying mechanisms of cha

  12. Enzymatic Catalysis of Proton Transfer and Decarboxylation Reactions

    OpenAIRE

    Richard, John P.

    2011-01-01

    Deprotonation of carbon and decarboxylation at enzyme active sites proceed through the same carbanion intermediates as for the uncatalyzed reactions in water. The mechanism for the enzymatic reactions can be studied at the same level of detail as for nonenzymatic reactions, using the mechanistic tools developed by physical organic chemists. Triosephosphate isomerase (TIM) catalyzed interconversion of D-glyceraldehyde 3-phosphate and dihydroxyacetone phosphate is being studied as a prototype f...

  13. Charge-changing reactions of secondary fragments produced in high-energy heavy ion collisions

    International Nuclear Information System (INIS)

    The authors have begun a program to measure charge changing cross sections of projectile fragments using a quite different technique that is capable of much higher data acquisition rates. The primary beam impinges on a stack of 50 Lucite strips having an average thickness of 3.17 mm, emitting Cerenkov light as its passes through them. Since at a given velocity the intensity of light is proportional to Z2, where Z is the charge of the particle, a fragmentation reaction in a particular strip will be registered as a drop in the light output from that and subsequent strips. The authors use total internal reflection to transport the light to photomultiplier tubes so that there is no wrapping between the strips. Since the energy threshold of the device is approx.1.1 GeV/nucleon, low energy target fragments will not contribute to the signal, a distinct advantage over similar schemes using energy loss to measure the fragment charge. The resolution of the individual strips is typically 0.58 charge units, full width at half maximum, allowing reactions to be well localized even for single unit charge changes. In addition to the C detectors, scintillators and Si(Li) detectors were used to measure precisely the position and charge of the incoming beam particle. The authors have taken data using two beams, 56Fe and 40Ar, at 1.88 and 1.82 GeV/nucleon respectively, and two trigger modes, a free trigger to measure the reaction rate of the incoming beam and an inelastic trigger in which a reaction was required to occur in one of the first 14 C detectors. A total of 909,000 56Fe interactions and 460,000 40Ar interactions have been analyzed so far

  14. Spectrofluorimetric study of the charge-transfer complexation of certain fluoroquinolones with 7,7,8,8-tetracyanoquinodimethane

    Science.gov (United States)

    Du, Li Ming; Yao, Hai Yan; Fu, Mi

    2005-01-01

    Simple, rapid and sensitive spectrofluorimetric methods are described, for the first time, for the determination of ciprofloxacin (CIP), norfloxacin (NOR), pefloxacin (PEF) and fleroxacin (FLE). The methods are based on the charge-transfer (CT) reaction of these drugs as n-electron donors with 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-electron acceptor. TCNQ was found to react with these drugs to produce intensely transfer reaction complexes and the fluorescence intensity of the complexes was enhanced in 21-35 fold higher than that of the studied fluoroquinolones itself. The formation of such complexes was also confirmed by both infrared and ultraviolet-visible measurements. The different experimental parameters that affect the fluorescence intensity were carefully studied. At the optimum reaction conditions, the drug-TCNQ complexes showed excitation maxima ranging from 277 to 284 nm and emission maxima ranging from 451 to 458 nm. Rectilinear calibration graphs were obtained in the concentration range of 0.03-0.9, 0.04-1.2, 0.04-1.3 and 0.08-2.4 μg ml -1 for CIP, NOR, PEF and FLE, respectively. The developed methods were applied successfully for the determination of the studied drugs in their pharmaceutical dosage forms with a good precision and accuracy compared to official and reported methods as revealed by t- and F-tests.

  15. Reaction mechanism and nuclear correlations study by low energy pion double charge exchange

    International Nuclear Information System (INIS)

    In pion double-charge-exchange (DCX) reactions, a positive (negative) pion is incident on a nucleus and a negative (positive) pion emerges. These reactions are of fundamental interest since the process must involve at least two nucleons in order to conserve charge. Although two nucleon processes are present in many reactions they are usually masked by the dominant single nucleon processes. DCX is unique in that respect since it is a two nucleon process in lowest order and thus may be sensitive to two-nucleon correlations. Measurements of low energy pion double-charge-exchange reactions to the double-isobaric-analog-state (DIAS) and ground-state (GS) of the residual nucleus provide new means for studying nucleon-nucleon correlations in nuclei. At low energies (Tπ 7/2 shell at energies ranging from 25 to 65 MeV. Cross sections were measured on 42,44,48Ca, 46,50Ti and 54Fe. The calcium isotopes make a good set of nuclei on which to study the effects of correlations in DCX reactions

  16. Ultrafast charge transfer in MoS2/WSe2 p–n Heterojunction

    Science.gov (United States)

    Peng, Bo; Yu, Guannan; Liu, Xinfeng; Liu, Bo; Liang, Xiao; Bi, Lei; Deng, Longjiang; Chien Sum, Tze; Loh, Kian Ping

    2016-06-01

    Atomically thin and sharp van der Waals heterojunction can be created by vertically stacking p-type monolayer tungsten diselenide (WSe2) onto n-type molybdenum disulfide (MoS2). Theory predicts that stacked MoS2 and WSe2 monolayer forms type II p–n junction, creating a built-in electric field across the interface which facilitates electron–hole separation and transfer. Gaining insights into the dynamics of charge transfer across van der Waals heterostructure is central to understanding light-photocurrent conversion at these ultrathin interfaces. Herein, we investigate the exciton dissociation and charge transfer in a MoS2/WSe2 van der Waals hetero-structure. Our results show that ultrafast electron transfer from WSe2 to MoS2 take place within 470 fs upon optical excitation with 99% charge transfer efficiency, leading to drastic photoluminescence quenching and decreased lifetime. Our findings suggest that van der Waals heterostructure may be useful as active components in ultrafast optoelectronic devices.

  17. Electron capture rates in stars studied with heavy ion charge exchange reactions

    CERN Document Server

    Bertulani, C A

    2015-01-01

    Indirect methods using nucleus-nucleus reactions at high energies (here, high energies mean $\\sim$ 50 MeV/nucleon and higher) are now routinely used to extract information of interest for nuclear astrophysics. This is of extreme relevance as many of the nuclei involved in stellar evolution are short-lived. Therefore, indirect methods became the focus of recent studies carried out in major nuclear physics facilities. Among such methods, heavy ion charge exchange is thought to be a useful tool to infer Gamow-Teller matrix elements needed to describe electron capture rates in stars and also double beta-decay experiments. In this short review, I provide a theoretical guidance based on a simple reaction model for charge exchange reactions.

  18. Measurement and study of the differential cross section variations corresponding to the n+p→p+n charge exchange reaction between 1 and 2GeV/c

    International Nuclear Information System (INIS)

    Twenty one differential cross section measurements for the np→pn charge exchange reaction have been carried out at the synchrotron Saturne (Saclay) for incident neutron momenta between 1 and 2GeV/c by step of 50MeV/c and in the squared four momentum transfer range 02. The results show that the mechanism of π exchange in the t-channel is clearly present at all the incident momenta; that is confirmed by the agreement with the ''poor man's absorption'' model, based on π exchange, in the range 02. The s dependence of the charge exchange peak shows weak structures which can be associated with the opening of the inelastic channel NΔ(1236) and NN*(1400). The results of an analysis of a set of np→pn amplitudes constructed from NN helicity amplitudes confirm that the π exchange in the t-channel is dominant in the charge exchange reaction

  19. Charge state distribution of 16O from the 4He(12C,16O)γ reaction of astrophysical interest studied both experimentally and theoretically

    International Nuclear Information System (INIS)

    In astrophysics, 4He(12C,16O)γ reaction places an important role. At Kyushu University Tandem accelerator Laboratory (KUTL), the measurement of 4He(12C,16O)γ cross section is in progress in the energy range of astrophysical nuclear reaction. Since the charge state of product 16O ions after passing through the gas target is spread and only one charge state can be measured at terminal detector, it is necessary to know the charge state distribution of 16O ions passing through the He gas target precisely. Here, we report the charge state distribution of the 16O recoils both experimentally and theoretically. Experimentally, we measured the equilibrium charge state distribution of 16O ions in the windowless helium gas target with the beam energy of primary 16O ions at 7.2, 4.5, and 3.45 MeV at KUTL. The measured results showed a Gaussian distribution for the charge state fraction. Theoretically, we proposed a framework for the charge state distribution study. Charge state distribution was computed by solving a set of differential equations including a series of charge exchange cross sections. For the ionization cross section, plane-wave Born approximation was applied and modified by taking target atomic screening as a function of momentum transfer into account. For the capture cross section, continuum distorted wave approximation was applied and the influence of the gas target density was taken into account in the process of electron capture. Using above charge exchange cross sections, the charge state evolution was simulated. According to the equilibrium distribution, we compared the theoretical calculation to the experimental data. After taking into account the density effects in the charge exchange process, the theoretical charge state distributions shows a good agreement with the experimental data. Both experimental and theoretical results are useful to understand the charge fraction of recoil oxygen created via 4He(12C,16O)γ reaction, especially in the energy

  20. Observation of the one- to six-neutron transfer reactions at sub-barrier energies

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, C.L.; Rehm, K.E.; Gehring, J. [and others

    1995-08-01

    It was suggested many years ago that when two heavy nuclei are in contact during a grazing collision, the transfer of several correlated neutron-pairs could occur. Despite considerable experimental effort, however, so far only cross sections for up to four-neutron transfers have been uniquely identified. The main difficulties in the study of multi-neutron transfer reactions are the small cross sections encountered at incident energies close to the barrier, and various experimental uncertainties which can complicate the analysis of these reactions. We have for the first time found evidence for multi-neutron transfer reactions covering the full sequence from one- to six-neutron transfer reactions at sub-barrier energies in the system {sup 58}Ni + {sup 100}Mo.

  1. Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique

    Directory of Open Access Journals (Sweden)

    Izhal Abdul Halin

    2009-11-01

    Full Text Available The partial charge transfer technique can expand the dynamic range of a CMOS image sensor by synthesizing two types of signal, namely the long and short accumulation time signals. However the short accumulation time signal obtained from partial transfer operation suffers of non-linearity with respect to the incident light. In this paper, an analysis of the non-linearity in partial charge transfer technique has been carried, and the relationship between dynamic range and the non-linearity is studied. The results show that the non-linearity is caused by two factors, namely the current diffusion, which has an exponential relation with the potential barrier, and the initial condition of photodiodes in which it shows that the error in the high illumination region increases as the ratio of the long to the short accumulation time raises. Moreover, the increment of the saturation level of photodiodes also increases the error in the high illumination region.

  2. Charge-transfer dynamics in multilayered PbS and PbSe quantum dot architectures

    International Nuclear Information System (INIS)

    We demonstrate control of the charge transfer process in PbS and PbSe quantum dot assemblies. We first demonstrate efficient charge transfer from donor quantum dots to acceptor quantum dots in a multi-layer PbSe cascade structure. Then, we assemble type-I and type-II heterostructures using both PbS and PbSe quantum dots via careful control of the band alignment. In type-I structures, photo-generated carriers are transferred and localized in the smaller bandgap (acceptor) quantum dots, resulting in a significant luminescence enhancement. In contrast, a significant luminescence quenching and shorter emission lifetime confirms an efficient separation of photo-generated carriers in the type-II architecture

  3. Broadband Tunable Microlasers Based on Controlled Intramolecular Charge-Transfer Process in Organic Supramolecular Microcrystals.

    Science.gov (United States)

    Dong, Haiyun; Wei, Yanhui; Zhang, Wei; Wei, Cong; Zhang, Chunhuan; Yao, Jiannian; Zhao, Yong Sheng

    2016-02-01

    Wavelength tunable micro/nanolasers are indispensable components for various photonic devices. Here, we report broadband tunable microlasers built by incorporating a highly polarized organic intramolecular charge-transfer (ICT) compound with a supramolecular host. The spatial confinement of the ICT dye generates an optimized energy level system that favors controlled population distribution between the locally excited (LE) state and the twisted intramolecular charge-transfer (TICT) state, which is beneficial for significantly broadening the tailorable gain region. As a result, we realized a wide tuning of lasing wavelength in the organic supramolecular microcrystals based on temperature-controlled population transfer from the LE to TICT state. The results will provide a useful enlightenment for the rational design of miniaturized lasers with desired performances. PMID:26756966

  4. Angular momentum transfer and equilibrium in heavy-ion reactions

    International Nuclear Information System (INIS)

    By concentrating on the microscopic degrees of freedom for two colliding ions, we have derived a probability density for angular momentum transfer assuming that, for equilibrium, this probability is proportional to the density of states taken from a fermi gas model. This density has been used to predict angular momentum transfer, assuming first, initial angular momentum fixed, and then, final energy fixed. The results are quite different. The density (final energy fixed) has been used to predict the results of angular momentum transfer experiments. The excellent agreement supports the validity of an assumption of equilibrium. (author)

  5. Charge and energy transfer interplay in hybrid sensitized solar cells mediated by graphene quantum dots

    International Nuclear Information System (INIS)

    Highlights: • We report a one pot synthesis metod of GQD with controlled size and optoelectronic properties. • An improvement of common N3-DSSC characteristics is achieved when GQDs are used as co-sensitiser. • The role of GQD as cosensitisers in hybrid DSSC was investigated and the interplay between charge and energy transfer phenomena mediated by GQDs was demonstrated. • The GQDs presence determines an inhibition of the recombination processes at the TiO2/electrolyte interface. - Abstract: We explored the role of graphene quantum dots (GQDs) as co-sensitizers in hybrid dye sensitized solar cell (DSSC) architectures, focusing on various concurring mechanisms, such as: charge transfer, energy transfer and recombination rate, towards light harvesting improvement. GQDs were prepared by the hydrothermal method that allows the tuning of electronic levels and optical properties by employing appropriate precursors and synthesis conditions. The aim was to realize a type II alignment for TiO2/GQD/dye hybrid configuration, using standard N3 Ru-dye in order to improve charge transfer. When GQDs were used as co-sensitizers together with N3 Ru-dye, an improvement in power conversion efficiency was achieved, as shown by electrical measurements. The experimental analysis indicates that this improvement arises from the interplay of various mechanisms mediated by GQDs: (i) enhancement of charge separation and collection due to the cascaded alignment of the energy levels; (ii) energy transfer from GQDs to N3 Ru-dye due to the overlap between GQD photoluminescence and N3 Ru-dye absorption spectra; and (iii) reduction of the electron recombination to the redox couple due to the inhibition of the back electron transfer to the electrolyte by the GQDs

  6. Antiproton small momentum transfer charge exchange scattering on protons at 30 GeV/c

    International Nuclear Information System (INIS)

    Antiproton charge exchange scattering on protons anti pp→anti nn is investigated with 30 GeV/c antiprotons at the IHEP accelerator. The experiment confirms the existence of a structure at small angles in the angular distribution of this reaction at high energies, observed earlier

  7. Photosynthetic reaction center mimicry: low reorganization energy driven charge stabilization in self-assembled cofacial zinc phthalocyanine dimer-fullerene conjugate.

    Science.gov (United States)

    D'Souza, Francis; Maligaspe, Eranda; Ohkubo, Kei; Zandler, Melvin E; Subbaiyan, Navaneetha K; Fukuzumi, Shunichi

    2009-07-01

    By employing well-defined self-assembly methods, a biomimetic bacterial photosynthetic reaction center complex has been constructed, and photoinduced electron transfer originating in this supramolecular donor-acceptor conjugate has been investigated. The biomimetic model of the bacterial "special pair" donor, a cofacial zinc phthalocyanine dimer, was formed via potassium ion induced dimerization of 4,5,4',5',4'', 5'',4''',5'''-zinc tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyanine. The dimer was subsequently self-assembled with functionalized fullerenes via "two-point" binding involving axial coordination and crown ether-alkyl ammonium cation complexation to form the donor-acceptor pair, mimicking the noncovalently bound entities of the bacterial photosynthetic reaction center. The adopted self-assembly methodology yielded a supramolecular complex of higher stability with defined geometry and orientation as revealed by the binding constant and computational optimized structure. Unlike the previously reported porphyrin analog, the present phthalocyanine macrocycle based model system exhibited superior electron-transfer properties including formation of a long-lived charge-separated state, a key step of the photosynthetic light energy conversion process. Detailed analysis of the kinetic data in light of the Marcus theory of electron transfer revealed that small reorganization energy of the relatively rigid phthalocyanine is primarily responsible for slower charge-recombination process. The importance of the cofacial dimer in stabilizing the charge-separated state is borne out in the present all-supramolecular "reaction center" donor-acceptor mimic. PMID:19505071

  8. Synthetic system mimicking the energy transfer and charge separation of natural photosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Gust, D.; Moore, T.A.

    1985-05-01

    A synthetic molecular triad consisting of a porphyrin P linked to both a quinone Q and a carotenoid polyene C has been prepared as a mimic of natural photosynthesis for solar energy conversion purposes. Laser flash excitation of the porphyrin moiety yields a charge-separated state Csup(+.)-P-Qsup(-.) within 100 ps with a quantum yield of more than 0.25. This charge-separated state has a lifetime on the microsecond time scale in suitable solvents. The triad also models photosynthetic antenna function and photoprotection from singlet oxygen damge. The successful biomimicry of photosynthetic charge separation is in part the result of multistep electron transfers which rapidly separate the charges and leave the system at high potential, but with a considerable barrier to recombination.

  9. Electroluminescence from charge transfer states in Donor/Acceptor solar cells

    DEFF Research Database (Denmark)

    Sherafatipour, Golenaz; Madsen, Morten

    Charge photocurrent generation is a key process in solar energy conversion systems. Effective dissociation of the photo-generated electron-hole pairs (excitons) has a strong influence on the efficiency of the organic solar cells. Charge dissociation takes place at the donor/acceptor interface via...... donor/acceptor interface is detected. As a less studied system, we examine here the interfacial charge transfer state recombination in DBP:C70 thin-films. The weak EL from the small molecule solar cell biased in the forward direction gives valuable information about the CT state recombination, from......-generated charges is a major limitation for the efficiency of the organic solar cells, a thorough understanding of this loss mechanism is crucial to improve the performance of the devices. Furthermore, examining this interfacial state is of great importance in order to maximize open-circuit voltage and photocurrent...

  10. Application of a BOSS-Gaussian interface for QM/MM simulations of Henry and methyl transfer reactions.

    Science.gov (United States)

    Vilseck, Jonah Z; Kostal, Jakub; Tirado-Rives, Julian; Jorgensen, William L

    2015-10-15

    Hybrid quantum mechanics and molecular mechanics (QM/MM) computer simulations have become an indispensable tool for studying chemical and biological phenomena for systems too large to treat with QM alone. For several decades, semiempirical QM methods have been used in QM/MM simulations. However, with increased computational resources, the introduction of ab initio and density function methods into on-the-fly QM/MM simulations is being increasingly preferred. This adaptation can be accomplished with a program interface that tethers independent QM and MM software packages. This report introduces such an interface for the BOSS and Gaussian programs, featuring modification of BOSS to request QM energies and partial atomic charges from Gaussian. A customizable C-shell linker script facilitates the interprogram communication. The BOSS-Gaussian interface also provides convenient access to Charge Model 5 (CM5) partial atomic charges for multiple purposes including QM/MM studies of reactions. In this report, the BOSS-Gaussian interface is applied to a nitroaldol (Henry) reaction and two methyl transfer reactions in aqueous solution. Improved agreement with experiment is found by determining free-energy surfaces with MP2/CM5 QM/MM simulations than previously reported investigations using semiempirical methods. PMID:26311531

  11. Thermodynamic chemical energy transfer mechanisms of non-equilibrium, quasi-equilibrium, and equilibrium chemical reactions

    International Nuclear Information System (INIS)

    Chemical energy transfer mechanisms at finite temperature are explored by a chemical energy transfer theory which is capable of investigating various chemical mechanisms of non-equilibrium, quasi-equilibrium, and equilibrium. Gibbs energy fluxes are obtained as a function of chemical potential, time, and displacement. Diffusion, convection, internal convection, and internal equilibrium chemical energy fluxes are demonstrated. The theory reveals that there are chemical energy flux gaps and broken discrete symmetries at the activation chemical potential, time, and displacement. The statistical, thermodynamic theory is the unification of diffusion and internal convection chemical reactions which reduces to the non-equilibrium generalization beyond the quasi-equilibrium theories of migration and diffusion processes. The relationship between kinetic theories of chemical and electrochemical reactions is also explored. The theory is applied to explore non-equilibrium chemical reactions as an illustration. Three variable separation constants indicate particle number constants and play key roles in describing the distinct chemical reaction mechanisms. The kinetics of chemical energy transfer accounts for the four control mechanisms of chemical reactions such as activation, concentration, transition, and film chemical reactions. - Highlights: • Chemical energy transfer theory is proposed for non-, quasi-, and equilibrium. • Gibbs energy fluxes are expressed by chemical potential, time, and displacement. • Relationship between chemical and electrochemical reactions is discussed. • Theory is applied to explore nonequilibrium energy transfer in chemical reactions. • Kinetics of non-equilibrium chemical reactions shows the four control mechanisms

  12. Study of intermediates from transition metal excited-state electron-transfer reactions

    Science.gov (United States)

    Hoffman, M. Z.

    1992-07-01

    Conventional and fast-kinetics techniques of photochemistry, photophysics, radiation chemistry, and electrochemistry were used to study the intermediates involved in transition metal excited-state electron-transfer reactions. These intermediates were excited state of Ru(II) and Cr(III) photosensitizers, their reduced forms, and species formed in reactions of redox quenchers and electron-transfer agents. Of particular concern was the back electron-transfer reaction between the geminate pair formed in the redox quenching of the photosensitizers, and the dependence of its rate on solution medium and temperature in competition with transformation and cage escape processes.

  13. Charge Transfer and Triplet States in High Efficiency OPV Materials and Devices

    Science.gov (United States)

    Dyakonov, Vladimir

    2013-03-01

    The advantage of using polymers and molecules in electronic devices, such as light-emitting diodes (LED), field-effect transistors (FET) and, more recently, solar cells (SC) is justified by the unique combination of high device performance and processing of the semiconductors used. Power conversion efficiency of nanostructured polymer SC is in the range of 10% on lab scale, making them ready for up-scaling. Efficient charge carrier generation and recombination in SC are strongly related to dissociation of the primary singlet excitons. The dissociation (or charge transfer) process should be very efficient in photovoltaics. The mechanisms governing charge carrier generation, recombination and transport in SC based on the so-called bulk-heterojunctions, i.e. blends of two or more semiconductors with different electron affinities, appear to be very complex, as they imply the presence of the intermediate excited states, neutral and charged ones. Charge transfer states, or polaron pairs, are the intermediate states between free electrons/holes and strongly bound excitons. Interestingly, the mostly efficient OLEDs to date are based on the so-called triplet emitters, which utilize the triplet-triplet annihilation process. In SC, recent investigations indicated that on illumination of the device active layer, not only mobile charges but also triplet states were formed. With respect to triplets, it is unclear how these excited states are generated, via inter-system crossing or via back transfer of the electron from acceptor to donor. Triplet formation may be considered as charge carrier loss channel; however, the fusion of two triplets may lead to a formation of singlet excitons instead. In such case, a generation of charges by utilizing of the so far unused photons will be possible. The fundamental understanding of the processes involving the charge transfer and triplet states and their relation to nanoscale morphology and/or energetics of blends is essential for the

  14. A molecular dynamics study of intramolecular proton transfer reaction of malonaldehyde in solutions based upon mixed quantum-classical approximation. I. Proton transfer reaction in water

    International Nuclear Information System (INIS)

    In order to investigate proton transfer reaction in solution, mixed quantum-classical molecular dynamics calculations have been carried out based on our previously proposed quantum equation of motion for the reacting system [A. Yamada and S. Okazaki, J. Chem. Phys. 128, 044507 (2008)]. Surface hopping method was applied to describe forces acting on the solvent classical degrees of freedom. In a series of our studies, quantum and solvent effects on the reaction dynamics in solutions have been analysed in detail. Here, we report our mixed quantum-classical molecular dynamics calculations for intramolecular proton transfer of malonaldehyde in water. Thermally activated proton transfer process, i.e., vibrational excitation in the reactant state followed by transition to the product state and vibrational relaxation in the product state, as well as tunneling reaction can be described by solving the equation of motion. Zero point energy is, of course, included, too. The quantum simulation in water has been compared with the fully classical one and the wave packet calculation in vacuum. The calculated quantum reaction rate in water was 0.70 ps−1, which is about 2.5 times faster than that in vacuum, 0.27 ps−1. This indicates that the solvent water accelerates the reaction. Further, the quantum calculation resulted in the reaction rate about 2 times faster than the fully classical calculation, which indicates that quantum effect enhances the reaction rate, too. Contribution from three reaction mechanisms, i.e., tunneling, thermal activation, and barrier vanishing reactions, is 33:46:21 in the mixed quantum-classical calculations. This clearly shows that the tunneling effect is important in the reaction

  15. Excitation Functions for Charged Particle Induced Reactions in Light Elements at Low Projectile Energies

    International Nuclear Information System (INIS)

    The present chapter has been formulated with the aim of making it useful in various fields of nuclear applications with emphasis on charged particle activation analysis. Activation analysis of light elements using charged particles has proved to be an important tool in solving various problems in analytical chemistry, e g those associated with metal surfaces. Scientists desiring to evaluate the distribution of light elements in the surface of various matrices using charged particle reactions require accurate data on cross sections in the MeV-region. A knowledge of cross section data and yield-functions is of great interest in many applied fields involving work with charged particles, such as radiological protection and health physics, material research, semiconductor material investigations and corrosion chemistry. The authors therefore decided to collect a limited number of data which find use in these fields. Although the compilation is far from being complete, it is expected to be of assistance in devising measurements of charged particle reactions in Van de Graaff or other low energy accelerators

  16. Intermolecular electron transfer from intramolecular excitation and coherent acoustic phonon generation in a hydrogen-bonded charge-transfer solid.

    Science.gov (United States)

    Rury, Aaron S; Sorenson, Shayne; Dawlaty, Jahan M

    2016-03-14

    Organic materials that produce coherent lattice phonon excitations in response to external stimuli may provide next generation solutions in a wide range of applications. However, for these materials to lead to functional devices in technology, a full understanding of the possible driving forces of coherent lattice phonon generation must be attained. To facilitate the achievement of this goal, we have undertaken an optical spectroscopic study of an organic charge-transfer material formed from the ubiquitous reduction-oxidation pair hydroquinone and p-benzoquinone. Upon pumping this material, known as quinhydrone, on its intermolecular charge transfer resonance as well as an intramolecular resonance of p-benzoquinone, we find sub-cm(-1) oscillations whose dispersion with probe energy resembles that of a coherent acoustic phonon that we argue is coherently excited following changes in the electron density of quinhydrone. Using the dynamical information from these ultrafast pump-probe measurements, we find that the fastest process we can resolve does not change whether we pump quinhydrone at either energy. Electron-phonon coupling from both ultrafast coherent vibrational and steady-state resonance Raman spectroscopies allows us to determine that intramolecular electronic excitation of p-benzoquinone also drives the electron transfer process in quinhydrone. These results demonstrate the wide range of electronic excitations of the parent of molecules found in many functional organic materials that can drive coherent lattice phonon excitations useful for applications in electronics, photonics, and information technology. PMID:26979698

  17. Charge separation in Rhodobacter sphaeroides mutant reaction centers with increased midpoint potential of the primary electron donor.

    Science.gov (United States)

    Khmelnitskiy, A Yu; Khatypov, R A; Khristin, A M; Leonova, M M; Vasilieva, L G; Shuvalov, V A

    2013-01-01

    Primary charge separation dynamics in four mutant reaction centers (RCs) of the purple bacterium Rhodobacter sphaeroides with increased midpoint potential of the primary electron donor P (M160LH, L131LH, M197FH, and M160LH + L131LH + M197FH) have been studied by femtosecond transient absorption spectroscopy at room temperature. The decay of the excited singlet state in the wild-type and mutant RCs is complex and has two main exponential components, which indicates heterogeneity of electron transfer rates or the presence of reverse electron transfer reactions. The radical anion band of monomeric bacteriochlorophyll B(A) at 1020 nm was first observed in transient absorbance difference spectra of single mutants. This band remains visible, although with somewhat reduced amplitude, even at delays up to tens of picoseconds when stimulated emission is absent and the reaction centers are in the P(+)H(A)(-) state. The presence of this band in this time period indicates the existence of thermodynamic equilibrium between the P(+)B(A)(-)H(A) and P(+)B(A)H(A)(-) states. The data give grounds for assuming that the value of the energy difference between the states P*, P(+)B(A)(-)H(A), and P(+)B(A)H(A)(-) at early times is of the same order of magnitude as the energy kT at room temperature. Besides, monomeric bacteriochlorophyll B(A) is found to be an immediate electron acceptor in the single mutant RCs, where electron transfer is hampered due to increased energy of the P(+)B(A)(-) state with respect to P*. PMID:23379560

  18. Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

    International Nuclear Information System (INIS)

    The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na+ and K+ ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications

  19. Site-specific probing of charge transfer dynamics in organic photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Arion, Tiberiu; Roth, Friedrich [Center for Free-Electron Laser Science/DESY, Notkestraße 85, D-22607 Hamburg (Germany); Neppl, Stefan; Shavorskiy, Andrey; Bluhm, Hendrik; Gessner, Oliver [Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Hussain, Zahid [ALS, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Eberhardt, Wolfgang [Center for Free-Electron Laser Science/DESY, Notkestraße 85, D-22607 Hamburg (Germany); ALS, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Institute of Optics and Atomic Physics, TU Berlin, Straße des 17. Juni 135, D-10623 Berlin (Germany)

    2015-03-23

    We report the site-specific probing of charge-transfer dynamics in a prototype system for organic photovoltaics (OPVs) by picosecond time-resolved X-ray photoelectron spectroscopy. A layered system consisting of approximately two monolayers of C{sub 60} deposited on top of a thin film of Copper-Phthalocyanine (CuPC) is excited by an optical pump pulse and the induced electronic dynamics are probed with 590 eV X-ray pulses. Charge transfer from the electron donor (CuPC) to the acceptor (C{sub 60}) and subsequent charge carrier dynamics are monitored by recording the time-dependent C 1s core level photoemission spectrum of the system. The arrival of electrons in the C{sub 60} layer is readily observed as a completely reversible, transient shift of the C{sub 60} associated C 1s core level, while the C 1s level of the CuPC remains unchanged. The capability to probe charge transfer and recombination dynamics in OPV assemblies directly in the time domain and from the perspective of well-defined domains is expected to open additional pathways to better understand and optimize the performance of this emerging technology.

  20. Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Yi; Berkowitz, Max L., E-mail: maxb@unc.edu, E-mail: ykanai@unc.edu; Kanai, Yosuke, E-mail: maxb@unc.edu, E-mail: ykanai@unc.edu [Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (United States)

    2015-12-28

    The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na{sup +} and K{sup +} ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.

  1. Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

    Science.gov (United States)

    Yao, Yi; Berkowitz, Max L.; Kanai, Yosuke

    2015-12-01

    The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na+ and K+ ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.

  2. Dynamics in charge transfer and ionization processes in fast ion-helium collisions

    International Nuclear Information System (INIS)

    In the course of this work transfer ionization (TI), radiative electron capture (REC), and single ionization (SI) in fast ion-helium collisions have been studied. For this purpose, two experimental techniques, a coincident ion-electron momentum spectrometer, namely a Reaction Microscope (REMI) and the heavy ion storage ring TSR, providing excellent beam properties, have been combined. In TI, i.e. the ejection of one plus the capture of a second target electron, the role of electron-electron correlations is of particular interest. In order to unravel different correlated as well as uncorrelated mechanisms, differential data has been recorded for different perturbations (projectile charge to speed ratio). For the first time strong evidence of a recently proposed, correlated TI process was found experimentally. In a second, pioneering experiment it has been attempted to perform the first kinematically complete measurement on REC. Here, an electron from the target is captured by the projectile simultaneously emitting a photon. In order to observe the emerging photons, a detector covering a large solid angle has been designed and implemented in the REMI. Although three particle coincidences have been recorded between recoil ions, projectile ions, and photons, experimental proof of the acquisition of REC coincidences was prevented due to limited statistics. Finally, in studies on SI, the influence of the projectile beam coherence properties on the collision dynamics has been investigated. The pronounced differences to earlier data taken with a projectile beam with much smaller coherence length provide evidence for its influence on the ionization dynamics, which is generally neglected in theoretical calculations. These results could pave the way to a final resolution of the long standing question on the origin of the discrepancies between theory and experiment in fully differential cross sections.

  3. Synthesis, characterization, crystal structure and solution studies of a novel proton transfer (charge transfer) complex of 2,2‧-dipyridylamine with 2,6-pyridine dicarboxylic acid

    Science.gov (United States)

    Ghasemi, Khaled; Rezvani, Ali Reza; Shokrollahi, Ardeshir; Zarghampour, Fereshteh; Moghimi, Abolghasem; García-Granda, Santiago; Mendoza-Meroño, Rafael

    2015-06-01

    Reaction between 2,2‧-dipyridylamine (DPA) and 2,6-pyridine dicarboxylic acid (dipicolinic acid, dipicH2), in water results in the formation of a proton transfer or charge transfer (CT) complex, (DPAH)+(dipicH)-·H2O, 1. The characterization was performed using 1H NMR and FTIR spectroscopy, elemental analysis and X-ray crystallography. The crystal system is triclinic with space group P1. The structural investigations exhibit that the hydrogen bonds and π-π stacking interactions stabilize the crystal structure of proton transfer complex. The protonation constants of 2,6-pyridine dicarboxylic acid, 2,2‧-dipyridylamine and the equilibrium constants for dipic-DPA (1:1) proton transfer system were calculated by potentiometric pH titration method using Hyperquad2008 program. The stoichiometries of the proton transfer species in solution was in agreement with the solid state result.

  4. Mass and charge transfer on various relevant scales in polymer electrolyte fuel cells[Dissertation 16991

    Energy Technology Data Exchange (ETDEWEB)

    Freunberger, S. A.

    2007-07-01

    This dissertation is concerned with the development, experimental diagnostics and mathematical modelling and simulation of polymer electrolyte fuel cells (PEFC). The central themes throughout this thesis are the closely interlinked phenomena of mass and charge transfer. In the face of developing a PEFC system for vehicle propulsion these phenomena are scrutinized on a broad range of relevant scales. Starting from the material related level of the membrane and the gas diffusion layer (GDL) we turn to length scales, where structural features of the cell additionally come into play. These are the scale of flow channels and ribs, the single cell and the cell stack followed by the cell, stack, and system development for an automotive power train. In Chapter 3 selected fundamental material models and properties, respectively, are explored that are crucial for the mathematical modelling and simulation of PEFC, as needed in some succeeding parts of this work. First, established mathematical models for mass and charge transfer in the membrane are compared within the framework of the membrane electrode assembly (MEA), which represents the electrochemical unit. Second, reliable values for effective diffusivities in the GDLs which are vital for the simulation of gaseous mass transport are measured. Therefore, a method is developed that allows measuring this quantity both as a function of compression and direction as this is a prerequisite of sophisticated more-dimensional numerical PEFC-models. Besides the cross section of the catalyst layer (CL) mass transfer under channels and ribs is considered as a major source of losses in particular under high load operation. As up to now there have been solely non-validated theoretical investigations, in Chapter 4 an experimental method is developed that is for the first time capable of resolving the current density distribution on the this scale. For this, the electron conductors in the cell are considered as 2-dimensional shunt

  5. Coarse-Grained Theory of Biological Charge Transfer with Spatially and Temporally Correlated Noise.

    Science.gov (United States)

    Liu, Chaoren; Beratan, David N; Zhang, Peng

    2016-04-21

    System-environment interactions are essential in determining charge-transfer (CT) rates and mechanisms. We developed a computationally accessible method, suitable to simulate CT in flexible molecules (i.e., DNA) with hundreds of sites, where the system-environment interactions are explicitly treated with numerical noise modeling of time-dependent site energies and couplings. The properties of the noise are tunable, providing us a flexible tool to investigate the detailed effects of correlated thermal fluctuations on CT mechanisms. The noise is parametrizable by molecular simulation and quantum calculation results of specific molecular systems, giving us better molecular resolution in simulating the system-environment interactions than sampling fluctuations from generic spectral density functions. The spatially correlated thermal fluctuations among different sites are naturally built-in in our method but are not readily incorporated using approximate spectral densities. Our method has quantitative accuracy in systems with small redox potential differences (charge delocalization and charge-transfer rates; however, in a system of units with different site energies, spatial correlations slow the fluctuations to bring units into degeneracy, in turn, slowing the charge-transfer rates. The spatial and temporal correlations of condensed phase medium fluctuations provide another source to control and tune the kinetics and dynamics of charge-transfer systems. PMID:27008541

  6. Decellular biological scaffold polymerized with PEDOT for improving peripheral nerve interface charge transfer.

    Science.gov (United States)

    Frost, Christopher M; Cederna, Paul S; Martin, David C; Shim, Bong Sup; Urbanchek, Melanie G

    2014-01-01

    Regenerative peripheral nerve interfaces (RPNIs) are for signal transfer between peripheral nerves inside the body to controllers for motorized prosthetics external to the body. Within the residual limb of an amputee, surgical construction of a RPNI connects a remaining peripheral nerve and spare muscle. Nerve signals become concentrated within the RPNI. Currently metal electrodes implanted on the RPNI muscle transfer signals but scarring around metal electrodes progressively diminishes charge transfer. Engineered materials may benefit RPNI signal transfer across the neural interface if they lower the power and charge density of the biologically meaningful signals. Poly3,4-ethylenedioxythiophene (PEDOT) is known to mediate ionic potentials allowing excitation across a critical nerve gap. We hypothesize that the capacity of an interface material to conduct electron mediated current is significantly increased by polymerized coating of PEDOT. SIS was either used plain or after PEDOT coating by electrochemical polymerization. Muscle forces are a direct representation of stimulating current distribution within an RPNI. In situ muscle forces were measured for the same muscle by electrically stimulating: a) the muscle's innervating nerve, b) directly on the muscle, c) on plain SIS laid on the muscle, and d) on SIS polymerized with PEDOT laid on the muscle. Electro-chemically coating PEDOT on SIS resulted in a thin, flexible material. PEDOT coated SIS distributed electrical stimulation more efficiently than SIS alone. Conductive polymer containing biological material allowed ionic signal distribution within the RPNI like muscle at lower charge density. PMID:25569986

  7. Charge transfer excitations from excited state Hartree-Fock subsequent minimization scheme

    Energy Technology Data Exchange (ETDEWEB)

    Theophilou, Iris, E-mail: i.theophilou@fz-juelich.de [Peter Grunberg Institut (PGI) Forschungszentrum Jülich, D-52425 Jülich (Germany); Tassi, M.; Thanos, S. [Institute for Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, ‘Demokritos’ National Center for Scientific Research, 15310 Athens (Greece)

    2014-04-28

    Photoinduced charge-transfer processes play a key role for novel photovoltaic phenomena and devices. Thus, the development of ab initio methods that allow for an accurate and computationally inexpensive treatment of charge-transfer excitations is a topic that nowadays attracts a lot of scientific attention. In this paper we extend an approach recently introduced for the description of single and double excitations [M. Tassi, I. Theophilou, and S. Thanos, Int. J. Quantum Chem. 113, 690 (2013); M. Tassi, I. Theophilou, and S. Thanos, J. Chem. Phys. 138, 124107 (2013)] to allow for the description of intermolecular charge-transfer excitations. We describe an excitation where an electron is transferred from a donor system to an acceptor one, keeping the excited state orthogonal to the ground state and avoiding variational collapse. These conditions are achieved by decomposing the space spanned by the Hartree-Fock (HF) ground state orbitals into four subspaces: The subspace spanned by the occupied orbitals that are localized in the region of the donor molecule, the corresponding for the acceptor ones and two more subspaces containing the virtual orbitals that are localized in the neighborhood of the donor and the acceptor, respectively. Next, we create a Slater determinant with a hole in the subspace of occupied orbitals of the donor and a particle in the virtual subspace of the acceptor. Subsequently we optimize both the hole and the particle by minimizing the HF energy functional in the corresponding subspaces. Finally, we test our approach by calculating the lowest charge-transfer excitation energies for a set of tetracyanoethylene-hydrocarbon complexes that have been used earlier as a test set for such kind of excitations.

  8. Charge transfer and structured vibrational distributions in H++CH4 low-energy collisions

    International Nuclear Information System (INIS)

    Inelastic and charge transfer collisions of protons with methane molecules have been investigated in a perpendicular-plane crossed beam experiment via the detection of the scattered protons and H atoms, respectively. Time-of-flight analysis of the protons and H atoms at scattering angles 00≤θ≤100 and collision energies 10≤E≤30 eV provided information on internal energy distributions of the CH4 and CH+4 products. Excitation of the n(ν1 ,ν3) +m (ν2 ,ν4) type vibrations, with n,m = 0, 1, 2,xxxwas found to be the most probable assignment of the observed structured energy distributions of CH4 (1 A1 ) at θ≤40. At θ>40, the energy transfer increases steeply up to the dissociation limit while the vibrational structure was no longer resolved. In the case of charge transfer, the observed narrow internal energy distributions corresponding to a most probable average internal energy of CH+4 of about 0.95 eV was centered at the recombination energy of the proton indicative of quasiresonant charge transfer. In addition, fragmentation of CH+4 formed in charge transfer collisions of H+ with CH4 was investigated in an independent experiment using mass spectrometric analysis to identify the individual fragment species. The relative intensities of the parent and fragment ions (i.e., of CH+4, CH+3, and CH+2) were found to be in good agreement with the known values of the appearance potentials of the fragment ions and the distribution of the CH+4 internal energy as obtained from the differential cross sections

  9. Visible Light Absorption of Binuclear TiOCoII Charge-Transfer UnitAssembled in Mesoporous Silica

    Energy Technology Data Exchange (ETDEWEB)

    Han, Hongxian; Frei, Heinz

    2007-01-30

    Grafting of CoII(NCCH3)2Cl2 onto mesoporous Ti-MCM-41 silicain acetonitrile solution affords binuclear Ti-O-CoII sites on the poresurface under complete replacement of the precursor ligands byinteractions with anchored Ti centers and the silica surface. The CoIIligand field spectrum signals that the Co centers are anchored on thepore surface in tetrahedral coordination. FT-infrared action spectroscopyusing ammonia gas adsorption reveals Co-O-Si bond modes at 831 and 762cm-1. No Co oxide clusters are observed in the as-synthesized material.The bimetallic moieties feature an absorption extending from the UV intothe visible to about 600 nm which is attributed to the TiIV-O-CoII?3TiIII-O-CoIII metal-to-metal charge-transfer (MMCT) transition. Thechromophore is absent in MCM-41 containing Ti and Co centers isolatedfrom each other; this material was synthesized by grafting CoII onto aTi-MCM-41 sample with the Ti centers protected by a cyclopentadienylligand. The result indicates that the appearance of the charge-transferabsorption requires that the metal centers are linked by an oxo bridge,which is additionally supported by XANES spectroscopy. The MMCTchromophore of Ti-O-CoII units has sufficient oxidation power to serve asvisible light electron pump for driving multi-electron transfer catalystsof demanding uphill reactions such as water oxidation.

  10. Electron transfer within a reaction path model calibrated by constrained DFT calculations: application to mixed-valence organic compounds.

    Science.gov (United States)

    Mangaud, E; de la Lande, A; Meier, C; Desouter-Lecomte, M

    2015-12-14

    The quantum dynamics of electron transfer in mixed-valence organic compounds is investigated using a reaction path model calibrated by constrained density functional theory (cDFT). Constrained DFT is used to define diabatic states relevant for describing the electron transfer, to obtain equilibrium structures for each of these states and to estimate the electronic coupling between them. The harmonic analysis at the diabatic minima yields normal modes forming the dissipative bath coupled to the electronic states. In order to decrease the system-bath coupling, an effective one dimensional vibronic Hamiltonian is constructed by partitioning the modes into a linear reaction path which connects both equilibrium positions and a set of secondary vibrational modes, coupled to this reaction coordinate. Using this vibronic model Hamiltonian, dissipative quantum dynamics is carried out using Redfield theory, based on a spectral density which is determined from the cDFT results. In a first benchmark case, the model is applied to a series of mixed-valence organic compounds formed by two 1,4-dimethoxy-3-methylphenylene fragments linked by an increasing number of phenylene bridges. This allows us to examine the coherent electron transfer in extreme situations leading to a ground adiabatic state with or without a barrier and therefore to the trapping of the charge or to an easy delocalization. PMID:26041466

  11. Reversible Tuning of Interfacial and Intramolecular Charge Transfer in Individual MnPc Molecules.

    Science.gov (United States)

    Zhong, Jian-Qiang; Wang, Zhunzhun; Zhang, Jia Lin; Wright, Christopher A; Yuan, Kaidi; Gu, Chengding; Tadich, Anton; Qi, Dongchen; Li, He Xing; Lai, Min; Wu, Kai; Xu, Guo Qin; Hu, Wenping; Li, Zhenyu; Chen, Wei

    2015-12-01

    The reversible selective hydrogenation and dehydrogenation of individual manganese phthalocyanine (MnPc) molecules has been investigated using photoelectron spectroscopy (PES), low-temperature scanning tunneling microscopy (LT-STM), synchrotron-based near edge X-ray absorption fine structure (NEXAFS) measurements, and supported by density functional theory (DFT) calculations. It is shown conclusively that interfacial and intramolecular charge transfer arises during the hydrogenation process. The electronic energetics upon hydrogenation is identified, enabling a greater understanding of interfacial and intramolecular charge transportation in the field of single-molecule electronics. PMID:26528623

  12. Fe1+-Fe2+ charge transfer process after 57Co decay in ZnTe

    International Nuclear Information System (INIS)

    We have performed Moessbauer absorption and emission experiments on 57Fe impurities in ZnTe. A transient Fe1+ charge state has been observed below 130K in the emission spectra. The dynamics of the Fe1+-Fe2+ charge transfer was shown to obey an activation process with an activation energy of 0.09eV. Low temperature Raman relaxation rates within the Fe2+ spin-orbit levels are found to be at least 100 times faster in ZnTe than in ZnS

  13. Measurements of Charge Transfer Inefficiency in a CCD with High-Speed Column Parallel Readout

    CERN Document Server

    Sopczak, Andre; Damerell, Chris; Greenshaw, Tim; Koziel, Michal; Stefanov, Konstantin; Tikkanen, Tuomo; Woolliscroft, Tim; Worm, Steve

    2008-01-01

    Charge Coupled Devices (CCDs) have been successfully used in several high energy physics experiments over the past two decades. Their high spatial resolution and thin sensitive layers make them an excellent tool for studying short-lived particles. The Linear Collider Flavour Identification (LCFI) collaboration is developing Column-Parallel CCDs (CPCCDs) for the vertex detector of a future Linear Collider. The CPCCDs can be read out many times faster than standard CCDs, significantly increasing their operating speed. A test stand for measuring the charge transfer inefficiency (CTI) of a prototype CPCCD has been set up. Studies of the CTI have been performed at a range of readout frequencies and operating temperatures.

  14. The dp{yields}ppn reaction as a method to study neutron-proton charge-exchange amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Chiladze, D. [Tbilisi State Univ., High Energy Physics Inst., Tbilisi (Georgia); Forschungszentrum Juelich GmbH, Institut fuer Kernphysik, Juelich (Germany); Juelich Centre for Hadron Physics, Juelich (Germany); Carbonell, J. [Laboratoire de Physique Subatomique et de Cosmologie, Grenoble (France); Dymov, S. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Universitaet Erlangen-Nuernberg, Physikalisches Institut II, Erlangen (Germany); Dzyuba, A.; Valdau, Yu. [Petersburg Nuclear Physics Institute, High Energy Physics Department, Gatchina (Russian Federation); Glagolev, V. [JINR, Laboratory of High Energies, Dubna (Russian Federation); Hartmann, M.; Kacharava, A.; Nekipelov, M.; Ohm, H.; Rathmann, F.; Stroeher, H. [Forschungszentrum Juelich GmbH, Institut fuer Kernphysik, Juelich (Germany); Juelich Centre for Hadron Physics, Juelich (Germany); Keshelashvili, I. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); University of Basel, Department of Physics, Basel (Switzerland); Khoukaz, A.; Mersmann, T.; Mielke, M. [Universitaet Muenster, Institut fuer Kernphysik, Muenster (Germany); Komarov, V.; Kulikov, A.; Uzikov, Yu. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Kulessa, P. [H. Niewodniczanski Institute of Nuclear Physics PAN, Krakow (Poland); Lomidze, N.; Mchedlishvili, D.; Nioradze, M.; Tabidze, M. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); Macharashvili, G. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Maeda, Y. [Osaka University, Research Center for Nuclear Physics, Osaka Ibaraki (Japan); Merzliakov, S. [Forschungszentrum Juelich GmbH, Institut fuer Kernphysik, Juelich (Germany); Juelich Centre for Hadron Physics, Juelich (Germany); JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation)] [and others

    2009-04-15

    The differential cross section and deuteron analysing powers of the (vector)dp{yields}{l_brace}pp{r_brace}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170MeV, data were obtained for small momentum transfers to a {l_brace}pp{r_brace} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable. (orig.)

  15. The low-lying πσ* state and its role in the intramolecular charge transfer of aminobenzonitriles and aminobenzethyne

    International Nuclear Information System (INIS)

    Electronic absorption spectra of the low-lying ππ* and πσ* states of several aminobenzonitriles and 4-dimethylaminobenzethyne have been studied by time-resolved transient absorption and time-dependent density functional theory calculation. In acetonitrile, the lifetime of the πσ*-state absorption is very short (picoseconds or subpicosecond) for molecules that exhibit intramolecular charge transfer (ICT), and very long (nanoseconds) for those that do not. Where direct comparison of the temporal characteristics of the πσ*-state and the ICT-state transients could be made, the formation rate of the ICT state is identical to the decay rate of the πσ* state within the experimental uncertainty. These results are consistent with the πσ*-mediated ICT mechanism, La (ππ*)→πσ*→ICT, in which the decay rate of the πσ* state is determined by the rate of the solvent-controlled πσ*→ICT charge-shift reaction. The ππ*→πσ* state crossing does not occur in 3-dimethylaminobenzonitrile or 2-dimethylaminobenzonitrile, as predicted by the calculation, and 4-aminobenzonitrile and 4-dimethylaminobenzethyne does not exhibit the ICT reaction, consistent with the higher energy of the ICT state relative to the πσ* state

  16. Radiation reaction and radiative losses derived from the kinetic power of the electric inertial mass of a charge

    CERN Document Server

    Singal, Ashok K

    2016-01-01

    It is shown that formulas for radiation reaction and radiative losses from a charge can be derived from the kinetic power of its electric inertial mass. The derivation assumes a non-relativistic but otherwise an arbitrary motion of the charge. We exploit the fact that as the charge velocity changes because of a constant acceleration, there are accompanying modifications in its electromagnetic fields which can remain concurrent with the charge motion because the velocity as well as acceleration information enters into the field expression. However, if the acceleration of the charge is varying, information about that being not present in the field expressions, the electromagnetic fields get "out of step" with the actual charge motion. Accordingly we arrive at a radiation reaction formula for an arbitrarily moving charge, obtained hitherto in literature from the self-force, derived in a rather cumbersome way from the detailed mutual interaction between various constituents of a small charged sphere. This way we ...

  17. Development of charged particle nuclear reaction data retrieval system on IntelligentPad

    International Nuclear Information System (INIS)

    An newly designed database retrieval system of charged particle nuclear reaction database system is developed with IntelligentPad architecture. We designed the network-based (server-client) data retrieval system, and a client system constructs on Windows95, 98/NT with IntelligentPad. We set the future aim of our database system toward the 'effective' use of nuclear reaction data: I. 'Re-produce, Re-edit, Re-use', II. 'Circulation, Evolution', III. 'Knowledge discovery'. Thus, further developments are under way. (author)

  18. A study of the electron transfer inhibition on a charged self-assembled monolayer modified gold electrode by odd random phase multisine electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    The interest of self-assembled monolayers (SAM) comes from their wide range of very specific technological applications. The SAMs having a terminal charged group are of great importance as model surfaces for electron transfer studies. The electron transfer for highly charged electroactive ions at a SAM modified electrode involves an electrostatic interaction. The present work studies a negatively charged SAM of 2-mercaptobenzimidazole-5-sulfonate (MBIS). The adsorption of the molecule on polycrystalline gold is described by X-ray photoelectron spectroscopy (XPS) and the reductive desorption of MBIS. The behavior of the MBIS monolayer towards the electron transfer of the ferri/ferrocyanide reaction is investigated by cyclic voltammetry and odd random phase multisine electrochemical impedance spectroscopy (ORP-EIS). This technique ensures reliable experiments and enables a statistically founded modeling. The combined electrochemical and surface study allows the investigation of the characteristics and electrochemical properties of the MBIS monolayer formed on polycrystalline gold to provide a quantitative modeling, which is physically and statistically validated. The major contribution of this work is the use of ORP-EIS and XPS to understand how the interaction between a charged SAM and electroactive ions affects the electron transfer

  19. Spectroscopic and computational investigations on the origin of charge transfer between included neutral guest molecules and a functionalized anionic layered host.

    Science.gov (United States)

    Dutta, Dipak; Tummanapelli, Anil Kumar

    2016-08-10

    Layered double hydroxides (LDHs) or anionic clays are an important class of ion-exchange materials, well known for drug and gene delivery and several other applications including catalysis, bioactive nanocomposite, electroactive and photoactive materials. Their structure is based on positively charged brucite-like inorganic sheets with the interlamellar space being occupied by charge-compensating exchangeable anions. In spite of having a vast scope many of the applications of LDHs are restricted as their host-guest chemistry is limited to ion-exchange reactions. Recently we have shown for the first time that charge-transfer interactions can be used as a driving force for the insertion of neutral guest molecules (ortho- and para-chloranil) within the galleries of an Mg-Al LDH by forming a charge-transfer complex with aniline pre-intercalated as p-aminobenzoate anion. Here, we have performed quantum chemical calculations in combination with molecular dynamics simulations to elucidate the nature of interactions, arrangement and the evaluation of electronic and Raman spectral signatures of the chloranil charge-transfer complex included within the galleries of the Mg-Al LDH. The natural bond orbital (NBO) analysis has been used to understand the nature and origin of the unidirectional charge-transfer that lead to the unusual insertion of chloranil in the galleries of the Mg-Al LDH. The NBO analysis reveals that a considerable amount of electronic charge redistribution occurs from the p-aminobenzoate to the chloranil during latter's insertion within the LDH galleries with a very negligible amount of back donation. This work is expected to pave the way for understanding the host-guest chemistry and targeted and controlled delivery of poorly soluble drugs. PMID:27461409

  20. Synthesis and Reactions of Five-Membered Heterocycles Using Phase Transfer Catalyst (PTC Techniques

    Directory of Open Access Journals (Sweden)

    Ahmed M. El-Sayed

    2014-01-01

    Full Text Available Phase transfer catalysts (PTCs have been widely used for the synthesis of organic compounds particularly in both liquid-liquid and solid-liquid heterogeneous reaction mixtures. They are known to accelerate reaction rates by facilitating formation of interphase transfer of species and making reactions between reagents in two immiscible phases possible. Application of PTC instead of traditional technologies for industrial processes of organic synthesis provides substantial benefits for the environment. On the basis of numerous reports it is evident that phase-transfer catalysis is the most efficient way for generation and reactions of many active intermediates. In this review we report various uses of PTC in syntheses and reactions of five-membered heterocycles compounds and their multifused rings.