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1

Chemistry of Halogen Charge Transfer Complexes.  

National Technical Information Service (NTIS)

Highlights are discussed of a project concerned with the study of the nature of halogen charge-transfer complexes and the mechanism of complex formation. Specifically interest was maintained in complex formation between heterocyclic amines and halogen, th...

A. I. Popov

1969-01-01

2

Validation of Diethoxyphosphonate as an Effective Agent for Charge Transfer in Anion Relay Chemistry (ARC)  

PubMed Central

The diethoxyphosphonate group comprises an effective agent to achieve negative charge migration in Type II Anion Relay Chemistry (ARC). The process involves a [1,4]-phosphorus-Brook rearrangement that proceeds via a phosphacyclic intermediate leading to an anion that can be captured by reactive electrophiles. In the absence of an exogenous electrophile, the anion derived via phosphorus migration undergoes internal displacement of the phosphonate group to produce a diasteriomeric mixture of cyclopropanes.

Sokolsky, Alexander

2012-01-01

3

Photoinduced Charge Transfer Process  

NASA Astrophysics Data System (ADS)

The photoinduced charge transfer process is the fundamental process in a photovoltaic system. Organic photovoltaics contain a donor-acceptor molecular system which undergoes photoinduced charge transfer leading to a large dipole moment. Often the charge transfer properties of such donor-acceptor systems are measured in solution. The dipole moments on the solvent molecules creates a reaction field. To simulate this reaction field we adopt an approach similar to the explicit solvent model proposed by Washel and co-workers. We use Monte Carlo simulations to determine various possible solvent structures. We use a carotenoid-porphyrin-C60 molecular triad as the light-harvesting system. This molecular triad has a very large dipole moment (153 Debye) in the charge separated state. The resulting solvent structures and the reaction field as a function of temperature will be presented.

Basurto, Luis; Baruah, Tunna; Zope, Rajendra; Rodriguez, Jose

2011-10-01

4

Charge Transfer Reactions  

NASA Astrophysics Data System (ADS)

Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe.

Dennerl, Konrad

2010-12-01

5

Charge Transfer Reactions Induce Born-Oppenheimer Breakdown in Surface Chemistry: Applications of Double Resonance Spectroscopy in Molecule-Surface Scattering  

NASA Astrophysics Data System (ADS)

Atomic and molecular interactions constitute a many-body quantum problem governed fundamentally only by the Coulomb forces between many electrons and nuclei. While simple to state, computers are simply not fast enough to solve this problem by brute force, except for the simplest examples. Combining the Born-Oppenheimer Approximation (BOA) with Density Functional Theory (DFT), however, allows theoretical simulations of extraordinarily complex chemical systems including molecular interactions at solid metal surfaces, the physical basis of surface chemistry. This lecture describes experiments demonstrating the limits of the BOA/DFT approximation as it relates to molecules interacting with solid metal surfaces. One of the most powerful experimental tools at our disposal is a form of double resonance spectroscopy, which allows us to define the quantum state of the molecule both before and after the collision with the surface, providing a complete picture of the resulting energy conversion processes. With such data, we are able to emphasize quantitative measurements that can be directly compared to first principles theories that go beyond the Born-Oppenheimer approximation. One important outcome of this work is the realization that Born-Oppenheimer breakdown can be induced by simple charge transfer reactions that are common in surface chemistry. J. D. White, J. Chen, D. Matsiev, D. J. Auerbach and A. M. Wodtke Nature {433}(7025), 503-505 (2005) Y. H. Huang, C. T. Rettner, D. J. Auerbach and A. M. Wodtke Science {290}(5489), 111-114 (2000) R. Cooper, I. Rahinov, Z. S. Li, D. Matsiev, D. J. Auerbach and A. M. Wodtke Chemical Science {1}(1), 55-61 (2010) J. Larue, T. Schäfer, D. Matsiev, L. Velarde, N. H. Nahler, D. J. Auerbach and A. M. Wodtke PCCP {13}(1), 97-99 (2011).

Wodtke, Alec M.

2013-06-01

6

Multiply-charged ions and interstellar chemistry.  

PubMed

Gaseous molecules and ions, and even dust grains, can accumulate charge in the interstellar medium (ISM) by harvesting the energy of UV photons, cosmic rays, helium ions and metastable atoms. This Perspective views the various modes of gas-phase formation of multiply-charged cations and the possible impact of their reactions on the chemical and ionization structure of the ISM, in the light of what is still very limited knowledge. Emphasis is given to gas-phase reactions of multiply-charged cations with atoms, molecules and electrons that lead to charge reduction, charge separation and chemical bond formation and these are examined for multiply-charged atoms, small molecules, hydrocarbons, polycyclic aromatic hydrocarbons and fullerenes, primarily as dications but also as a function of charge state. The increased electrostatic interaction due to multiple charge is seen to promote bonding to individual charge sites on large molecules (e.g. fullerenes) and allow ensuing "surface" chemistry under the influence of Coulomb repulsion. The unique ability of multiply charged cations to undergo charge separation reactions, either unimolecular or bimolecular, can feature in the production in the ISM of internally cold, but translationally hot, cations of lower charge state or hot atoms that may provide the driving force for subsequent chemical reactions in what is otherwise an ultracold environment. Available chemical kinetic models that account for the role of multiply-charged ions in the ISM are few and of limited scope and the observation of these ions in the ISM has remained elusive. PMID:21869973

Böhme, Diethard Kurt

2011-08-25

7

Charge transfer in buried-channel charge-coupled devices  

Microsoft Academic Search

A detailed numerical simulation of the charge-transfer process in buried-channel CCDs will be presented. The limitations on the device performance due to incomplete free charge transfer, device parameters and clocking waveforms will be discussed.

Yoshiak Daimon; Amr M. Mohsen; Thomas C. McGill

1974-01-01

8

Dispersive analysis of charge transfer models  

Microsoft Academic Search

We prove the dispersive estimates for charge transfer Hamiltonians, including\\u000athe matrix non-selfadjoint generalizations. The charge transfer models appear\\u000anaturally in the study of stability of multi-soliton systems.

I. Rodnianski; W. Schlag; A. Soffer

2005-01-01

9

Detecting QGP with Charge Transfer Fluctuations  

Microsoft Academic Search

In this study, we analyze the recently proposed charge transfer fluctuations\\u000awithin a finite pseudo-rapidity space. As the charge transfer fluctuation is a\\u000ameasure of the local charge correlation length, it is capable of detecting\\u000ainhomogeneity in the hot and dense matter created by heavy ion collisions. We\\u000apredict that going from peripheral to central collisions, the charge transfer\\u000afluctuations

Sangyong Jeon; Lijun Shi; Marcus Bleicher

2005-01-01

10

Charge Transfer Fluctuations as a QGP Signal  

Microsoft Academic Search

In this study, we analyze the recently proposed charge transfer fluctuations\\u000awithin a finite pseudo-rapidity space. As the charge transfer fluctuation is a\\u000ameasure of the local charge correlation length, it is capable of detecting\\u000ainhomogeneity in the hot and dense matter created by heavy ion collisions. We\\u000apredict that going from peripheral to central collisions, the charge transfer\\u000afluctuations

Sangyong Jeon; Lijun Shi

2005-01-01

11

Charge transfer in small hydrogen bonded clusters  

NASA Astrophysics Data System (ADS)

High level ab initio and density functional calculations on clusters of water with acetate, methylammonium, and dimethylphosphate show that charge is transferred from the hydrogen bond acceptor to the hydrogen bond donor. The amounts of charge transferred are small, between 0.01 and 0.05 electron per hydrogen bond, but increase nearly linearly with the number of hydrogen bonds. The transfer of charge is not an artifact of the computation, since charge is also transferred in the limit of zero basis set superposition error. Calculations on a number of hydrogen bonded clusters show that the semiempirical AM1 and PM3 methods give excellent agreement with high level MP2 charge transfer effects, especially for AM1. Our results indicate the importance of charge transfer in hydrogen bond interactions.

van der Vaart, Arjan; Merz, Kenneth M.

2002-05-01

12

Interfacial charge transfer in nanoscale polymer transistors  

Microsoft Academic Search

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

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

2008-01-01

13

Interfacial Charge Transfer in Nanoscale Polymer Transistors  

NASA Astrophysics Data System (ADS)

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 resistance and the zero gate voltage conductance are consistent with such charge transfer. Short channel conduction in devices with Pt contacts is greatly enhanced compared to analogous devices with Au contacts, consistent with charge transfer expectations. Alternating current scanning tunneling microscopy (ACSTM) provides further evidence that holes are transferred from Pt into P3HT, while much less charge transfer takes place at the Au/P3HT interface. We have also begun to use these same techniques to investigate the nature of interfacial charge transfer between metal electrodes and pentacene. We use these data together with our previous results to develop a more complete picture of metal/organic interfaces.

Worne, Jeffrey; Giridharagopal, Rajiv; Kelly, Kevin; Natelson, Douglas; Anthony, John

2009-03-01

14

Interfacial charge transfer in nanoscale polymer transistors  

Microsoft Academic Search

Interfacial charge transfer plays an essential role in establishing the relative alignment of the metal Fermi level and the\\u000a energy bands of organic semiconductors. While the details remain elusive in many systems, this charge transfer has been inferred\\u000a in a number of photoemission experiments. We present electronic transport measurements in very short channel (L < 100 nm) transistors made from

Jeffrey H. Worne; Rajiv Giridharagopal; Kevin F. Kelly; Douglas Natelson

2008-01-01

15

Charge Transfer during Alkali-Surface Collisions  

NASA Astrophysics Data System (ADS)

The transfer of electrons between atoms and solid surfaces is the driving force behind ionic bond formation in adsorption and determines the final charge state in particle-surface collisions. Despite its importance, however, many aspects of charge transfer are not completely understood. The experiments presented in this dissertation use the scattering of ^7Li ^+ ions from surfaces to study several aspects of charge transfer. Primarily, the effects of alkali adsorption on the surface local electrostatic potential (LEP) are investigated via resonant charge transfer. In addition, the effects of charge promotion on the final charge state distributions of scattered ^7Li ^+ ions are determined. On metal surfaces, large differences in the final charge state distributions of ^7Li ^+ ions scattered from substrate and adsorbate sites are observed at low alkali coverages, which disappear at high coverages. The final charge state distribution of ^7Li^+ ions is determined primarily by resonant charge transfer, which is dependent on the LEP. Thus, there is a transition in the LEP from inhomogeneous to nearly homogeneous as the adsorbate coverage increases. The LEP is modeled as a collection of isolated dipoles positioned at the adsorbate sites. Calculations of the final charge state distributions of ions scattered from such model surfaces do an excellent job of reproducing the measured charge state distributions. From these calculations, it is shown that the inhomogeneous to homogeneous transition in the LEP is due to a coverage dependent depolarization of the adsorbate dipoles. For the alkali-covered Si(111)-7 x 7 surface, the final charge state distribution is independent of scattering site. This behavior is not attributed to a homogeneous LEP, rather, it is due to the dangling bonds of the Si(111) -7 x 7 surface, which allow resonant charge transfer to take place well above the surface. As a consequence, variations in the LEP near the adsorbate sites are not detected. During the Li-Al charge promotion process, a Li 1s hole is created, which later decays by electron emission. Because of this, the charge state distributions of promoted ions differ significantly from those of non-promoted ions. From a combination of charge state distributions and secondary electron spectra, it is shown that the lifetime of the hole is on the order of the ion-surface interaction time, i.e., 10 fs.

Weare, Christopher Bruce

16

Towards XUV lasers with charge transfer pumping  

Microsoft Academic Search

Detailed studies of charge exchange pumping of ions in femtosecond laser-produced plasmas colliding with a pulsed gas jet are presented. Strong selective excitation of XUV ionic transitions in the reaction C4+ + H --> C3+ + H+ is observed. Dependences of line intensities on various experimental parameters are reported which are in good agreement with the theory of charge transfer

I. F. Shaikhislamov; V. A. Vorontsov; M. Born; B. N. Chichkov; B. Wellegehausen

2006-01-01

17

Photoinduced charge transfer in helical polypeptides  

Microsoft Academic Search

Investigation of electron transfer in synthetic polypeptides provides an important probe of how charge entrainment is mediated in redox-active proteins, including photosynthetic reaction centers. Interest in this field has focused increasingly on experimental probes of photoinduced electron transfer kinetics and thermodynamics, and the influence of various features of polypeptide templates (e.g. the hydrogen bonding network, the permanent dipole moment for

Valentine I. Vullev; Guilford Jones II

2002-01-01

18

Charge transfer of doubly charged and trebly charged ions with atomic hydrogen at thermal energies  

Microsoft Academic Search

The charge transfer of doubly charged and trebly charged ions of C, N, O, and Ne with atomic hydrogen at thermal energies is studied. Adiabatic potential-energy curves and radial coupling matrix elements are presented. The collision cross sections are calculated after transforming to a diabatic basis. For the trebly charged ions, there exists at least one exit channel into which

T. G. Heil; S. E. Butler; A. Dalgarno

1983-01-01

19

Charge Transfer in Polar Glasses  

Microsoft Academic Search

Classical electron transfer is described by a theory based on a model microscopic Hamiltonian which includes both discreteness and randomness of the glassy polar modes and ordinary polar dipole fluctuations. When configurational dynamics is fast, the reaction evolves exponentially in time with the rate constant of non-Arrhenius type. The temperature dependence resembles the tunneling rate in spite of the classical

Yuri Dakhnovskii; Vassiliy Lubchenko; Peter Wolynes

1997-01-01

20

Covalent electron transfer chemistry of graphene with diazonium salts.  

PubMed

Graphene is an atomically thin, two-dimensional allotrope of carbon with exceptionally high carrier mobilities, thermal conductivity, and mechanical strength. From a chemist's perspective, graphene can be regarded as a large polycyclic aromatic molecule and as a surface without a bulk contribution. Consequently, chemistries typically performed on organic molecules and surfaces have been used as starting points for the chemical functionalization of graphene. The motivations for chemical modification of graphene include changing its doping level, opening an electronic band gap, charge storage, chemical and biological sensing, making new composite materials, and the scale-up of solution-processable graphene. In this Account, we focus on graphene functionalization via electron transfer chemistries, in particular via reactions with aryl diazonium salts. Because electron transfer chemistries depend on the Fermi energy of graphene and the density of states of the reagents, the resulting reaction rate depends on the number of graphene layers, edge states, defects, atomic structure, and the electrostatic environment. We limit our Account to focus on pristine graphene over graphene oxide, because free electrons in the latter are already bound to oxygen-containing functionalities and the resulting chemistries are dominated by localized reactivity and defects. We describe the reaction mechanism of diazonium functionalization of graphene and show that the reaction conditions determine the relative degrees of chemisorption and physisorption, which allows for controlled modulation of the electronic properties of graphene. Finally we discuss different applications for graphene modified by this chemistry, including as an additive in polymer matrices, as biosensors when coupled with cells and biomolecules, and as catalysts when combined with nanoparticles. PMID:22946516

Paulus, Geraldine L C; Wang, Qing Hua; Strano, Michael S

2012-09-04

21

Towards XUV lasers with charge transfer pumping  

Microsoft Academic Search

Detailed studies of charge exchange pumping of ions in femtosecond laser-produced plasmas colliding with a pulsed gas jet are presented. Strong selective excitation of XUV ionic transitions in the reaction C4++H?C3++H+ is observed. Dependences of line intensities on various experimental parameters are reported which are in good agreement with the theory of charge transfer processes. Analyses of experimental data provide

I. F. Shaikhislamov; V. A. Vorontsov; M. Born; B. N. Chichkov; B. Wellegehausen

2006-01-01

22

Charge transfer reactions in Xe plasma expansion  

NASA Astrophysics Data System (ADS)

Charge transfer reactions of fast Xe ions with hydrocarbons including methane (CH4), ethene (C2H4), and propane (C3H8) are studied by adding these hydrocarbon gases into a cross flowing Xe plasma expansion. Branching ratios and relative reaction rates for the charge transfers of fast Xe+ with each of the three hydrocarbon gases are measured under different rf powers of the inductively coupled Xe discharge. For CH4/Xe system, we find that fast Xe+ reacts readily with CH4 generating CH4+ and CH3+ in a ratio of 1:0.56, with an estimated rate coefficient of (2.3+/-0.3)×10-10 cm3/s at 75 W rf power which slowly increases to (2.9+/-0.3)×10-10 cm3/s at 250 W (error bars reflect only the uncertainties due to the unknown extent of the ion recombination that follows the charge transfer reaction). These observed charge transfer reactions are made possible by the kinetically excited Xe ions produced by free expansion of the plasma. For the C2H4/Xe system product ions C2H4+ and C2H2+ are observed, and for C3H8/Xe, C2H4+ and C2H5+ and minor product ions including C2H2+ and C3H7+ are observed.

Jiao, C. Q.; Garscadden, A.; Ganguly, B. N.

2007-04-01

23

Dynamical Treatment of Charge Transfer through Duplex Nucleic Acids Containing Modified Adenines.  

PubMed

We address the issue of whether chemical alterations of nucleobases are an effective tool to modulate charge transfer through DNA molecules. Our investigation uses a multilevel computational approach based on classical molecular dynamics and quantum chemistry. We find yet another piece of evidence that structural fluctuations are a key factor to determine the electronic structure of double-stranded DNA. We argue that the electronic structure and charge transfer ability of flexible polymers is the result of a complex intertwining of various structural, dynamical and chemical factors. Chemical intuition may be used to design molecular wires, but this is not the sole component in the complex charge transfer mechanism through DNA. PMID:24060008

Brancolini, Giorgia; Migliore, Agostino; Corni, Stefano; Fuentes-Cabrera, Miguel; Luque, F Javier; Di Felice, Rosa

2013-09-30

24

Charge transfer luminescence of Yb 3+  

Microsoft Academic Search

A systematic study of charge transfer (CT) luminescence from Yb3+ is presented. CT luminescence was observed in LiYF4 (?7eV), aluminates, phosphates, oxides (?4eV) and oxysulfides (?3eV). In all cases the CT emission bands are broad and the Stokes shifts are large, ranging from 7000cm?1 in oxysulfides and LiYF4 and up to 17000cm?1 in aluminates. The influence of the size of

L. van Pieterson; M. Heeroma; E. de Heer; A. Meijerink

2000-01-01

25

Electronic parameters for charge transfer along DNA  

Microsoft Academic Search

.  We systematically examine all the tight-binding parameters pertinent to charge transfer along DNA. The molecular structure of the four DNA bases (adenine, thymine, cytosine, and guanine) is investigated by using the linear combination\\u000a of atomic orbitals method with a recently introduced parametrization. The HOMO and LUMO wave functions and energies of DNA\\u000a bases are discussed and then used for calculating

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

2010-01-01

26

Conductometric study of charge transfer complexes  

Microsoft Academic Search

A conductometric titration technique has been used for determining the stoichio-metry of charge-transfer complexes which ionise\\u000a in polar media. The systems studied are: Iodine complexes of acetone, methyl ethyl ketone,iso-butyl methyl ketone, dimethylsulphoxide triphenyl phosphine, triphenyl arsine, triphenyl stibene, methanol, ethanol andn-propanol. The stoichiometry of the above complexes (in highly polar media) were found to be?2:3 (except in the cases

Bharati Bhattacharjee; S N Bhat

1991-01-01

27

Intramolecular photoinduced charge transfer in rotaxanes.  

PubMed

We report the synthesis and photophysical investigation of a series of rotaxanes in which the physical confinement of the donor and acceptor (DA) pair leads, in some cases, to emissive exciplexes. As a comparison, we examined the photoinduced charge-transfer processes in the same DA mixtures under intermolecular conditions. The interlocked configuration of the rotaxane facilitates pi orbital overlap of the excited state DA pair by keeping their center-to-center distance extremely small. This increased interaction between the DA pair significantly lowers the activation energy for exciplex formation (E(a)) and helps stabilize the highly polar charge-transfer complex. We find that the stabilizing effect of the rotaxane architecture compensates for the modest thermodynamic driving force for some charge-transfer interactions. In addition, we examined the temperature dependence on the rotaxanes' optical properties. Metal coordination to the tetrahedral cavity disrupts the cofacial conformation of the DA pair and quenches the fluorescence. Binding of alkali metal ions to the 3,4-ethylenedioxythiophene (EDOT)-based rotaxane, however, gives rise to the emergence of a new weak emission band at even lower energies, indicative of a new emissive exciplex. PMID:15839689

Kwan, Phoebe H; Swager, Timothy M

2005-04-27

28

Charge transfer in the living matrix.  

PubMed

The living matrix is defined as the continuous molecular fabric of the organism, consisting of fascia, the other connective tissues, extracellular matrices, integrins, cytoskeletons, nuclear matrices and DNA. The extracellular, cellular and nuclear biopolymers or ground substances constitute a body-wide reservoir of charge that can maintain electrical homeostasis and "inflammatory preparedness" throughout the organism. Recent research has emphasized the significance of charge transfer in relation to the scavenging or neutralization of free radicals delivered to sites of injury during and after the oxidative burst. Evidence comes from studies of the role of electrons in mitigating the consequences of inflammation when living systems are connected to the earth (earthing). The phenomenon helps explain how bodywork and movement therapies can facilitate the resolution of acute or chronic injuries, and how patients with inflammatory conditions may "deplete" a therapist during hands-on treatments. It is suggested that barefoot contact with the earth as well as hands-on and hands-off therapies facilitate healing by stimulating the migration of charges into sites of acute or chronic inflammation. One hypothesis to explain the effects of earthing is that charges from the ground substance reservoir prevent "collateral damage" to healthy tissues in the vicinity of an injury. A second hypothesis is that earthing allows electrons to replenish charge in the ground substance reservoirs, making electrons available throughout the body. PMID:19524846

Oschman, James L

2008-07-30

29

Electronic parameters for charge transfer along DNA.  

PubMed

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 wave functions and energies of DNA bases are discussed and then used for calculating the corresponding wave functions 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 necessary parameters for a tight-binding phenomenological description based on the pi molecular overlap. We find that usually the hopping parameters for holes are higher in magnitude compared to the ones for electrons. Our findings are also compared with existing calculations from first principles. PMID:20680380

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

2010-08-01

30

Real-time observation of the charge transfer to solvent dynamics  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

31

Students' Understanding of the Transfer of Charge between Conductors.  

ERIC Educational Resources Information Center

|Investigates students' understanding of the transfer of charge between two charged conductors. Findings indicate that a considerable number of students from eighth grade to college in advanced physics courses were unable to predict the transfer of charge correctly from one conductor to another. Discusses implications for instruction. (JRH)|

Guruswamy, Chitra; And Others

1997-01-01

32

Flavin Charge Transfer Transitions Assist DNA Photolyase Electron Transfer.  

PubMed

This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH(-)-containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH(-), upon photo-excitation of FADH(-) with 350-450 nm light. We compute the lowest singlet excited states of FADH(-) in DNA photolyase using INDO/S configuration interaction, time-dependent density-functional, and time-dependent Hartree-Fock methods. The calculations identify the lowest singlet excited state of FADH(-) that is populated after photo-excitation and that acts as the electron donor. For this donor state we compute conformationally-averaged tunneling matrix elements to empty electron- acceptor states of a thymine dimer bound to photolyase. The conformational averaging involves different FADH(-) - thymine dimer confromations obtained from molecular dynamics simulations of the solvated protein with a thymine dimer docked in its active site. The tunneling matrix element computations use INDO/S-level Green's function, energy splitting, and Generalized Mulliken-Hush methods. These calculations indicate that photo-excitation of FADH(-) causes a ? ? ?(*) charge-transfer transition that shifts electron density to the side of the flavin isoalloxazine ring that is adjacent to the docked thymine dimer. This shift in electron density enhances the FADH(-) - to - dimer electronic coupling, thus inducing rapid electron transfer. PMID:23226907

Skourtis, Spiros S; Prytkova, Tatiana; Beratan, David N

2007-01-01

33

Flavin Charge Transfer Transitions Assist DNA Photolyase Electron Transfer  

PubMed Central

This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH?-containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH?, upon photo-excitation of FADH? with 350–450 nm light. We compute the lowest singlet excited states of FADH? in DNA photolyase using INDO/S configuration interaction, time-dependent density-functional, and time-dependent Hartree-Fock methods. The calculations identify the lowest singlet excited state of FADH? that is populated after photo-excitation and that acts as the electron donor. For this donor state we compute conformationally-averaged tunneling matrix elements to empty electron- acceptor states of a thymine dimer bound to photolyase. The conformational averaging involves different FADH? - thymine dimer confromations obtained from molecular dynamics simulations of the solvated protein with a thymine dimer docked in its active site. The tunneling matrix element computations use INDO/S-level Green’s function, energy splitting, and Generalized Mulliken-Hush methods. These calculations indicate that photo-excitation of FADH? causes a ? ? ?* charge-transfer transition that shifts electron density to the side of the flavin isoalloxazine ring that is adjacent to the docked thymine dimer. This shift in electron density enhances the FADH? - to - dimer electronic coupling, thus inducing rapid electron transfer.

Skourtis, Spiros S.; Prytkova, Tatiana; Beratan, David N.

2012-01-01

34

Charge Transfer Statistics in Quantum Point Contact  

NASA Astrophysics Data System (ADS)

We present the results of the experimental study of the Charge Transfer Statistics for a Quantum Point Contact up to the third cumulant. QPC creates a variable transmission probability barrier, and therefore allows to check the CTS predictions [1] beyond the Poissonian limit. It has been recently understood that the intrinsic CTS is strongly affected by the measurement circuit, see [2] and references therein. We calculated the effect of the measurement circuit for a simple and realistic model of a capacitively shunted resistive load. We found the experimental results to be consistent with the calculations. We believe the results to be the first measurements of the third cumulant in a system different from the low transmission tunneling junction. [1] L.,. Levitov, G.,. Lesovik, JETP Lett. 58, 230 (1993). [2] B. Reulet, J. Senzier and D. E. Prober, Phys. Rev. Let. 91, 196601 (2003).

Gershon, G.; Bomze, Y.; Sukhorukov, E.; Reznikov, M.

2007-03-01

35

Charge transfer in positron-hydrogen collisions  

SciTech Connect

The nonperturbative approach developed recently by Tripathy and Rao for the study of charge transfer in proton-hydrogen collisions has been applied to the problem of positronium formation in positron-hydrogen collisions. The cross section for capture into the ground state has been calculated by partially taking into account the Coulomb distortions but neglecting the polarization effect of the target atom. The calculated cross section has a maximum at an incident energy of 10.2 eV, and as the incident positron energy increases it approaches the results of the first Born approximation (FBA) of Massey and Mohr. The calculated results for capture cross sections and differential scattering cross sections for various incident energies have been compared with those from the FBA and other theoretical calculations.

Satapathy, U.C.; Tripathy, D.N.; Rao, B.K.

1982-03-01

36

Transfer ionization processes in charge-transfer reactions between slowly moving, highly charged ions and atoms  

NASA Astrophysics Data System (ADS)

We study charge-transfer reactions between slowly moving, highly charged ions and neutral atoms using an energy-loss spectroscopy method. In this study, Xeq+ (q = 4-11) ions (incident energy: 5.0 keV) are used as the incident ions and Ar as the target atom. Transfer-ionization (TI) processes are identified for one-electron capture reactions by application of a coincidence technique. We find that the TI process represents approximately 25% of the total one-electron capture reaction for q\\geqq 8 . The measured energy gains agree well with theoretical predictions for one-electron capture, but the agreement between the measured and theoretical energy gains is not as good for two-electron capture processes.

Nakajima, Yusuke; Koizumi, Tetsuo

2013-09-01

37

Phase Transfer Catalysis in Phosphorus Chemistry  

Microsoft Academic Search

Phase-transfer catalysis (PTC) has been widely used for the synthesis of organic compounds for more than three decades. The scope and mechanistic features of PTC have been the aim of numerous studies. This review focuses on the application of phase transfer catalysis in synthesis of phosphorus compounds.

Gheorghe Ilia; Lavinia Macarie; Erika Bálint; György Keglevich

2011-01-01

38

Charge transfer between reduced graphene oxide sheets on insulating substrates  

NASA Astrophysics Data System (ADS)

Understanding the electrical communications between graphene sheets placed on insulating substrates is of great value to rational design of functional graphene nanoelectronics. In this paper, we report charge transfer between reduced graphene oxide (rGO) sheets separated in hundreds of nanometers on insulating substrates. We found that the rGO sheet collects charges from the adjacent charged rGO sheet through the dielectric surfaces. The efficiency of charge transfer between the separated rGO sheets is dependent on their separation distance, gap length, and the substrate type. The findings suggest that the charge interflow should not be neglected in a graphene circuit.

Shen, Yue; Zhang, Xueqiang; Wang, Ying; Zhou, Xuejiao; Hu, Jun; Guo, Shouwu; Zhang, Yi

2013-07-01

39

Charge Transfer Fluctuations as a Signal for QGP  

Microsoft Academic Search

In this work, the charge transfer fluctuation which was previously used for\\u000a$pp$ collisions is proposed for relativistic heavy-ion collisions as a QGP\\u000aprobe. We propose the appearance of a local minimum at midrapidity for the\\u000acharge transfer fluctuation as a signal for a QGP. Within a two-component\\u000aneutral cluster model, we demonstrate that the charge transfer fluctuation can\\u000adetect

Lijun Shi; Sangyong Jeon

2005-01-01

40

Transfer of Algebraic and Graphical Thinking between Mathematics and Chemistry  

ERIC Educational Resources Information Center

|Students in undergraduate chemistry courses find, as a rule, topics with a strong mathematical basis difficult to master. In this study we investigate whether such mathematically related problems are due to deficiencies in their mathematics foundation or due to the complexity introduced by transfer of mathematics to a new scientific domain. In…

Potgieter, Marietjie; Harding, Ansie; Engelbrecht, Johann

2008-01-01

41

Charge transfer in collisions of C{sup 2+} carbon ions with CO and OH targets  

SciTech Connect

The charge transfer in collisions of C{sup 2+} ions with the CO molecule and the OH radical has been studied theoretically by means of ab initio quantum chemistry molecular methods followed by a semiclassical dynamical treatment in the keV collision energy range. The comparison of the cross sections calculated for these two collision systems exhibits interesting features with regard to the anisotropy of these processes and the influence of the vibration of the molecular target.

Bene, E. [Institute of Nuclear Research, Hungarian Academy of Sciences, P.O. Box 51, H-4001 Debrecen (Hungary); Martinez, P. [Departamento de Quimica, Laboratorio Asociado al CIEMAT de Fisica Atomica y Molecular en Plasmas de Fusion, Universidad Autonoma de Madrid, Madrid 28049 (Spain); Halsaz, G. J. [Department of Information Technology, University of Debrecen, P.O. Box 12, H-4010 Debrecen (Hungary); Vibok, A. [Department of Theoretical Physics, University of Debrecen, P.O. Box 5, H-4010 Debrecen (Hungary); Bacchus-Montabonel, M. C. [Laboratoire de Spectrometrie Ionique et Moleculaire, CNRS et Universite de Lyon, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex (France)

2009-07-15

42

Charge transfer in transition-metal alloying: Charge-tailing effects  

Microsoft Academic Search

Charge transfer in alloys is normally discussed in terms of band hybridization, band filling, and screening, but at times experiment and theory yield apparently odd results where, for example, rare-earth actinides or elements from the Ti column apparently gain charge from electronegative transition metals such as Fe, Pt, or Au. Here it is observed that there are charge-tailing terms, due

R. E. Watson; M. Weinert; G. W. Fernando

1991-01-01

43

Dynamics of charge transfer and chemical reactions of doubly-charged ions at low collision energies  

Microsoft Academic Search

Results of beam scattering studies on the dynamics of single charge transfer and chemical reactions of doubly-charged ions carried out in Prague are reviewed. Investigation of several atomic ion-atom charge transfer processes at collision energies 0·1-10 eV provides data on differential and relative total cross-sections of state-to-state processes. Populations of electronic and vibrational states of molecular product ions are obtained

Zdenek Herman

1996-01-01

44

How intermolecular charge transfer influences the air-water interface  

NASA Astrophysics Data System (ADS)

The interfacial properties of three water models that allow for intermolecular charge rearrangement were examined with molecular dynamics simulations. They included the TIP4P water model, the TIP4P-FQ water model, which recently were modified to include intermolecular charge transfer [A. J. Lee and S. W. Rick, J. Chem. Phys. 134, 184507 (2011)]. Furthermore, another model with intermolecular charge transfer was developed for this work that was both flexible and polarizable. The effect of including intermolecular charge transfer is modest on most interfacial properties, including surface tension, electrostatic potential, interfacial dipole, and structure. However, a negative charge was found to build up at the air-water interface, but much smaller than has been measured experimentally.

Wick, Collin D.; Lee, Alexis J.; Rick, Steven W.

2012-10-01

45

Interfacial charge transfer absorption: Application to metal molecule assemblies  

NASA Astrophysics Data System (ADS)

Optically induced charge transfer between adsorbed molecules and a metal electrode was predicted by Hush to lead to new electronic absorption features, but has been only rarely observed experimentally. Interfacial charge transfer absorption (IFCTA) provides information concerning the barriers to charge transfer between molecules and the metal/semiconductor and the magnitude of the electronic coupling and could thus provide a powerful tool for understanding interfacial charge-transfer kinetics. Here, we utilize a previously published model [C. Creutz, B.S. Brunschwig, N. Sutin, J. Phys. Chem. B 109 (2005) 10251] to predict IFCTA spectra of metal molecule assemblies and compare the literature observations to these predictions. We conclude that, in general, the electronic coupling between molecular adsorbates and the metal levels is so small that IFCTA is not detectable. However, few experiments designed to detect IFCTA have been done. We suggest approaches to optimizing the conditions for observing the process.

Creutz, Carol; Brunschwig, Bruce S.; Sutin, Norman

2006-05-01

46

Charge transfer at very high pressure in NiO  

Microsoft Academic Search

We use resonant inelastic x-ray scattering to study the electronic structure of nickel oxide, the prototype charge-transfer insulator, as a function of pressure. At ambient pressure, we observe spectral features due to the charge-transfer excitation and the Coulomb correlation energy which progressively smear up to a pressure of 100 GPa. These changes are interpreted as due to increased dispersion of

Abhay Shukla; Jean-Pascal Rueff; James Badro; Gyorgy Vanko; Aleksi Mattila; F. M. F. de Groot; Francesco Sette

2003-01-01

47

Relaxation process of charge transfer in C60: A normal mode analysis  

NASA Astrophysics Data System (ADS)

By normal mode analysis a novel picture of the relaxation process of charge transfer in C60 is discovered. It is found that after one electron is transferred to C60, only a few normal modes with even parity can be invoked. A Jahn-Teller (J-T) theorem predicts that only the Ag and Hg modes are J-T active, while our results show that theAg mode exchanges energy with the system nearly harmonically, and the Hg mode dominates the relaxation process. This can be understood from their explicit eigenvectors. Implications for mode-selective chemistry and biological processes are discussed.

Zhang, P. G.; Zong, X. F.; Sun, X.; George, Thomas F.; Pandey, Lakshmi N.

1996-02-01

48

Charge transfer dynamics in squaraine-naphthalene diimide copolymers.  

PubMed

The synthesis of an alternating squaraine-naphthalene diimide donor-acceptor low band gap polymer (1.14-1.40 eV) as well as its monomolecular analogue is presented. Spectroelectrochemistry experiments and transient absorption spectroscopy in the fs-time regime reveal an ultrafast population of a charge separated state for both polymer and monomer. Local excitation of the squaraine moiety is followed by population of intermediate states, presumably charge transfer states, followed by full charge separation, which occurs within a ca. 2 ps. Charge recombination takes place within 5.2 ps, probably because the system is close to the Marcus optimal region for barrierless ET. For the polymer, measurements of the transient absorption anisotropy show that neither charge nor does energy transfer take place within the lifetime of the charge separated state, indicating that this state is essentially confined within one donor-acceptor pair. PMID:24145596

Völker, Sebastian F; Schmiedel, Alexander; Holzapfel, Marco; Böhm, Christoph; Lambert, Christoph

2013-10-21

49

Charge transfer reactions in nematic liquid crystals  

SciTech Connect

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.

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

50

Charge transfer excitations in cofacial fullerene-porphyrin complexes  

NASA Astrophysics Data System (ADS)

Porphyrin and fullerene donor-acceptor complexes have been extensively studied for their photo-induced charge transfer characteristics. We present the electronic structure of ground states and a few charge transfer excited states of four cofacial porphyrin-fullerene molecular constructs studied using density functional theory at the all-electron level using large polarized basis sets. The donors are base and Zn-tetraphenyl porphyrins and the acceptor molecules are C60 and C70. The complexes reported here are non-bonded with a face-to-face distance between the porphyrin and the fullerene of 2.7 to 3.0 A?. The energies of the low lying excited states including charge transfer states calculated using our recent excited state method are in good agreement with available experimental values. We find that replacing C60 by C70 in a given dyad may increase the lowest charge transfer excitation energy by about 0.27 eV. Variation of donor in these complexes has marginal effect on the lowest charge transfer excitation energy. The interfacial dipole moments and lowest charge transfer states are studied as a function of face-to-face distance.

Zope, Rajendra R.; Olguin, Marco; Baruah, Tunna

2012-08-01

51

Phonons and charge-transfer excitations in HTS superconductors  

SciTech Connect

Some of the experimental and theoretical evidence implicating phonons and charge-transfer excitations in HTS superconductors is reviewed. It is suggested that superconductivity may be driven by a synergistic interplay of (anharmonic) phonons and electronic degrees of freedom (e.g., charge fluctuations, excitons). 47 refs., 5 figs.

Bishop, A.R.

1989-01-01

52

SEMICONDUCTOR DEVICES: Simulation for signal charge transfer of charge coupled devices  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

53

INTRAMOLECULAR CHARGE AND ENERGY TRANSFER IN MULTICHROMOPHORIC AROMATIC SYSTEMS  

SciTech Connect

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.

Edward C. Lim

2008-09-09

54

Theoretical treatment of charge transfer processes of relevance to astrophysics  

SciTech Connect

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.

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

1997-12-01

55

Conformational control of benzophenone-sensitized charge transfer in dinucleotides.  

PubMed

Charge transfer in DNA cannot be understood without addressing the complex conformational flexibility, which occurs on a wide range of timescales. In order to reduce this complexity four dinucleotide models consisting of benzophenone linked by a phosphodiester to one of the natural nucleosides = , , , were studied in water and methanol. The theoretical work focuses on the dynamics and electronic structure of . Predominant conformations in the two solvents were obtained by molecular dynamics simulations. in MeOH adopts mainly an open geometry with a distance of 12-16 Å between the two aromatic parts. In H2O the two parts of form primarily a stacked conformation yielding a distance of 5-6 Å. The low-lying excited states were investigated by electronic structure theory in a QM/MM environment for representative snapshots of the trajectories. Photo-induced intramolecular charge transfer in the S1 state occurs exclusively in the stacked conformation. Ultrafast transient absorption spectroscopy with reveals fast charge transfer from S1 in both solvents with varying yields. Significant charge transfer from the T1 state is only found for the nucleobases with the lowest oxidation potential: in H2O, charge transfer occurs with 3.2 × 10(9) s(-1) for and 6.0 × 10(9) s(-1) for . The reorganization energy remains nearly unchanged going from MeOH to the more polar H2O. The electronic coupling is rather low even for the stacked conformation with HAB = 3 meV and explains the moderate charge transfer rates. The solvent controls the conformational distribution and therefore gates the charge transfer due to differences in distance and stacking. PMID:24084688

Merz, Thomas; Wenninger, Matthias; Weinberger, Michael; Riedle, Eberhard; Wagenknecht, Hans-Achim; Schütz, Martin

2013-10-01

56

Assessment of atomic partial charge schemes for polarisation and charge transfer effects in ionic liquids.  

PubMed

In this work, we assess several popular atomic partial charge schemes with the view of accurately quantifying charge distribution, dipole moments and charge transfer in routinely used ionic liquids (ILs). We investigated a series of ion pairs of imidazolium-based ILs such as [C((1-4))mim]X (where X = Cl, BF(4) and NTf(2)) and ionic clusters of [NMe(4)][BF(4)], [C(1)mim][BF(4)] and [C(1)mim]Cl that were composed of two, four and eight ion pairs. Assessed partial charge schemes include restrained electrostatic potentials (RESP) employing ChelpG, Connolly and Geodesic point selection algorithms, as well as density matrix partitioning schemes including Mulliken, Löwdin and Natural Population Analysis (NPA). The quality of charge distribution was analysed using the following criteria: (1) treatment of symmetry identical atoms, (2) invariance of charge in the imidazolium ring with increasing alkyl chain and (3) recalculation to dipole moments as a measure of electronic polarisation. The RESP schemes such as Connolly and Geodesic clearly outperform the ChelpG scheme as well as the density matrix-based schemes for these three criteria. Calculated partial charges reveal that dipole moments were best represented by the RESP schemes and confirmed the presence of charge transfer in ILs to a various degree. The degree of charge transfer was dependent on anions as well as cluster size. In the ion pairs, the chloride anion showed the largest charge transfer, followed by the NTf(2) and BF(4) anions. In ionic clusters the charge transfer was shown to gradually converge from two to eight ion pairs in the case of the [NMe(4)][BF(4)] and [C(1)mim][BF(4)] ILs to a value, close to that for corresponding ion pairs. In contrast, charge transfer in the [C(1)mim]Cl clusters converges to a lower value, showing an unusually strong inter-ionic bond with the chloride anion. NPA charges were found to perform poorly, with near-unity charges being retained on the anions and cations in ion pairs and ionic clusters. Mulliken and Löwdin charges were shown to be highly basis set dependent and unpredictable with marked fluctuations in partial charges and therefore their use for ILs is particularly discouraged. Ability of the partial charge schemes to capture fluctuations in the dipole moment within the ionic clusters was also examined. The Connolly and Geodesic RESP schemes were found to slightly outperform ChelpG. Evidence to suggest that chloride-based ILs might be poor model systems for ILs is also presented. PMID:23247883

Rigby, Jason; Izgorodina, Ekaterina I

2013-02-01

57

Light-Induced Charge Separation and Transfer in Bacteriorhodopsin  

NASA Astrophysics Data System (ADS)

The photo-voltage signals in bacteriorhodopsin(bR) excited by 1064 nm 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.

Huang, Yu-Hua; Zhao, You-Yuan; Zhang, Zhong-Bin; Ou-Yang, Xiao-Ping; Gong, Qin-Gan; Chen, Ling-Bing; Li, Fu-Ming; Liu, Jian; Ding, Jian-Dong; Li, Qing-Guo

2000-04-01

58

Charge transfer, charge tailing, cohesion and electron promotion in the transition metals  

Microsoft Academic Search

Two issues will be considered in this paper. The first recalls Art Freeman's early interest in charge and magnetic hyperfine effects and is concerned with the factors involved in the ``charge transfer in solid compounds'', either as measured in experiment or as calculated by band theory. The second matter, which will be inspected briefly, follows up on ideas of Gunnarsson

R. E. Watson; M. Weinert; G. W. Fernando; J. W. Davenport

1991-01-01

59

Projectile charge dependence of multi-electron transfer processes in highly charged ion-atom collisions  

Microsoft Academic Search

We have measured the absolute multi-electron transfer cross sections and branching ratios for the decay of multiply excited Rydberg ions in slow Iq+-Xe, Ar (10 <= q <= 20) collisions combining the initial growth rate method with coincidence method. We report the incident ion charge dependence of transfer cross sections and branching ratios.

H. A. Sakaue; H. Tawara; I. Yamada; K. Hosaka; F. Krok; F. J. Currell; N. Nakamura; S. Ohtani; H. Watanabe; A. Danjo; M. Kimura; A. Matsumoto; M. Sakurai; M. Yoshino

1997-01-01

60

Charge-transfer water potential for solvated protein dynamics  

NASA Astrophysics Data System (ADS)

Water plays a critical role in simulations of complex structure-function relationships such as the mechanochemistry of molecular motor proteins, wherein solvating water molecules interact with divalent cations such as Mg^+2, salt bridges, and polar or charged amino acids. Existing fixed-charge and fluctuating charge water models are inadequate in these environments, since they do not support reactive charge transfer with proper long-range dissociation behavior. The charge-transfer embedded atom method (CT-EAM) potential of Valone and Atlas was developed to address these challenges. It includes charge-polarized and ionic embedding terms that describe many-body atomistic interactions as a statistical ensemble of integer-charge excitations; background embedding densities are functions of local pseudoatom electron density distributions that integrate to non-integer charges and evolve dynamically under chemical potential equalization. Here we report first results from simulations of water using the CT-EAM potential of [1] and compare with characteristic properties of the liquid as determined via conventional force fields. [1] K. Muralidharan, S. M. Valone, and S.R. Atlas. arXiv:cond-mat/0705.0857v1, submitted.

Janardhanam, Vijay; Amo-Kwao, Godwin; Atlas, Susan R.

2010-03-01

61

Oxidation and Metal-Insertion in Molybdenite Surfaces: Evaluation of Charge-Transfer Mechanisms and Dynamics  

SciTech Connect

Molybdenum sulfide (MoS2), an important representative member of the layered transition-metal dichalcogenides, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and industrial science and technology. 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. On the other hand understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is quite important to utilize these minerals in technological applications. Furthermore, such a detailed investigation of thermal oxidation behavior and intercalation process will provide a basis to further explore and model the mechanism of adsorption of metal ions on to geomedia. Therefore, the present work was performed to understand the oxidation and intercalation processes of molybdenite surfaces. The results obtained, using a wide variety of analytical techniques, are presented and discussed in this paper.

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

2008-06-05

62

Charge-transfer in quasilinear push–pull polyene chains  

NASA Astrophysics Data System (ADS)

We used a TD-DFT approach relying on range-separated hybrids to evaluate the photon induced charge-transfer of substituted polyene oligomers of increasingly long chains. Several exchange–correlation functionals have been considered. Push, pull and push–pull systems containing up to 20 unit cells have been compared. A cooperative, but non additive, impact of the donor and acceptor groups is found. In long oligomers, the changes in the electronic density are mainly located on the central segment and not on the terminal electroactive groups, but the charge-transfer distance remains large, which contrasts with most push–pull compounds.

Anne, Fréderic B.; Purpan, Florent D.; Jacquemin, Denis

2013-08-01

63

The Impact of Pore Water Chemistry on Carbonate Surface Charge and Oil Wettability  

Microsoft Academic Search

Water chemistry has been shown experimentally to affect the stability of water films and the sorption of organic oil components\\u000a on mineral surfaces. When oil is displaced by water, water chemistry has been shown to impact oil recovery. At least two mechanisms\\u000a could account for these effects, the water chemistry could change the charge on the rock surface and affect

A. Hiorth; L. M. Cathles; M. V. Madland

2010-01-01

64

Semiempirical and ab initio Calculations of Charged Species Used in the Physical Organic Chemistry Course.  

ERIC Educational Resources Information Center

Concentrates on the semiempirical methods MINDO/3, MNDO, and AMI available in the program AMPAC from the Quantum Chemistry Program Exchange at Indiana University. Uses charged ions in the teaching of computational chemistry. Finds that semiempirical methods are accurate enough for the general use of the bench chemist. (MVL)

Gilliom, Richard D.

1989-01-01

65

Layered charge transfer complex cathodes or solid electrolyte cells  

Microsoft Academic Search

Layered charge transfer complex cathodes for use in solid electrolyte cells are described wherein one layer of the cathode contains an electronic conductor which is isolated from the cell's solid electrolyte by a second layer of the cathode that does not contain an electronic conductor.

Louzos

1981-01-01

66

Twisted intramolecular charge transfer emission of dimethylaminobenzonitrile in ?-cyclodextrine cavities  

NASA Astrophysics Data System (ADS)

The absorption and emission of 4-(N,N-dimethylamino)benzonitrile (DMABN) in ?-cyclodextrine (?-CD) cavities is reported. The twisted intramolecular charge transfer emission is enhanced on complexation with ?-CD. This is attributed to the reduced polarity of the CD environment.

Nag, Ashis; Bhattacharyya, Kankan

1988-10-01

67

Tight-binding parameters for charge transfer along DNA  

Microsoft Academic Search

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

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

2009-01-01

68

Valence topological charge-transfer indices for dipole moments  

Microsoft Academic Search

New topological valence charge-transfer (CT) indices are applied to the calculation of dipole moments. The dipole moments calculated by algebraic and vector semisums of the CT indices are defined. The combination of the CT 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

Francisco Torrens

2003-01-01

69

Monte Carlo model for describing charge transfer in irradiated CCDs  

Microsoft Academic Search

Radiation exposure of CCD devices degrades the charge transfer inefficiency (CTI) by the creation of electron trap sights within the bulk silicon. The presence of electron traps tend to smear the signal of a point-like image. This affects CCDs used in star trackers where sub-pixel centroiding is required for accurate pointing knowledge. To explore the effects of radiation damage in

Dennis J. Gallagher; Raymond Demara; Gary Emerson; Wayne W. Frame; Alan W. Delamere

1998-01-01

70

Attosecond snapshots: imaging charge transfer in molecules using EUV light  

NASA Astrophysics Data System (ADS)

Electron dynamics underlie the charge and energy transfer processes in molecules. These processes, although extremely fast, can be resolved by sub-femtosecond light pulses and the electron motion can, to some extent, be controlled. A novel scheme for electron localization using intense IR lasers has recently been developed using phase-locked multiple pulses, in which the charge centre can be isolated. This process can be identified by the asymmetry in the dissociation products. We propose the use of an extreme ultraviolet probe of the molecular ion prior to dissociation to image the density and phase of the electron orbital. We hope this will provide rich insight into the charge transfer process in small molecules, which may be extended to larger systems.

McCann, J. F.; McLaughlin, B. M.; Calvert, C. R.; King, R. B.; Bryan, W. A.; Newell, W. R.; Greenwood, J. B.; Williams, I. D.

2012-11-01

71

Double proton transfer and charge transfer transitions in hydrogen-bonded systems: formic acid dimer  

NASA Astrophysics Data System (ADS)

The barriers for double proton transfer in the ground and lowest ?-? * and ?-? * excited states of the formic acid dimer have been calculated within a modified INDO scheme. Analysis of the nature of the excited electronic states, with emphasis on charge-transfer transitions, has been performed. The results indicate a lower barrier in the excited ?-? * states than in the ground state.

Lipi?ski, J.; Sokalski, W. A.

1980-11-01

72

Ionization and charge transfer in collisions of highly charged ions with helium at low velocity  

Microsoft Academic Search

Ionization and charge transfer in slow collisions between highly charged projectiles and helium atoms are studied by the two-center atomic orbital close-coupling method within the independent electron approximation. The relative importance of single ionization to single capture is investigated. Our calculations show that ionization cross sections for C{sup 6+}, N{sup 7+}, and O{sup 8+} projectiles increase rapidly between {ital v}=1

Y. D. Wang; C. D. Lin; N. Toshima; Z. Chen

1995-01-01

73

Ionization and charge transfer in collisions of highly charged ions with helium at low velocity  

Microsoft Academic Search

Ionization and charge transfer in slow collisions between highly charged projectiles and helium atoms are studied by the two-center atomic orbital close-coupling method within the independent electron approximation. The relative importance of single ionization to single capture is investigated. Our calculations show that ionization cross sections for C6+, N7+, and O8+ projectiles increase rapidly between v=1 and 2 a.u. The

Y. D. Wang; C. D. Lin; N. Toshima; Z. Chen

1995-01-01

74

A model for charge transfer in buried-channel charge-coupled devices at low temperature  

Microsoft Academic Search

Charge transfer in buried-channel charge-coupled devices (CCDs) is explored with a one-dimensional numerical model which describes the capture and emission of electrons from a shallow donor level in silicon through the use of the Shockley-Read-Hall generation-recombination theory. Incorporated in the model are the three-dimensional Poole-Frenkel barrier lowering theory of A. K. Jonscher (1967) and J. L. Hartke (1968) and the

Edmund K. Banghart; James P. Lavine; Eugene A. Trabka; Edward T. Nelson; Bruce C. Burkey

1991-01-01

75

Suppression of intersite charge transfer in charge-disproportionated perovskite YCu3Fe4O12.  

PubMed

A novel iron perovskite YCu3Fe4O12 was synthesized under high pressure and high temperature of 15 GPa and 1273 K. Synchrotron X-ray and electron diffraction measurements have demonstrated that this compound crystallizes in the cubic AA'3B4O12-type perovskite structure (space group Im3, No. 204) with a lattice constant of a = 7.30764(10) Å at room temperature. YCu3Fe4O12 exhibits a charge disproportionation of 8Fe(3.75+) ? 3Fe(5+) + 5Fe(3+), a ferrimagnetic ordering, and a metal-semiconductor-like transition simultaneously at 250 K, unlike the known isoelectronic compound LaCu3Fe4O12 that currently shows an intersite charge transfer of 3Cu(2+) + 4Fe(3.75+) ? 3Cu(3+) + 4Fe(3+), an antiferromagnetic ordering, and a metal-insulator transition at 393 K. This finding suggests that intersite charge transfer is not the only way of relieving the instability of the Fe(3.75+) state in the A(3+)Cu(2+)3Fe(3.75+)4O12 perovskites. Crystal structure analysis reveals that bond strain, rather than the charge account of the A-site alone, which is enhanced by large A(3+) ions, play an important role in determining which of intersite charge transfer or charge disproportionation is practical. PMID:23560478

Etani, Hidenobu; Yamada, Ikuya; Ohgushi, Kenya; Hayashi, Naoaki; Kusano, Yoshihiro; Mizumaki, Masaichiro; Kim, Jungeun; Tsuji, Naruki; Takahashi, Ryoji; Nishiyama, Norimasa; Inoue, Toru; Irifune, Tetsuo; Takano, Mikio

2013-04-15

76

Charge transfer mediated by nigericin in black lipid membranes.  

PubMed

Nigericin, in the concentration range (10(-6) M or higher) at which it uncouples intact mitochondria, was found to increase the conductance of black lipid membranes (BLM) by several orders of magnitude. The dependence of the membrane conductance on pH and K+ concentration suggests a mechanism for the transfer of charge mediated by this ionophore based on a mobile dimer with both nigericin molecules protonated and complexed with one K+. This charged complex accounts for the uncoupling effect observed in intact mitochondria. PMID:8444

Toro, M; Gómez-Lojero, C; Montal, M; Estrada-O, S

1976-02-01

77

Ultrafast photo-induced charge transfer unveiled by two-dimensional electronic spectroscopy.  

PubMed

The interaction of exciton and charge transfer (CT) states plays a central role in photo-induced CT processes in chemistry, biology, and physics. In this work, we use a combination of two-dimensional electronic spectroscopy (2D-ES), pump-probe measurements, and quantum chemistry to investigate the ultrafast CT dynamics in a lutetium bisphthalocyanine dimer in different oxidation states. It is found that in the anionic form, the combination of strong CT-exciton interaction and electronic asymmetry induced by a counter-ion enables CT between the two macrocycles of the complex on a 30 fs timescale. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra, and we monitor how the excited state charge density ultimately localizes on the macrocycle closest to the counter-ion within 100 fs. A comparison with the dynamics in the radical species further elucidates how CT states modulate the electronic structure and tune fs-reaction dynamics. Our experiments demonstrate the unique capability of 2D-ES in combination with other methods to decipher ultrafast CT dynamics. PMID:22667567

Bixner, Oliver; Lukeš, Vladimír; Man?al, Tomáš; Hauer, Jürgen; Milota, Franz; Fischer, Michael; Pugliesi, Igor; Bradler, Maximilian; Schmid, Walther; Riedle, Eberhard; Kauffmann, Harald F; Christensson, Niklas

2012-05-28

78

Modelling charge transfer in a radiation damaged charge coupled device for Euclid  

NASA Astrophysics Data System (ADS)

As electrons are transferred through a radiation damaged Charge Coupled Device (CCD), they may encounter traps in the silicon in which they will be captured and subsequently released. This capture and release of electrons can lead to a 'smearing' of the image. The dynamics of the trapping process can be described through the use of Shockley-Read-Hall theory, in which exponential time constants are used to determine the probability of capture and release. If subjected to a hostile radiation environment, such as in space where the dominant charged particle is the proton, these incident protons can cause displacement damage within the CCD and lead to the formation of stable trap sites. As the trap density increases, the trapping and release of signal electrons can have a major impact on the Charge Transfer Efficiency (CTE) to the detriment of device performance. As the science goals for missions become ever more demanding, such as those for the ESA Euclid and Gaia missions, the problem of radiation damage must be overcome. In order to gain a deeper understanding of the trapping process and the impact on device performance, a Monte Carlo simulation has been developed to model the transfer of charge in a radiation damaged CCD. This study investigates the various difficulties encountered when developing such a model: the incorporation of appropriate clocking mechanisms, the use of suitable trap parameters and their degeneracy, and the development of methods to model the charge storage geometry within a pixel through the use of three-dimensional Silvaco simulations.

Hall, David J.; Holland, Andrew; Murray, Neil; Gow, Jason; Clarke, Andrew

2012-07-01

79

Relative charge transfer cross section from Rb(4d)  

SciTech Connect

Relative charge transfer cross section measurements for the excited state Rb(4d) with 7 keV Na{sup +} is reported. The specific channels reported are Na{sup +}+Rb(4d{sub 5/2}){yields}Na(nl)+Rb{sup +}, where the dominant transfer cross sections channels were nl=3d and 4s. Using a combination of a magneto-optical trap and recoil ion momentum spectroscopy (MOTRIMS methodology), the cross sections were measured relative to the previously studied Na{sup +}+Rb(5s,5p) systems at the same collision energy.

Shah, M.H.; Camp, H.A.; Trachy, M.L.; De Paola, B.D. [J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States); Flechard, X. [LPC CAEN, Boulevard du Marechal Juin, 14050 CAEN CEDEX (France); Gearba, M.A. [Department of Physics and Astronomy, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (United States); Nguyen, H. [Department of Physics and Astronomy, University of Wisconsin-Stevens Point, Stevens Point, Wisconsin 55481 (United States); Bredy, R. [Laboratoire de Spectrometrie Ionique et Moleculaire, Universite Claude Bernard Lyon1, 69622 Villeurbanne Cedex (France); Lundeen, S.R. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States)

2005-08-15

80

Binuclear TiOMn charge-transfer chromophore in mesoporous silica.  

PubMed

An all-inorganic heterobinuclear chromophore consisting of Ti(IV) oxo-bridged to a Mn(II) center has been assembled on the surface of silica pores of MCM-41 material. The key step of covalent attachment on the pore surface is the reaction of a Mn(II) precursor featuring weakly held CH3CN ligands with the OH group of a previously anchored titanol site. The optical diffuse reflectance spectrum reveals a Ti(IV)OMn(II) --> Ti(III)OMn(III) metal-to-metal charge-transfer (MMCT) absorption extending from the UV throughout to visible into the red spectral region. FT-IR, FT-Raman and optical spectroscopy confirm that the material is free of Mn oxide clusters, while EPR and Mn K-edge X-ray absorption spectra indicate that the donor center is predominantly in oxidation state +2. In situ FT-IR spectroscopy allowed detection of visible light-induced redox chemistry of the MMCT unit using O2 (18O2) and methanol as acceptor and donor probe molecules, respectively. Formate and water were observed as primary products, with methyl formate emerging as a secondary condensation product. The observed photochemistry demonstrates that excitation of the Ti(IV)OMn(II) --> Ti(III)OMn(III) results in complete transfer of an electron from donor to acceptor center, with the charge separation sufficiently long lived for initiation of redox chemistry to occur. With donor and acceptor redox potentials appropriate for driving multi-electron catalysts for water oxidation, proton or CO2 reduction, the TiOMn(II) unit is an attractive candidate as a charge-transfer chromophore in a solar fuel generating system. PMID:19904439

Wu, Xiuni; Weare, Walter W; Frei, Heinz

2009-10-13

81

Charge transfer magnetoexciton formation at vertically coupled quantum dots.  

PubMed

A theoretical investigation is presented on the properties of charge transfer excitons at vertically coupled semiconductor quantum dots in the presence of electric and magnetic fields directed along the growth axis. Such excitons should have two interesting characteristics: an extremely long lifetime and a permanent dipole moment. We show that wave functions and the low-lying energies of charge transfer exciton can be found exactly for a special morphology of quantum dots that provides a parabolic confinement inside the layers. To take into account a difference between confinement potentials of an actual structure and of our exactly solvable model, we use the Galerkin method. The density of energy states is calculated for different InAs/GaAs quantum dots' dimensions, the separation between layers, and the strength of the electric and magnetic fields. A possibility of a formation of a giant dipolar momentum under external electric field is predicted. PMID:23092373

Gutiérrez, Willian; Marin, Jairo H; Mikhailov, Ilia D

2012-10-23

82

Why do Physicists Love Charge-Transfer Salts?  

NASA Astrophysics Data System (ADS)

I describe some of the phenomena encountered in charge-transfer salts that make them very attractive for condensed-matter physicists. These materials exhibit many interesting electronic properties, including reduced dimensionality, strong electron-electron and electron-phonon interactions and the proximity of antiferromagnetism, insulator states and superconductivity. A wide variety of low-temperature groundstates have been observed in the salts; frequently, one is able to move between these states by applying magnetic field, temperature, pressure or ``chemical pressure''. In spite of this complex behavior, the charge-transfer salts possess very simple electronic bandstructure which it is often possible to measure in great detail. Hence, one can use the salts as ``model systems'' in which tractable theoretical calculations for phenomena such as superconductivity are compared directly with experiment.

Singleton, John

2002-11-01

83

Charge transfer between point contacts in high magnetic fields  

NASA Astrophysics Data System (ADS)

We present the calculated and the measured data on charge transfer between two closely spaced point contacts inserted in a magnetic field parallel to the trigonal face of a bismuth single crystal. The problem has been analyzed with the geometry of a transverse electron focusing (TEF) experiment, and different relations between the contact-to-contact distance L and the mean free path of electrons l. The TEF method permits us to observe the subsurface skin layer formation beginning with very low fields and it allows control of the specular reflectivity of electrons from the metal boundary. If L < l, electrons moving along the surface generate the collector signal for H?L proportional to H. For large contact-to-contact separations (L > l), the charge transfer is mainly accomplished through a diffuse motion of electrons from contact to contact through the bulk of the sample.

Andrievskii, V. V.; Kolesnichenko, Yu. A.; Rozhok, S. V.

1995-06-01

84

Charge transfer in the presence of a magnetic field  

Microsoft Academic Search

Symmetric resonant charge transfer in atomic collisions in the presence of a homogeneous constant magnetic field is investigated within the impact parameter method and the atomic two-state expansion. The novelties brought about by the presence of the magnetic field are discussed in detail. The most peculiar new feature is the appearance of a magnetic-field-dependent phase factor in the process wavefunction,

S. Bivona; B. Spagnolo; G. Ferrante

1984-01-01

85

"Inverted" Solvent Effect on Charge Transfer in the Excited State.  

PubMed

Faster in cyclohexane than in acetonitrile is the fluorescence quenching of the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by amines and sulfides. Although this photoreaction is induced by charge transfer (CT; see picture) and exciplexes are formed, the increase in the dipole moment of the exciplex is not large enough to offset the solvent stabilization of the excited reactants, and an "inverted" solvent effect results. PMID:10540381

Nau; Pischel

1999-10-01

86

Charge transfer in intermetallics: HfPt3  

Microsoft Academic Search

The charge transfer in HfPt3 is discussed on the basis of the 4f core-electron binding-energy shifts of the constituent elements. Based on binding energies measured relative to the Fermi levels, both Hf and Pt have positive shifts in the compound. According to a Born-Haber cycle analysis these shifts are directly attributable to the large enthalpy of formation of HfPt3. Corrections

G. K. Wertheim; D. N. E. Buchanan; J. H. Wernick

1989-01-01

87

Charge transfer in intermetallics: HfPt sub 3  

Microsoft Academic Search

The charge transfer in HfPtâ is discussed on the basis of the 4{ital f} core-electron binding-energy shifts of the constituent elements. Based on binding energies measured relative to the Fermi levels, both Hf and Pt have positive shifts in the compound. According to a Born-Haber cycle analysis these shifts are directly attributable to the large enthalpy of formation of HfPtâ.

G. K. Wertheim; D. N. E. Buchanan; J. H. Wernick

1989-01-01

88

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

PubMed Central

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 significant increase in size associated with a decrease in density with further annealing.

Ramana, CV; Becker, U; Shutthanandan, V; Julien, CM

2008-01-01

89

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

PubMed

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 increase in size associated with a decrease in density with further annealing. PMID:18534025

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

2008-06-05

90

Reflection mechanism for generating spin transfer torque without charge current  

NASA Astrophysics Data System (ADS)

A reflection mechanism for generating spin-transfer torque is proposed. It is due to interference of bias-driven nonequilibrium electrons incident on a switching junction, with the electrons reflected from an insulating barrier inserted in the junction after the switching magnet. It is shown, using the rigorous Keldysh formalism, that this out-of-plane torque T? is proportional to an applied bias and is as large as the torque in a conventional junction generated by a strong charge current. However, the charge current and the in-plane torque T? are almost completely suppressed by the insulating barrier. This junction thus offers the highly applicable possibility of bias-induced switching of magnetization without charge current.

Autès, G.; Mathon, J.; Umerski, A.

2012-03-01

91

Computer Science and Technology: Impact of Charge-Transfer Device Technology on Computer Systems.  

National Technical Information Service (NTIS)

The document assesses the status of charge-transfer device technology as displayed by foreign research and manufacturing facilities for a period up to September 1975. Capabilities and accomplishments of charge-transfer device research facilities in Japan,...

R. B. J. Warnar

1977-01-01

92

Energy transfer in ion-Rydberg charge exchange  

NASA Astrophysics Data System (ADS)

The charge transfer process between slow ions and Rydberg atoms was studied using resonant laser excitation to detect specific energy states of the collision products. The collisions were studied for ions of charge q = 2-11 at a velocity of v = 0.100 a.u. and for velocities v = 0.031-0.130 a.u. at a charge of q = 3. The Rydberg target was excited by three lasers into a final state where the primary quantum number could be varied from nt = 7 to nt = 26. The apparatus used to implement the detection scheme is discussed in detail. The apparatus includes a device to remove the primary ion beam prior to the detector while transmitting the q-1 charge transfer beam. The development and characterization of this device are described in detail. Also described is the flexible low noise detector developed to measure the laser excited state in the collision product. The data collected show a clear resonance in the capture cross section to a particular energy state as the binding energy of the Rydberg target is varied. The resonance varies significantly over the range of charges and velocities studied and agrees very well with the classical trajectory Monte Carlo (CTMC) theory over nearly the entire range of measurements. Only at the lowest and highest velocities studied are any significant disagreements seen. The measurement shows a slightly larger width than CTMC theory at the lowest two velocities studied, v = 0.031 and 0.046 a.u. At the highest velocity studied v = 0.130 a.u. significant disagreement with CTMC theory is seen. However, the measured resonance position clearly disagrees with the predictions of the classical over barrier (COB) model. The variation of width with both charge and velocity is similar to what would be expected from a simple uncertainty principle argument, however the overall agreement with CTMC suggests a quantum mechanical argument may not be necessary to explain this behavior.

Fisher, Daniel Scott

93

Effect of conformational degrees of freedom on the charge transfer in model tripeptide  

Microsoft Academic Search

An extensive conformational dependence of the intramolecular charge transfer (both hole and electron) between intermediate residues of the model tripeptide in gas phase has been studied. The charge transfer integral, spatial overlap integral and site-energy for both hole and electron transfer between the intermediate residues in the tripeptides were calculated using the fragment orbital method. The site-energies and the charge

N. Santhanamoorthi; P. Kolandaivel; K. Senthilkumar

2009-01-01

94

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

NASA Astrophysics Data System (ADS)

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 oscillation of the spin density - charge migration - between the N atom and the phenyl ring with a period of 4 fs. When the nuclear motion becomes coupled, this oscillation persists in a damped form, followed by an effective charge transfer after 30 fs.

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

2013-07-01

95

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

PubMed

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 oscillation of the spin density--charge migration--between the N atom and the phenyl ring with a period of 4 fs. When the nuclear motion becomes coupled, this oscillation persists in a damped form, followed by an effective charge transfer after 30 fs. PMID:23901963

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

2013-07-28

96

Charge transfer efficiency in proton damaged CCD`s  

SciTech Connect

The authors have performed detailed measurements of the charge transfer efficiency (CTE) in a thinned, backside-illuminated imaging charge-coupled device (CCD). The device had been damaged in three separate sections by proton radiation typical of that which a CCD would receive in space-borne experiments, nuclear imaging, or particle detection. They examined CTE as a function of signal level, temperature, and radiation dose. The dominant factor affecting the CTE in radiation-damaged CCD`s is seen to be trapping by bulk states. They present a simple physical model for trapping as a function of transfer rate, trap concentration, and temperature. They have made calculations using this model and arrived at predictions which closely match the measured results. The CTE was also observed to have a nonlinear dependence on signal level. Using two-dimensional device simulations to examine the distribution of the charge packets in the CCD channel over a range of signal levels, they were able to explain the observed variation.

Hardy, T. [Simon Fraser Univ., Burnaby, British Columbia (Canada). School of Engineering Science]|[National Research Council of Canada, Victoria, British Columbia (Canada). Herzberg Inst. of Astrophysics; Murowinski, R. [National Research Council of Canada, Victoria, British Columbia (Canada). Herzberg Inst. of Astrophysics; Deen, M.J. [Simon Fraser Univ., Burnaby, British Columbia (Canada). School of Engineering Science

1998-04-01

97

Raman scattering studies of organic semiconducting charge-transfer compounds  

NASA Astrophysics Data System (ADS)

Organic semiconductors offer the possibility of devices with greater mechanical flexibility and lower production costs compared to existing materials. Reports of carrier mobilities in monomolecular organic semiconductors in the 10-50 cm^2/V-s range and success in fabricating electronic devices from organic materials has increased the interest in their properties for electronic applications. However, the range of properties displayed by the monomolecular crystals is rather narrow. Charge-transfer compounds composed of two different organic molecules in which one acts as a donor and the other as an acceptor may represent the next generation of organic semiconductors. Control of their properties by modification of the molecules or changes in stoichiometry and crystalline structure makes them particularly attractive for a wide range of applications provided that the relationship between the structure and constituents of the compounds and their physical properties can be elucidated. Raman scattering studies of single crystals of two representative charge-transfer compounds, perylene-TCNQ and anthracene-TCNQ, will be presented. Theoretical calculations suggest that these materials have the potential for ambipolar charge transport, and so intermolecular interactions in these compounds are of particular interest.

McNeil, Laurie; Kloc, Christian

2011-03-01

98

Super-iron Nanoparticles with Facile Cathodic Charge Transfer  

SciTech Connect

Super-irons contain the + 6 valence state of iron. One advantage of this is that it provides a multiple electron opportunity to store additional battery charge. A decrease of particle size from the micrometer to the nanometer domain provides a higher surface area to volume ratio, and opportunity to facilitate charge transfer, and improve the power, voltage and depth of discharge of cathodes made from such salts. However, super-iron salts are fragile, readily reduced to the ferric state, with both heat and contact with water, and little is known of the resultant passivating and non-passivating ferric oxide products. A pathway to decrease the super-iron particle size to the nano-domain is introduced, which overcomes this fragility, and retains the battery capacity advantage of their Fe(VI) valence state. Time and power controlled mechanosynthesis, through less aggressive, dry ball milling, leads to facile charge transfer of super-iron nanoparticles. Ex-situ X-ray Absorption Spectroscopy is used to explore the oxidation state and structure of these iron oxides during discharge and shows the significant change in stability of the ferrate structure to lower oxidation state when the particle size is in the nano-domain.

M Farmand; D Jiang; B Wang; S Ghosh; D Ramaker; S Licht

2011-12-31

99

Atypical charge redistribution over a charge-transfer monolayer on a metal  

NASA Astrophysics Data System (ADS)

We report an atypical charge distribution in a highly ordered monolayer of sodium (Na) and tetracyanoquinodimethane (TCNQ) on a Au(111) surface. Na atoms incorporated in the charge-transfer layer donate their 3s electron to the lowest unoccupied orbital of the TCNQ acceptor. A fingerprint of such a TCNQ anion is observed in scanning tunneling spectroscopy as a zero-bias peak characteristic of the Kondo effect. Spatial maps of the Kondo resonance surprisingly reveal that it appears most intense on top of the Na sites. Supported by density functional theory simulations, we interpret this peculiar charge distribution pattern as originating from the extension of the singly occupied molecular orbital beyond the molecular backbone, and cloaking the Na cations. We further suggest that this deformation of molecular orbitals is a consequence of the electrostatic potential landscape of the polar Na–TCNQ layer.

Umbach, T. R.; Fernández-Torrente, I.; Ruby, M.; Schulz, F.; Lotze, C.; Rurali, R.; Persson, M.; Pascual, J. I.; Franke, K. J.

2013-08-01

100

Polarization and charge transfer in the hydration of chloride ions  

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

101

Charge transfer in gold-alkali-metal systems  

NASA Astrophysics Data System (ADS)

Based on conventional electronegativity arguments, gold-alkali-metal compounds are expected to be among the most ``ionic'' of metallic compounds. The concepts of ionicity and charge transfer are difficult to quantify. However, the changes in bonding in the 50/50 Au-alkali-metal systems between the elemental metals and the compounds are so severe that observations can readily be made concerning their character. The results, as obtained from self-consistent electronic-structure calculations, lead to the apparently odd observation that the electron density at the alkali-metal sites in the compound increases significantly and this involves high l componennts in the charge density. This increase, however, can be attributed to Au-like orbitals spatially overlapping the alkali-metal sites. In a chemical sense, it is reasonable to consider the alkali-metal transferring charge to these Au orbitals. While normally the difference in heats of formation between muffin-tin and full-potential calculations for transition-metal-transition-metal and transition-metal-main-group (e.g., Al) compounds having high site symmetry are small, for the gold-alkali-metal systems, the changes in bonding in the compounds cause differences of ~0.5 eV/atom between the two classes of potential. Any serious estimate of the electronic structure in these systems must account for these aspherical bonding charges. The origin of the semiconducting behavior of the heavy-alkali-metal Au compounds is shown to arise from a combination of the Au-Au separations and the ionic character of the compounds; the light-alkali-metal Au compounds, with their smaller Au-Au separations, do not have a semiconducting gap. Core-level shifts and isomer shifts are also briefly discussed.

Watson, R. E.; Weinert, M.

1994-03-01

102

Intramolecular charge transfer in donor-acceptor molecules  

SciTech Connect

The photophysical properties of donor-acceptor molecules, push-pull polyenes and carotenoids, have been studied by absorption and fluorescence spectroscopy. The compounds bear various acceptor and donor groups, linked together by chains of different length and structure. The position of the absorption and fluorescence maxima and their variation in solvents of increasing polarity are in agreement with long-distance intramolecular charge-transfer processes, the linker acting as a molecular wire. The effects of the linker length and structure and of the nature of acceptor and donor are presented.

Slama-Schwok, A.; Blanchard-Desce, M.; Lehn, J.M. (College de France, Paris (France))

1990-05-17

103

Diamagnetism and charge transfer in bromine graphite intercalation compounds  

NASA Astrophysics Data System (ADS)

The relationship of the magnetic susceptibility anisotropy and the charge-transfer parameter f in graphite-Br intercalation compounds is investigated theoretically. It is argued that the good fit to experimental data obtained by Tsang and Resing (1984) in calculations with f = 0.3 is based on an error in plotting the data of Hennig and McClelland (1955), indicating that the true value of f for these compounds must be significantly smaller. A corrected plot is shown, and the treatment of several other experimental details by Tsang and Resing is discussed.

Marchand, A.

1985-04-01

104

Supramolecular glycolipid based on host-enhanced charge transfer interaction.  

PubMed

Supramolecular glycolipid has been fabricated based on ternary complex system, which is composed of naphthyl glucosamine (GlcNap), alkyl viologen (RV8), and cucurbit[8]uril (CB[8]). CB[8] plays a key role to connect the other two building blocks together, and the process is driven by host-enhanced charge transfer interaction. Compared with the classic glycolipids, supramolecular glycolipids display redox responsiveness. Supramolecular glycolipids are able to self-assemble in water to form spherical aggregations, such as vesicle like structure. In addition, spherical aggregations can specifically interact with Concanavalin A, indicating that the carbohydrate groups are available on the surfaces of the aggregates. PMID:24024646

Yang, Liulin; Yang, Hui; Li, Fei; Zhang, Xi

2013-09-24

105

Importance of Charge Transfer Excitations in DNA Electron Spectrum:  

NASA Astrophysics Data System (ADS)

Electron spectra of DNA model compounds, adenosine-thymidine and guanosine-cytidine nucleoside base pairs, as well as the relevant homogeneous stacked base pair steps in A-DNA and B-DNA conformations, were investigated using ZINDO semiempirical quantum-chemical method. This work confirms that, in DNA with intact Watson-Crick hydrogen bonding and base stacking, the highest occupied molecular orbitals (HOMO) are residing on purine base residues, whereas the lowest unoccupied molecular orbitals (LUMO) — on pyrimidine base residues. In general, the present results are satisfactorily comparable with the available experimental data. The role of charge transfer excitations in the polymer DNA 260 nm spectral band is discussed.

Starikov, E. B.

106

Electrochemical charge transfer at a metallic electrode: A simulation study  

SciTech Connect

The calculation of the Marcus free energy curves for electron transfer events between a redox species and a metallic electrode in an atomistic simulation designed to model the electrochemical interface with an ionic liquid is described. The calculation is performed on a system comprising a molten salt mixture confined between model metallic electrodes [Reed et al., J. Chem. Phys. 126, 084704 (2007)] which are maintained at a constant electrical potential. The calculation therefore includes a self-consistent description of the screening of the electrode potential by the liquid and the polarization of the electrode by the ions (image charge effects). The purpose of the study was to examine how the Marcus curves depend on the applied potential and on the distance of the redox species from an electrode. The pronounced oscillations in the mean electrical potential seen in molten salt systems in the ''double-layer'' region are not reflected in the reaction free energy for the electron transfer event. The reorganization energy depends markedly on the distance of the redox ion from the electrode surface because of image charge effects.

Reed, Stewart K.; Madden, Paul A. [School of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ (United Kingdom); Papadopoulos, Aristides [Edinburgh Parallel Computer Centre, University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom)

2008-03-28

107

Electrochemical charge transfer at a metallic electrode: a simulation study.  

PubMed

The calculation of the Marcus free energy curves for electron transfer events between a redox species and a metallic electrode in an atomistic simulation designed to model the electrochemical interface with an ionic liquid is described. The calculation is performed on a system comprising a molten salt mixture confined between model metallic electrodes [Reed et al., J. Chem. Phys. 126, 084704 (2007)] which are maintained at a constant electrical potential. The calculation therefore includes a self-consistent description of the screening of the electrode potential by the liquid and the polarization of the electrode by the ions (image charge effects). The purpose of the study was to examine how the Marcus curves depend on the applied potential and on the distance of the redox species from an electrode. The pronounced oscillations in the mean electrical potential seen in molten salt systems in the "double-layer" region are not reflected in the reaction free energy for the electron transfer event. The reorganization energy depends markedly on the distance of the redox ion from the electrode surface because of image charge effects. PMID:18376954

Reed, Stewart K; Madden, Paul A; Papadopoulos, Aristides

2008-03-28

108

Spectrophotometric determination of boron based on charge transfer reaction.  

PubMed

Boron determination by a charge transfer spectrophotometric method is described. Accompanied the reaction, a charge transfer complex can be formed by lysine with sodium 1, 2-naphthoquinone-4-sulfonate and boron in alkaline solution (pH 12.00). Subsequently, a new reaction mechanism has been proposed and discussed. The absorbance at the maximal absorption wavelength is 574 nm and boron concentration agrees well with Beer's law in a range of 2.16-43.24 ?g mL(-1). The linear regression equation is A=-0.01867+0.01326C (?g mL(-1)), with a linearly correlation coefficient of 0.9935. The relative standard deviation (R.S.D.) of eleven parallel determinations is 2.1% with a detection limit (3?/k) of 2.00 ?g mL(-1). The recovery ranges from 96.4% to 104.5% with the satisfactory results. This method has been successfully applied to determine boron in pharmaceutical samples directly. PMID:21530377

Ma, Linjin; Zhang, Zhenxuan; Li, Quanmin

2011-04-02

109

Monte Carlo model for describing charge transfer in irradiated CCDs  

NASA Astrophysics Data System (ADS)

Radiation exposure of CCD devices degrades the charge transfer inefficiency (CTI) by the creation of electron trap sights within the bulk silicon. The presence of electron traps tend to smear the signal of a point-like image. This affects CCDs used in star trackers where sub-pixel centroiding is required for accurate pointing knowledge. To explore the effects of radiation damage in CCD devices, we have developed a Monte-Carlo model for simulating charge transfer in buried channel CCDs. The model is based on the Shockley-Read-Hall generation-recombination theory. The CTI in CCD devices was measured before and after exposure to mono-energetic 61 MeV protons. Our data show that displacement damage in the bulk silicon increases the CTI of the CCD device. CTI was measure don irradiated CCD devices at various temperatures form -10 to -150 C, thus providing estimates of the electron trap energy levels created in the CCD silicon. The dominate post-radiation rap energy level was the silicon E-center found to be at an energy of 0.46 eV, which is in good agreement with other published values. To fit our data over the complete temperature range, we also required electron traps of 0.36 eV and 0.21 eV. Our model also includes the effects of charge cloud growth with signal volume and clocking rates of the CCD device. Determining the types and levels of radiation a CCD device will encounter during its operational life is very important for choosing CCD operating parameters.

Gallagher, Dennis J.; Demara, Raymond; Emerson, Gary; Frame, Wayne W.; Delamere, Alan W.

1998-04-01

110

Charge-transfer efficiency in a buried-channel charge-coupled device at very low signal levels  

Microsoft Academic Search

A measurement of charge-transfer efficiency (CTE) is described for a 256-element charge-coupled linear imaging device operated below room temperature and at a very low total charge level per charge packet, that is, at a level of approximately 1\\/20 000th of saturation. This measurement was carried out at a register frequency near 15.75 kHz, the standard television-line frequency. CTE was measured

M. D. Jack; R. H. Dyck

1976-01-01

111

Smart CMOS Charge Transfer Readout Circuit for Time Delay and Integration Arrays  

Microsoft Academic Search

This paper presents a novel CMOS charge transfer readout circuit for X-ray time delay and integration (TDI) arrays with a depth of 64. The proposed circuit uses a charge transfer readout similar to CCD; thus, the summing of the signal charges can be implemented easily compared with other typical CMOS readout circuits for TDI arrays. The weakness of TDI arrays

Chul Bum Kim; Byung-Hyuk Kim; Yong Soo Lee; Han Jung; Hee Chul Lee

2006-01-01

112

46 CFR 35.35-35 - Duties of person in charge of transfer-TB/ALL.  

Code of Federal Regulations, 2011 CFR

... false Duties of person in charge of transfer-TB/ALL. 35.35-35 Section 35...35-35 Duties of person in charge of transferâTB/ALL. The person in charge of the transfer of liquid cargo in bulk, fuel oil in...

2011-10-01

113

Electronic structure and charge transfer states of a multichromophoric heptad  

NASA Astrophysics Data System (ADS)

A multichromophoric Heptad molecule containing Zn-tetraphenyl porphyrin, BDPY dye, bisphenyl anthracene, and C60 attached to a hexaphenyl -benzene core was synthesized by Gust et al. (J. Phys. Chem. B, 113, 7147 (2009)). The snowflake like molecule behaves like an antenna capturing photons at different wavelengths and transferring the energy to the porphyrin. We present a DFT based study on the ground state of the complex and also on the lowest two charge transfer (CT) states of the complex carried out using a perturbative delta-SCF method. The calculations, done using a mixed all-electron and pseudo-potential approach, show that the ionization potential of porphyrin and the electron affinity of C60 in the complex changes significantly from isolated molecules. Our calculated value of the lowest CT state is within 0.2 eV of the experimental estimate. This CT state contains a hole on porphyrin HOMO and a particle on the C60 LUMO. A comparison of the energetics with experiment indicates that the process probably involves excitation from the HOMO-1 of porphyrin to the porphyrin LUMO followed by electron transfer and hole bubbling up resulting in a CT state with the hole on porphyrin HOMO and particle on C60 LUMO.

Basurto, Luis; Zope, Rajendra; Baruah, Tunna

2013-03-01

114

Low-energy state-selective charge transfer by multiply charged ions.  

PubMed

We present a combined rf-guided ion beam and photon emission spectroscopy method, which facilitates state-selective charge-transfer measurements at energies of direct relevance for astrophysics and fusion-plasma diagnostics and modeling. Ion energies have been varied from 1000 eV/amu down to energies as low as 5 eV/amu. Absolute state-selective cross sections have been obtained for He (2+) and N (5+) ions colliding on molecular hydrogen. Orders of magnitude differences are found between theory and the present results. This indicates clearly that such data are valuable as benchmarks for the necessary advancement of theoretical descriptions. PMID:11177895

Lubinski, G; Juhász, Z; Morgenstern, R; Hoekstra, R

2001-01-22

115

Ab initio study of charge-transfer dynamics in collisions of C{sup 2+} ions with hydrogen chloride  

SciTech Connect

Ab initio quantum chemistry molecular calculations followed by a semiclassical dynamical treatment in the keV collision energy range have been developed for the study of the charge-transfer process in collisions of C{sup 2+} ions with hydrogen chloride. The mechanism has been investigated in detail in connection with avoided crossings between states involved in the reaction. A simple mechanism driven by a strong nonadiabatic coupling matrix element has been pointed out for this process. A comparative analysis with the halogen fluoride target corresponding to a similar electronic configuration shows a quite different charge-transfer mechanism leading to a very different behavior of the cross sections. Such behavior may be correlated to specific nonadiabatic interactions observed in these collision systems.

Rozsalyi, E.; Vibok, A. [Department of Theoretical Physics, University of Debrecen, P.O. Box 5, H-4010 Debrecen (Hungary); Bene, E. [Institute of Nuclear Research, Hungarian Academy of Sciences, P.O. Box 51, H-4001 Debrecen (Hungary); Halasz, G. J. [Department of Information Technology, University of Debrecen, P.O. Box 12, H-4010 Debrecen (Hungary); Bacchus-Montabonel, M. C. [Laboratoire de Spectrometrie Ionique et Moleculaire, Universite de Lyon (Lyon I), CNRS-UMR5579, 43 Bd. du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France)

2011-05-15

116

Electron solvation in water clusters following charge transfer from iodide  

SciTech Connect

The dynamics following charge transfer to solvent from iodide to a water cluster are studied using time-resolved photoelectron imaging of I{sup -}(H{sub 2}O){sub n} and I{sup -}(D{sub 2}O){sub n} clusters with n{<=}28. The results show spontaneous conversion, on a time scale of {approx}1 ps, from water cluster anions with surface-bound electrons to structures in which the excess electron is more strongly bound and possibly more internalized within the solvent network. The resulting dynamics provide valuable insight into the electron solvation dynamics in water clusters and the relative stabilities between recently observed isomers of water cluster anions.

Verlet, Jan R.R.; Kammrath, Aster; Griffin, Graham B.; Neumark, Daniel M. [Department of Chemistry, University of California, Berkeley, California 94720 and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2005-12-15

117

Probing charge transfer at surfaces using graphene transistors.  

PubMed

Graphene field effect transistors (FETs) are extremely sensitive to gas exposure. Charge transfer doping of graphene FETs by atmospheric gas is ubiquitous but not yet understood. We have used graphene FETs to probe minute changes in electrochemical potential during high-purity gas exposure experiments. Our study shows quantitatively that electrochemistry involving adsorbed water, graphene, and the substrate is responsible for doping. We not only identify the water/oxygen redox couple as the underlying mechanism but also capture the kinetics of this reaction. The graphene FET is highlighted here as an extremely sensitive potentiometer for probing electrochemical reactions at interfaces, arising from the unique density of states of graphene. This work establishes a fundamental basis on which new electrochemical nanoprobes and gas sensors can be developed with graphene. PMID:21141990

Levesque, Pierre L; Sabri, Shadi S; Aguirre, Carla M; Guillemette, Jonathan; Siaj, Mohamed; Desjardins, Patrick; Szkopek, Thomas; Martel, Richard

2010-12-09

118

Photophysical properties and intramolecular charge transfer in substituted polyimides  

SciTech Connect

The relationship between the geometric and electronic structure and the photophysical properties of a series of isoelectronic aromatic polyimides is explored. The polymer backbone geometries are computed using the semiempirical quantum-chemical AM1 method, while the electronic structure and photophysical properties are computed using the spectroscopically parametrized CNDO/S3 model. It is shown that an analysis of the geometric changes at the isoelectronic substitution site and the effect of the geometric changes on the electronic structure permit the prediction of changes in the intermolecular charge transfer (ICT) band of the optical absorption spectra and in the emission spectra. Moreover, this work demonstrates how experimentally observed differences in the photophysical properties of this class of polymers can be correlated to backbone conformation differences. 16 refs., 6 figs., 4 tabs.

LaFemina, J.P. (Pacific Northwest Lab., Richland, WA (United States)); Kafafi, S.A. (Johns Hopkins Univ., Baltimore, MD (United States))

1993-02-18

119

Charge-Transfer-Induced Cesium Superlattices on Graphene  

NASA Astrophysics Data System (ADS)

We investigate cesium (Cs) adsorption on graphene formed on a 6H-SiC(0001) substrate by a combined scanning tunneling microscopy and density functional theory study. Individual Cs atoms adsorb preferentially at the rim region of the well-defined 6×6 substrate superstructure and on multilayer graphene. By finely controlling the graphene thickness and Cs coverages (1/3ML and 1 ML), we here demonstrate two intriguing and well-ordered Cs superlattices on bilayer and multilayer graphene (<6 layers). Statistical analysis of the Cs-Cs interatomic distance reveals a hitherto unobserved Cs-Cs long-range electrostatic potential caused by charge transfer from Cs to graphene, which couples with the inhomogeneous substrate potential to stabilize the observed Cs superlattices. The present study provides a new avenue to fabricate atomic and molecular superlattices for applications in high-density recording and data storage.

Song, Can-Li; Sun, Bo; Wang, Yi-Lin; Jiang, Ye-Ping; Wang, Lili; He, Ke; Chen, Xi; Zhang, Ping; Ma, Xu-Cun; Xue, Qi-Kun

2012-04-01

120

Charge transfer in model bioinspired carotene-porphyrin dyads.  

PubMed

We present a computational study based on accurate DFT and TD-DFT methods on model bioinspired donor-acceptor dyads, formed by a carotenoid covalently linked to a tetraphenylporphyrin (TPP) at the ortho position of one of the TPP phenyl rings. Dyadic systems can be used in the construction of organic solar cells and development of efficient photocatalytic systems for the solar energy conversion, due to the unique advantages they offer in terms of synthetic feasibility. This study aims to describe the influence of chemical modifications on the absorption spectra, in particular on the lowest energy charge transfer bands. Effects of different metals of biological interest, i.e., Mg, Fe, Ni, and Zn, and of H(2)O and histidine molecules coordinated to the metals in different axial positions are rationalized. PMID:22429261

Orian, Laura; Carlotto, Silvia; Di Valentin, Marilena; Polimeno, Antonino

2012-04-05

121

Photoinduced charge transfer from polymers to fullerene molecules revisited.  

NASA Astrophysics Data System (ADS)

We study the process of photoinduced charge transfer (PCT) between conjugated polymers and fullerene molecules as electron acceptors, using the technique of picosecond transient, and steady state photomodulation at various modulation frequencies and temperatures. The polymers studied were MEH-PPV and regio-regular P3HT [RR-P3HT], which are some of the common polymers that are used in organic photovoltaic, as well as polyfluorene [PFO] with optical gap in the blue spectral range; whereas the fullerene molecules where C60, C70 and their PCBM variations. In all cases we found PCT as evident by the formation of strong photoinduced absorption (PA) polaron bands in the mid ir spectral range. Surprisingly we also found PCT with photon energy below the polymer optical gap. This below-gap PCT process will be discussed and compared with the more usual PCT process with above gap excitation.

Drori, Tomer; Sheng, Chuanxiang; Ndobe, Alex; Yang, Cungeng; Tong, Minghong; Vardeny, Valy

2007-03-01

122

Modeling charge transfer in the photosynthetic reaction center  

NASA Astrophysics Data System (ADS)

In this work, we present a model to elucidate the unidirectionality of the primary charge-separation process in the bacterial reaction centers. We have used a model of three sites/molecules with electron transfer beginning at site 1 with an option to proceed to site 2 or site 3. We used a stochastic model with arbitrary correlation functions. We get the quantum yields of electron escape via the sites 2,3 in two limiting cases that correspond to a spectral density of underdamped and overdamped Brownian oscillator. In the fast modulation limit of an overdamped regime we get the effect, which was named “fear of death,” in which for strong enough sink parameters the electron has a tendency to avoid the place with greater sink. The presented model was used to provide a plausible explanation of the temperature dependence of the quantum yields of the Rhodobacter sphaeroides photosynthetic reaction center in the high-temperature regime.

Pudlak, Michal; Pin?ak, Richard

2003-12-01

123

Charge transfer at interfaces in MoxV1-x\\/V superlattices  

Microsoft Academic Search

The influence of alloying and strain upon charge transfer across interfaces was investigated in MoxV1-x\\/V (x=0.5, 0.75, 1) superlattices. The extension of the charge transfer was measured using the relation between the hydrogen solubility and the electron density. The hydrogen concentration was measured by means of the 1H(15N,alphagamma)12C nuclear reaction. In Mo\\/V superlattices, the extension of the charge transfer was

S. Ólafsson; B. Hjörvarsson; F. Stillesjö; E. Karlsson; J. Birch; J.-E. Sundgren

1995-01-01

124

Charge transfer and polarization at interfaces with conjugated molecules  

NASA Astrophysics Data System (ADS)

The function and efficiency of organic electronic devices is determined to a significant extent by the electronic properties of organic/organic heterojunctions and interfaces between electrodes and organic semiconductors. The energy level alignment between metal electrodes and active organic layers can be adjusted over wide ranges by employing interlayers of strong molecular acceptors and donors that undergo charge transfer reactions with the metal. It will be shown that such interlayers lead to lower charge injection barriers than pristine metals, even when the work function is the same. It is argued that the molecularly modified electrodes are electronically more rigid than their pristine metal counterparts, i.e., the electron spill-out at the organic-terminated surface is less pronounced compared to metal surfaces. The energy levels at organic/organic heterojunctions comprising donors and acceptors as used in organic photovoltaic cells are essentially independent of deposition sequence, as long as supporting electrodes to not induce energy level pinning. When a high work function electrode is used, the energy levels may become Fermi-level pinned and an electric field drops right at the heterojunction. This effect is exemplified for the donor diindenoperylene and the acceptor C60. The electric field distribution within an organic opto-electronic device may thus be adjusted locally by employing interfacial energy level pinning, even at weakly interacting organic/organic interfaces.

Koch, Norbert

2012-02-01

125

Return stroke peak current versus charge transfer in rocket-triggered lightning  

NASA Astrophysics Data System (ADS)

We examined data on 117 return strokes in 31 rocket-and-wire-triggered lightning flashes acquired during experiments conducted from 1999 through 2004 at the International Center for Lightning Research and Testing at Camp Blanding, Florida, in order to compare the peak currents of the lightning return strokes with the corresponding charges transferred during various time intervals within 1 ms after return stroke initiation. We find that the determination coefficient (R2) for lightning return stroke peak current versus the corresponding charge transfer decreases with increasing the duration of the charge transfer starting from return stroke onset. For example, R2 = 0.91 for a charge transfer duration of 50 ?s after return stroke onset, R2 = 0.83 for a charge transfer duration of 400 ?s, and R2 = 0.77 for a charge transfer duration of 1 ms. Our results support the view that (1) the charge deposited on the lower portion of the leader channel determines the current peak and that (2) the charge transferred at later times is increasingly unrelated to both the current peak and the charge deposited on the lower channel section. Additionally, we find that the relation between triggered-lightning peak current and charge transfer to 50 ?s in Florida is essentially the same as that for subsequent strokes in natural lightning in Switzerland, further confirming the view that triggered-lightning strokes are very similar to subsequent strokes in natural lightning.

Schoene, J.; Uman, M. A.; Rakov, V. A.

2010-06-01

126

Substrate-mediated charge transfer plasmons in simple and complex nanoparticle clusters.  

PubMed

A conductive substrate can provide a simple and straightforward way to induce charge-transfer plasmon modes in Au nanoparticle clusters. For a simple dimer structure, a remarkably narrow charge transfer plasmon, which differs dramatically from the dipolar plasmon mode of the electrically isolated nanostructure, is clearly observed. For a more complex nonamer cluster that supports a strong Fano resonance on an insulating substrate, a mixed charge transfer-dipole mode is observed, where charge transfer is induced on the outer nanoparticles, establishing an opposing dipole on the intervening central particles, resulting in a strongly damped far field response. PMID:23979142

Wang, Yumin; Li, Ziwei; Zhao, Ke; Sobhani, Ali; Zhu, Xing; Fang, Zheyu; Halas, Naomi J

2013-09-26

127

Doping graphene films via chemically mediated charge transfer.  

PubMed

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. PMID:21711624

Ishikawa, Ryousuke; Bando, Masashi; Morimoto, Yoshitaka; Sandhu, Adarsh

2011-01-31

128

Interface charge transfer in polypyrrole coated perovskite manganite magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Different hybrid structures were obtained by coating magnetic nanoparticles of perovskite type manganite at optimal doping (La0.67Sr0.33MnO3,LSMO) with different quantities of polypyrrole (PPy). The amorphous layer of polypyrrole surrounding the crystalline magnetic core was observed by high resolution transmission electron microscopy (HRTEM) and analyzed by using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements in near edge structure (XANES) techniques. By analyzing the magnetic behavior of the samples one can observe that the surface modification of magnetic nanoparticles by PPy results in an increase in the saturation magnetization of the composites. The process is ascribed to paired electrons transferred from the delocalized ? states of the PPy into the outer disordered layers of the manganite. The analysis of pre-edge peak of the Mn K-edge XANES spectra in the case of PPy coated LSMO nanoparticles indicates that the charge transfer between polymer and nanoparticles is (directed) going to missing or distorted oxygen positions, hence increasing the 3d electrons' mobility and orbital hybridization between the neighboring manganese ion. As a consequence, within the surface layers of LSMO nanoparticles, both energy bands disrupted the structure, and the double exchange process between Mn ions was reestablished determining the saturation magnetizations and pre-edge features increase, respectively.

Pana, O.; Soran, M. L.; Leostean, C.; Macavei, S.; Gautron, E.; Teodorescu, C. M.; Gheorghe, N.; Chauvet, O.

2012-02-01

129

Doping graphene films via chemically mediated charge transfer  

NASA Astrophysics Data System (ADS)

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.

Ishikawa, Ryousuke; Bando, Masashi; Morimoto, Yoshitaka; Sandhu, Adarsh

2011-12-01

130

Charge Transfer Characteristics and Initiation Mechanisms of Long Delayed Sprites  

NASA Astrophysics Data System (ADS)

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 the slow intensification itself plays an important role in sprite initiation. For events analyzed, the predicted altitude from the FDTD simulation agree well with the measurement from high speed video images. Both the measurements and the simulations indicate that sprites with long time delay tend to initiate at a lower altitude comparing to short delayed sprites.

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

2007-12-01

131

DFT Studies on Charge Transfer States of a Multi-chromophoric Organic Heptad Antenna  

NASA Astrophysics Data System (ADS)

The electronic structure of the ground and the lowest charge transfer excited state of a molecular complex containing BODIPY dye, Zn-porphyrin, bisphenyl anthracene and fullerene are studied using density functional theory. The snowflaked shaped molecule behaves like an antenna capturing photons at different frequencies and transferring the energy to the porphyrin where electron transfer occurs from the porphyrin to the fullerene. We have claculated the energy of the lowest charge transfer state with a hole on prophyrin and an electron on the fullerene using a perturbative delta-SCF method. Our calculated values are in good agreement with the experimental charge transfer energy.

Basurto, Luis

2012-10-01

132

Extended Hubbard Models for Transition Metal Oxides and Halides: Importance of Spin and Charge Fluctuations in Charge Transfer Metals  

Microsoft Academic Search

The atomic parameters used in the extended Hubbard (EHB) models for transition metal oxides were determined so as to reproduce ab initio results and experimental results. The EHB model was investigated in relation to classification of transition metal oxides into the Mott-Hubbard and charge transfer (CT) semiconductors. The model calculations indicate that both spin and charge fluctuations are of importance

Kizashi Yamaguchi; Masayoshi Nakano; Hideo Namimoto; Takayuki Fueno

1988-01-01

133

Charge transfer processes in collisions of slow highly charged ions with polar molecules CO and C3H8  

Microsoft Academic Search

Charge transfer processes resulting from low energy collisions of polar molecules CO and C3H8 with highly charged Be2+ and B2+ ions have been investigated experimentally and theoretically. The potential for the one-electron exchange interaction between a polar molecule and highly charged atomic ion were obtained in closed analytical form in the framework of a semiclassical approach. Obtained results were used

M. V. Khoma; Makoto Imai; O. M. Karbovanets; Y. Kikuchi; M. Saito; Y. Haruyama; M. I. Karbovanets; I. Yu Kretinin; A. Itoh; R. J. Buenker

2009-01-01

134

Charge transfer processes in collisions of slow highly charged ions with polar molecules CO and C3H8  

NASA Astrophysics Data System (ADS)

Charge transfer processes resulting from low energy collisions of polar molecules CO and C3H8 with highly charged Be2+ and B2+ ions have been investigated experimentally and theoretically. The potential for the one-electron exchange interaction between a polar molecule and highly charged atomic ion were obtained in closed analytical form in the framework of a semiclassical approach. Obtained results were used for close-coupling calculations of total cross sections for single electron transfer in the studied reactions.

Khoma, M. V.; Imai, Makoto; Karbovanets, O. M.; Kikuchi, Y.; Saito, M.; Haruyama, Y.; Karbovanets, M. I.; Kretinin, I. Yu; Itoh, A.; Buenker, R. J.

2009-04-01

135

An enhanced glucose biosensor using charge transfer techniques.  

PubMed

An enhanced glucose biosensor based on a charge transfer technique glucose sensor (CTTGS) is described and demonstrated experimentally. In the proposed CTTGS, which is accumulation method (d-gluconate+H(+)) ion perception system, the quality of output signal with "signal integration cycles" is high. With the proposed CTTGS it is possible to amplify the sensing signals without an external amplifier by using an accumulation cycle. It can be supposed that measurements of small (d-gluconate+H(+)) ion fluctuation are difficult by ion-sensitive field effect transistor (ISFET) because the theoretical maximum sensitivity is only 59 mV/pH and the small output signals are buried in the 1/f noise component of the metal-insulator-semi-conductor field-effect transistor (MISFET). Therefore, the CTTGS has many advantages, such as high sensitivity, high accuracy, high signal-to-noise ratio (SNR), and has been successfully demonstrated using a charge transfer technique. The CTTGS exhibited excellent performance for glucose with a large span (1445 mV) and good reproducibility. Moreover, the CTTGS has good sensitivity in this range of 7.22mV/mM, a lower detection limit of about 0.01 mM/L and an upper detection limit of about 200 mM/L compared with amperometric glucose analysis which has been studied recently. Under optimum conditions, the proposed CTTGS exceeds the performance of the widely used ISFET glucose sensor. The sensitivity of the CTTGS (7.22 mV/mM) was seven times higher than that of the ISFET (1 mV/mM). Furthermore, the sensitivity obtained for human glucose levels was 29.06 mV/mM with a non-linear error of +/-0.27%; the linearity is y=0.0294x+1.8612 and R(2)=0.9999, which is acceptable for clinical application. Real sample analysis is investigated in blood glucose level by our developed CTTGS ISFET system. PMID:18640027

Lee, Seung-Ro; Sawada, Kazuaki; Takao, Hidekuni; Ishida, Makoto

2008-06-17

136

'Tunable' positive and negative surface charges on a capillary wall: exploiting the Immobiline chemistry.  

PubMed

The Immobiline (weak acrylamido acids and bases) chemistry has been applied to the covalent attachment of a positively (or, if needed, negatively) charged layer onto the inner surface of the silica wall. In particular, the following basic Immobilines have been used: pK 6.2, pK 7.0, pK 8.5 and pK 9.3. In order to avoid pK changes, the charged Immobilines are mixed with neutral acrylamido derivatives (in particular the highly resistant and hydrophilic N-acryloyl aminoethoxyethanol) so as to form a co-polymer having a 1:5 molar ratio (charged to neutral). The mu(eo) vs. pH curves have a slope opposite to that of a naked capillary and fan out on the pH scale following the titration curves of the different weak bases. Such chemistry allows the covalent attachment of charged species having known pK values and offering controlled charged densities on the wall. However, with the atomic force microscope, it is found that such soft coatings (whether charged or neutral) do not seem to provide complete coverage of the surface: naked patches of fused silica are found interdispersed among the polymer-coated ones. A good solution is a hybrid bonded and dynamic coating, obtained by adding short chain linear polyacrylamides to the background electrolyte. Good separations of polycations [poly(L-histidine)] and of histones are reported up to pH 5.7. PMID:8796483

Capelli, L; Ermakov, S V; Righetti, P G

1996-05-14

137

Charged Membrane Surfaces Impede the Protein-Mediated Transfer of Glycosphingolipids between Phospholipid Bilayers  

PubMed Central

A lipid transfer protein that facilitates the transfer of glycolipids between donor and acceptor membranes has been investigated using a fluorescence resonance energy transfer assay. The glycolipid transfer protein (23-24 kDa, pI 9.0) catalyzes the high specificity transfer of lipids that have sugars ?-linked to either a ceramide or a diacylglycerol backbone, such as simple glycolipids and gangliosides, but not the transfer of phospholipids, cholesterol, or cholesterol esters. In this study, we examined the effect of different charged lipids on the rate of transfer of anthrylvinyl-labeled galactosylceramide (1 mol %) from a donor to acceptor vesicle population at neutral pH. Compared to neutral donor vesicle membranes, introduction of negatively charged lipid at 5 or 10 mol % into the donor vesicles significantly decreased the transfer rate. Introduction of the same amount of negative charge into the acceptor vesicle membrane did not impede the transfer rate as effectively. Also, positive charge in the donor vesicle membrane was not as effective at slowing the transfer rate as was negative charge in the donor vesicle. Increasing the ionic strength of the buffer with NaCl significantly reversed the charge effects. At neutral pH, the transfer protein (pI ? 9.0) is expected to be positively charged, which may promote association with the negatively charged donor membrane. Based on these and other experiments, we conclude that the transfer process follows first-order kinetics and that the off-rate of the transfer protein from the donor vesicle surface is the rate-limiting step in the transfer process.

Mattjus, Peter; Pike, Helen M.; Molotkovsky, Julian G.; Brown, Rhoderick E.

2009-01-01

138

Alpha-particle induced charge transfer between closely spaced trench capacitor memory cells  

Microsoft Academic Search

A detailed analysis of various mechanisms involved in alpha-particle induced charge transfer between two trench type dRAM cells is reported and an analytical model has been developed to represent the transfered charge. The results compare very favorably with detailed simulation results.

J. H. Chern; P. Yang; P. Pattnaik; J. A. Seitchik; K. C.-K. Weng

1985-01-01

139

Theory of charge and mass transfer in ice-ice collisions  

Microsoft Academic Search

A new model describes charge and mass transfer in ice-ice collisions in terms of fundamental molecular physics. Drawing on clues from results of recent and earlier experiments, the theory treats the collisions as interlinked events acting in three stages: before collision, during contact, and withdrawal. The theory provides quantitative descriptions of charge and mass transfer and their dependence on growth

J. G. Dash; B. L. Mason; J. S. Wettlaufer

2001-01-01

140

Substrate-mediated charge transfer plasmons in simple and complex nanoparticle clusters  

NASA Astrophysics Data System (ADS)

A conductive substrate can provide a simple and straightforward way to induce charge-transfer plasmon modes in Au nanoparticle clusters. For a simple dimer structure, a remarkably narrow charge transfer plasmon, which differs dramatically from the dipolar plasmon mode of the electrically isolated nanostructure, is clearly observed. For a more complex nonamer cluster that supports a strong Fano resonance on an insulating substrate, a mixed charge transfer-dipole mode is observed, where charge transfer is induced on the outer nanoparticles, establishing an opposing dipole on the intervening central particles, resulting in a strongly damped far field response.A conductive substrate can provide a simple and straightforward way to induce charge-transfer plasmon modes in Au nanoparticle clusters. For a simple dimer structure, a remarkably narrow charge transfer plasmon, which differs dramatically from the dipolar plasmon mode of the electrically isolated nanostructure, is clearly observed. For a more complex nonamer cluster that supports a strong Fano resonance on an insulating substrate, a mixed charge transfer-dipole mode is observed, where charge transfer is induced on the outer nanoparticles, establishing an opposing dipole on the intervening central particles, resulting in a strongly damped far field response. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02835f

Wang, Yumin; Li, Ziwei; Zhao, Ke; Sobhani, Ali; Zhu, Xing; Fang, Zheyu; Halas, Naomi J.

2013-09-01

141

Double electron transfer in slow, highly charged ion-molecule collisions  

Microsoft Academic Search

During collisions between slow highly charged ions and neutral atoms or molecules, a lot of electrons can be transferred into multiply excited levels of the highly charged ions, and finally the product ions are stabilized by ejection of electrons (autoionization decay) or photons (radiative decay). The ratios of the radiative decay to the autoionization decay after double-electron transfer processes in

F. Krok; H. Tawara; I. Yu Tolstikhina; H. A. Sakaue; I. Yamada; K. Hosaka; M. Kimura; A. Matsumoto; N. Nakamura; S. Ohtani; M. Sakurai; H. Watanabe; M. Yoshino

1997-01-01

142

Some pi-Molecular Complexes Showing No Charge Transfer Spectra Formed by p-Toluenesulfonic Esters.  

National Technical Information Service (NTIS)

In an earlier paper, a criticism was made of the Mulliken approach to pi-molecular complexes ('charge transfer complexes') on the grounds that there is no evidence that charge transfer makes a major contribution to their heats of formation. It was pointed...

M. D. Bentley M. J. S. Dewar

1968-01-01

143

Wire transfer of charge packets using a CCD-BBD structure for charge-domain signal processing  

NASA Astrophysics Data System (ADS)

A structure for the virtual transfer of charge packets across metal wires is described theoretically and is experimentally verified. The structure is a hybrid of charge-coupled device (CCD) and bucket-brigade device (BBD) elements and permits the topological crossing of charge-domain signals in low power signal processing circuits. A test vehicle consisting of 8-, 32-, and 96-stage delay lines of various geometries implemented in a double-poly, double-metal foundry process is used to characterize the wire-transfer operation. Transfer efficiency ranging between 0.998 and 0.999 is obtained for surface n-channel devices with clock cycle times in the range from 40 ns to 0.3 ms. Transfer efficiency as high as 0.9999 is obtained for buried n-channel devices. Good agreement is found between experiment and simulation.

Fossum, Eric R.

1991-02-01

144

Ultrafast charge transfer processes in ordered molecular systems  

NASA Astrophysics Data System (ADS)

Using ultrafast emission and absorption spectroscopies, rates of DNA-mediated electron-transfer reactions have been established between a series of metal complex donors and acceptors bound by intercalation to the DNA double helix. In the presence of intercalating rhodium(III) acceptors, a substantial fraction of photoexcited (M(phen)2dppz) 2+ (M = Ru, Os) exhibits fast oxidative quenching (k q > 3 × 1010 s-1), while the remaining excited-state species exhibit a range of quenching constants less than 108 s-1. Transient-absorption experiments on the picosecond timescale indicate that, for all donors bound to mixed sequence DNA, the majority of back electron transfer is also very fast (ca. 1010 s-1) and its rate constant is independent of the loading of Rh complexes on the helix. We report a Monte Carlo simulation combined with an electron-tunneling kinetics program to model transient- absorption and emission data monitoring reactions between a series of metallointercalators on a variety of DNA. Our simplistic model simulates sub-ns transient absorption, sub-ns TCSPC and ns luminescence spectroscopy remarkably well. The apparent simple first-order kinetics are reproduced by an electron tunneling mechanism with a ? value near 1.0 A-1. The extent of reaction is reproduced by assuming a preferential binding of acceptors near donors. (Ru(phen)2dppz) 2+ (phen = 1,10- phenanthroline, dppz = dipyridophenazine) and closely related complexes have previously been observed to have an undetectably small quantum yield of photoluminescence in water but a moderate emission yield when bound to DNA. This so-called 'light-switch' effect is a critical factor in the utility of these complexes as spectroscopic probes for DNA. Here we describe a detailed investigation of the photophysics of (Ru(phen)2dppz) 2+ in aqueous solution, and in mixtures of acetonitrile and water, by time-resolved absorption and emission spectroscopies. Atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) are used in conjunction with bulk absorption and fluorescence measurements to correlate the morphological and photophysical properties of titanyl phthalocyanine/perylene phenethylimide (TiOPc/PPEI) bilayer systems. Steady-state fluorescence intensity and fluorescence lifetime measurements are used as a measure of interfacial charge-transfer quenching efficiencies.

Olson, Eric James Crane

1998-11-01

145

Dynamical excimer formation in rigid carbazolophane via charge transfer state.  

PubMed

Formation dynamics of intramolecular excimer in dioxa[3.3](3,6)carbazolophane (CzOCz) was studied by time-resolved spectroscopic methods and computational calculations. In the ground state, the most stable conformer in CzOCz is the anti-conformation where two carbazole rings are in antiparallel alignment. No other isomers were observed even after the solution was heated up to 150 °C, although three characteristic isomers were found by the molecular mechanics calculation: the first is the anti-conformer, the second is the syn-conformer where two carbazole rings are stacked in the same direction, and the third is the int-conformer where two carbazole rings are aligned in an edge-to-face geometry. Because of the anti-conformation, the interchromophoric interaction in CzOCz is negligible in the ground state. Nonetheless, the intramolecular excimer in CzOCz was dynamically formed in an acetonitrile (MeCN) solution, indicating strong interchromophoric interaction and the isomerization from the anti- to syn-conformation in the excited state. The excimer formation in CzOCz is more efficient in polar solvents than in less polar solvents, suggesting the contribution of the charge transfer (CT) state to the excimer formation. The stabilization in the excited state is discussed in terms of molecular orbital interaction between two carbazole rings. The solvent-polarity-induced excimer formation is discussed in terms of the CT character in the int-conformation. PMID:23905591

Tamai, Yasunari; Ohkita, Hideo; Shimada, Jiro; Benten, Hiroaki; Ito, Shinzaburo; Yamanaka, Sho; Hisada, Kenji; Tani, Keita; Kubono, Koji; Shinmyozu, Teruo

2013-08-02

146

Charge transfer photodissociation of phenol on Ag(111)  

NASA Astrophysics Data System (ADS)

The photochemistry of phenol on Ag(111) has been investigated by post-irradiation temperature programmed desorption (TPD). Ultraviolet (UV) irradiation at 355 and 266 nm was found to affect only the chemisorption layer in direct contact with the metal surface, while leaving the multilayer virtually intact. The main photoinduced reaction was found to be photodissociation of the O-H bond of phenol. Two new peaks were observed at the mass of phenol in the post-irradiation TPD spectrum at 335 K and 455 K. These peaks were assigned to the recombinative desorption of phenoxy with the hydrogen from O-H bond photodissociation and from thermal C-H bond fission, respectively. The photodissociation cross section was measured at different wavelengths and coverages. A charge transfer type photodissociation mechanism was proposed, where hot electrons generated in the substrate by UV photons attach to the affinity level of the adsorbed phenol. The transition to the transient anionic potential then leads to facile dissociation of O-H bond. The affinity level of phenol has been estimated to lie at 3.2-3.5 eV above the Fermi level for the 1 ML case.

Lee, Junseok; Ryu, Sunmin; Ku, Jong Seok; Kim, Seong Keun

2001-12-01

147

Graphene-ferromagnet interfaces: hybridization, magnetization and charge transfer.  

PubMed

Electronic and magnetic properties of graphene-ferromagnet interfaces are investigated using first-principles electronic structure methods in which a single layer graphene is adsorbed on Ni(111) and Co(111) surfaces. Due to the symmetry matching and orbital overlap, the hybridization between graphene p? and Ni (or Co) d(z(2)) states is very strong. This pd hybridization, which is both spin and k dependent, greatly affects the electronic and magnetic properties of the interface, resulting in a significantly reduced (by about 20% for Ni and 10% for Co) local magnetic moment of the top ferromagnetic layer at the interface and an induced spin polarization on the graphene layer. The calculated induced magnetic moment on the graphene layer agrees well with a recent experiment. In addition, a substantial charge transfer across the graphene-ferromagnet interfaces is observed. We also investigate the effects of thickness of the ferromagnet slab on the calculated electronic and magnetic properties of the interface. The strength of the pd hybridization and the thickness-dependent interfacial properties may be exploited to design structures with desirable magnetic and transport properties for spintronic applications. PMID:23354276

Abtew, Tesfaye; Shih, Bi-Ching; Banerjee, Sarbajit; Zhang, Peihong

2013-03-01

148

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

SciTech Connect

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.

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

2008-04-02

149

Analysis of the charge transfer of models for electrostatic discharge (ESD) and semiconductor devices  

Microsoft Academic Search

Various models are used to simulate the electrostatic discharge (ESD) event associated with semiconductor devices; these include the human body model (HBM), the charged device model (CDM), and the field induced charged device model (FCDM). Maxwell's method is used to analyze these models to determine device potentials and the transfer of charge during typical discharges; existing test methods are also

William D. Greason

1996-01-01

150

Role of the charge transfer state in organic donor-acceptor solar cells.  

PubMed

Charge transfer complexes are interfacial charge pairs residing at the donor-acceptor heterointerface in organic solar cell. Experimental evidence shows that it is crucial for the photovoltaic performance, as both photocurrent and open circuit voltage directly depend on it. For charge photogeneration, charge transfer complexes represent the intermediate but essential step between exciton dissotiation and charge extraction. Recombination of free charges to the ground state is via the bound charge transfer state before being lost to the ground state. In terms of the open circuit voltage, its maximum achievable value is determined by the energy of the charge transfer state. An important question is whether or not maximum photocurrent and maximum open circuit voltage can be achieved simultaneously. The impact of increasing the CT energy-in order to raise the open circuit voltage, but lowering the kinetic excess energy of the CT complexes at the same time-on the charge photogeneration will accordingly be discussed. Clearly, the fundamental understanding of the processes involving the charge transfer state is essential for an optimisation of the performance of organic solar cells. PMID:20803527

Deibel, Carsten; Strobel, Thomas; Dyakonov, Vladimir

2010-10-01

151

Electrospray Charging of Minerals: Surface Chemistry and Applications to High-Velocity Microparticle Impacts  

NASA Astrophysics Data System (ADS)

Electrospray is a soft ionization technique commonly used to charge large biomolecules; it has, however, also been applied to inorganic compounds. We are extending this technique to mineral microparticles. Electrospray-charged mineral microparticles are interesting in the context of surface science because surface chemistry dictates where and how charge carriers can bond to mineral surfaces. In addition, using electrospray to charge mineral particles allows these particles to be electrostatically accelerated as projectiles in high- and hyper-velocity impacts. Since current techniques for producing high- and hyper-velocity microparticle impacts are largely limited to metal or metal-coated projectiles, using minerals as projectiles is a significant innovation. Electrospray involves three steps: creation of charged droplets containing solute/particles, evaporation and bifurcation of droplets, and desolvation of the solute/particles. An acidified solution is slowly pumped through a needle in a strong DC field, which causes the solution to break into tiny, charged droplets laden with protons. Solvent evaporates from the electrosprayed droplets as they move through the electric field toward a grounded plate, causing the charge on the droplet to increase relative to its mass. When the electrosprayed droplet’s charge becomes such that the droplet is no longer stable, it bifurcates, and each of the resulting droplets carries some of the original droplet’s charge. Evaporation and bifurcation continues until the solute particle is completely desolvated. The result is a protonated solute molecule or particle. We built an instrument that electrosprays particles into vacuum and measures them using an image charge detector. Mineral microparticles were prepared by grinding natural mineral samples to ~2 µm diameter. These microparticles are then added to a 4:1 methanol:water solution to create a 0.005% w/v suspension. The suspension is electrosprayed into vacuum, where the charge detector measures the electrosprayed mineral particles’ speed and charge. Quartz microparticles have been successfully electrosprayed. Variation in quartz microparticles’ charge as a function of pH is being evaluated. In addition, we are studying how to completely desolvate electrosprayed mineral particles. Desolvation is not trivial and often requires more than the passive passage of the droplets from the needle to the grounded plate and into vacuum. We are testing two desolvation methods: a heated beam tube and a heated capillary. Preliminary data suggests we have achieved complete desolvation with a hot beam tube. Although quartz’s surface chemistry is rather unique, successful electrospray of quartz microparticles strongly suggests that other minerals may also be electrosprayed. We are preparing olivine samples for electrospray. In addition, an instrument that creates high-velocity microparticle impacts using electrospray-charged mineral microparticles is being developed. This instrument will not only permit minerals to be used as projectiles, but also allows direction characterization of chemical speciation occurring during microparticle impacts.

Daly, T.; Call, S.; Austin, D. E.

2010-12-01

152

Probing the charge-transfer dynamics in DNA at the single-molecule level.  

PubMed

Photoinduced charge-transfer fluorescence quenching of a fluorescent dye produces the nonemissive charge-separated state, and subsequent charge recombination makes the reaction reversible. While the information available from the photoinduced charge-transfer process provides the basis for monitoring the microenvironment around the fluorescent dyes and such monitoring is particularly important in live-cell imaging and DNA diagnosis, the information obtainable from the charge recombination process is usually overlooked. When looking at fluorescence emitted from each single fluorescent dye, photoinduced charge-transfer, charge-migration, and charge recombination cause a "blinking" of the fluorescence, in which the charge-recombination rate or the lifetime of the charge-separated state (?) is supposed to be reflected in the duration of the off time during the single-molecule-level fluorescence measurement. Herein, based on our recently developed method for the direct observation of charge migration in DNA, we utilized DNA as a platform for spectroscopic investigations of charge-recombination dynamics for several fluorescent dyes: TAMRA, ATTO 655, and Alexa 532, which are used in single-molecule fluorescence measurements. Charge recombination dynamics were observed by transient absorption measurements, demonstrating that these fluorescent dyes can be used to monitor the charge-separation and charge-recombination events. Fluorescence correlation spectroscopy (FCS) of ATTO 655 modified DNA allowed the successful measurement of the charge-recombination dynamics in DNA at the single-molecule level. Utilizing the injected charge just like a pulse of sound, such as a "ping" in active sonar systems, information about the DNA sequence surrounding the fluorescent dye was read out by measuring the time it takes for the charge to return. PMID:21875061

Kawai, Kiyohiko; Matsutani, Eri; Maruyama, Atsushi; Majima, Tetsuro

2011-09-12

153

Threshold formation of an intermolecular charge transfer complex of a semiconducting polymer  

NASA Astrophysics Data System (ADS)

It has been found that the formation of an intermolecular charge transfer complex in the ground electronic state between the model conjugated polymer (poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and the low-molecular-weight organic acceptor (2,4,7-trinitrofluorenone, TNF) occurs stepwise with an increase in the acceptor concentration in the blend as is observed in the optical absorption spectra of solutions. The threshold dependence of the absorption of the charge transfer complex is attributed to the stepwise change in the concentration of the charge transfer complexes, which is not explained by the standard model describing the optical characteristics of intermolecular charge transfer complexes. A kinematic model has been proposed to explain the threshold increase in the concentration of charge transfer complexes: at low acceptor concentrations, the charge transfer complex is formed primarily on the surface of a polymer coil, whereas as the acceptor fraction in the solution increases, TNF molecules penetrate inside the polymer coils, forming the charge transfer complex with the units of the polymer inside the coil.

Parashchuk, O. D.; Sosorev, A. Yu.; Bruevich, V. V.; Paraschuk, D. Yu.

2010-04-01

154

Fostering Analogical Transfer: The Multiple Components Approach to Algebra Word Problem Solving in a Chemistry Context  

ERIC Educational Resources Information Center

|Holyoak and Koh (1987) and Holyoak (1984) propose four critical tasks for analogical transfer to occur in problem solving. A study was conducted to test this hypothesis by comparing a multiple components (MC) approach against worked examples (WE) in helping students to solve algebra word problems in chemistry classes. The MC approach incorporated…

Ngu, Bing Hiong; Yeung, Alexander Seeshing

2012-01-01

155

Charge transfer and x-ray emission in collisions between slow, highly charged ions and neutral atoms  

Microsoft Academic Search

The Classical Trajectory Monte Carlo method was used to study Charge transfer between slow (<50 eV\\/amu) highly charged ions (Ne^10+, Ar^18+) and their respective neutral atoms. State specific electron capture cross sections were calculated and used to estimate cross sections for the resulting x-ray emissions. The calculated x-ray line emissions are compared with measurements made at Lawrence Livermore National Laboratory

J. A. Perez; B. P. Thomas; R. E. Olson; P. Beiersdorfer

2002-01-01

156

Double-charge-transfer spectrometry and the measurement of electronic-state energies of doubly charged ions  

Microsoft Academic Search

The use of three commercial double-focussing mass spectrometers for double-charge-transfer spectrometry is described. Electronic-state energies of numerous triatomic and polyatomic doubly charged ions have been measured, and examples are given which illustrate the value of the information obtained. Where possible, the results are compared with those obtained by other experimental techniques and with data and state assignments from theoretical studies.

F. M. Harris

1992-01-01

157

46 CFR 153.957 - Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks.  

Code of Federal Regulations, 2011 CFR

...false Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks...DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS...957 Persons in charge of transferring liquid cargo in bulk or cleaning cargo...

2011-10-01

158

46 CFR 153.957 - Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks.  

Code of Federal Regulations, 2012 CFR

...false Persons in charge of transferring liquid cargo in bulk or cleaning cargo tanks...DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS...957 Persons in charge of transferring liquid cargo in bulk or cleaning cargo...

2012-10-01

159

Time-resolved studies of charge recombination in the pyrene/TCNQ charge-transfer crystal: evidence for tunneling.  

PubMed

Previous studies of solid-state tetracyanobenzene-based donor-acceptor complexes showed that these materials were highly susceptible to both laser and mechanical damage that complicated the analysis of their electron-transfer kinetics. In this paper, we characterize the optical properties of a pyrene/tetracyanoquinodimethane charge-transfer crystal that is much more robust than the tetracyanobenzene compounds. This donor-acceptor complex has a charge-transfer absorption that extends into the near-infrared, rendering the crystal black. We use time-resolved fluorescence and diffuse reflectance transient absorption to study its dynamics after photoexcitation. We show that the initially excited charge-transfer state undergoes a rapid, monoexponential decay with a lifetime of 290 ps at room temperature. There is no evidence for any long-lived intermediate or dark states; therefore, this decay is attributed to charge recombination back to the ground state. Fluorescence lifetime measurements demonstrate that this process becomes temperature-independent below 60 K, indicative of a thermally activated tunneling mechanism. The subnanosecond charge recombination makes this low-band-gap donor-acceptor material a poor candidate for generating long-lived electron-hole pairs. PMID:22591413

Dillon, Robert J; Bardeen, Christopher J

2012-05-16

160

Reduced charge transfer exciton recombination in organic semiconductor heterojunctions by molecular doping.  

PubMed

We investigate the effect of molecular doping on the recombination of electrons and holes localized at conjugated-polymer-fullerene interfaces. We demonstrate that a low concentration of p-type dopant molecules (<4% weight) reduces the interfacial recombination via charge transfer excitons and results in a favored formation of separated carriers. This is observed by the ultrafast quenching of photoluminescence from charge transfer excitons and the increase in photoinduced polaron density by ~70%. The results are consistent with a reduced formation of emissive charge transfer excitons, induced by state filling of tail states. PMID:22026799

Deschler, Felix; Da Como, Enrico; Limmer, Thomas; Tautz, Raphael; Godde, Tillmann; Bayer, Manfred; von Hauff, Elizabeth; Yilmaz, Seyfullah; Allard, Sybille; Scherf, Ullrich; Feldmann, Jochen

2011-09-15

161

The coordination and atom transfer chemistry of titanium porphyrin complexes  

SciTech Connect

Preparation, characterization, and reactivity of ({eta}{sup 2}- alkyne)(meso-tetratolylpoprphrinato)titanium(II) complexes are described, along with inetermetal oxygen atom transfer reactions involving Ti(IV) and Ti(III) porphyrin complexes. The {eta}{sup 2}- alkyne complexes are prepared by reaction of (TTP)TiCl{sub 2} with LiAlH{sub 4} in presence of alkyne. Structure of (OEP)Ti({eta}{sup 2}-Ph-C{triple_bond}C-Ph) (OEP=octaethylporphryin) was determined by XRD. The compounds undergo simple substitution to displace the alkyne and produce doubly substituted complexes. Structure of (TTP)Ti(4-picoline){sub 2} was also determined by XRD. Reaction of (TTP)Ti{double_bond}O with (OEP)Ti-Cl yields intermetal O/Cl exchange, which is a one-electron redox process mediated by O atom transfer. Also a zero-electron redox process mediated by atom transfer is observed when (TTP)TiCl{sub 2} is reacted with (OEP)Ti{double_bond}O.

Hays, J.A.

1993-11-05

162

Ultrafast dynamics of a charge-transfer dimer as a model for the photoinduced phase transition of charge-transfer compounds.  

PubMed

By applying ultrafast pump-probe spectroscopy with 15 fs temporal resolution to (TMTTF(+))(2) dimers we provide a full picture of the structural relaxation following photoexcitation of their CT transition. Both population and coherent phonon dynamics allow tracking wave packet motion onto the multidimensional excited state potential energy surface, as obtained by density functional theory calculations. We show that the vibrations that are strongly coupled to the charge-transfer transition of the dimer correspond to those driving the photoinduced phase transition occurring in charge-transfer crystalline solids. PMID:17678257

Lüer, Larry; Manzoni, Cristian; Cerullo, Giulio; Lanzani, Guglielmo; Meneghetti, Moreno

2007-07-09

163

Intermolecular charge transfer and vibrational analysis of hydrogen bonding in acetazolamide.  

PubMed

In the present work the structural and spectral characteristics of acetazolamide have been studied by methods of infrared, Raman spectroscopy and quantum chemistry. Electrostatic potential surface, optimized geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by density functional theory (DFT) employing B3LYP with complete relaxation in the potential energy surface using 6-311++G(d,p) basis set. Based on these results, we have discussed the correlation between the vibrational modes and the structure of the dimers of acetazolamide. The calculated vibrational spectra of three dimers of acetazolamide have been compared with observed spectra, and the assignment of observed bands was carried out using potential energy distribution. The observed spectra agree well with the values computed from the DFT. A comparison of observed and calculated vibrational spectra clearly shows the effect of hydrogen bonding. The frequency shifts observed for the different dimers are in accord with the hydrogen bonding in acetazolamide. Natural bond orbital (NBO) analyses reflect the charge transfer interaction in the individual hydrogen bond units and the stability of different dimers of acetazolamide. PMID:23063858

Chaturvedi, Deepika; Gupta, Vineet; Tandon, Poonam; Sharma, Anamika; Baraldi, C; Gamberini, M C

2012-09-12

164

An evaluation of 2-phase charge pump topologies with charge transfer switches for green mobile technology  

Microsoft Academic Search

The development of charge pumps has been motivated by the power supply requirements of portable electronic devices. Charge pumps are inductorless DC-DC converters that are small size and high integration. The quality of the charge pump greatly depends on the effectiveness of switches to turn on and off at the designated clock phases. However, to date, no analysis has been

Yan Chiew Wong; Nurul H. Noordin; Ahmed O. El-Rayis; Nakul Haridas; Ahmet T. Erdogan; Tughrul Arslan

2011-01-01

165

On the impedance of porous electrodes – double-layer charging and charge transfer on an inhomogeneous inside electrode surface  

Microsoft Academic Search

A model of the impedance of porous electrodes was derived. The model generalized the de Levie model in so far that an inhomogeneous inside electrode surface is assumed. Then the charge transfer resistance and the double-layer capacity were assumed to be distributed. The width of the distribution is characterized by a distribution parameter. The inhomogeneities led to characteristic deviations of

A. Hasbach; U. Retter; K. Siegler; W. Kautek

2004-01-01

166

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

NASA Astrophysics Data System (ADS)

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.

Wang, Xin; Liang, Shi-Dong

2013-02-01

167

33 CFR 127.1301 - Persons in charge of transfers for the facility: Qualifications and certification.  

Code of Federal Regulations, 2013 CFR

...false Persons in charge of transfers for the facility: Qualifications and certification. 127.1301...OF HOMELAND SECURITY (CONTINUED) WATERFRONT FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED...

2013-07-01

168

Energy collection and charge transfer processes in thin film photocells and photoelectrochemical cells: Final report  

Microsoft Academic Search

The following paragraphs describe accomplishments and significant results for the two lines of research: (1) studies of energy collection and charge transfer processes in thin film systems and (2) solar energy utilization by photosensitized electrode processes at semiconductor electrodes.

Tachikawa

1981-01-01

169

Charge transfer cross section calculation and evaluation for Beq++H collisions  

NASA Astrophysics Data System (ADS)

The charge transfer processes for the Beq++H(q = 1-4) collisions are investigated by the quantum-mechanical and semiclassical methods in wide energy ranges. The total, n-selective, nl-selective, singlet and triplet charge transfer cross sections are obtained and compared with other available theoretical data. The total and n-selective data are presented. The validity of different methods is discussed. The recommend cross section data are given for all collision systems.

Liu, C. H.; Liu, L.; Qu, Y. Z.; Wang, J. G.; Janev, R. K.

2013-07-01

170

Single- and double-electron charge transfer in collisions of ?-particles with hydrogen molecules  

NASA Astrophysics Data System (ADS)

Total, partial, and angular differential cross sections of single- and double-electron charge transfer in collisions between ?-particles and hydrogen molecules in the ground state in the interval of collision energies from 3 to 80 keV have been calculated. New data for charge transfer cross sections can be used for simulations and spectroscopy of ?-particles in thermonuclear diverter plasma of nuclear reactors.

Nikulin, V. K.; Gushchina, N. A.; Tsarev, Yu. N.

2013-07-01

171

Polymerization of Methyl Methacrylate by Charge-Transfer Mechanism with Amines and Carbon Tetrachloride  

Microsoft Academic Search

The charge-transfer complex formed between an amine and carbon tetrachloride can initiate the polymerization of vinyl monomers in a nonaqueous solvent such as dimethylsulfoxide. Here we use cyclopentylamine (CPA) and heptylamine (HA) as the donor compounds for charge-transfer initiation of the polymerization of methl methacrylate (MMA). The rate of polymerization Rp = k[MMA] [amine] [CCl4] when [CCl4] [amine] ? 1;

N. N. Dass; A. K. Gogoi

1983-01-01

172

Electronic and Nuclear Factors in Charge and Excitation Transfer  

SciTech Connect

We report the and/or state of several subprojects of our DOE sponsored research on Electronic and Nuclear Factors in Electron and Excitation Transfer: (1) Construction of an ultrafast Ti:sapphire amplifier. (2) Mediation of electronic interactions in host-guest molecules. (3) Theoretical models of electrolytes in weakly polar media. (4) Symmetry effects in intramolecular excitation transfer.

Piotr Piotrowiak

2004-09-28

173

Charge Transfer Efficiency modeling/measurements as function of CCD pixel rate  

SciTech Connect

We have developed a charge transport model for predicting the effects on Charge Transfer Efficiency (CTE) of Charge Coupled Devices (CCDs) as functions of number of transfers, pixel charge flow rate, and magnitude in the CCD`s vertical and horizontal charge transport mediums. The model uses carrier lifetime an mobility criteria to establish pixel speed arguments and limitations for various CCD architectures. The model is compared with experimental measurements obtained using strobed single pixel illumination and a variant of the deferred charge tail technique while independently varying the CCD pixel rates for both the vertical and horizontal readout phases. The generic model is discussed and applied to specific real CCDs. Agreement between predicted performance and actual measured performance is presented.

Yates, G.J.; Gallegos, R.; Pena, C. [Los Alamos National Lab., NM (United States); Zagarino, P. [Sharpenit, Ellwood, CA (United States)

1995-09-01

174

The influence of electric charge transferred during electro-mechanical reshaping on mechanical behavior of cartilage  

NASA Astrophysics Data System (ADS)

Electromechanical reshaping (EMR) of cartilage has been suggested as an alternative to the classical surgical techniques of modifying the shape of facial cartilages. The method is based on exposure of mechanically deformed cartilaginous tissue to a low level electric field. Electro-chemical reactions within the tissue lead to reduction of internal stress, and establishment of a new equilibrium shape. The same reactions offset the electric charge balance between collagen and proteoglycan matrix and interstitial fluid responsible for maintenance of cartilage mechanical properties. The objective of this study was to investigate correlation between the electric charge transferred during EMR and equilibrium elastic modulus. We used a finite element model based on the triphasic theory of cartilage mechanical properties to study how electric charges transferred in the electro-chemical reactions in cartilage can change its mechanical responses to step displacements in unconfined compression. The concentrations of the ions, the strain field and the fluid and ion velocities within the specimen subject to an applied mechanical deformation were estimated and apparent elastic modulus (the ratio of the equilibrium axial stress to the axial strain) was calculated as a function of transferred charge. The results from numerical calculations showed that the apparent elastic modulus decreases with increase in electric charge transfer. To compare numerical model with experimental observation we measured elastic modulus of cartilage as a function of electric charge transferred in electric circuit during EMR. Good correlation between experimental and theoretical data suggests that electric charge disbalance is responsible for alteration of cartilage mechanical properties.

Protsenko, Dimitry E.; Lim, Amanda; Wu, Edward C.; Manuel, Cyrus; Wong, Brian J. F.

2011-02-01

175

Picosecond charge-transfer events in the photosensitization of colloidal TiO sub 2  

SciTech Connect

The charge transfer from the singlet excited anthracene-9-carboxylic acid (9AC) into the conduction band of a large band gap semiconductor, TiO{sub 2}, and the recombination of injected charge with the cation radical 9AC{sup {sm bullet}+} have been time resolved in the picosecond-nanosecond time domain with the aid of picosecond laser flash photolysis.

Kamat, P.V. (Notre Dame Radiation Laboratory, IN (USA))

1990-02-01

176

Second harmonic generation investigations of charge transfer at chemically-modified semiconductor interfaces  

Microsoft Academic Search

Charge transfer and accumulation at semiconductor devices can lead to device degradation. Understanding and controlling such a process is therefore important. Second harmonic generation has been shown to be a sensitive probe of charging of semiconductor interfaces, with the added advantages of high spatial and temporal resolution. We have investigated the use of self assembled monolayers (SAMs) as a means

Vasiliy Fomenko; Cédric Hurth; Tao Ye; Eric Borguet

2002-01-01

177

Electrostatic sensors applied to the measurement of electric charge transfer in gas–solids pipelines  

Microsoft Academic Search

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

S R Woodhead; J C Denham; D I Armour-Chelu

2005-01-01

178

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

Microsoft Academic Search

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

S. R. Woodhead; J. C. Denham; D. I. Armour-Chelu

2005-01-01

179

Energy transfer through a multi-layer liner for shaped charges  

Microsoft Academic Search

This invention relates to the determination of parameters for selecting materials for use as liners in shaped charges to transfer the greatest amount of energy to the explosive jet. Multi-layer liners constructed of metal in shaped charges for oil well perforators or other applications are selected in accordance with the invention to maximize the penetrating effect of the explosive jet

S. Skolnick; A. Goodman

1985-01-01

180

Methodological Aspects of the Partial Charge Transfer in the Adsorption of Anions. Part II  

Microsoft Academic Search

The partial charge transfer coefficient and the electrosorption valence of anions on metals, as well as the role of electron tunneling in the formation of contact electric resistance (CER) signal are discussed. The CER value is shown to depend on the potential (E), the surface coverage with adsorbate particles, and their apparent charge. Bell-shaped CER–E curves of copper, silver, and

V. A. Marichev

2004-01-01

181

Chemistry  

NSDL National Science Digital Library

Finds ChemEd DL resources related to the sections of the General Chemistry textbook, Chemistry, by Kenneth W. Whitten, Raymond E. Davis, M. Larry Peck, George G. Stanley published by Brooks/Cole, 2010.

182

Modelling electrified interfaces in quantum chemistry: constant charge vs. constant potential.  

PubMed

The proper description of electrified metal/solution interfaces, as they occur in electrochemical systems, is a key component for simulating the unique features of electrocatalytic reactions using electronic structure calculations. While in standard solid state (plane wave, periodic boundary conditions) density functional theory (DFT) calculations several models for describing electrochemical environments exist, for cluster models in a quantum chemistry approach (atomic orbital basis, finite system) this is not straightforward. In this work, two different approaches for the theoretical description of electrified interfaces of nanoparticles, the constant charge and the constant potential model, are discussed. Different schemes for describing electrochemical reactions including solvation models are tested for a consistent description of the electrochemical potential and the local chemical behavior for finite structures. The different schemes and models are investigated for the oxygen reduction reaction (ORR) on a hemispherical cuboctahedral platinum nanoparticle. PMID:23329171

Benedikt, Udo; Schneider, Wolfgang B; Auer, Alexander A

2013-02-28

183

Optimal battery chemistry, capacity selection, charge\\/discharge schedule, and lifetime of energy storage under time-of-use pricing  

Microsoft Academic Search

Energy storage units (ESU) can reduce the cost of purchased electricity under time-of-use (TOU) pricing. To maximize the cost reduction, the chemistries, capacities, and charge\\/discharge schedules of the batteries used in the ESU must be selected appropriately. The batteries must have sufficient capacities to supply the energy demanded by the charge\\/discharge profiles and to meet the project lifetime. The ESU

Arthur K. Barnes; Juan Carlos Balda; Scott O. Geurin; Andres Escobar-Mejia

2011-01-01

184

Time delay and integration detectors using charge transfer devices  

NASA Astrophysics Data System (ADS)

An imaging system comprises a multi-channel matrix array of CCD devices wherein a number of sensor cells (pixels) in each channel are subdivided and operated in discrete intercoupled groups of subarrays with a readout CCD shift register terminating each end of the channels. Clock voltages, applied to the subarrays, selectively cause charge signal flow in each subarray in either direction independent of the other subarrays. By selective application of four phase clock voltages, either one, two or all three of the sections subarray sections cause charge signal flow in one direction, while the remainder cause charge signal flow in the opposite direction. This creates a form of selective electronic exposure control which provides an effective variable time delay and integration of three, six or nine sensor cells or integration stages. The device is constructed on a semiconductor sustrate with a buried channel and is adapted for front surface imaging through transparent doped tin oxide gates.

McCann, D. H.; White, M. H.; Turly, A. P.

1981-07-01

185

Charge transfer and band gap of ferrocene intercalated into TiSe 2  

NASA Astrophysics Data System (ADS)

We have investigated the charge transfer characteristics and electronic structure of ferrocene-intercalated TiSe 2. The spectroscopic results revealed that an intercalation of metallocene molecules leads to changes in the ionic valence of Fe atom in ferrocene molecule and the band gap, which is in accordance with electrical resistivity measurements showing metallic conductivity. Our analysis of 57Fe Mössbauer and Fe 2 p XAS spectra suggested that the suppression of charge-density-wave state in TiSe 2 and an appearance of metallic conductivity are attributed to charge transfer of electrons from ferrocene intercalant to the dichalcogenide host material.

Titov, A. N.; Yarmoshenko, Yu. M.; Bazylewski, P.; Yablonskikh, M. V.; Kurmaev, E. Z.; Wilks, R.; Moewes, A.; Tsurin, V. A.; Fedorenko, V. V.; Suvorova, O. N.; Ketkov, S. Yu.; Neumann, M.; Chang, G. S.

2010-09-01

186

Particle\\/Turbulence Interactions, Mass Transfer and Gas\\/Solid Chemistry in a CFBC Riser  

Microsoft Academic Search

Gas\\/solid chemistry in the upper, dilute region of a circulating fluidised bed combustor (CFBC) riser is addressed. The limitations\\u000a of turbulent mixing are illustrated by the example of the heterogeneous NO\\/CO\\/char reaction, relevant in CFB combustion of\\u000a nitrogen-containing solid fuels. The mass transfer of the gaseous reactants to the char surface is determined, and how the\\u000a conversion is influenced by

Ron Zevenhoven; Mika Järvinen

2001-01-01

187

Single and double charge transfer of He2+ ions with molecules at near-thermal energies  

NASA Astrophysics Data System (ADS)

Rate coefficients have been measured for charge-transfer reactions of He2+ ions with H2, N2, O2, CO, CO2, and H2O. The experiments were carried out using a selected-ion drift-tube mass spectrometer. Total rate coefficients are found to be very large and are generally close to the limiting Langevin capture rate coefficients or the corresponding ADO coefficients. The product-ion spectra indicate that both single and double charge transfer and possibly transfer ionization occur in these reactions.

Tosh, R. E.; Johnsen, R.

1993-02-01

188

Charge transfer fluctuations as a signal for quark-gluon plasma  

SciTech Connect

In this work, the charge transfer fluctuation that was previously used for pp collisions is proposed for relativistic heavy-ion collisions as a quark-gluon plasma (QGP) probe. We propose the appearance of a local minimum at midrapidity for the charge transfer fluctuation as a signal for a QGP. Within a two-component neutral cluster model, we demonstrate that the charge transfer fluctuation can detect the presence of a QGP as well as the size of the QGP in the rapidity space. We also show that the forward-backward correlation of multiplicity can be a similarly good measure of the presence of a QGP. Further, we show that the previously proposed net charge fluctuation is sensitive to the existence of the second phase only if the QGP phase occupies a large portion of the available rapidity space.

Shi Lijun; Jeon, Sangyong [Physics Department, McGill University, Montreal, Quebec, H3A 2T8 (Canada); Physics Department, McGill University, Montreal, Quebec, H3A 2T8 (Canada) and RIKEN-BNL Research Center, Upton, New York 11973 (United States)

2005-09-01

189

Applications of Atom-Photon Coincidence Measurements to Charge Transfer  

Microsoft Academic Search

Measurements have been made of the polarization of characteristic radiation of excited states, formed in charge exchange collisions, in delayed time coincidence with the neutral particles formed and scattered during the collision. Such information directly provides ratios of populations of orbital magnetic sublevels and phase differences between scattering amplitudes. This relative phase data, in conjunction with an appropriate model of

D. H. Jaecks; F. Eriksen; L. Fornari; A. Goldberger

1979-01-01

190

Palm size charging platform with uniform wireless power transfer  

Microsoft Academic Search

In this paper, the design of wireless inductive charger for portable electronic devices is present. There are two main parts have been included. The first part is the exciting circuit in which to provide sufficient input power to the primary charging platform. The exciting circuit is comprised by oscillator circuit and power amplifier circuit. Both of the two circuits have

Yun You; Boon-Hee Soong; Selvakumaran Ramachandran; Wei Liu

2010-01-01

191

Drift-Tube Studies of Exoergic Ion-Molecule Collisions and Photon-Induced Charge Transfer.  

NASA Astrophysics Data System (ADS)

Rate coefficients and product-ion yields were determined for ion-molecule collisions at near-thermal energies involving the molecule dimethyl-methylphosphonate (DMMP) and several atmospheric ions. A similar study was done with He^{++} ions and several atmospheric gases. A third experiment was an attempt to observe the laser-stimulated charge transfer in collisions of Ne^+ with He. All measurements were carried out using a selected-ion drift tube mass spectrometer. The results of the study with DMMP showed that most reactions appear to proceed by dissociative charge transfer, although some evidence for ion-molecule reaction was found in the case of O_sp{2} {+}. Also, the only loss mechanism for ground state NO^+ ions is three -body association, and hydronium ions transfer a proton to DMMP. Rate coefficients obtained in the study with He^{++} ions were found to be quite close to the predictions of ion-molecule capture theories. Singly and doubly charged product ions were observed in several cases, indicating that both single and double charge transfer, and possibly transfer ionization, occur. The experiment on laser-stimulated charge transfer produced measurements of upper limits to the cross section that are considerably lower than some theoretical predictions.

Tosh, Ronald E.

1992-01-01

192

Charge transfer and x-ray emission in collisions between slow, highly charged ions and neutral atoms  

NASA Astrophysics Data System (ADS)

The Classical Trajectory Monte Carlo method was used to study Charge transfer between slow (<50 eV/amu) highly charged ions (Ne^10+, Ar^18+) and their respective neutral atoms. State specific electron capture cross sections were calculated and used to estimate cross sections for the resulting x-ray emissions. The calculated x-ray line emissions are compared with measurements made at Lawrence Livermore National Laboratory using the electron beam ion traps EBIT-II and SuperEBIT. Although the calculated line emissions compare favorably with the experimental measurments, there are still unresolved discrepencies.

Perez, J. A.; Thomas, B. P.; Olson, R. E.; Beiersdorfer, P.

2002-05-01

193

Analysis of incomplete charge transfer effects in a CMOS image sensor  

NASA Astrophysics Data System (ADS)

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 0.18 ?m 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.

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

2013-05-01

194

Wire transfer of charge packets for on-chip CCD signal processing  

NASA Astrophysics Data System (ADS)

A structure for the virtual transfer of charge packets across metal wires is described theoretically and is experimentally verified. The structure is a hybrid of charge-coupled device (CCD) and bucket-brigade device (BBD) elements and permits the topological crossing of charge-domain signals in low power signal processing circuits. A test vehicle consisting of 8-, 32- and 96-stage delay lines of various geometries implemented in a double-poly, double-metal foundry process was used to characterize the wire-transfer operation. Transfer efficiency ranging between 0.998 and 0.999 was obtained for surface n-channel devices with clock cycle times in the range from 40 nsec to 0.3 msec. Transfer efficiency as high as 0.9999 was obtained for buried n-channel devices. Good agreement is found between experiment and simulation.

Fossum, Eric R.

195

The effects of charge transfer on the aqueous solvation of ions  

NASA Astrophysics Data System (ADS)

Ab initio-based charge partitioning of ionic systems results in ions with non-integer charges. This charge-transfer (CT) effect alters both short- and long-range interactions. Until recently, the effects of CT have been mostly neglected in molecular dynamics (MD) simulations. The method presented in this paper for including charge transfer between ions and water is consistent with ab initio charge partitioning and does not add significant time to the simulation. The ions of sodium, potassium, and chloride are parameterized to reproduce dimer properties and aqueous structures. The average charges of the ions from MD simulations (0.900, 0.919, and -0.775 for Na+, K+, and Cl-, respectively) are consistent with quantum calculations. The hydration free energies calculated for these ions are in agreement with experimental estimates, which shows that the interactions are described accurately. The ions also have diffusion constants in good agreement with experiment. Inclusion of CT results in interesting properties for the waters in the first solvation shell of the ions. For all ions studied, the first shell waters acquire a partial negative charge, due to the difference between water-water and water-ion charge-transfer amounts. CT also reduces asymmetry in the solvation shell of the chloride anion, which could have important consequences for the behavior of chloride near the air-water interface.

Soniat, Marielle; Rick, Steven W.

2012-07-01

196

Four-body charge transfer processes in heavy particle collisions  

NASA Astrophysics Data System (ADS)

Fully differential cross sections (FDCS) for proton + helium single capture and transfer-excitation collisions are presented using the Four-Body Transfer-Excitation (4BTE) model. This is a first order perturbative model that allows for any two-particle interaction to be studied. For single capture, the effect of the projectile-nuclear term in the perturbation is examined. It is shown that inclusion of this term results in an unphysical minimum in the FDCS, but is required to correctly predict the magnitude of the experimental results. For transfer-excitation, the role of electron correlation in the target helium atom is studied, and shown to be unimportant in the calculation of the FDCS.

Harris, A. L.; Peacher, J. L.; Schulz, M.; Madison, D. H.

2010-02-01

197

Modulation of terrestrial ion escape flux composition (by low-altitude acceleration and charge exchange chemistry)  

SciTech Connect

Motivated by recent observations of highly variable hot plasma composition in the agnetosphere, control of the ionospheric escape flux composition by low-altitude particle dynamics and ion chemistry has been investigated for an e/sup -/, H/sup +/, O/sup +/ ionosphere. Theoretical polar wind results of Banks and Holzer and observations of highly nonthermal ion escape have been used as guides. It is found that the fraction of the steady state escape flux which is O/sup +/ can be controlled very sensitively by the occurrence of parallel or transverse ion acceleration at altitudes below the altitude where the neutral oxygen density falls rapidly below the neutral hydrogen density and the ionospheric source of O/sup +/ tends to be rapidly converted by charge exchange to H/sup +/. The acceleration is required both to overcome the gravitational confinement of O/sup +/ and to violate charge exchange equilibrium so that the neutral hydrogen atmosphere appears 'optically' thin to escaping O/sup +/. Constraints are placed on the acceleration processes, and it is shown that O/sup +/ escape is facilitated by observed ionospheric responses to magnetic activity.

Moore, T.E.

1980-05-01

198

Chemically intuitive indices for charge-transfer excitation based on SAC-CI and TD-DFT calculations.  

PubMed

A recently proposed charge-transfer (CT) index and some related quantities aimed to the description of CT excitations in push-pull donor-acceptor model systems were computed in vacuum and in ethanol by the direct symmetry-adapted cluster-configuration interaction (SAC-CI) method including solvent effects by means of the nonequilibrium state-specific approach. The effects of both solvation and electron correlations on these quantities were found to be significant. The present results are also in line with previous time-dependent (TD) density functional theory calculations and they demonstrate that SAC-CI provides a description of the excitation character close to that of TD-PBE0. Indeed, CT indices evaluated by the SAC-CI and TD-PBE0 would be useful in the field of materials chemistry, for the design and development of novel molecular materials. © 2013 Wiley Periodicals, Inc. PMID:24037799

Ehara, Masahiro; Fukuda, Ryoichi; Adamo, Carlo; Ciofini, Ilaria

2013-08-26

199

Photophysics of charge transfer in a polyfluorene/violanthrone blend  

NASA Astrophysics Data System (ADS)

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 .

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

2005-01-01

200

Systematic behaviour in trivalent lanthanide charge transfer energies  

Microsoft Academic Search

Information on the energy that is needed to transfer an electron from the valence band of an inorganic compound to a trivalent lanthanide impurity is presented. The energy is a measure of the location of the ground state of the divalent lanthanide relative to the top of the valence band. A variation with type of lanthanide is found that is

P. Dorenbos

2003-01-01

201

Energy and charge transfer in organic light-emitting diodes: A soluble quinacridone study  

NASA Astrophysics Data System (ADS)

A soluble derivative of quinacridone, N,N'-di-isoamyl quinacridone (DIQA), has been synthesized and used to study the mechanisms of Förster energy transfer and charge transfer in organic light-emitting diodes (OLEDs) based on 8-hydroxyquinoline (Alq3). Quantum efficiencies and spectra were measured for both photoluminescence (PL) and electroluminescence (EL) for films of poly(9-vinylcarbazole) (PVK) doped with Alq3 and DIQA. Both PL and EL showed an efficiency enhancement in films of PVK:Alq3:DIQA compared to films of PVK:Alq3. However, the optimal DIQA doping concentration was found to be lower for EL than for PL. Examination of the spectra revealed that more emission originated from DIQA for EL than for PL at a given doping level. We conclude that Förster energy transfer from Alq3 to DIQA occurs in both cases of PL and EL, but that charge transfer to DIQA occurs in the operation of the OLED resulting in additional pathways to DIQA emission. Ultraviolet photoelectron spectroscopy measurements showed that electron transfer from Alq3 to DIQA, hole transfer from PVK to DIQA, and hole transfer from Alq3 to DIQA are all energetically favorable processes. These results suggest that charge transfer is an important mechanism in the efficiency enhancement seen in OLEDs based on a host-dopant scheme, and that both the electronic properties and the optical properties of the dopant material are important parameters for device optimization.

Shaheen, S. E.; Kippelen, B.; Peyghambarian, N.; Wang, J.-F.; Anderson, J. D.; Mash, E. A.; Lee, P. A.; Armstrong, N. R.; Kawabe, Y.

1999-06-01

202

Interstellar Chemistry Gets More Complex With New Charged-Molecule Discovery  

NASA Astrophysics Data System (ADS)

Astronomers using data from the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) have found the largest negatively-charged molecule yet seen in space. The discovery of the third negatively-charged molecule, called an anion, in less than a year and the size of the latest anion will force a drastic revision of theoretical models of interstellar chemistry, the astronomers say. Molecule formation Formation Process of Large, Negatively-Charged Molecule in Interstellar Space CREDIT: Bill Saxton, NRAO/AUI/NSF Click on image for page of graphics and detailed information "This discovery continues to add to the diversity and complexity that is already seen in the chemistry of interstellar space," said Anthony J. Remijan of the National Radio Astronomy Observatory (NRAO). "It also adds to the number of paths available for making the complex organic molecules and other large molecular species that may be precursors to life in the giant clouds from which stars and planets are formed," he added. Two teams of scientists found negatively-charged octatetraynyl, a chain of eight carbon atoms and one hydrogen atom, in the envelope of gas around an old, evolved star and in a cold, dark cloud of molecular gas. In both cases, the molecule had an extra electron, giving it a negative charge. About 130 neutral and about a dozen positively-charged molecules have been discovered in space, but the first negatively-charged molecule was not discovered until late last year. The largest previously-discovered negative ion found in space has six carbon atoms and one hydrogen atom. "Until recently, many theoretical models of how chemical reactions evolve in interstellar space have largely neglected the presence of anions. This can no longer be the case, and this means that there are many more ways to build large organic molecules in cosmic environments than have been explored," said Jan M. Hollis of NASA's Goddard Space Flight Center (GSFC). Ultraviolet light from stars can knock an electron off a molecule, creating a positively-charged ion. Astronomers had thought that molecules would not be able to retain an extra electron, and thus a negative charge, in interstellar space for a significant time. "That obviously is not the case," said Mike McCarthy of the Harvard-Smithsonian Center for Astrophysics. "Anions are surprisingly abundant in these regions." Remijan and his colleagues found the octatetraynyl anions in the envelope of the evolved giant star IRC +10 216, about 550 light-years from Earth in the constellation Leo. They found radio waves emitted at specific frequencies characteristic of the charged molecule by searching archival data from the GBT, the largest fully-steerable radio telescope in the world. Another team from the Harvard-Smithsonian Center for Astrophysics (CfA) found the same characteristic emission when they observed a cold cloud of molecular gas called TMC-1 in the constellation Taurus. These observations also were done with the GBT. In both cases, preceding laboratory experiments by the CfA team showed which radio frequencies actually are emitted by the molecule, and thus told the astronomers what to look for. "It is essential that likely interstellar molecule candidates are first studied in laboratory experiments so that the radio frequencies they can emit are known in advance of an astronomical observation," said Frank Lovas of the National Institute of Standards and Technology (NIST). Both teams announced their results in the July 20 edition of the Astrophysical Journal Letters. "With three negatively-charged molecules now found in a short period of time, and in very different environments, it appears that many more probably exist. We believe that we can discover more new species using very sensitive and advanced radio telescopes such as the GBT, once they have been characterized in the laboratory," said Sandra Bruenken of the CfA. "Further detailed studies of anions, including astronomical observations, laboratory studies, and theo

2007-07-01

203

46 CFR 154.1831 - Persons in charge of transferring liquid cargo in bulk or preparing cargo tanks.  

Code of Federal Regulations, 2011 CFR

...false Persons in charge of transferring liquid cargo in bulk or preparing cargo tanks...1831 Persons in charge of transferring liquid cargo in bulk or preparing cargo tanks...on duty to safely conduct a transfer of liquid cargo in bulk or a cool-down,...

2011-10-01

204

46 CFR 154.1831 - Persons in charge of transferring liquid cargo in bulk or preparing cargo tanks.  

Code of Federal Regulations, 2012 CFR

...false Persons in charge of transferring liquid cargo in bulk or preparing cargo tanks...1831 Persons in charge of transferring liquid cargo in bulk or preparing cargo tanks...on duty to safely conduct a transfer of liquid cargo in bulk or a cool-down,...

2012-10-01

205

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

NASA Astrophysics Data System (ADS)

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 powdered materials can lead to electrostatic discharge and so is of interest from a safety viewpoint. The charging of powders can also adversely affect their mechanical handling characteristics and so is of interest to handling equipment engineers. The paper presents the design of the sensors, the design of the electric charge test rig and electric charge measurement test results.

Woodhead, S. R.; Denham, J. C.; Armour-Chelu, D. I.

2005-01-01

206

Spectrophotometric study of the charge transfer complex between 2-amino-4-picoline with chloranilic acid  

NASA Astrophysics Data System (ADS)

Charge transfer complex formation between 2-amino-4-picoline (2A4P) as the electron donor with chloranilic acid (CLA) as the electron acceptor has been studied spectrophotometrically in different polar solvents included acetone (AcN), ethanol (EtOH) and acetonitrile (AN). The molecular composition of the formed complex was recognized utilizing Job's, photometric and conductometric titration methods to be 1:1. The formation constants and molecular extinction coefficients were estimated using Benesi-Hildebrand equation; they recorded high values confirming high stability of the formed complex. Moreover, the results showed that the complex is more stable in acetone with lower electric permittivity compared with ethanol or acetonitrile of higher ones. The values of some spectroscopic physical parameters like oscillator strength f, transition dipole moment ?, resonance energy RN, charge transfer energy ECT, dissociation energy W, ionization potential IP and standard free energy ?Go were determined and evaluated. The solid complex was isolated and its molecular composition was determined by elemental analysis to be 1:1. Furthermore, the solid complex was characterized using FTIR and 1H NMR measurements. They confirmed the presence of proton transfer beside charge transfer in the obtained complex. Molecular orbital calculations utilizing GAMESS computations were carried out to predict infrared spectra. They also confirmed the presence of proton transfer beside charge transfer in the formed complex.

Alghanmi, Reem M.; Al-Attas, Amirah S.; Habeeb, Moustafa M.

2013-02-01

207

Molecular ionic junction for enhanced electronic charge transfer.  

PubMed

We present the first evidence of charge injection improvement in an organic electroluminescent device provided by a single ionic molecular layer. A hole-dominated, hybrid organic-inorganic light-emitting device is used as a probe to verify the effectiveness of the ionic compound monolayer on modifying the metal oxide cathode. The rearrangement of ions under an applied bias induces a strong field at the electrode-organic interface resulting in an enhancement of the electron injection into the organic semiconductor. A strong decrease in turn-on voltage for electroluminescence is observed for the device containing the ionic molecular monolayer. PMID:19209442

Bolink, Henk J; Baranoff, Etienne; Clemente-León, Miguel; Coronado, Eugenio; Lopéz-Muñoz, Angel; Repetto, Diego; Sessolo, Michele; Nazeeruddin, Md K

2009-01-01

208

(1) Modeling emissive charge-transfer states in solution phase functionalized silsesquioxanes. (2) On symmetry hidden charge transfer states: Lessons for the design of functionals  

NASA Astrophysics Data System (ADS)

Range separate hybrid functionals are used to study the charge transfer processes in chromophores attached to silsesquioxanes molecular species. We investigate the experimentally observed red shifting of the emission spectra in comparison to the spectral shift for the individual ligand. Solvent effects are accounted for via a combination of constrained density functional theory and the polarizable continuum (PCM) model. We quantitatively reproduce the experimental red shift and identify the emissive state as a ligand-to-ligand, rather than a ligand-to-silsesquioxane, charge-transfer state. We also find that the enhanced red-shift cannot be explained without accounting for solvation effects and demonstrate the importance of using a range-separated hybrid functional, as opposed to more traditional functionals such as B3LYP, to obtain reliable predictions regarding the emissive state. If time allows we will also discuss the limitations and successes of RSH functionals in treating the case of charge transfer processes that are hidden by system symmetry. We use related models to draw insight for designing improved functionals.

Dunietz, Barry D.; Zheng, Shaohui; Phillips, Heidi; Geva, Eitan

2012-02-01

209

Evidences For Charge Transfer-Induced Conformational Changes In Carbon Nanostructure-Protein Corona.  

PubMed

The binding of proteins to a nanostructure often alters protein secondary and tertiary structures. However, the main physical mechanisms that elicit protein conformational changes in the presence of the nanostructure have not yet been fully established. Here we performed a comprehensive spectroscopic study to probe the interactions between bovine serum albumin (BSA) and carbon-based nanostructures of graphene and single-walled carbon nanotubes (SWNTs). Our results showed that the BSA "corona" acted as a weak acceptor to facilitate charge transfer from the carbon nanostructures. Notably, we observed that charge transfer occurred only in the case of SWNTs but not in graphene, resulting from the sharp and discrete electronic density of states of the former. Furthermore, the relaxation of external ?-helices in BSA secondary structure increased concomitantly with the charge transfer. These results may help guide controlled nanostructure-biomolecular interactions and prove beneficial for developing novel drug delivery systems, biomedical devices and engineering of safe nanomaterials. PMID:23243478

Podila, R; Vedantam, P; Ke, P C; Brown, J M; Rao, A M

2012-09-26

210

A Molecular Switch Made of Charge Transfer Complexes on Au (111)  

NASA Astrophysics Data System (ADS)

A low temperature scanning tunneling microscope (STM) and spectroscopy study of organic charge transfer complexes is presented. The complexes are formed by self assembly of the electron donor ?- sexithiophene (6T) and the electron acceptor tetrafluro-tetracyano-quinodimethane (F4TCNQ) on Au (111) surface. The formation of new hybrid molecular orbitals in CTCs is evident by STM imaging at different bias voltages as well as by differential conductance spectra. The charge transfer lead to the shift of HOMO and LUMO orbitals of the molecules in complexes with respect to the pure molecular orbitals. Finally, we use a voltage dependent resonance-tunneling scheme to demonstrate a molecular switch made of F4TCNQ/6T charge transfer complexes. This work is financially supported by the US-DOE grant DE-FG02-02ER46012.

Perera, U. G. E.; Jäckel, F.; Iancu, V.; Braun, K.-F.; Koch, N.; Rabe, J. P.; Hla, S.-W.

2008-03-01

211

Attosecond timing the ultrafast charge-transfer process in atomic collisions  

SciTech Connect

By solving the three-dimensional, time-dependent Schroedinger equation, we have demonstrated that the ultrafast charge-transfer process in ion-atom collisions can be mapped out with attosecond extreme uv (xuv) pulses. During the dynamic-charge transfer from the target atom to the projectile ion, the electron coherently populates the two sites of both nuclei, which can be viewed as a 'short-lived' molecular state. A probing attosecond xuv pulse can instantly unleash the delocalized electron from such a ''transient molecule,'' so that the resulting photoelectron may exhibit a ''double-slit'' interference. On the contrary, either reduced or no photoelectron interference will occur if the attosecond xuv pulse strikes well before or after the collision. Therefore, by monitoring the photoelectron interference visibility, one can precisely time the ultrafast charge-transfer process in atomic collisions with time-delayed attosecond xuv pulses.

Hu, S. X. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States)

2011-04-15

212

Charge transfer and ionization in ion collisions with circular Rydberg atoms  

NASA Astrophysics Data System (ADS)

Explorations of the classical phase space for ion collisions with Rydberg atom targets provide insight into mechanisms for ionization and charge transfer. Thomas's analysis of charge transfer at high impact energies [Proc. Roy. Soc. London 114, 561 (1927)] is extended here to intermediate- and low-energy ??? and ionization processes through numerical integration of the classical equations of motion. Parameter space maps correlating initial conditions with final outcomes have well-defined zones corresponding to Thomas capture, direct capture, binary encounter ionization, saddle-point ionization, and ionization by S superpromotion. The relative contributions to charge transfer (or ionization) cross sections from these distinct classical collision channels are qualitatively interpreted by analysis of the parameter space maps.

Homan, D. M.; Cavagnero, M. J.; Harmin, D. A.

1996-03-01

213

Detection of single-nucleotide variations by monitoring the blinking of fluorescence induced by charge transfer in DNA.  

PubMed

Charge transfer dynamics in DNA: Photo-induced charge separation and charge-recombination dynamics in DNA was assessed by monitoring the blinking of fluorescence. Single nucleotide variations, mismatch and one base deletion, were differentiated based on the length of the off-time of the blinking, which corresponds to the lifetime of the charge-separated state. PMID:23846860

Kawai, Kiyohiko; Majima, Tetsuro; Maruyama, Atsushi

2013-07-11

214

Continuum electrostatic investigations of charge transfer processes in biological molecules using a microstate description.  

PubMed

Charge transfer through biological macromolecules is essential for many biological processes such as for instance photosynthesis and respiration. In these processes, protons or electrons are transferred between titratable residues or redox-active cofactors, respectively. Often their transfer is tightly coupled. Computational methods based on continuum electrostatics are widely used in theoretical biochemistry to analyze the function of even very complex biochemical systems. These methods allow one to consider the pH and the redox potential of the solution as well as explicitly considering membrane potentials in the calculations. Combining continuum electrostatic calculations with a statistical thermodynamic analysis, it is possible to calculate equilibrium parameters such as protonation or oxidation probabilities. Moreover, it is also possible to simulate reaction kinetics by using parameters calculated from continuum electrostatics. One needs to consider that the transfer rate between two sites depends on the current charge configuration of neighboring sites. We formulate the kinetics of charge transfer systems in a microstate formalism. A unique transfer rate constant can be assigned to the interconversion of microstates. Mutual interactions between sites participating in the transfer reactions are naturally taken into account. This formalism is applied to the kinetics of electron transfer in the tetraheme-subunit and the special pair of the reaction center of Blastochloris viridis. It is shown that continuum electrostatic calculations can be used in combination with an existing rate law to obtain electron transfer rate constants. The relaxation electron transfer kinetics after photo-oxidation of the special pair of photosynthetic reaction center is simulated by a microstate formalism and it is shown to be in good agreement with experimental data. A flux analysis is used to follow the individual electron transfer steps. This method of simulating the complex kinetics of biomolecules based on structural data is a first step on the way from structural biology to systems biology. PMID:21322484

Bombarda, Elisa; Ullmann, G Matthias

2011-01-01

215

Ensemble density functional theory, the atom-in-molecule problem, and reactive charge transfer  

NASA Astrophysics Data System (ADS)

A major challenge in large-scale simulations of complex biomolecular and materials systems is the ability to accurately describe reactive dynamics. We have previously described a new multiscale formalism, based on density functional theory and the embedded-atom method, that enables the rigorous encoding of quantum mechanical excitation effects such as charge polarization and charge transfer within a classical potential. Here we describe a new formulation of a key element of the theory: the deconstruction of molecular densities into subsystem atom-in-molecule components via ensemble constrained-search density functional theory. The method is implemented via the self-consistent solution of coupled sets of Kohn-Sham equations in conjunction with chemical potential equalization across subsystems. This leads to a natural interpretation of dynamical charge transfer and charge polarization in terms of an electronic entropy, thus extending the seminal work of Gross, Oliveira, and Kohn (1988).

Atlas, Susan; Valone, Steven

2008-03-01

216

SF4: electron affinity determination by charge-transfer reactions  

NASA Astrophysics Data System (ADS)

A selected-ion flow drift tube was used to conduct an extensive study of the negative ion/molecule reaction of SF4 and SF-4. Thirteen reactions proceed by electron transfer. Data from these reactions, and information from systems that do not react at all, are used to determine the electron affinity of SF4, EA(SF4) = 1.5 ± 0.2 eV. Additional thermochemical data are used to determine the fluoride affinity of SF3, D(SF3-F-) = 1.8 ± 0.3 eV.

Viggiano, A. A.; Miller, Thomas M.; Stevens Miller, Amy E.; Morris, Robert A.; van Doren, Jane M.; Paulson, John F.

1991-11-01

217

Dependency of the Transferred Charge of Provoked Discharges from Insulated Surfaces on Temperature and Humidity  

Microsoft Academic Search

The maximum transferred charge of provoked discharges from different insulating materials charged by spraying ions, rubbing or streaming liquids was investigated in the temperature interval -20degC to +45degC at a relative humidity between 5% and 75%. The results obtained did not correlate with the absolute humidity but with the surface resistance and the relative humidity. In the case of streaming

Ulrich von Pidoll

2007-01-01

218

Stability and charge transfer levels of extrinsic defects in LiNbO3  

Microsoft Academic Search

The technologically important incorporation of extrinsic defects ( Mg2+ , Fe2+ , Fe3+ , Er3+ , and Nd3+ ) in LiNbO3 is investigated using density-functional theory combined with thermodynamic calculations. Defect energies, the charge compensation mechanisms, and charge transfer levels, are determined for congruent and stoichiometric compositions. In general, under congruent ( Nb2O5 -rich) conditions impurities occupy lithium sites, compensated

Haixuan Xu; Aleksandr Chernatynskiy; Donghwa Lee; Susan B. Sinnott; Venkatraman Gopalan; Volkmar Dierolf; Simon R. Phillpot

2010-01-01

219

Direct Observation of Charge Transfer in Double-Perovskite-Like RbMn[Fe(CN)6  

Microsoft Academic Search

The charge density distribution has been determined for a transition metal cyanide, RbMn[Fe(CN)6], by means of the maximum entropy Rietveld method combined with the highly angularly resolved synchrotron radiation x-ray powder diffraction at SPring-8 BL02B2. We directly observed a charge transfer from the Mn site to the Fe site in the low-temperature phase. On the basis of a local density

K. Kato; Y. Moritomo; M. Takata; M. Sakata; M. Umekawa; N. Hamada; S. Ohkoshi; H. Tokoro; K. Hashimoto

2003-01-01

220

Direct evidence for charge-transfer photodissociation at a metal surface: CCl4\\/Ag(111)  

Microsoft Academic Search

Observation of negative ions desorbing from an adsorbate-covered metal surface following UV laser irradiation gives direct evidence that the mechanism responsible is charge-transfer photodissociation (CT-PDIS). We have studied photoemission of ions for CCl4\\/Ag(111)+hnu-->Cl-(g)+CCl3\\/Ag(111). The CT-PDIS mechanism is supported by comparison of the yield of desorbing Cl- and photoemitted electrons with the variation in UV photon energy and surface coverage. Charge

St.-J. Dixon-Warren; E. T. Jensen; J. C. Polanyi

1991-01-01

221

Ultrafast inter-ionic charge transfer of transition-metal complexes mapped by femtosecond x-ray powder diffraction  

NASA Astrophysics Data System (ADS)

Transient electron density maps are derived from x-ray diffraction patterns of photoexcited [Fe(bpy)3]2+(PF6-)2 powder. Upon photoexcitation, the 5T2 quintet state reveals a charge transfer from the PF6- ions and from the Fe atoms to neighboring bpy units. The charge transfer from the Fe points to a partial and weak charge-transfer character of this state.

Zamponi, F.; Freyer, B.; Juvé, V.; Stingl, J.; Woerner, M.; Chergui, M.; Elsaesser, T.

2013-03-01

222

Photoinduced charge and energy transfer in dye-doped conjugated polymers  

Microsoft Academic Search

Conjugated polymer-molecular dye blends of MDMO-PPV (poly[2-methoxy-5-(3?,7?-dimethyloctyloxy)-1,4-phenylenevinylene]) and PF1CVTP (poly[9,9-dioctylfluorene-2,7-diyl-alt-2,5-bis(2-thienyl-1-cyanovinyl)-1-(3?,7?-dimethyloctyloxy)-4-methoxybenzene-5?,5?-diyl]) with three dipyrrometheneboron difluoride (bodipy) dyes were studied by (time-resolved) fluorescence and photoinduced absorption spectroscopy to determine quantitatively the relation between the electronic HOMO and LUMO levels and the occurrence of energy or charge transfer after optical excitation. We find that for MDMO-PPV photoinduced charge transfer to the dyes occurs,

Dirk Veldman; Jolanda J. A. M. Bastiaansen; Bea M. W. Langeveld-Voss; Jörgen Sweelssen; Marc M. Koetse; Stefan C. J. Meskers; René A. J. Janssen

2006-01-01

223

Photoinduced charge transfer involving a MoMo quadruply bonded complex to a perylene diimide.  

PubMed

Evidence, based on femtosecond transient absorption and time resolved infrared spectroscopy, is presented for photoinduced charge transfer from the Mo2? orbital of the quadruply bonded molecule trans-Mo2(T(i)PB)2(BTh)2, where T(i)PB = 2,4,6-triisopropyl benzoate and BTh = 2,2'-bithienylcarboxylate, to di-n-octyl perylene diimide and di-n-hexylheptyl perylene diimide in thin films and solutions of the mixtures. The films show a long-lived charge separated state while slow back electron transfer, ?BET ~ 500 ps, occurs in solution. PMID:23412626

Alberding, Brian G; Brown-Xu, Samantha E; Chisholm, Malcolm H; Epstein, Arthur J; Gustafson, Terry L; Lewis, Sharlene A; Min, Yong

2013-02-15

224

Mean-trajectory approximation for charge- and energy-transfer processes at surfaces  

SciTech Connect

We discuss electronic energy and charge-transfer processes at surfaces in terms of curve-crossing models. We suggest that at low kinetic energies the trajectory approximation should be replaced by a mean-trajectory approximation (MTA), in which the nuclear motion gets feedback from and adjusts to the curve-crossing dynamics. We discuss two derivations of MTA by using an eikonal approximation and a path-integral method. The effects of phonon or electron-hole pair excitations on the charge-transfer process are also incorporated.

Sawada, S.; Nitzan, A.; Metiu, H.

1985-07-15

225

Scanning tunneling microscope-based thermochemical hole burning on a series of charge transfer complexes  

SciTech Connect

A thermochemical hole burning effect was observed on a series of 7, 7, 8, 8-tetra cyanoquinodimethane charge transfer complexes when applying a suitable voltage pulse using scanning tunneling microscope, which is attributed to the localized thermochemical decomposition of the complex induced by the current heating effect. The decomposition reaction evolves the low boiling point decomposition components of the charge transfer complex, leaving a nanometer-sized hole on the crystal surface. This effect demonstrates the possibility of creating a ultrahigh density thermochemical hole burning memory, in which information bit is recorded as a hole.

Yu Xuechun; Peng Hailin; Ran Chunbo; Sun Lei; Zhang Ran; Liu Zhongfan [Center for Nanoscale Science and Technology (CNST), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

2005-03-28

226

Photoinduced charge-transfer dissociation of hydrogen halides on silver and potassium  

SciTech Connect

The photodissociation of HCl(ad) and HI(ad) on Xe/Ag(111) and Xe/K/Ag(111) surfaces at 248, 308, and 350 nm has been studied by measuring the time-of-flight spectra of H atoms recoiling from the surface. In each case, HCl(ad) and HI(ad), the lower work function metal gave photodissociation out to much longer wavelengths, indicative of a charge-transfer mechanism. For HCl(ad) on Xe/K/Ag(111) the photoinduced charge-transfer dissociation occurred at photon energies well below the bond dissociation energy, ruling out direct dissociation of the adsorbate.

Dixon-Warren, S.J.; Polanyi, J.C.; Stanners, C.D.; Xu, G.Q. (Univ. of Toronto, Ontario (Canada))

1990-07-26

227

Direct evidence for charge-transfer photodissociation at a metal surface: CCl4/Ag(111)  

NASA Astrophysics Data System (ADS)

Observation of negative ions desorbing from an adsorbate-covered metal surface following UV laser irradiation gives direct evidence that the mechanism responsible is charge-transfer photodissociation (CT-PDIS). We have studied photoemission of ions for CCl4/Ag(111)+h?-->Cl-(g)+CCl3/Ag(111). The CT-PDIS mechanism is supported by comparison of the yield of desorbing Cl- and photoemitted electrons with the variation in UV photon energy and surface coverage. Charge transfer leading to negative-ion emission is also shown to occur in the absence of photoelectron emission (i.e., h?

Dixon-Warren, St.-J.; Jensen, E. T.; Polanyi, J. C.

1991-10-01

228

33 CFR 155.715 - Contents of letter of designation as a person-in-charge of the transfer of fuel oil.  

Code of Federal Regulations, 2013 CFR

...as a person-in-charge of the transfer of fuel oil. 155.715 Section...PREVENTION REGULATIONS FOR VESSELS Transfer Personnel, Procedures, Equipment, and...a person-in-charge of the transfer of fuel oil. The letter...

2013-07-01

229

Charge Transfer in Fullerene-Conducting Polymer Compositex: Electronic and Excitonic Properties  

Microsoft Academic Search

C60 doping into conducting polymer with highly extended ?-electron system in the main chain induces remarkable quenching of photoluminescence in conducting polymer and drastic enhancement of photoconductivity. These results can be explained in terms of photo-induced charge transfer between conducting polymer and C60. That is, photoexcited excitons or exciton-polarons on conducting polymer are effectively dissociated at C60 molecules transferring electrons

Katsumi Yoshino; Kazuya Tada; Akihiko Fujii; Kazuhisa Hosoda; Shin-ichi Kawabe; Hirotake Kajii; Masaharu Hirohata; Rahmat Hidayat; Hisashi Araki; Anvar A. Zakhidov; Ryu-ichi Sugmoto; Masahiko Iyoda; Mitsuo Ishikawa; Toshio Masuda

1997-01-01

230

Possible charge analogs of spin-transfer torques in bulk superconductors  

NASA Astrophysics Data System (ADS)

Spin transfer torques (STTs) occur when electric currents travel through inhomogeneously magnetized systems and are important for the motion of magnetic textures such as domain walls. Since superconductors are easy-plane ferromagnets in particle-hole (charge) space, it is natural to ask whether any charge duals of STT phenomena exist therein. We find that the superconducting analog of the adiabatic STT vanishes in a bulk superconductor with a momentum-independent order parameter, while the superconducting counterpart of the nonadiabatic STT does not vanish. This nonvanishing superconducting torque is induced by heat (rather than charge) currents and acts on the charge (rather than spin) degree of freedom. It can become significant in the vicinity of the superconducting transition temperature, where it generates a net quasiparticle charge and alters the dispersion and linewidth of low-frequency collective modes.

Garate, Ion

2013-09-01

231

Charge transfer in FeO: a combined molecular-dynamics and ab initio study.  

PubMed

Molecular-dynamics simulations and ab initio electronic structure calculations were carried out to determine the rate of charge transfer in stoichiometric wustite (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 FeO(6) octahedra. Molecular-dynamics simulations predict charge-transfer rates of 3.7 x 10(11) and 1.9 x 10(9) s(-1) for the edge and corner transfers, respectively, in good agreement with those calculated using an ab initio cluster approach (1.6 x 10(11) and 8.0 x 10(8) s(-1), respectively). The calculated rates are also similar to those along the basal and c-axis directions in hematite (alpha-Fe(2)O(3)) determined previously. Therefore, as is the case for hematite, wustite 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 of 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 nondefective case in a small radius around the defect. PMID:16375500

Kerisit, Sebastien; Rosso, Kevin M

2005-12-01

232

Nonadiabatic dynamics of charge transfer in diatomic anion clusters  

SciTech Connect

We have studied the photodissociation and recombination dynamics of the diatomic anions X{sub 2}{sup -} and XY{sup -} designed to mimic I{sub 2}{sup -} and ICl{sup -}, respectively, by using a one-electron model in size-selected N{sub 2}O clusters. The one-electron model is composed of two nuclei and an extra electron moving in a two-dimensional plane including the two nuclei. The main purpose of this study is to explain the salient features of various dynamical processes of molecular ions in clusters using a simple theoretical model. For heteronuclear diatomic anions, a mass disparity and asymmetric electron affinity between the X and Y atoms lead to different phenomena from the homonuclear case. The XY{sup -} anion shows efficient recombination for a smaller cluster size due to the effect of collision-mediated energy transfer and an inherent potential wall on excited state at asymptotic region, while the recombination for the X{sub 2}{sup -} anion is due to rearrangement of solvent configuration and faster nonadiabatic transitions. The results of the present study illustrate the microscopic details of the electronically nonadiabatic processes which control the photodissociation dynamics of molecular ions in clusters.

Cho, Eunseog; Shin, Seokmin [School of Chemistry, Seoul National University, Seoul 151-747 (Korea, Republic of)

2007-12-28

233

Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics  

NASA Astrophysics Data System (ADS)

Photocurrent generation in organic photovoltaics (OPVs) relies on the dissociation of excitons into free electrons and holes at donor/acceptor heterointerfaces. The low dielectric constant of organic semiconductors leads to strong Coulomb interactions between electron-hole pairs that should in principle oppose the generation of free charges. The exact mechanism by which electrons and holes overcome this Coulomb trapping is still unsolved, but increasing evidence points to the critical role of hot charge-transfer (CT) excitons in assisting this process. Here we provide a real-time view of hot CT exciton formation and relaxation using femtosecond nonlinear optical spectroscopies and non-adiabatic mixed quantum mechanics/molecular mechanics simulations in the phthalocyanine-fullerene model OPV system. For initial excitation on phthalocyanine, hot CT excitons are formed in 10-13?s, followed by relaxation to lower energies and shorter electron-hole distances on a 10-12?s timescale. This hot CT exciton cooling process and collapse of charge separation sets the fundamental time limit for competitive charge separation channels that lead to efficient photocurrent generation.

Jailaubekov, Askat E.; Willard, Adam P.; Tritsch, John R.; Chan, Wai-Lun; Sai, Na; Gearba, Raluca; Kaake, Loren G.; Williams, Kenrick J.; Leung, Kevin; Rossky, Peter J.; Zhu, X.-Y.

2013-01-01

234

Chemistry  

NSDL National Science Digital Library

Chemistry is the scientific study of matter and its interaction with other matter and with energy. It is the branch of natural science that deals with the composition of substances and their properties and reactions.

K-12 Outreach,

235

Ionization and charge-transfer: basic data for track structure calculations.  

PubMed

It is widely accepted that an understanding of the detailed structure of charged particle tracks is essential for interpreting the mechanistic consequences of energy deposition by high linear energy transfer (LET) radiation. The spatial relationship of events along the path of a charged particle, including excitation, ionization, and charge-transfer, govern subsequent chemical, biochemical, and biological reactions that can lead to adverse biologic effects. The determination of spatial patterns of ionization and excitation relies on a broad range of cross-section data relating the interactions of charged particles to the molecular constituents of the absorbing medium. It is important that these data be absolute in magnitude, comprehensive in scope, and reliable if accurate assessment of track structure parameters is to be achieved. Great strides have been made in the development of this database, understanding the underlying theory, and developing analytic models, particularly for interactions involving electrons and protons with atoms and molecules. The database is less comprehensive for interactions involving heavier charged particles, especially those that carry bound electrons, and for interactions in condensed phase media. Although there has been considerable progress in understanding the physical mechanisms for interactions involving fast heavy ions and atomic targets during the past few years, we still lack sufficient understanding to confidently predict cross-sections for these ions with biologically relevant material. In addition, little is known of the interaction cross-sections for heavy charged particles as they near the end of their track, i.e., for low velocity ions where collision theory is less well developed and where the particle's net charge fluctuates owing to electron capture and loss processes. This presentation focuses on the current status of ionization and charge-transfer data. Compilations, reviews, Internet sources, theoretical models, and recent data applicable to track structure calculations are discussed. PMID:10052672

Toburen, L H

1998-12-01

236

Charge transfer dynamics between photoexcited CdS nanorods and mononuclear Ru water-oxidation catalysts.  

PubMed

We describe the charge transfer interactions between photoexcited CdS nanorods and mononuclear water oxidation catalysts derived from the [Ru(bpy)(tpy)Cl](+) parent structure. Upon excitation, hole transfer from CdS oxidizes the catalyst (Ru(2+) ? Ru(3+)) on a 100 ps to 1 ns timescale. This is followed by 10-100 ns electron transfer (ET) that reduces the Ru(3+) center. The relatively slow ET dynamics may provide opportunities for the accumulation of multiple holes at the catalyst, which is necessary for water oxidation. PMID:23406271

Tseng, Huan-Wei; Wilker, Molly B; Damrauer, Niels H; Dukovic, Gordana

2013-02-25

237

Camptothecins guanine interactions: mechanism of charge transfer reaction upon photoactivation  

NASA Astrophysics Data System (ADS)

The potent activity exhibited by the antitumoral camptothecin (CPT) and its analog irinotecan (CPT-11) is known to be related to a close contact between the drug and the nucleic acid base guanine. This specificity of interaction between these two chromophores was examined by following changes in the photophysical properties of the drug using steady-state as well as time-resolved absorption and fluorescence methods. The observed effects on absorption, fluorescence emission and singlet excited state lifetimes give evidence for the occurrence of a stacking complex formation restricted to the quinoline part of CPT or CPT-11 and the guanine base but also with the adenine base. The triplet excited state properties of the drugs have been also characterized in absence and in presence of guanosine monophosphate and reveal the occurrence of an electron transfer from the guanine base to the drug. Support for this conclusion was obtained from the studies of a set of biological targets of various oxido-reduction potentials, adenosine monophosphate, cytidine, cytosine, tryptophan, tyrosine and phenylalanine. This finding gives an interpretation of the CPT-induced guanine photolesions previously reported in the literature. These data taken together are discussed in connection with the drug activity. The stacking complex CPT/guanine is necessary but not sufficient to explain the role of the chirality and of the lactone structure in the function of the drug. A stereospecific interaction with the enzyme topoisomerase I seems necessary to stabilize the stacking complex. The first experiments using time-resolved fluorescence by two-photon excitation confirms that CPT does not bind to the isolated enzyme.

Steenkeste, K.; Guiot, E.; Tfibel, F.; Pernot, P.; Mérola, F.; Georges, P.; Fontaine-Aupart, M. P.

2002-01-01

238

Oscillations in the Total Cross Section for Resonant Charge Transfer in Li-Li(+) collisions.  

National Technical Information Service (NTIS)

A simplified two-state theory is used to predict the total cross section for resonant charge transfer in Li-Li(+) collisions. This cross section exhibits oscillations for collision energies below 10 keV and is in qualitative agreement with preliminary exp...

J. Perel J. M. Peek T. A. Green H. H. Michels

1968-01-01

239

The microstructure of and charge transfer in thin films based on metal-polymer nanocomposites  

Microsoft Academic Search

Charge transfer in nanostructured metal-polymer composites was studied. The frequency dependences of film conductance and susceptance were obtained at various metal concentrations. The susceptance of samples above the percolation threshold was negligibly small, which corresponded to the purely metallic conductivity type. For samples below the percolation threshold, susceptance and conductance were comparable in magnitude, which was evidence of an important

S. A. Zav'yalov; L. Yu. Kupriyanov; A. N. Pivkina; J. Shounman

2006-01-01

240

High-mobility field effect transistors based on supramolecular charge transfer nanofibres.  

PubMed

Self-assembled charge transfer supramolecular nanofibres of coronene tetracarboxylate (CS) and dodecyl substituted unsymmetric viologen derivative (DMV) behave as active channel in field effect transistors exhibiting high mobility. These devices work in ambient conditions and can regenerate in the presence of a single drop of water. PMID:23132547

Sagade, Abhay A; Rao, K Venkata; Mogera, Umesha; George, Subi J; Datta, Ayan; Kulkarni, Giridhar U

2012-11-07

241

REFLECTIVITY OF YIG AND YGG: OBSERVATION OF CHARGE TRANSFER AND CRYSTAL FIELD TRANSITIONS  

Microsoft Academic Search

The reflectivity spectra of yttrium iron garnet (YIG, Y3Fe5O12) and yttrium gallium garnet (YGG, Y3Ga5O12) have been measured in the energy range 2–7.5 eV. Structure is observed in YIG which can be attributed to charge-transfer-enhanced crystal field transitions and in YGG to critical point transitions.

Paul M. Grant

1967-01-01

242

Influence of solution acidity on the adsorption and charge transfer kinetics of parabanic acid reduction  

Microsoft Academic Search

Parabanic acid reduction has been studied in the ? 1.4 ? H0 ? 0.9 acidity range by the ac impedance technique. Changes in the adsorption of reactant and products with solution acidity lead to protonation equilibrium constants that differ from their bulk values. The observed pKa shifts were consistent with interfacial dielectric saturation. Variation of the charge transfer parameters with

J. J. Calvente; R. Andreu; E. Roldán; M. Domínguez

1995-01-01

243

Charge Transfer to the Continuum by Heavy Ions in Atomic Hydrogen.  

National Technical Information Service (NTIS)

Design and installation of an atomic hydrogen target for measurements of charge transfer to the continuum by heavy ions are discussed. The design consists of a tungsten gas cell operated at temperatures of 2500 to 2600 exp 0 K. Initial testing is underway...

I. A. Sellin

1981-01-01

244

The Use of Computers to Study the Penultimate and the Charge-Transfer Polymerization Models.  

National Technical Information Service (NTIS)

Three programs have been written for evaluating the charge-transfer copolymerization model when operating in competition with the terminal model. The first program (Program CT-1) permits the calculation of r(1), r(1c2), r(1c2), r(2), r(2c2), r(2c1), and K...

C. U. Pittman T. D. Rounsefell

1975-01-01

245

Elastic, excitation, ionization and charge transfer cross sections of current interest in fusion energy research  

SciTech Connect

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.

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

1996-12-31

246

Light-induced change of charge transfer band in nanocrystalline Y2O3:Eu3+  

NASA Astrophysics Data System (ADS)

In this letter, we report the observation of ultraviolet light-induced change of excited charge-transfer band in nanocrystalline Y2O3:Eu3+, which is attributed to the rearrangements of local environments surrounding the Eu3+ ions in the near surface of nanoparticles.

Song, Hongwei; Chen, Baojiu; Peng, Hongshang; Zhang, Jisen

2002-09-01

247

Nonlinear optical properties of fullerenes and charge-transfer complexes of fullerenes  

Microsoft Academic Search

The authors present results on the second- and third-order nonlinear optical properties of fullerenes and some of their derivatives. This is part of their effort to study general nonlinear properties of clusters. Polarizability measurements in fullerenes and in N,N-diethylaniline charge transfer complexes are reported.

Ying Wang; Lap-Tak Cheng

1992-01-01

248

Nonlinear optical properties of fullerenes and charge-transfer complexes of fullerenes  

SciTech Connect

The authors present results on the second- and third-order nonlinear optical properties of fullerenes and some of their derivatives. This is part of their effort to study general nonlinear properties of clusters. Polarizability measurements in fullerenes and in N,N-diethylaniline charge transfer complexes are reported.

Wang, Ying; Cheng, Lap-Tak [Du Pont Co., Wilmington, DE (United States)

1992-02-20

249

FT-IR determinations in charge-transfer interactions between phenylhydrazones and organic acceptors  

Microsoft Academic Search

Unhindered phenylhydrazones form charge-transfer complexes with organic acceptors like tetracyanoethylene and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. FT-IR determinations on starting hydrazones allow to predict the possibility of suitable molecular associations.

Paolo Bruni; Liberato Cardellini; Giorgio Tosi

1988-01-01

250

Architecture of the fast Walsh-Hadamard and fast Fourier transforms with charge transfer devices  

Microsoft Academic Search

This paper presents a novel approach for charge transfer device (CTD) implementation of the fast Walsh-Hadamard and fast Fourier transforms. This is achieved by first expressing the Hadamard matrix as a power of a matrix, which allows for efficient CTD implementation. These results are then used in CTD implementation of fast Fourier transforms. The errors which accrue on using CTDs

RAO YARLAGADDA; JOHN E. HERSHEY

1981-01-01

251

Doping single-walled carbon nanotubes through molecular charge-transfer: a theoretical study.  

PubMed

We study the effect of the molecular charge transfer on the electronic structure of metallic (5,5) and semiconducting (8,0) single-walled carbon nanotubes (SWNTs) induced by surface adsorption of various organic donor-acceptor molecules of different affinities using ab initio density functional theory. Our results, obtained from first-principles spin-polarized calculations show that the adsorption of molecules with different affinities reflects the difference in interaction strength that measure the overall energy of adsorption. Moderate values of the binding energy of these surface adsorbed molecular charge-transfer complexes suggest that the nature of interaction is in the physisorption regime, and mainly governs by Coulombic forces. We also find that the large band gap of semiconducting (8,0) SWNT can be tuned through the surface adsorption of selective organic molecules which gives rise to mid-gap localized molecular levels near the Fermi energy with tuning of band gap region. Interestingly, we find that the metallic (5,5) SWNT and semiconducting (8,0) SWNT turn into semiconducting and metallic nanotubes respectively in presence of selective surface adsorbed molecules, corroborating recent experimental findings. We also suggest that these charge transfer effect can be probed through optical conductivity measurement, as the low-frequency profiles are affected by charge transfer. PMID:20648348

Manna, Arun K; Pati, Swapan K

2010-04-14

252

Ultrafast photoinduced electron transfer reactions in supramolecular arrays: From charge separation and storage to molecular switches  

SciTech Connect

Photoinduced charge separation reactions form the basis for energy storage processes in both natural and artificial photosynthesis. Moreover, rapid reversible photoinduced electron transfer reactions are a class of photophysical phenomena that can be exploited to develop schemes for optical switching. Examples from each of these fields are discussed.

Wasielewski, M.R.

1992-08-01

253

Ultrafast photoinduced electron transfer reactions in supramolecular arrays: From charge separation and storage to molecular switches  

SciTech Connect

Photoinduced charge separation reactions form the basis for energy storage processes in both natural and artificial photosynthesis. Moreover, rapid reversible photoinduced electron transfer reactions are a class of photophysical phenomena that can be exploited to develop schemes for optical switching. Examples from each of these fields are discussed.

Wasielewski, M.R.

1992-01-01

254

Charge transfer in metal-atom-containing molecules in the gas phase  

Microsoft Academic Search

The presence of charge transfer (CT) is ubiquitous in metal-atom-containing molecules in the gas phase. The states of interest range from ground states to the lower excited states, given the generally low ionisation potentials of metal atoms. This review is written from an experimentalist's perspective, to describe the specifics of CT states in stable molecules containing a metal atom or

Niloufar Shafizadeh; Benoit Soep; Jean Michel Mestdagh; W. H. Breckenridge

2009-01-01

255

Ultrafast photoinduced electron transfer reactions in supramolecular arrays: From charge separation and storage to molecular switches  

NASA Astrophysics Data System (ADS)

Photoinduced charge separation reactions form the basis for energy storage processes in both natural and artificial photosynthesis. Moreover, rapid reversible photoinduced electron transfer reactions are a class of photophysical phenomena that can be exploited to develop schemes for optical switching. Examples from each of these fields are discussed.

Wasielewski, M. R.

256

The first molecular charge transfer salt containing layers of an alkali metal  

Microsoft Academic Search

We report the first molecular charge transfer salt containing layers of Na+ within its lattice. From the crystal structure and from C=C and C-S bond lengths and Raman stretching frequencies we obtain\\u000a a formula a?\\

Lee Martin; Peter Day; Peter Horton; Ann Bingham; Michael B. Hursthouse

2006-01-01

257

Luminescence Measurements of Xe+ + N2 and Xe2+ + N2 Hyperthermal Charge Transfer Collisions (Postprint).  

National Technical Information Service (NTIS)

Luminescence spectra are recorded for collisions between Xe+/Xe2+ and molecular nitrogen at energies ranging from 4.5 to 316 eV in the center-of- mass frame. In the Xe+ + N2 collision system, evidence for luminescent charge- transfer products is only foun...

B. D. Prince Y. Chiu

2012-01-01

258

Intramolecular electron transfer across amino acid spacers in the picosecond time regime. Charge-transfer interaction through peptide bonds  

SciTech Connect

For a series of alanine-based peptides having 1--3 amino acid residues as spacers, the chromophore, pyrenesulfonyl (Pyr), has been attached at the N-terminus and an electron donor, dimethyl-1,4-benzenediamine (DMPD), covalently bound at the C-terminus. Evidence for an intramolecular charge-transfer interaction involving the electron donor and acceptor groups has been obtained from absorption spectra. Intramolecular electron transfer involving the end groups, Pyr (electron acceptor) and DMPD (electron donor) has been confirmed by ultrafast pump-probe methods. The radical-ion pair states that are generated on Ti/sapphire laser excitation at 400 nm decay in the picosecond to nanosecond time domain and generally show multiexponential decay kinetics. These rates of charge recombination are among the fastest yet observed involving electron transfer between terminal groups for peptide oligomers. The falloff of rate constants for ion pair recombination is irregular in terms of the through-bond distance that separates Pyr and DMPD groups for the various peptide links; i.e., back electron transfer remains fast for the tripeptide, Pyr-Ala-Ala-Ala-DMPD, despite an average through-bond distance between photoactive groups that reaches 18 {angstrom}. Molecular modeling studies show that the peptides are free to adopt conformations in essentially random fashion, without showing evidence for long range ordering of the peptide chain.

Jones, G. II; Lu, L.N.; Fu, H.; Farahat, C.W.; Oh, C. [Boston Univ., MA (United States); Greenfield, S.R.; Gosztola, D.J. [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

1999-01-21

259

Surface modification and charge transfer studies at silicon and gallium arsenide interfaces  

NASA Astrophysics Data System (ADS)

This thesis describes chemical modifications of Si and GaAs surfaces, as a means of gaining control over the physical, chemical and electrical properties of these surfaces and of the interfaces formed from these surfaces. The Current-voltage properties of n-GaAs photoanodes were evaluated in KOH-Sesp{-/2-}(aq), CHsb3CN-ferrocene (Fc)sp{+/0}, and CHsb3CN-methyl viologen (MV)sp{2+/+} solutions. Chemisorption of transition-metal ions (Rhsp{III},\\ Rhsp{III},\\ Cosp{III},\\ Ossp{III}) onto GaAs has been shown previously to effect improved photoanode behavior for n-GaAs/KOH-Sesp{-/2-}(aq) contacts, but it is not clear whether the chemisorbed metal forms a buried semiconductor/metal (Schottky) junction or results in a "hybrid" semiconductor/metal/liquid contact. Metal ion treated n-GaAs photoanodes displayed different open circuit voltages in contact with each electrolyte solution investigated. The role of the chemisorbed metal in the n-GaAs/KOH-Sesp{-/2-}(aq) system is, therefore, best described as catalyzing interfacial charge transfer at the semiconductor/liquid interface, as opposed to forming a semiconductor/metal or semiconductor/insulator/metal contact. The ability to modify Si surface without partial oxidation or formation of electrical defects is potentially important. However, little is known about the chemistry of these surfaces under ambient temperature and pressure. A two-step halogenation/alkylation route to chemical functionalization of Si(111) surface is described, that allows covalent attachment of alkyl functionalities without concomitant oxidation of the silicon surface. In the first step, a hydrogen terminated silicon surface is chlorinated to obtain a chlorine terminated silicon surface. In the second step, the chlorinated surface is reacted with alkyl lithium or alkyl Grignard to obtain an alkyl terminated surface. The surface of silicon is extensively analyzed using a number of techniques such as XPS, HREELS, IRS, AES, TPD etc. The alkyl terminated surfaces are more resistant to oxidation in air and in contact with wet chemical environments than the H-terminated surface. Current-voltage and capacitance-voltage measurements of the alkyl terminated surfaces in CHsb3OH-Mesb2Fcsp{+/0} indicate that the electrical properties of these surfaces are very similar to those of a H-terminated surface. The alkyl overlayers provide a small resistance to charge transfer across the Si/liquid interface but do not shift the band edges or induce additional surface recombination. I-V characteristics of n-Si/alkyl/Au MIS devices indicate that these junctions behave largely like n-Si/Au Schottky junctions. The efficacy of alkyl overlayers in preventing photooxidation and photocorrosion of n-silicon surfaces was measured in contact with Fe(CN)sb6sp{3-/4-}(aq) and with CHsb3OH-Mesb2Fcsp{+/0} containing known amounts of water. The alkyl terminated surfaces consistently show better I-V characteristics and lower oxidation than the H-terminated surface, indicating that stability to oxidation had been achieved without any significant compromise in the electrical quality of the silicon surface.

Bansal, Ashish

260

Photo-induced charge transfer. A critical test of the mechanism and range of biological electron transfer processes.  

PubMed Central

The vibronic coupling theory of electron tunneling between biomolecules requires that all such tunnelings involve vibronic coupling, finds temperature dependence to tunneling at finite temperatures, and predicts relatively short tunneling distances. This theory might be expected to apply to most electron transfers involved in the membrane-bound electron transfer reactions of photosynthesis and oxidative phosphorylation. This paper calculates the properties of a weak charge-transfer optical absorption band, whose predicted characteristics are a direct and simple consequence of the model that describes vibronically coupled tunneling. The new absorption band provides the basis for a critical experimental test of the constructs and parameters of the tunneling theory. If the tunneling theory is valid, the oscillator strength of such bands will be the most reliable measure of the tunneling matrix element and of the distance between the sites exchanging an electron.

Hopfield, J J

1977-01-01

261

On charge transfer in the adsorbed molecules-graphene monolayer-SiC substrate system  

SciTech Connect

A step-by-step consideration of charge transfer in the molecule-single-layer graphene-SiC substrate system is presented. At the first step, a simple model of the density of states of a single graphene monolayer adsorbed on silicon carbide (the graphene-SiC system) is suggested, which allows the calculation of the corresponding occupation numbers of graphene atoms. It is shown that the graphene monolayer accumulates a negative charge. At the second step, the graphene-SiC system is considered as a substrate that adsorbs molecules with a high electron affinity. The charge of these molecules as a function of their surface concentration is calculated. It is shown that, in the case of a monolayer coating, the negative surface charge density of molecules in the molecule-graphene monolayer-SiC substrate system is considerably higher than the surface charge density transferring from the SiC substrate to the graphene layer. This suggests that it is possible to neutralize the excess charge in the graphene layer via adsorption of proper particles on the layer.

Davydov, S. Yu., E-mail: sergei_davydov@mail.ru [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-05-15

262

Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique.  

PubMed

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. PMID:22303133

Shafie, Suhaidi; Kawahito, Shoji; Halin, Izhal Abdul; Hasan, Wan Zuha Wan

2009-11-26

263

Monovalent counterion distributions at highly charged water interfaces: Proton-transfer and Poisson-Boltzmann theory  

SciTech Connect

Surface sensitive synchrotron-x-ray scattering studies reveal the distributions of monovalent ions next to highly charged interfaces. A lipid phosphate (dihexadecyl hydrogen phosphate) was spread as a monolayer at the air-water interface, containing CsI at various concentrations. Using anomalous reflectivity off and at the L{sub 3} Cs{sup +} resonance, we provide spatial counterion distributions (Cs{sup +}) next to the negatively charged interface over a wide range of ionic concentrations. We argue that at low salt concentrations and for pure water the enhanced concentration of hydroniums H{sub 3}O{sup +} at the interface leads to proton transfer back to the phosphate group by a high contact potential, whereas high salt concentrations lower the contact potential resulting in proton release and increased surface charge density. The experimental ionic distributions are in excellent agreement with a renormalized-surface-charge Poisson-Boltzmann theory without fitting parameters or additional assumptions.

Bu, W.; Vaknin, D.; Travesset, A. (Iowa State)

2010-07-13

264

Photoinduced charge-transfer dynamics of sequentially aligned donor-acceptor systems in an ionic liquid.  

PubMed

Photoinduced charge separation processes of linear phenyleneethynylene derivatives (PEN) with different sequences of electron-withdrawing perfluorophenyl groups (A) and electron-donating phenyl groups (D) were investigated in an ionic liquid (IL), BmimTFSI, by picosecond time-resolved fluorescence (TRF) and transient absorption (TA) spectroscopies. Very rapid photoinduced charge separation within 10 ps in AADD was followed by the stabilization of the charge-transfer (CT) state by the solvation, while the excited states in ADAD and ADDA were ascribable to the locally excited (LE) state. Equilibrium between the LE and CT states was established for DAAD with time constants of forward and backward processes much faster than the solvation time. The relative population of the CT state increases with time owing to the dynamic stabilization of the CT state by the solvation. The elementary charge separation process, the increase in the CT population, and their relation to the solvation time were discussed. PMID:23969616

Muramatsu, Masayasu; Katayama, Tetsuro; Ito, Syoji; Nagasawa, Yutaka; Matsuo, Daisuke; Suzuma, Yoshinori; Peng, Lifen; Orita, Akihiro; Otera, Junzo; Miyasaka, Hiroshi

2013-10-23

265

Ultrafast dynamics of the excited Cl atom-benzene charge transfer complex  

SciTech Connect

The ultrafast measurements of the return electron-transfer kinetics have been made for the excited benzene/Cl complex in benzene solution. The excited state of the complex is prepared by ultrafast optical excitation of the charge-transfer band of the complex. Formation constant of the benzene/Cl was measured in carbon tetrachloride solution, using picosecond transient absorption spectroscopy. The benzene/Cl complex (K=52 M{sup -1}) is stronger than the benzene/Br {pi} complex (K=0.2 M{sup -1}). Ab initio calculations of the benzene/Cl complex indicate that the equilibrium geometry has Cs symmetry with the Cl atom positioned over the C-C bond, i.e., a {pi} complex. A {sigma} complex of comparable energy is also observed. Ultrafast transient absorption studies of the benzene/Cl charge-transfer band show the ground-state recovery of the complex on the time scale near 400 fs. The return electron transfer for the excited benzene/Cl complex is very fast similarly to the return electron transfer for the excited benzene/Br complex in benzene solution. In the last case it was shown that the ultrafast electron transfer is due to interactions of two donor molecules with Br anion.

Jarzeba, Wleodzimierz [Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

1996-04-01

266

Excitation transfer, charge transfer and hydrogen abstraction reaction, kinetic studies of modification of DNA components  

NASA Astrophysics Data System (ADS)

Laser induced acetone-sensitized excitation of DNA components offered, for the first time, T-T absorption spectra and direct measurement of triplet states kinetics of cytosine, cytidine, and dCMP, adenine, adenosine and dAMP and guanosine. Mechanisms and kinetics of electron transfer reactions between triplet acetone and purine bases and triplet thymine and electrophilic modifiers have been elucidated. Rapid electron transfer from hydroxycinnamic acid derivatives to oxidizing OH adducts of pyrimidines have been performed. Fast reduction and repair of oxidizing damage of pyrimidines have been achieved using pulse radiolysis techniques.

Y. Lin, N.

1996-02-01

267

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

PubMed Central

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.

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

2012-01-01

268

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

PubMed Central

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 the neutral-ionic state crossing in, for example, hydrogen halides or alkali halides, the path from separated reactants to the conical intersection region is uphill and the charge-transferred state is a biradical. The lowest-energy adiabatic singlet state shows at least two minima along a single approach path of Ca to the ? system: (i) a van der Waals complex with a doubly occupied highest molecular orbital, denoted , and a small negative charge on Ca and (ii) an open-shell singlet (biradical) at intermediate approach (Ca?C distance ?2.5–2.7 ?) with molecular orbital structure ?1?2, where ?2 is an orbital showing significant charge transfer form Ca to the ?-system, leading to a one-electron multicentered bond. A third minimum (iii) at shorter distances along the same path corresponding to a closed-shell state with molecular orbital structure has also been found; however, it does not necessarily represent the ground state at a given Ca?C distance in all three systems. The topography of the lowest adiabatic singlet potential energy surface is due to the one- and two-electron bonding patterns in Ca-? complexes.

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

2010-01-01

269

Brookhaven National Laboratory: Chemistry Department  

NSDL National Science Digital Library

At this website, the Brookhaven National Laboratory presents its chemistry research dealing primarily with imaging and neuroscience, charge transfer for energy conversion, chemistry with ionizing radiation, catalysis and surface science, nanoscience, combustion, and nuclear chemistry. Within each category, users can find instructive text and supportive images about the specific projects and the leading researchers. Visitors can learn about the Beamline U7A at the National Synchrotron Light Source, the Laser-Electron Accelerator Facility (LEAF), the Positron Emission Tomography (PET) Facility, and other exceptional research facilities. The website features histories of the chemistry department and of the Brookhaven National Laboratory.

270

Environmental doping of graphene: Calculation of charge transfer and molecular binding energies  

NASA Astrophysics Data System (ADS)

The adsorption of molecules from the environment can strongly affect the electronic properties of graphene by doping and/or by producing scattering centers. We have studied the nature of the interaction between common important molecules such as CO2, NO2 and NH3 with graphene. Using density functional theory estimates of the molecular binding energies, molecular positions and orientations as well as charge transfer have been calculated. It is found that ammonia has a binding energy of 122 -- 162 meV depending on the position and orientation of the N atom relative to the graphene layer and is an n-type dopant transferring 0.006 e -- 0.01 e per NH3 molecule adsorbed to graphene. NO2 is found to be a p-type dopant accepting ˜0.01 e per NO2 molecule adsorbed from the graphene layer and has a binding energy of 150 - 188 meV. Finally, CO2 is found to be an n-type dopant with a binding energy and charge transfer that depends strongly on orientation and adsorption site. We discuss these results in the context of understanding the electrical and electronic behaviour of graphene after environmental exposure and their significance for graphene based devices. Such studies are significant, in particular, for graphene based molecule sensors where charge transfer is important.

Carey, David; Roome, Nathanael; Samuels, Alexander

2010-03-01

271

trans-2 addition pattern to power charge transfer in dendronized metalloporphyrin C60 conjugates.  

PubMed

Coordinating different transition metals--manganese(III), iron(III), nickel(II), and copper(II)--by a dendronized porphyrin afforded a new family of redox-active metalloporphyrins to which C(60) was attached as a ground-state electron acceptor. Such a strategy introduced an additional center of redoxactivity, that is, a change of the oxidation state of the metal. Cyclic voltammetry and absorption/fluorescence measurements provided support for mutual interactions between the redox-active constituents in the ground state. In particular, slightly anodic shifted reduction potentials/cathodic shifted oxidation potentials and the occurrence of new charge transfer features in the 700-900 nm range prompt to sizable electronic coupling in the range of 300 cm(-1). Photophysical means--steady-state/time-resolved fluorescence and transient absorption measurements--shed light on the excited-state interactions. To this end, we have added pulse radiolytic investigations to characterize the radical cation (i.e., metalloporphyrins) and radical anion (i.e., fullerene) characteristics. Pi-pi stacking of the excited state electron donor and the electron acceptor is key to overcome the intrinsically fast deactivation of the excited states in these metalloporphyrins and to power an exothermic charge transfer. The lifetimes of the rapidly and efficiently generated radical ion pair states, which range from 15 to >3000 ps, revealed several important trends. First, they were found to depend on the solvent polarity. Second, the nature of the transition metal plays a similarly decisive role. It is important that the product of charge recombination, namely tripmultiplet excited states versus ground state, had a great impact. Finally, a correlation between the charge transfer rate (i.e., charge separation and charge recombination) and the free energy change for the underlying reaction reveals a parabolic dependence with parameters of the reorganization energy (0.84 eV) and electronic coupling (70 cm(-1)) closely resembling that seen for the zinc(II) and free base analogues. PMID:19566102

Spänig, Fabian; Ruppert, Michaela; Dannhäuser, Jörg; Hirsch, Andreas; Guldi, Dirk M

2009-07-01

272

Molecular control of photoexcited charge transfer and recombination at a quaterthiophene/zinc oxide interface  

NASA Astrophysics Data System (ADS)

Nonadiabatic quantum molecular dynamics simulations are performed to study photoexcited charge transfer (CT) and charge recombination (CR) at an interface between a conjugated oligomer donor, quaterthiophene (QT), and an inorganic acceptor (ZnO). Simulations reveal a detrimental effect of static disorder in QT conformation on the efficiency of hybrid QT/ZnO solar cells due to increased CR. On the contrary, dynamic disorder (i.e., fluctuation of carbon-hydrogen bonds in QT) is essential for high efficiency by assisting CT. The separate controllability of CT and CR at the molecular level has impacts on molecular design for efficient solar cells and explains recent experimental observations.

Mou, Weiwei; Ohmura, Satoshi; Shimojo, Fuyuki; Nakano, Aiichiro

2012-05-01

273

Photochemical charge separation in zeolites: Electron transfer dynamics, nanocrystals and zeolitic membranes. Final technical report  

SciTech Connect

Aluminosilicate zeolites provide an excellent host for photochemical charge separation. Because of the constraints provided by the zeolite, the back electron transfer from the reduced acceptor to the oxidized sensitizer is slowed down. This provides the opportunity to separate the charge and use it in a subsequent reaction for water oxidation and reduction. Zeolite-based ruthenium oxide catalysts have been found to be efficient for the water splitting process. This project has demonstrated the usefulness of zeolite hosts for photolytic splitting of water.

Dutta, Prabir K.

2001-09-30

274

Photoinduced intramolecular charge transfer process of betaine pyridinium: A theoretical spectroscopic study  

NASA Astrophysics Data System (ADS)

Using Time-Dependent Density Functional Theory and taking into account bulk solvent effects, we investigate the absorption and emission spectra of a betaine pyridinium molecule, the 2-(1-pyridinio) benzimidazolate (SBPa). This molecule exhibits strong photoinduced intramolecular charge transfer (ICT). We have identified two different electronic states involved, respectively, in the strong bathochromic ICT absorption band (S 2) and in the moderate emission band (S 1). The ICT process is analyzed in terms of charge distribution and dipole moment evolutions upon photoexcitation. These results are compared with steady-state spectroscopic measurements.

Perrier, Aurélie; Aloïse, Stéphane; Pawlowska, Zuzanna; Sliwa, Michel; Maurel, François; Abe, Jiro

2011-10-01

275

Chiral selectivity in the charge-transfer bleaching of single-walled carbon-nanotube spectra  

NASA Astrophysics Data System (ADS)

Chiral selective reactivity and redox chemistry of carbon nanotubes are two emerging fields of nanoscience. These areas hold strong promise for producing methods for isolating nanotubes into pure samples of a single electronic type, and for reversible doping of nanotubes for electronics applications. Here, we study the selective reactivity of single-walled carbon nanotubes with organic acceptor molecules. We observe spectral bleaching of the nanotube electronic transitions consistent with an electron-transfer reaction occurring from the nanotubes to the organic acceptors. The reaction kinetics are found to have a strong chiral dependence, with rates being slowest for large-bandgap species and increasing for smaller-bandgap nanotubes. The chiral-dependent kinetics can be tuned to effectively freeze the reacted spectra at a fixed chiral distribution. Such tunable redox chemistry may be important for future applications in reversible non-covalent modification of nanotube electronic properties and in chiral selective separations.

O'Connell, Michael J.; Eibergen, Ezra E.; Doorn, Stephen K.

2005-05-01

276

Resonance energy transfer between polar charge-transfer dyes: A focus on the limits of the dipolar approximation  

NASA Astrophysics Data System (ADS)

Resonance energy transfer (RET) is investigated in a pair of polar charge-transfer (CT) chromophores, adopting essential-state models and time dependent density functional theory (TDDFT) calculations. Essential-state models describe in an efficient way linear and nonlinear optical properties of CT dyes, and prove very useful to rationalize the effects of electrostatic interchromophoric interactions on optical properties of multichromophoric systems. In this paper we adopt the same strategy developed for multichromophoric systems to investigate interchromophoric interactions responsible for RET. In the late forties, Th. Förster proposed a powerful method, based on the dipolar approximation, that directly relates the rate of the RET process to experimental accessible quantities. Here we discuss the applicability of the dipolar approximation for RET between CT dyes. The results obtained with essential-state models are confirmed by TDDFT calculations.

Sissa, C.; Terenziani, F.; Painelli, A.; Manna, A. K.; Pati, S. K.

2012-08-01

277

Four-body charge transfer processes in proton-helium collisions  

NASA Astrophysics Data System (ADS)

Recent advancements in experimental techniques now allow for the study of fully differential cross sections (FDCS) for four-body collisions. The simplest four-body problem is a charged particle collision with a helium atom, in which both atomic electrons change state. This type of collision can result in many different outcomes, such as double excitation, excitation ionization, double ionization, transfer excitation, transfer ionization and double charge transfer. In this paper, we compare absolute experimental proton-helium FDCS for transfer excitation with the fully quantum mechanical 4BTTE (four-body transfer with target excitation) model. This model was previously used to study TTE for proton energies between 25 and 75 keV and reasonable agreement was found with the experimental data for large scattering angles, but not small angles. Since this is a first-order model, which contains contributions from all higher order terms, one would expect improved agreement with increasing energy and the purpose of this work was to look at higher energies. We found that the agreement with the magnitude of the experimental data became worse with increasing energy while the agreement with the shape of the data was reasonably good. Consequently, we conclude that the model contains the physical effects that determine the shape but not the magnitude of the cross section.

Chowdhury, U.; Harris, A. L.; Peacher, J. L.; Madison, D. H.

2012-02-01

278

Multiple electron transfer in slow collisions of very high-charged Xe-ions and atoms  

SciTech Connect

We have measured absolute cross sections for processes of one and multi-electron capture in slow (0.1--0.2 a.u.) Xe[sup q+]-Xe collisions in the charge state regime 15[le]q[le]37. The transfer of two to six electrons from the target to the projectile, where two electrons stay on the projectile after deexcitation is studied. We find that the probability for keeping two electrons on the projectile (i.e. radiative stabilization of two electrons) increases rapidly with q and with the number of electrons initially transferred.

Biedermann, C.; Cederquist, H.; Selberg, N. (Manne Siegbahn Institute of Physics, S-10405 Stockholm (Sweden)); Hutton, R. (Manne Siegbahn Institute of Physics, S-10405 Stockholm (Sweden) University of Lund, S-22362 Lund (Sweden)); Levin, J.C. (Manne Siegbahn Institute of Physics, S-10405 Stockholm (Sweden) The University of Tennessee, Knoxville, Tennessee 37996-1200 (United States)); Beebe, E.; Liljeby, L.; Engestroem, A. (Manne Siegbahn Institute of Physics, S-10405 Stockholm (Sweden))

1993-06-05

279

Structural charge transfer in the aluminophosphate molecular sieves by diffuse reflectance spectroscopy  

NASA Astrophysics Data System (ADS)

Influence of water adsorption in AlPO-5, SAPO-5, AlPO-11 and SAPO-11 has been studied with UV diffuse reflectance spectroscopy. The observed UV absorption spectra in the as-synthesized, template free and hydrated materials are related to the charge transfer processes between aluminum and oxygen atoms of the aluminophosphate and water molecules. As-synthesised materials show two distinct and well-defined bands at about 220 and 260-280 nm correlated to framework aluminum and organic templates, respectively. Upon calcination, the band of occluded template disappears and the band assigned to the framework aluminum shifts at about 240 nm. When the calcined samples are completely hydrated, broadening of the aluminum charge transfer band is observed. This is due to coordination of water molecules to the part of the framework aluminum. Broadening occurs more in AlPO-5 possibly because of higher water capacity and homogenity with respect to SAPO-5.

Zanjanchi, M. A.; Rashidi, M. K.

1999-05-01

280

Low Energy Charge Transfer between C5+ and Atomic Hydrogen  

SciTech Connect

Charge transfer (CT) with carbon ions has been identified for a long time as important in both magnetic fusion plasma devices and more recently in solar wind interactions with comets, planets, or neutrals in the heliosphere. A merged-beams technique is used to measure the absolute total charge transfer cross section for C5+ and atomic H over four orders of magnitude in collision energy, from 12,000 eV/u to 0.64 eV/u. The present measurements are compared with previous measurements using an atomic hydrogen target and benchmark available classical trajectory Monte-Carlo and molecular-orbital close-coupling calculations. An increasing cross section below 10 eV/u is attributed to trajectory effects due to the ion-induced dipole attraction between reactants.

Draganic, Ilija N [ORNL; Seely, D. G. [Albion College; Havener, Charles C [ORNL

2011-01-01

281

Low-energy charge transfer between C{sup 5+} and atomic hydrogen  

SciTech Connect

Charge transfer with carbon ions has been identified as important in both magnetic fusion plasma devices and, more recently, in solar wind interactions with comets, planets, or neutrals in the heliosphere. A merged-beams technique is used to measure the absolute total charge-transfer cross section for C{sup 5+} and atomic H over four orders of magnitude in collision energy, from 12 000 to 0.64 eV/u. The present measurements are compared with previous measurements using an atomic hydrogen target and benchmark available classical trajectory Monte Carlo and molecular-orbital close-coupling calculations. An observed increasing cross section below 10 eV/u is attributed to trajectory effects due to the ion-induced dipole attraction between reactants.

Draganic, I. N.; Havener, C. C. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States); Seely, D. G. [Department of Physics, Albion College, Albion, Michigan 49224 (United States)

2011-05-15

282

Low-energy charge transfer between C5+ and atomic hydrogen  

SciTech Connect

Charge transfer with carbon ions has been identified as important in both magnetic fusion plasma devices and, more recently, in solar wind interactions with comets, planets, or neutrals in the heliosphere. A merged-beams technique is used to measure the absolute total charge-transfer cross section for C{sup 5+} and atomic H over four orders of magnitude in collision energy, from 12,000 to 0.64 eV/u. The present measurements are compared with previous measurements using an atomic hydrogen target and benchmark available classical trajectory Monte Carlo and molecular-orbital close-coupling calculations. An observed increasing cross section below 10 eV/u is attributed to trajectory effects due to the ion-induced dipole attraction between reactants.

Draganic, Ilija N [ORNL; Havener, Charles C [ORNL; Seely, D. G. [Albion College

2011-01-01

283

Surface modification of nanoporous 1,2-polybutadiene by atom transfer radical polymerization or click chemistry.  

PubMed

Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based on nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide functional groups were attached onto the pore walls before click reaction with alkynated MPEG. Following ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while the morphology was investigated by small-angle X-ray scattering and transmission electron microscopy. PMID:20099923

Guo, Fengxiao; Jankova, Katja; Schulte, Lars; Vigild, Martin E; Ndoni, Sokol

2010-02-01

284

Charge transfer through DNA/DNA duplexes and DNA/RNA hybrids: Complex theoretical and experimental studies.  

PubMed

Oligonucleotides conduct electric charge via various mechanisms and their characterization and understanding is a very important and complicated task. In this work, experimental (temperature dependent steady state fluorescence spectroscopy, time-resolved fluorescence spectroscopy) and theoretical (Density Functional Theory) approaches were combined to study charge transfer processes in short DNA/DNA and RNA/DNA duplexes with virtually equivalent sequences. The experimental results were consistent with the theoretical model - the delocalized nature of HOMO orbitals and holes, base stacking, electronic coupling and conformational flexibility formed the conditions for more effective short distance charge transfer processes in RNA/DNA hybrids. RNA/DNA and DNA/DNA charge transfer properties were strongly connected with temperature affected structural changes of molecular systems - charge transfer could be used as a probe of even tiny changes of molecular structures and settings. PMID:23968861

Kratochvílová, Irena; Vala, Martin; Weiter, Martin; Spérová, Miroslava; Schneider, Bohdan; Páv, Ond?ej; Sebera, Jakub; Rosenberg, Ivan; Sychrovský, Vladimír

2013-07-31

285

Final-state distributions in charge transfer from sodium Rydberg atoms near the matching velocity  

Microsoft Academic Search

Reports measurements of the distribution of final n states that are populated in charge transfer collisions of Na+ ions with Na in highly-excited Rydberg states. Relative cross sections for final principal quantum numbers n'=18-42 are shown for laser-excited Na initial states 24d, 25s, 28d, 29s, 33d and 34s at kinetic energies 550-2000 eV. These results span the velocity-matching region in

R. G. Rolfes; K. B. MacAdam

1982-01-01

286

The microstructure of and charge transfer in thin films based on metal-polymer nanocomposites  

Microsoft Academic Search

Charge transfer in nanostructured metal-polymer composites was studied. The frequency dependences of film conductance and\\u000a susceptance were obtained at various metal concentrations. The susceptance of samples above the percolation threshold was\\u000a negligibly small, which corresponded to the purely metallic conductivity type. For samples below the percolation threshold,\\u000a susceptance and conductance were comparable in magnitude, which was evidence of an important

S. A. Zav’yalov; L. Yu. Kupriyanov; A. N. Pivkina; J. Shounman

2006-01-01

287

Charge-transfer luminescence and spectroscopic properties of Yb 3+ in aluminium and gallium garnets  

Microsoft Academic Search

Luminescence of Yb3+ from the charge-transfer state with broad emission bands and short radiative lifetimes (few to tens of nanoseconds depending on the host lattice and the temperature) is attractive for the development of fast scintillators capable of discriminating very short events. The most important currently considered application is that in solar neutrino (?e) real-time spectroscopy, since the ?e capture

N. Guerassimova; C. Dujardin; N. Garnier; C. Pédrini; A. G Petrosyan; I. A Kamenskikh; V. V. Mikhailin; I. N Shpinkov; D. A Spassky; K. L Ovanesyan; G. O Shirinyan; R. Chipaux; M. Cribier; J. Mallet; J.-P Meyer

2002-01-01

288

Spectral and Kinetic Characterization of the Michaelis Charge Transfer Complex in Monomeric Sarcosine Oxidase†  

PubMed Central

Monomeric sarcosine oxidase is a flavoenzyme that catalyzes the oxidation of the methyl group in sarcosine (N-methylglycine). Rapid reaction kinetic studies under anaerobic conditions at pH 8.0 show that the enzyme forms a charge transfer Michaelis complex with sarcosine (E-FADox·sarcosine) that exhibits an intense long wavelength absorption band (?max = 516 nm, ?516 =4800 M?1 cm?1). Since charge transfer interaction with sarcosine as donor is possible only with the anionic form of the amino acid, the results indicate that the pKa of enzyme-bound sarcosine must be considerably lower than the free amino acid (pKa = 10.0). No redox intermediate is detectable during sarcosine oxidation, as judged by the isosbestic spectral course observed for conversion of E-FADox·sarcosine to reduced enzyme at 25 or 5 °C. The limiting rate of the reductive half-reaction at 25 °C (140 ± 3 s?1) is slightly faster than turnover (117 ± 3 s?1). The kinetics of formation of the Michaelis charge transfer complex can be directly monitored at 5 °C where the reduction rate is 4.5-fold slower and complex stability is increased 2-fold. The observed rate of complex formation exhibits a hyperbolic dependence on sarcosine concentration with a finite y-intercept, consistent with a mechanism involving formation of an initial complex followed by isomerization to yield a more stable complex. Similar results are obtained for charge transfer complex formation with methylthioacetate. The observed kinetics are consistent with structural studies which show that a conformational change occurs upon binding of methylthioacetate and other competitive inhibitors.

Zhao, Gouhua; Jorns, Marilyn Schuman

2008-01-01

289

Charge transfer excitation energies in pyridine–silver complexes studied by a QM\\/MM method  

Microsoft Academic Search

We utilize a density functional theory (DFT) based quantum mechanical\\/molecular mechanical (QM\\/MM) approach for the investigation of charge transfer (CT) excitation energies in molecule–metal systems. We perform calculations on a pyridine–Ag20 system treating the most distant, with respect to pyridine, silver atoms using molecular mechanics by assigning atomic polarizabilities to each of these silver atoms. We investigate how additional silver

Vaida Arcisauskaite; Jacob Kongsted; Thorsten Hansen; Kurt V. Mikkelsen

2009-01-01

290

Valence-bond analysis of extended Hubbard models: Charge-transfer excitations of molecular conductors  

Microsoft Academic Search

The low-energy charge transfer (CT) excitation characteristic of both pi-molecular conductors and complex-ion-radical salts is interpreted as a nearest-neighbor Coulomb interaction V that is comparable to the bandwidth, 4|t|. Partly filled segregated regular stacks in organic conductors are represented by extended Hubbard models, whose exact CT energies and intensities are obtained by diagrammatic valence-bond (VB) methods for four electrons on

S. Mazumdar; Z. G. Soos

1981-01-01

291

Measurement of charge transfer in sprite-producing lightning using ELF radio atmospherics  

Microsoft Academic Search

Transient high altitude optical emissions referred to as “sprites” are believed to occur as a result of the transfer of large amounts of charge (?100–300 C) from cloud altitudes of 5–10 km to the ground. Using a general subionospheric ELF propagation model, we quantitatively interpret magnetic field waveforms of ELF radio atmospherics originating in mid-western U.S. lightning discharges and observed

S. A. Cummer

1997-01-01

292

Measurement of charge transfer in sprite-producing lightning using ELF radio atmospherics  

Microsoft Academic Search

Transient high altitude optical emissions referred to as ``sprites'' are believed to occur as a result of the transfer of large amounts of charge (~100-300C) from cloud altitudes of 5-10 km to the ground. Using a general subionospheric ELF propagation model, we quantitatively interpret magnetic field waveforms of ELF radio atmospherics originating in mid-western U.S. lightning discharges and observed at

S. A. Cummer

1997-01-01

293

Spectrophotometric determination of clobetasol propionate, halobetasol propionate, quinagolide hydrochloride, through charge transfer complexation  

Microsoft Academic Search

Two spectrophotometric procedures are described for the determination of clobetasol propionate(I), halobetasol propionate(II) (corticosteroids) and quinagolide hydrochloride(III) (prolactin inhibitor). For corticosteroid drugs, the procedures are based on the formation of phenyl hydrazones of the corticosteroids which are subsequently subjected to charge transfer complexation reaction with either 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as ?-acceptor or with iodine as ?-acceptor. Prolactin inhibitor was reacted directly

Azza A. Mostafa; Lories I. Bebawy; Heba H. Refaat

2002-01-01

294

A selective colorimetric chemosensor for thiols based on intramolecular charge transfer mechanism  

Microsoft Academic Search

Compound 1 as an electron donor–acceptor compound with N,N-dimethylaniline and quinone units was designed for a highly selective colorimetric determination of thiol-containing amino acids and peptides, by making use of the unique reactivity of thiol towards quinone. Compound 1 shows a strong intramolecular charge transfer (ICT) band around 582nm; but, it decreased after addition of either cysteine (Cys) or glutathione

Yan Zeng; Guanxin Zhang; Deqing Zhang

2008-01-01

295

Radiative charge-transfer lifetime of the excited state of (NaCa){sup +}  

SciTech Connect

New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom-ion trap under high-vacuum conditions. We study the collisional cooling of laser precooled Ca{sup +} ions by ultracold Na atoms. Modeling this process requires knowledge of the radiative lifetime of the excited singlet A {sup 1}{sigma}{sup +} state of the (NaCa){sup +} molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using complete active space self-consistent field and Moeller-Plesset second-order perturbation theory with an extended Gaussian basis, 6-311+G (3df). The semiclassical charge-transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition, we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be 2.3x10{sup -16} cm{sup 3}/sec, while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher (1.1x10{sup -8} cm{sup 3}/sec and 2.3x10{sup -9} cm{sup 3}/sec, respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms is favorable with the respect to low loss of calcium ions due to the charge transfer.

Makarov, Oleg P.; Cote, R.; Michels, H.; Smith, W.W. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269-3046 (United States)

2003-04-01

296

Utilization of films with complex charge-transferring backings for holographic recording  

NASA Astrophysics Data System (ADS)

Grishina (1979) has shown that in polymer films containing aromatic amines (Am), diphenylbenzylamine, and tetracarbon bromide (CBr4), there form charge-transferring complexes of the composition AmCBr4 which are responsible for the sensitivity of the polymer films to light (0.3 to 0.5 microns). In the present study it is shown that such polymer films can be used for holographic recording.

Gilels, A. M.; Chernov, G. M.; Brodzeli, M. I.; Vannikov, A. V.; Grishina, A. D.; Eligulashvili, I. A.

1980-10-01

297

Prominent Charge-Transfer State at ?-Sexithiophene/C60 Interface  

NASA Astrophysics Data System (ADS)

We performed femtosecond time-resolved spectroscopy in ?-sexithiophene (6T)/C60 bilayer and mixed films. We observed sharp and intense photoinduced absorption (PIA) at 1.2 eV and ascribed it to the charge-transfer (CT) state. The spectral features are interpreted in terms of homogenous molecular stacking at 6T/C60 interface and quantum confinement effect in 6T.

Takahashi, Yousuke; Yonezawa, Kouhei; Kamioka, Hayato; Yasuda, Takeshi; Han, Liyuan; Moritomo, Yutaka

2013-06-01

298

Direct observation of charge transfer in solid electrolyte for electrochemical metallization memory.  

PubMed

X-ray absorption spectroscopy study on an electrochemical metallization cell of GeS(x) :Ag shows clear experimental evidence of chemical ionization of the active metal atoms (Ag) and consequent transfer of charge to the electrolyte (GeS(x) ). The valence electron density and its change upon the Ag intercalation are depicted schematically as transparent waves on the Ge-S bond structure in amorphous GeS(x) . PMID:22786689

Cho, Deok-Yong; Valov, Ilia; van den Hurk, Jan; Tappertzhofen, Stefan; Waser, Rainer

2012-07-12

299

Direct involvement of acid centers of polyaniline in charge transfer on organic acceptor  

Microsoft Academic Search

Electrochemical behavior of hydroquinone and 4F-hydroquinone has been studied on Pt\\/polyaniline (PANI) electrodes in 1 M H2SO4 solution. Redox transformation of quinone\\/hydroquinone systems takes place on PANI practically without overpotential and, probably, the two-electron charge transfer processes are realized in such systems. Reaction currents depend on PANI quantities deposited on the Pt electrode and the molecular complex is formed. There

E. S. Matveeva; I. Hernández-Fuentes; V. Parkhutik; R. Díaz-Calleja

1996-01-01

300

Charge Transfer Excitation in Resonant X-ray Emission Spectroscopy of NiO  

Microsoft Academic Search

We analyze Ni 2 p \\\\to 3d \\\\to 2 p resonant X-ray emission spectroscopy (RXES) of NiO with the impurity Anderson model. We pay attention to the inelastic X-ray scattering structures arising from the interatomic charge transfer (CT) from ligand state to 3d state. We take into account a finite width of the O 2 p valence band in order

Masahiko Matsubara; Takayuki Uozumi; Akio Kotani; Jean Claude Parlebas

2005-01-01

301

Charge-transfer gap closure in transition-metal halides under pressure  

SciTech Connect

Insulator-to-metal transition induced by pressure has been studied in three transition metal iodides: NiI{sub 2}, CoI{sub 2} and FeI{sub 2} using optical absorption and resistivity measurements at room temperature. Comparisons between the results obtained by these two techniques suggested that the closure of the charge-transfer gap is the principal mechanism responsible for the insulator-to-metal transition in these materials.

Chen, A.L.; Yu, P.Y.

1995-01-01

302

Luminescence measurements of Xe+ + N2 and Xe2+ + N2 hyperthermal charge transfer collisions  

Microsoft Academic Search

Luminescence spectra are recorded for collisions between Xe+\\/Xe2+ and molecular nitrogen at energies ranging from 4.5 to 316 eV in the center-of-mass frame. In the Xe+ + N2 collision system, evidence for luminescent charge-transfer products is only found through Xe I emission lines. The most intense features of the luminescence spectra are attributed to atomic N emissions observed above ~20

Benjamin D. Prince; Yu-Hui Chiu

2011-01-01

303

Charge transfer in collisions of Be3+ ions with H atoms  

NASA Astrophysics Data System (ADS)

The nonradiative charge-transfer processes for the Be3+(1s)+H(1s) collisions are investigated by the quantum-mechanical molecular orbital close-coupling method in the energy range of 0.01-10 keV/u. The radiative charge-transfer cross sections are calculated by the optical potential and semiclassical methods in the energy range 10-6-103 eV/u. The needed molecular data are obtained by the ab initio multireference single- and double-excitation configuration interaction method. Total and state-selective cross sections are presented and compared with other available theoretical data. Our calculation agrees well with the atomic orbital close-coupling results of Liu [L. Liu, D. Jakimovski, J. G. Wang, and R. K. Janev, J. Phys. BJPAPEH0953-407510.1088/0953-4075/43/14/144005 43, 144005 (2010)], but there exist some discrepancies with the semiclassical molecular orbital close-coupling results of Shimakura [N. Shimakura, J. Phys. BJPAMA40953-407510.1088/0953-4075/21/13/015 21, 2485 (1988)]. The present results show that the capture to Si2+(1s3l) states is dominant in the whole energy range with the exception of a narrow range of 2-4 keV/u. Rotational couplings play an important role not only in the state-selective cross sections, but also in the total charge-transfer results. At energies below 40 eV/u, the radiative charge transfer exceeds the nonradiative process.

Liu, C. H.; Wang, J. G.

2013-04-01

304

A density functional study on the formation of charge transfer complexes between alkaloids and iodine monochloride  

Microsoft Academic Search

The formation of charge-transfer (CT) complexes between N-methyl-6,7-methylenedioxy-tetrahydro-4-isoquinolone (MMDTIQ, the model molecule of alkaloids) and iodine monochloride has been studied with the density functional B3LYP method. The competition for ICl between n-donor(s) and ?-donor in the same molecule has been compared for the first time. The results indicate that the electron-donating ability of various donor sites decreases in the following

Ling-Tian Tang; Yu Wei; Yi Wang; Shao-Wen Hu; Xin-Qi Liu; Tai-Wei Chu; Xiang-Yun Wang

2004-01-01

305

Charge transfer complex studies between some non-steroidal anti-inflammatory drugs and ?-electron acceptors  

Microsoft Academic Search

Charge transfer (CT) complexes of some non-steroidal anti-inflammatory drugs, naproxen and etodolac which are electron donors with some ?-acceptors, such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranil (p-CHL), have been investigated spectrophotometrically in chloroform at 21°C. The coloured products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptors. Beer's law is obeyed and colours were

Hulya Duymus; Mustafa Arslan; Mustafa Kucukislamoglu; Mustafa Zengin

2006-01-01

306

Spectroscopic studies of charge transfer complexes between colchicine and some ? acceptors  

Microsoft Academic Search

Charge transfer complexes between colchicine as donor and ? acceptors such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranil (p-CHL) have been studied spectrophotometrically in dichloromethane at 21°C. The stoichiometry of the complexes was found to be 1:1 ratio by the Job method between donor and acceptors with the maximum absorption band at a wavelength of 535, 585 and 515nm. The equilibrium

Mustafa Arslan; Hulya Duymus

2007-01-01

307

Charge-transfer complex formation between p-chloranil and 1, n-dicarbazolylalkanes  

Microsoft Academic Search

Dimer model compounds of polyvinylcarbazoles (1,n-di(N-carbazolyl)alkanes, when n=1–5) were synthesized to model the effects of distance and orientation between carbazole groups in polymeric systems. Charge-transfer (CT) complexes of carbazole, N-ethylcarbazole and 1,n-di(N-carbazolyl)alkanes with p-chloranil (p-CHL) have been investigated spectrophotometrically in dichloromethane. The colored products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptor. The

Mustafa Arslan; John Masnovi; Randolph Krafcik

2007-01-01

308

Spectrophotometric and electrical studies of charge-transfer complexes of sodium flucloxacillin with ?-acceptors  

Microsoft Academic Search

The present study is interested to develop a simple, rapid and accurate spectrophotometric method for determination of sodium flucloxacillin (fluc) in pure form and pharmaceutical formulations. The charge-transfer (CT) interactions between sodium flucloxacillin as electron donor and chloranilic acid (CLA), dichloroquinone 4-chloroimide (DCQ), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8 tetracyano-p-quinodimethane (TCNQ), as ?-electron acceptors have been investigated spectrophotometrically. Different variables affecting the

Moamen S. Refat; Akram M. El-Didamony

2006-01-01

309

Organic Nano-transistors Wired by Oriented Charge Transfer Complex Crystal  

Microsoft Academic Search

We have fabricated high conducting organic wires and self-wired nano-transistors of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) charge transfer complex using co-evaporation method with an electric field. The conducting wires which directly bridge two gold electrodes indicated high-conductive ohmic contact with the gold electrode. Self-wired organic field effect transistor was formed at the connecting point of conductive wires. Field effect transistor

Masatoshi Sakai; Eiji Yajima; Hirotaka Sakuma; Masaaki Iizuka; Masakazu Nakamura; Kazuhiro Kudo

2004-01-01

310

Charge transfer inefficiency in the Hubble Space Telescope since Servicing Mission 4  

NASA Astrophysics Data System (ADS)

We update a physically motivated model of radiation damage in the Hubble Space Telescope Advanced Camera for Surveys/Wide Field Channel, using data up to mid-2010. We find that charge transfer inefficiency increased dramatically before shuttle Servicing Mission 4, with ~1.3 charge traps now present per pixel. During detector readout, charge traps spuriously drag electrons behind all astronomical sources, degrading image quality in a way that affects object photometry, astrometry and morphology. Our detector readout model is robust to changes in operating temperature and background level, and can be used to iteratively remove the trailing by pushing electrons back to where they belong. The result is data taken in mid-2010 that recovers the quality of imaging obtained within the first six months of orbital operations.

Massey, Richard

2010-11-01

311

Ab initio calculation of H+He{sup +} charge-transfer cross sections for plasma physics  

SciTech Connect

The charge-transfer in low-energy (0.25 to 150 eV/amu) H(nl)+He{sup +}(1s) collisions is investigated using a quasimolecular approach for the n=2,3 as well as the first two n=4 singlet states. The diabatic potential energy curves of the HeH{sup +} molecular ion are obtained from the adiabatic potential energy curves and the nonadiabatic radial coupling matrix elements using a two-by-two diabatization method, and a time-dependent wave-packet approach is used to calculate the state-to-state cross sections. We find a strong dependence of the charge-transfer cross section on the principal and orbital quantum numbers n and l of the initial or final state. We estimate the effect of the nonadiabatic rotational couplings, which is found to be important even at energies below 1 eV/amu. However, the effect is small on the total cross sections at energies below 10 eV/amu. We observe that to calculate charge-transfer cross sections in an n manifold, it is only necessary to include states with n{sup '{<=}}n, and we discuss the limitations of our approach as the number of states increases.

Loreau, J.; Vaeck, N. [Laboratoire de Chimie Quantique et Photophysique, Universite Libre de Bruxelles, CP 160/09 50, avenue F. D. Roosevelt, B-1050 Bruxelles (Belgium); Sodoga, K. [Laboratoire de Chimie Physique, Batiment 349, Universite de Paris-Sud, UMR8000, F-91405 Orsay (France); Faculte des Sciences, Departement de Physique, Universite de Lome, Boite Postale 1515 Lome (Togo); Lauvergnat, D. [Laboratoire de Chimie Physique, Batiment 349, Universite de Paris-Sud, UMR8000, F-91405 Orsay (France); Desouter-Lecomte, M. [Laboratoire de Chimie Physique, Batiment 349, Universite de Paris-Sud, UMR8000, F-91405 Orsay (France); Departement de Chimie, B6c, Universite de Liege, Sart-Tilman, B-4000 Liege 1 (Belgium)

2010-07-15

312

Environmental and Structural Effects on Intramolecular Charge Transfer Exhibited by 4-Aminobenzoic Acid and its Derivatives  

NASA Astrophysics Data System (ADS)

This study inspected intramolecular charge transfer in a variety of conditions by methodically adjusting the parent compound structure and solvent properties under spectroscopic analysis. 4-aminobenzoic acid and its derivatives were analyzed in three buffers of varying pH (2, 7, 10). The various compounds were used to study structural effects, while the placement in buffers allowed control of the protonation states of the molecules. The samples were each scanned for absorbance to determine excitation wavelengths which were used for subsequent fluorescent spectroscopic analysis. The charge transfer, when exhibited, is recognized by dual fluorescence. Varying the temperature of the scans allowed analysis of the thermodynamic driving forces for the reaction while the particular solvent-solute combinations that exhibited the phenomenon lend insight to the conditions conducive to charge transfer. To study what controlled the extent of the phenomenon, titrations were carried out to determine the amine pKa and computational models were generated to inspect hybridization and its influence on photophysical behavior.

Thayer, Mitchell; Schmidtke, Sarah

2009-10-01

313

Ab initio calculation of H+He+ charge-transfer cross sections for plasma physics  

NASA Astrophysics Data System (ADS)

The charge-transfer in low-energy (0.25 to 150 eV/amu) H(nl)+He+(1s) collisions is investigated using a quasimolecular approach for the n=2,3 as well as the first two n=4 singlet states. The diabatic potential energy curves of the HeH+ molecular ion are obtained from the adiabatic potential energy curves and the nonadiabatic radial coupling matrix elements using a two-by-two diabatization method, and a time-dependent wave-packet approach is used to calculate the state-to-state cross sections. We find a strong dependence of the charge-transfer cross section on the principal and orbital quantum numbers n and l of the initial or final state. We estimate the effect of the nonadiabatic rotational couplings, which is found to be important even at energies below 1 eV/amu. However, the effect is small on the total cross sections at energies below 10 eV/amu. We observe that to calculate charge-transfer cross sections in an n manifold, it is only necessary to include states with n'?n, and we discuss the limitations of our approach as the number of states increases.

Loreau, J.; Sodoga, K.; Lauvergnat, D.; Desouter-Lecomte, M.; Vaeck, N.

2010-07-01

314

Charge transfer in covalently-linked porphyrin-donor complexes from picosecond transient absorption spectroscopy  

SciTech Connect

Octaalkyl free base porphyrins have been synthesized with covalently attached electron donors at a single meso position. Singlet-state lifetimes were determined from fluorescence quenching in three solvents and were found to be [le]1.5 ps for the N,N,N[prime],N[prime]-tetramethyl-1,4-phenylenediamine (TMPD) appended complex, 1.3 ns for the phenyl-TMPD-appended complex, and [ge]5 ns for the phenyl-appended, N,N-dimethylaniline (DMA) appended, and DMA-TMPD-appended porphyrin complexes in o-difluorobenzene. Single photon counting measurements and fluorescence quantum yield quenching studies of the phenyl-appended control and phenyl-TMPD charge-transfer complex gave 14 [+-] 3 and 2 [+-] 0.3 ns excited-state lifetimes, respectively. Fluorescence quantum yields of the TMPD and phenyl-TMPD porphyrins were higher in solvents with lower dielectric constants. Picosecond absorption spectroscopy was performed on molecules exhibiting fluorescence quenching to characterize the charge-transfer state and to determine the recombination kinetics. Conclusive evidence of charge transfer was obtained by observing the donor cation absorption at 606 nm for the TMPD and phenyl-TMPD porphyrins. 49 refs., 10 figs., 2 tabs.

Loppnow, G.R.; Melamed, D.; Hamilton, A.D.; Spiro, T.G. (Princeton Univ., NJ (United States))

1993-09-02

315

Inhomogeneous charge transfer within monolayer zinc phthalocyanine absorbed on TiO2(110).  

PubMed

The d-orbital contribution from the transition metal centers of phthalocyanine brings difficulties to understand the role of the organic ligands and their molecular frontier orbitals when it adsorbs on oxide surfaces. Here we use zinc phthalocyanine (ZnPc)/TiO(2)(110) as a model system where the zinc d-orbitals are located deep below the organic orbitals leaving room for a detailed study of the interaction between the organic ligand and the substrate. A charge depletion from the highest occupied molecular orbital is observed, and a consequent shift of N1s and C1s to higher binding energy in photoelectron spectroscopy (PES). A detailed comparison of peak shifts in PES and near-edge X-ray absorption fine structure spectroscopy illustrates a slightly uneven charge distribution within the molecular plane and an inhomogeneous charge transfer screening between the center and periphery of the organic ligand: faster in the periphery and slower at the center, which is different from other metal phthalocyanine, e.g., FePc/TiO(2). Our results indicate that the metal center can substantially influence the electronic properties of the organic ligand at the interface by introducing an additional charge transfer channel to the inner molecular part. PMID:22519339

Yu, Shun; Ahmadi, Sareh; Sun, Chenghua; Adibi, Pooya Tabib Zadeh; Chow, Winnie; Pietzsch, Annette; Göthelid, Mats

2012-04-21

316

Raman Spectroscopy of Charge Transfer Interactions Between Single Wall Carbon Nanotubes and [FeFe] Hydrogenase  

SciTech Connect

We report a Raman spectroscopy study of charge transfer interactions in complexes formed by single-walled carbon nanotubes (SWNTs) and [FeFe] hydrogenase I (CaHydI) from Clostridium acetobutylicum. The choice of Raman excitation wavelength and sample preparation conditions allows differences to be observed for complexes involving metallic (m) and semiconducting (s) species. Adsorbed CaHydI can reversibly inject electronic charge into the LUMOs of s-SWNTs, while charge can be injected and removed from m-SWNTs at lower potentials just above the Fermi energy. Time-dependent enzymatic assays demonstrated that the reduced and oxidized forms of CaHydI are deactivated by oxygen, but at rates that varied by an order of magnitude. The time evolution of the oxidative decay of the CaHydI activity reveals different time constants when complexed with m-SWNTs and s-SWNTs. The correlation of enzymatic assays with time-dependent Raman spectroscopy provides a novel method by which the charge transfer interactions may be investigated in the various SWNT-CaHydI complexes. Surprisingly, an oxidized form of CaHydI is apparently more resistant to oxygen deactivation when complexed to m-SWNTs rather than s-SWNTs.

Blackburn, J. L. Svedruzic, D.; McDonald, T. J.; Kim, Y. H.; King, P. W.; Heben, M. J.

2008-01-01

317

Forster Resonance Energy Transfer and Conformational Stability of Proteins: An Advanced Biophysical Module for Physical Chemistry Students  

ERIC Educational Resources Information Center

|Protein folding is an exploding area of research in biophysics and physical chemistry. Here, we describe the integration of several techniques, including absorption spectroscopy, fluorescence spectroscopy, and Forster resonance energy transfer (FRET) measurements, to probe important topics in protein folding. Cytochrome c is used as a model…

Sanchez, Katheryn M.; Schlamadinger, Diana E.; Gable, Jonathan E.; Kim, Judy E.

2008-01-01

318

Studies of Photosynthetic Energy and Charge Transfer by Two-dimensional Fourier transform electronic spectroscopy  

NASA Astrophysics Data System (ADS)

Two-dimensional (2D) Fourier transform electronic spectroscopy has recently emerged as a powerful tool for the study of energy transfer in complex condensed-phase systems. Its experimental implementation is challenging but can be greatly simplified by implementing a pump-probe geometry, where the two phase-stable collinear pump pulses are created with an acousto-optic pulse-shaper. This approach also allows the use of a continuum probe pulse, expanding the available frequency range of the detection axis and allowing studies of energy transfer and electronic coupling over a broad range of frequencies. We discuss several benefits of 2D electronic spectroscopy and present 2D data on the D1-D2 reaction center complex of Photosystem II from spinach. We discuss the ability of 2D spectroscopy to distinguish between current models of energy and charge transfer in this system.

Ogilvie, Jennifer

2010-03-01

319

H+ and He2+ impact charge transfer cross sections of magnesium  

NASA Astrophysics Data System (ADS)

H+ impact single and He2+ impact single and double electron capture cross sections of magnesium atoms have been calculated in the modified binary encounter approximation (BEA). The accurate expressions of ion impact ? _{? {E}} (cross section for energy transfer ? E) and Hartree-Fock momentum distributions of the target electrons have been used throughout the calculations. On the basis of the present work it is concluded that inner shell captures by H+ and He2+ ions incident on magnesium atoms contribute partly to single electron capture and partly to transfer ionization cross sections. The calculated He2+ impact double electron capture cross sections of magnesium are in reasonably good agreement with the experimental observations. This indicates the success of the present theoretical approach in study of charge transfer cross sections of atoms as indirect mechanisms do not interfere with double electron capture processes in this case.

Kumari, S.; Chatterjee, S. N.; Jha, L. K.; Roy, B. N.

2011-01-01

320

Ion imaging study of dissociative charge transfer in the N2(+) + CH4 system.  

PubMed

The velocity map ion imaging method is applied to the dissociative charge transfer reactions of N2(+) with CH4 studied in crossed beams. The velocity space images are collected at four collision energies between 0.5 and 1.5 eV, providing both product kinetic energy and angular distributions for the reaction products CH3(+) and CH2(+). The general shapes of the images are consistent with long range electron transfer from CH4 to N2(+) preceding dissociation, and product kinetic energy distributions are consistent with energy resonance in the initial electron transfer step. The branching ratio for CH3(+):CH2(+) is 85:15 over the full collision energy range, consistent with literature reports. PMID:23556720

Pei, Linsen; Farrar, James M

2013-03-28

321

Charge transfer through single molecule contacts: How reliable are rate descriptions?  

PubMed

Background: The trend for the fabrication of electrical circuits with nanoscale dimensions has led to impressive progress in the field of molecular electronics in the last decade. However, a theoretical description of molecular contacts as the building blocks of future devices is challenging, as it has to combine the properties of Fermi liquids in the leads with charge and phonon degrees of freedom on the molecule. Outside of ab initio schemes for specific set-ups, generic models reveal the characteristics of transport processes. Particularly appealing are descriptions based on transfer rates successfully used in other contexts such as mesoscopic physics and intramolecular electron transfer. However, a detailed analysis of this scheme in comparison with numerically exact solutions is still elusive.Results: We show that a formulation in terms of transfer rates provides a quantitatively accurate description even in domains of parameter space where strictly it is expected to fail, e.g., at lower temperatures. Typically, intramolecular phonons are distributed according to a voltage driven steady state that can only roughly be captured by a thermal distribution with an effective elevated temperature (heating). An extension of a master equation for the charge-phonon complex, to effectively include the impact of off-diagonal elements of the reduced density matrix, provides very accurate solutions even for stronger electron-phonon coupling.Conclusion: Rate descriptions and master equations offer a versatile model to describe and understand charge transfer processes through molecular junctions. Such methods are computationally orders of magnitude less expensive than elaborate numerical simulations that, however, provide exact solutions as benchmarks. Adjustable parameters obtained, e.g., from ab initio calculations allow for the treatment of various realizations. Even though not as rigorously formulated as, e.g., nonequilibrium Green's function methods, they are conceptually simpler, more flexible for extensions, and from a practical point of view provide accurate results as long as strong quantum correlations do not modify the properties of the relevant subunits substantially. PMID:22003449

Kast, Denis; Kecke, L; Ankerhold, J

2011-08-03

322

Computer simulation studies of charge transfer through biological and artificial membrane channels  

NASA Astrophysics Data System (ADS)

Biological membrane channels provide the fast and selective exchange of different substances (water, ions, etc...) between intra- and extracellular compartments. Recent determination of the atomic structures of the most important types of membrane channels makes it possible to attempt to derive macroscopically measurable properties of these channels (e.g., ionic current) from their atomic structures and thus to understand the physical mechanism of their action. In this dissertation such structure-function relationships are studied by means of computer simulation. The limited power of modem supercomputers makes it impossible to simulate actual time-dependent charge transfer through membrane channels using all-atom simulations. In order to overcome this problem an integrated hierarchical approach is used. It combines all-atom MD or QM(EVB)/MM simulations with semi-microscopic calculations of the electrostatic free energy barrier which then is used in stochastic simulations of charge transfer through the channel. Main results of the dissertation include: (1) an explanation of the mechanism of proton blockage in aquaporin water channels (AQP); (2) application of this mechanism for the theoretical construction of a water nanofilter based on a carbon nanotube membrane; (3) development of the multilevel model for simulation of current and selectivity of single ion channel based on its X-Ray structure and its application to KcsA potassium channel; (4) development of stochastic QM(EVB)/MM models for simulation of proton transport in solution and their application to the proton transport in the gramicidin channel. The results of the simulations show that in all cases charge (both ion and proton) transport is controlled mainly by electrostatic effects (the interplay between the change of the charge self-energy and the energy of its interactions with protein polar groups). These results are of interest for both basic science (understanding of fundamental physical mechanisms of charge transport in channels) and for (bio)nanotechnology (artificial water/ion channels).

Burykin, Anton

323

Gas-Phase Chemistry of Multiply Charged Bioions in Analytical Mass Spectrometry  

PubMed Central

Ion chemistry has long played an important role in molecular mass spectrometry (MS), as it is central to the use of MS as a structural characterization tool. With the advent of ionization methods capable of producing gaseous ions from large biomolecules, the chemistry of gaseous bioions has become a highly active area of research. Gas-phase biomolecule-ion reactions are usually driven by interactions with neutral molecules, photons, electrons, ions, or surfaces. Ion dissociation or transformation into different ion types can be achieved. The types of reaction products observed depend on the characteristics of the ions, the transformation methods, and the time frame of observation. This review focuses on the gas-phase chemistries of ions derived from the electrospray ionization of peptides, proteins, and oligonucleotides, with particular emphasis on their utility in bioanalysis. Various ion-transformation strategies, which further facilitate structural interrogation by converting ions from one type to another, are also summarized.

Huang, Teng-Yi; McLuckey, Scott A.

2011-01-01

324

Charge Density Quantification of Polyelectrolyte Polysaccharides by Conductometric Titration: An Analytical Chemistry Experiment  

ERIC Educational Resources Information Center

An easy analytical method for determination of the charge density of polyelectrolytes, including polysaccharides and other biopolymers, is presented. The basic principles of conductometric titration, which is used in the pulp and paper industry as well as in colloid and interface science, were adapted to quantify the charge densities of a…

Farris, Stefano; Mora, Luigi; Capretti, Giorgio; Piergiovanni, Luciano

2012-01-01

325

Charge Density Quantification of Polyelectrolyte Polysaccharides by Conductometric Titration: An Analytical Chemistry Experiment  

ERIC Educational Resources Information Center

|An easy analytical method for determination of the charge density of polyelectrolytes, including polysaccharides and other biopolymers, is presented. The basic principles of conductometric titration, which is used in the pulp and paper industry as well as in colloid and interface science, were adapted to quantify the charge densities of a…

Farris, Stefano; Mora, Luigi; Capretti, Giorgio; Piergiovanni, Luciano

2012-01-01

326

Measurement of charge transfer during bacterial adhesion to an indium tin oxide surface in a parallel plate flow chamber.  

PubMed

An experimental method is described for the measurement of charge transfer during bacterial adhesion in situ to a transparent, semiconducting indium tin oxide (ITO) coated glass plate in a parallel plate flow chamber. Bacterial adhesion is measured simultaneously with either the electric potential or the capacitance of the surface. Initial bacterial adhesion was accompanied by a change in electric potential of the surface with no measurable change in capacitance. Consequently, it can be assumed that the change in electric potential of the surface is due to charge transfer between bacteria and the surface, and it can be calculated that, on average, a charge of about 10(-14) C per bacterium is exchanged during initial adhesion, which corresponds to only several percent of the total surface charge of a bacterium. Charge transfer could either be to or from the bacterial cell surface, dependent on the bacterial strain involved and the ionic strength used. PMID:10541431

Poortinga, A T; Bos, R; Busscher, H J

1999-11-01

327

Experimental observation of sub-femtosecond charge transfer in a model water splitting dye-sensitized solar cell.  

PubMed

Charge transfer from photoexcited dye molecules to a semiconductor substrate forms the basis of dye sensitized solar cells (DSCs); the overall effectiveness of a DSC device is critically dependent upon the efficiency of this process due to competition with other de-excitation channels. In this paper, we experimentally derive timescales for the charge transfer process in model water splitting DSCs. We studied two organometallic dye complexes adsorbed onto a rutile TiO(2)(110) substrate, the dye molecules were deposited in ultra-high vacuum using electrospray deposition. DFT simulations were used to calculate the spatial distribution of orbitals relevant to the charge transfer process. The core-hole clock implementation of resonant photoemission spectroscopy was used to determine upper limits on charge transfer timescales for previously unoccupied orbitals, which were found to be in the low-femtosecond regime apart from one orbital found to have an upper limit in the sub-femtosecond regime. PMID:23249025

Weston, Matthew; Handrup, Karsten; Reade, Thomas J; Champness, Neil R; O'Shea, James N

2012-12-14

328

UV-induced Charge Transfer at the Si-SiO2 Interface Probed with Second Harmonic Generation  

NASA Astrophysics Data System (ADS)

Using the interfacial specificity of second harmonic generation we have previously shown(J.G. Mihaychuk, J. Bloch, Y. Liu and H.M. van Driel, Opt. Lett. 20, 2063 (1995).) how <= 100 fW of UV light can induce charge transfer across the Si-SiO2 interface. Here we demonstrate that the charge transfer is observed on Si(100) and Si(111) surfaces with a threshold energy of 4.2 eV, corresponding to the valence (Si) to conduction band (SiO_2) energy offset. The charge transfer is most effective for oxides with thickness <= 100 ÅThe disappearance of charge transfer and trapping with reduced oxygen pressure indicates that adsorbed oxygen at the top interface plays at least a catalytic role in inducing electron trapping. Measurements for silicon wafers with different oxide layers grown under ``dry'' and ``wet'' conditions allow us to noninvasively determine carrier trapping and detrapping times.

Bloch, J.; Mihaychuk, J. G.; van Driel, H. M.

1996-03-01

329

Comparisons of the proton-induced dark current and charge transfer efficiency responses of n- and p-channel CCDs  

Microsoft Academic Search

The proton-induced charge transfer efficiency (CTE) behavior for the Lawrence Berkeley National Laboratory (LBNL) p-channel CCD [being developed for the Supernovae Acceleration Probe (SNAP)] is compared with the Hubble Space Telescope\\

Cheryl J. Marshall; Paul W. Marshall; Augustyn Wacynski; Elizabeth Polidan; Scott D. Johnson; Art Campbell

2004-01-01

330

Jahn-Teller effects in transition-metal compounds with small charge-transfer energy  

NASA Astrophysics Data System (ADS)

We have studied Jahn-Teller effects in Cs2Au2Br6, ACu3Co4O12(A=Ca or Y), and IrTe2 in which the ligand p-to-transition-metal d charge-transfer energy is small or negative. The Au+/Au3+ charge disproportionation of Cs2Au2Br6 manifests in Au 4f photoemission spectra. In Cs2Au2Br6 with negative ? and intermediate U, the charge disproportionation can be described using effective d orbitals constructed from the Au 5d and Br 4p orbitals and is stabilized by the Jahn-Teller distortion of the Au3+ site with low-spin d8 configuration. In ACu3Co4O12, ?s for Cu3+ and Co4+ are negative and Us are very large. The Zhang-Rice picture is valid to describe the electronic state, and the valence change from Cu2+/Co4+ to Cu3+/Co3+ can be viewed as the O 2p hole transfer from Co to Cu or d9 + d6L ? d9L + d6. In IrTe2, both ? and U are small and the Ir 5d and Te 5p electrons are itinerant to form the multi-band Fermi surfaces. The ideas of band Jahn-Teller transition and Peierls transition are useful to describe the structural instabilities.

Mizokawa, Takashi

2013-04-01

331

Trifluoromethylmetallate anions as components of molecular charge transfer salts and superconductors.  

SciTech Connect

Whereas polymeric and common inorganic anions frequently deprive the synthetic chemist of a chance to modify a charge transfer salt's structure through anion alterations, discrete organometallic anions provide a vast opportunity to probe the structure/property correlations of a material through rational synthetic methods. We have recently undertaken a research effort aimed at the crystallization of conducting charge transfer salts which possess modifiable, organometallic anions as the charge compensating entities. This research has been richly rewarded with the discovery of a new family of bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF or ET) based molecular superconductors. Herein is presented a summary of over twenty {kappa}(ET){sub 2}M(CF{sub 3}){sub 4}(1,1,2-trihaloethane) (M = Cu, Ag, Au) superconducting salts. Three new related salts are also reported: (ET){sub 2} [trans-Ag(CF{sub 3}),(CN){sub 2}], {kappa}{sub L}(BEDT-TSF){sub 2}Ag(CF{sub 3}){sub 4}(TCE), and {kappa}{sub L}(ET){sub 2}Ag(CF{sub 3}){sub 3}Cl(TCE).

Schlueter, J. A.

1998-10-14

332

Fowler-Nordheim tunneling induced charge transfer plasmons between nearly touching nanoparticles.  

PubMed

Reducing the gap between two metal nanoparticles down to atomic dimensions uncovers novel plasmon resonant modes. Of particular interest is a mode known as the charge transfer plasmon (CTP). This mode has been experimentally observed in touching nanoparticles, where charges can shuttle between the nanoparticles via a conductive path. However, the CTP mode for nearly touching nanoparticles has only been predicted theoretically to occur via direct tunneling when the gap is reduced to ~0.4 nm. Because of challenges in fabricating and characterizing gaps at these dimensions, experiments have been unable to provide evidence for this plasmon mode that is supported by tunneling. In this work, we consider an alternative tunneling process, that is, the well-known Fowler-Nordheim (FN) tunneling that occurs at high electric fields, and apply it for the first time in the theoretical investigation of plasmon resonances between nearly touching nanoparticles. This new approach relaxes the requirements on gap dimensions, and intuitively suggests that with a sufficiently high-intensity irradiation, the CTP can be excited via FN tunneling for a range of subnanometer gaps. The unique feature of FN tunneling induced CTP is the ability to turn on and off the charge transfer by varying the intensity of an external light source, and this could inspire the development of novel quantum devices. PMID:23215253

Wu, Lin; Duan, Huigao; Bai, Ping; Bosman, Michel; Yang, Joel K W; Li, Erping

2012-12-12

333

Molecular dynamics study of cristobalite silica using a charge transfer three-body potential: Phase transformation and structural disorder  

Microsoft Academic Search

Structural and dynamic properties of cristobalite silica have been studied using molecular dynamics simulations based on a charge transfer three-body potential model. In this potential model, the directional covalent bonding of SiO2 is characterized by a charge transfer function of the interatomic distance between Si and O atoms, and in the form of Si-O-Si and O-Si-O three-body interactions. The dynamic

Liping Huang; John Kieffer

2003-01-01

334

Creation of ternary multicomponent crystals by exploitation of charge-transfer interactions.  

PubMed

Four new ternary crystalline molecular complexes have been synthesised from a common 3,5-dinitrobenzoic acid (3,5-dnda) and 4,4'-bipyridine (bipy) pairing with a series of amino-substituted aromatic compounds (4-aminobenzoic acid (4-aba), 4-(N,N-dimethylamino)benzoic acid (4-dmaba), 4-aminosalicylic acid (4-asa) and sulfanilamide (saa)). The ternary crystals were created through the application of complementary charge transfer and hydrogen-bonding interactions. For these systems a dimer was created through a charge-transfer interaction between two of the components, while hydrogen bonding between the third molecule and this dimer completed the construction of the ternary co-crystal. All resulting structures display the same acid???pyridine interaction between 3,5-dnba and bipy. However, changing the third component causes the proton of this bond to shift from neutral OH???N to a salt form, O(-) ???HN(+) , as the nature of the group hydrogen bonding to the carboxylic acid was changed. This highlights the role of the crystal environment on the level of proton transfer and the utility of ternary systems for the study of this process. PMID:23794534

Seaton, Colin C; Blagden, Nicholas; Munshi, Tasnim; Scowen, Ian J

2013-06-21

335

Buried-channel CCDs with high charge transfer efficiency and large charge capacity for low-temperature readout of long-wavelength infrared detectors  

Microsoft Academic Search

Double ion implantation has been used to fabricate buried-channel CCDs that exhibit good charge transfer efficiency at temperatures down to 50 K while retaining large charge storage capacity. Monolithic IR focal plane arrays integrating such CCDs and Ge(x)Si(1-x)\\/Si heterojunction detectors show good imaging performance in both the 3-5 micron and 8-10 micron IR spectral bands.

A. L. Lattes; B.-Y. Tsaur

1992-01-01

336

Charge Transfer in Collisions between Bare Ions and Hydrogenic Carbon Ions  

NASA Astrophysics Data System (ADS)

Cross sections have been calculated for electron transfer, as well as ionization, in collisions between 125-1000 keV/amu protons, ? particles, Li^2+ ions, etc. and C^5+(1s) ions. The dependence of cross sections on projectile charge has been determined and compared with results of first-order perturbation theory. This study parallels an earlier one in which the target nuclear charge was instead varied.(T. G. Winter, Phys. Rev. A 35), 3799 (1987). A coupled-Sturmian-pseudostate approach is again taken, yielding capture cross sections accurate to at least a few per cent. In the case of ?-particle projectiles, the results are important for understanding ? losses to the walls of the TFTR, (H. Herrmann (private communication, 1996).) and are much larger than existing published results.(M. Lal, M. K. Srivastava, and A. N. Tripathi, Phys. Rev. A 26), 305 (1982).

Winter, T. G.

1997-04-01

337

Charged pion spectra and energy transfer following antiproton annihilation at rest in carbon and uranium  

NASA Astrophysics Data System (ADS)

The momentum spectra of charged pions following antiproton annihilation at rest in carbon and uranium have been measured. This information complements our previous measurement of the neutral pion spectra. The total charged pion multiplicity is 2.84±0.10 and 2.47±0.09 for carbon and uranium, respectively, in good agreement with recent INC model predictions of 2.96 and 2.48 for the same quantities. However, structures predicted by the model near 200 MeV/c and 300 MeV/c related to delta-resonance production are not seen in the data. The total energy transfers to the nucleus are calculated to be 119±59 MeV(carbon) and 455±50 MeV(uranium). The possibility of exciting multifragmentation with a ¯p beam impinging on heavy nuclei is discussed.

Minor, E. D.; Armstrong, T. A.; Bishop, R.; Harris, V.; Lewis, R. A.; Smith, G. A.

1990-12-01

338

Doping Dependent Charge Transfer Gap and Realistic Electronic Model of n-type Cuprate Superconductors  

SciTech Connect

Based on the analysis of the measurement data of angle-resolved photoemission spectroscopy (ARPES) and optics, we show that the charge transfer gap is significantly smaller than the optical one and is reduced by doping in electron doped cuprate superconductors. This leads to a strong charge fluctuation between the Zhang-Rice singlet and the upper Hubbard bands. The basic model for describing this system is a hybridized two-band t-J model. In the symmetric limit where the corresponding intra- and inter-band hopping integrals are equal to each other, this two-band model is equivalent to the Hubbard model with an antiferromagnetic exchange interaction (i.e. the t-U-J model). The mean-field result of the t-U-J model gives a good account for the doping evolution of the Fermi surface and the staggered magnetization.

Xiang, T.

2010-05-03

339

Charge transfer equilibria in ambient-exposed epitaxial graphene on (0001) 6 H-SiC  

NASA Astrophysics Data System (ADS)

The transport properties of electronic materials have been long interpreted independently from both the underlying bulk-like behavior of the substrate or the influence of ambient gases. This is no longer the case for ultra-thin graphene whose properties are dominated by the interfaces between the active material and its surroundings. Here, we show that the graphene interactions with its environments are critical for the electrostatic and electrochemical equilibrium of the active device layers and their transport properties. Based on the prototypical case of epitaxial graphene on (0001) 6 H-SiC and using a combination of in-situ thermoelectric power and resistance measurements and simulations from first principles, we demonstrate that the cooperative occurrence of an electrochemically mediated charge transfer from the graphene to air, combined with the peculiar electronic structure of the graphene/SiC interface, explains the wide variation of measured conductivity and charge carrier type found in prior reports.

Sidorov, Anton N.; Gaskill, Kurt; Buongiorno Nardelli, Marco; Tedesco, Joseph L.; Myers-Ward, Rachel L.; Eddy, Charles R.; Jayasekera, Thushari; Kim, Ki Wook; Jayasingha, Ruwantha; Sherehiy, Andriy; Stallard, Robert; Sumanasekera, Gamini U.

2012-06-01

340

Spectra of the Heliospheric X-ray and EUV Emission Induced by Charge Transfer Collisions  

NASA Astrophysics Data System (ADS)

Spectra of the heliospheric X-ray and extreme ultraviolet (EUV) emission induced by highly charged solar wind ions are investigated. Intensities of various ion emission lines are calculated taking into account selective populations of the excited states of heavy solar wind ions in charge transfer collisions with hydrogen and helium atoms of the neutral interstellar gas. Photon cascading spectra of excited solar wind ions are computed for different compositions of the solar wind. The brightest spectral lines of the X-ray and EUV heliospheric emission are predicted for the fast and slow components of the solar wind. Polarization of these lines is analyzed. The contribution of the solar wind ion emission to the observed soft X-ray background is discussed. The time variability and the anisotropy of the heliospheric X-ray and EUV radiation are investigated.

Kharchenko, V.; Rigazio, M.; Dalgarno, A.

2001-12-01

341

Sequential protonation of meso-(p-(dimethylamino)phenyl)porphyrins. Charge-transfer excited states producing hyperporphyrins  

SciTech Connect

Successive protonation by trifluoroacetic acid of meso-tetraphenylporphyrin derivatives bearing one, two, or four p-dimethylamino groups gives rise to new types of spectra. With one free amino group, the spectrum of the centrally protonated porphyrin shows a strong far-red band, a broad, flat absorption in the visible, and a less intense Soret band. With two or more free amino groups, the Soret band of the centrally protonated porphyrin is further split into two components. Complete protonation, including the peripheral amino groups, in all cases restores the spectral structure of the unsubstituted tetraphenylporphyrin dication. The spectra of the dianions of tetraanilino- and tetraphenylporphyrins are also similar. These results, and the related behavior of p-oxyphenylporphyrins and protonated Schiff base porphyrins, lead to a general interpretation of hyperporphyrin spectra in terms of charge-transfer excited states, involving charge movement either into or out of the porphyrin ring. 26 refs., 4 figs., 2 tabs.

Ojadi, E.C.A. (Brandeis Univ., Waltham, MA (United States) Univ. of Massachusetts, Dartmouth, MA (United States)); Linschitz, H.; Droupadi, P.R.; Wang, W. (Brandeis Univ., Waltham, MA (United States)); Gouterman, M. (Univ. of Washington, Seattle, WA (United States)); Walter, R.I. (Univ. of Illinois, Chicago, IL (United States)); Lindsey, J.S.; Wagner, R.W. (Carnegie-Mellon Univ., Pittsburgh, PA (United States))

1993-12-16

342

Charge transfer and electronic transitions in polycrystalline BiFeO3  

NASA Astrophysics Data System (ADS)

We report on the electronic energy-level diagram of polycrystalline BiFeO3 using the elemental, optical, and current-density-electric field (J-E) characteristics. The elemental, electronic composition, and valence-band structure of BiFeO3 ceramics were studied using x-ray photoelectron spectroscopy. The diffuse reflectance spectrum of a mixture of BiFeO3 and BaSO4 , used as a standard, was recorded to test the Kubelka-Munk model. From the graph of the Kubelka-Munk function versus wavelength, two charge-transfer bands and two doubly degenerated d-d transitions ( A61g?T42g and A61g?T41g ) were observed in polycrystalline BiFeO3 . The J-E curves measured on the BiFeO3 ceramics showed space-charge-limited conduction mechanism.

Ramachandran, B.; Dixit, A.; Naik, R.; Lawes, G.; Rao, M. S. Ramachandra

2010-07-01

343

Charge transfer in metal-atom-containing molecules in the gas phase  

NASA Astrophysics Data System (ADS)

The presence of charge transfer (CT) is ubiquitous in metal-atom-containing molecules in the gas phase. The states of interest range from ground states to the lower excited states, given the generally low ionisation potentials of metal atoms. This review is written from an experimentalist's perspective, to describe the specifics of CT states in stable molecules containing a metal atom or of transient CT states in dynamical processes. The large body of experimental evidence allows the description of such states in an empirical or semi-empirical manner, including partial point charges and polarised electron clouds on the ions. These simple models are compared with more quantitative models, allowing the development of sophisticated descriptions. The simple perspective deriving from experimental evidence is justified, when it is possible via accurate quantum calculations and allows building a rather complete framework for the ionic bond or CT-induced dynamics.

Shafizadeh, Niloufar; Soep, Benoit; Mestdagh, Jean Michel; Breckenridge, W. H.

344

Molecule/Surface Interactions and the Control of Electronic Structure In Epitaxial Charge Transfer Salts  

NASA Astrophysics Data System (ADS)

The two-dimensionality of the fulvalene-based superconducting charge transfer salts has lead to an increasing interest in the epitaxial growth and local probe analysis of monolayer CTS films. Curiously, these studies have shown remarkable differences in both the electronic structure and topography of the monolayers grown on metals, suggesting that the organic/metal interactions introduced by epitaxial growth strongly influence the resulting structures. Through recent experiments on monolayer films of the CTS (ET)2SF5CH2CF2SO3 and the bare fulvalene ET grown on Ag(111), we illustrate what effect the metal-molecule interaction has on the electronic structure and 2D charge transport of epitaxial CTS and how this differs from the bare fulvalene. Through a comparative analysis of the differences in stoichiometry and topography of these and heretofore published systems, the relative roles of ionic bonding, surface chemisorption, and hybridization for the preparation of this and future compounds are explored.

Rojas, Geoffrey; Ganesh, P.; Kelly, Simon; Sumpter, Bobby; Schlueter, John; Maksymovych, Petro

2013-03-01

345

Solvent-Mediated Electron Leapfrogging: Charge Transfer in IBr^-(CO_2) Photodissociation  

NASA Astrophysics Data System (ADS)

In this work, we investigate the time-resolved photoelectron spectra of IBr^-(CO_2). In the photodetachment studies performed by Lineberger and co-workers,^a IBr^-(CO_2) is prepared in its electronic ground state (^2?1/2^+) whereupon it is excited to its ~A'^ (^2?3/2) excited state, before electron photodetachment/photoionization and dissociation on the Ctilde (^1?_1) excited state of IBr. Previous experimental work showed that dissociation of bare IBr^- yields only I^- + Br products. However in IBr^-(CO_2), a small fraction (˜ 3%) of the dissociating molecules undergo an electron transfer from I to Br at 350 fs after the initial excitation. Thus a single solvent molecule can initiate a non-adiabatic transition from the ~A' state to either the lower ~A or ~X state, thereby producing I + Br^- (+ CO_2) prior to photoionization. To study the dynamics, we perform high level ab initio calculations (MR-SO-CISD/aug-cc-pVTZ(-PP)) as well as classical molecular dynamics (MD) simulations. The MD simulations capture much of the dynamics of the photodissociation but underestimate the charge-transfer channel. Results of the ab initio calculations show how CO_2 bend vibrational excitation could increase the percentage of non-adiabatic transitions and how the CO_2 modifies the charge distribution of IBr^- to make the charge transfer accessible. The proposed mechanism and timescales are consistent with the observed Br^- products. L. Sheps, E. M. Miller, S. Horvath, M. A. Thompson, R. Parson, A. B. McCoy, and W. C. Lineberger, Science, 2010, in press R. Mabbs, K. Pichugin, and A. Sanov, J. Chem. Phys., 2005, 122, 174305.

Horvath, Samantha; McCoy, Anne B.; Sheps, Leonid; Miller, Elisa M.; Thompson, Matthew A.; Parson, Robert; Lineberger, W. Carl

2010-06-01

346

Carotenoid Charge Transfer States and Their Role in Energy Transfer Processes in LH1-RC Complexes from Aerobic Anoxygenic Phototrophs.  

PubMed

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

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

2012-11-21

347

Excited state intramolecular proton transfer and charge transfer dynamics of a 2-(2'-hydroxyphenyl)benzoxazole derivative in solution.  

PubMed

Excited state intramolecular proton transfer (ESIPT) and subsequent intramolecular charge transfer (ICT) dynamics of a 2-(2'-hydroxyphenyl)benzoxazole derivative conjugated with an electron withdrawing group (HBOCE) in solutions and a polymer film has been investigated by femtosecond time-resolved fluorescence (TRF) and TRF spectra measurements without the conventional spectral reconstruction method. TRF with high enough resolution (<100 fs) reveals that the ESIPT dynamics of HBOCE in liquids proceeds by at least two time constants of approximately 250 fs and approximately 1.2 ps. The relative amplitude of the slower picosecond component is smaller in the polymer film than that in solution. Conformational heterogeneity in the ground state originating from the dispersion of the dihedral angle between the phenolic and benzoxazole groups is invoked to account for the dispersive ESIPT dynamics in liquids. From the TRF spectra of both the enol and keto isomers, we have identified the ICT reaction of the keto isomer occurring subsequent to the ESIPT. The ICT proceeds also by two time constants of near instantaneous and 2.7 ps. Since the ICT dynamics of HBOCE is rather close to the polar solvation dynamics, we argue that the ICT is barrierless and determined mostly by the solvent fluctuation. PMID:20397709

Kim, Chul Hoon; Park, Jaehun; Seo, Jangwon; Park, Soo Young; Joo, Taiha

2010-05-13

348

EV Charging Through Wireless Power Transfer: Analysis of Efficiency Optimization and Technology Trends  

SciTech Connect

This paper is aimed at reviewing the technology trends for wireless power transfer (WPT) for electric vehicles (EV). It also analyzes the factors affecting its efficiency and describes the techniques currently used for its optimization. The review of the technology trends encompasses both stationary and moving vehicle charging systems. The study of the stationary vehicle charging technology is based on current implementations and on-going developments at WiTricity and Oak Ridge National Lab (ORNL). The moving vehicle charging technology is primarily described through the results achieved by the Korean Advanced Institute of Technology (KAIST) along with on-going efforts at Stanford University. The factors affecting the efficiency are determined through the analysis of the equivalent circuit of magnetic resonant coupling. The air gap between both transmitting and receiving coils along with the magnetic field distribution and the relative impedance mismatch between the related circuits are the primary factors affecting the WPT efficiency. Currently the industry is looking at an air gap of 25 cm or below. To control the magnetic field distribution, Kaist has recently developed the Shaped Magnetic Field In Resonance (SMFIR) technology that uses conveniently shaped ferrite material to provide low reluctance path. The efficiency can be further increased by means of impedance matching. As a result, Delphi's implementation of the WiTricity's technology exhibits a WPT efficiency above 90% for stationary charging while KAIST has demonstrated a maximum efficiency of 83% for moving vehicle with its On Line Vehicle (OLEV) project. This study is restricted to near-field applications (short and mid-range) and does not address long-range technology such as microwave power transfer that has low efficiency as it is based on radiating electromagnetic waves. This paper exemplifies Delphi's work in powertrain electrification as part of its innovation for the real world program geared toward a safer, greener and more connected driving. Moreover, it draws from and adds to Dr. Andrew Brown Jr.'s SAE books 'Active Safety and the Mobility Industry', 'Connectivity and Mobility Industry', and 'Green Technologies and the Mobility Industry'. Magnetic resonant coupling is the foundation of modern wireless power transfer. Its efficiency can be controlled through impedance matching and magnetic field shaping. Current implementations use one or both of these control methods and enable both stationary and mobile charging with typical efficiency within the 80% and 90% range for an air gap up to 25 cm.

Miller, John M [ORNL; Rakouth, Heri [Delphi Automotive Systems, USA; Suh, In-Soo [Korea Advanced Institute of Science and Technology

2012-01-01

349

Photoinduced charge transfer between fullerenes and TiO{sub 2} semiconductor colloids  

SciTech Connect

A photocatalytic method has been presented to carry out one-electron reduction of C{sub 60} and C{sub 70} in 50/50 (v/v) benzene/ethanol. The fullerene reduction was carried out in colloidal TiO{sub 2} suspension using UV excitation. The charge transfer between the excited TiO{sub 2} semiconductor colloid and fullerene molecule occurs with a quantum efficiency of 13% for C{sub 70} and 24% for C{sub 60}. Laser flash photolysis measurements have been carried out to elucidate the mechanism of photocatalytic reduction.

Kamat, P.V. [Univ. of Notre Dame, IN (United States). Radiation Lab.; Bedja, I.; Hotchandani, S. [Universite du Quebec a Trois Rivieres (Canada). Centre de Recherche en Photobiophysique

1994-10-01

350

Observation of Frenkel and charge transfer excitons in pentacene single crystals using spectroscopic generalized ellipsometry  

NASA Astrophysics Data System (ADS)

We report on the emerging and admixture of Frenkel and charge transfer (CT) excitons near the absorption onset in pentacene single crystals. Using high energy-resolution spectroscopic generalized ellipsometry with in-plane polarization dependence, the excitonic nature of three lowest lying excitations is discussed. Their distinct polarization dependence strongly indicates the presence of both Frenkel and CT types of excitons near the excitation onset. In particular, the peculiar polarization behavior of the second excitation can only be rationalized by taking into account the inherent CT transition dipole moment. This observation has important implications for the pentacene-based optoelectronic devices.

Qi, Dongchen; Su, Haibin; Bastjan, M.; Jurchescu, O. D.; Palstra, T. M.; Wee, Andrew T. S.; Rübhausen, M.; Rusydi, A.

2013-09-01

351

Investigating Molecular Charge Transfer Complexes with a Low Temperature Scanning Tunneling Microscope  

NASA Astrophysics Data System (ADS)

Electron donor-acceptor molecular charge transfer complexes (CTCs) formed by ?-sexithiophene (6T) and tetrafluoro-tetracyano-quinodimethane (F4TCNQ) on a Au(111) surface are investigated by scanning tunneling microscopy, spectroscopy, and spectroscopic imaging at 6 K. New hybrid molecular orbitals are formed in the CTCs, and the highest occupied molecular orbital of the CTC is mainly located on the electron accepting F4TCNQ while the lowest unoccupied molecular orbital is predominantly positioned on the electron donating 6T. We observed the conductance switching of F4TCNQ inside CTCs, which may find potential applications in novel molecular device operations.

Jäckel, F.; Perera, U. G. E.; Iancu, V.; Braun, K.-F.; Koch, N.; Rabe, J. P.; Hla, S.-W.

2008-03-01

352

Charge-transfer photodissociation of adsorbed molecules via electron image states  

SciTech Connect

The 248 and 193 nm photodissociations of submonolayer quantities of CH{sub 3}Br and CH{sub 3}I adsorbed on thin layers of n-hexane indicate that the dissociation is caused by dissociative electron attachment from subvacuum level photoelectrons created in the copper substrate. The characteristics of this photodissociation-translation energy distributions and coverage dependences show that the dissociation is mediated by an image potential state which temporarily traps the photoelectrons near the n-hexane-vacuum interface, and then the charge transfers from this image state to the affinity level of a coadsorbed halomethane which then dissociates.

Jensen, E. T. [Physics Department, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia V2N 4Z9 (Canada)

2008-01-28

353

Theoretical fully differential cross sections for double-charge-transfer collisions  

SciTech Connect

We present a four-body model for double charge transfer, called the four-body double-capture model. This model explicitly treats all four particles in the collision, and we apply it here to fully differential cross sections (FDCSs) for proton+helium collisions. The effects of initial- and final-state electron correlations are studied, as well as the role of the projectile-nucleus interaction. We also present results for proton+helium single capture, as well as single-capture:double-capture ratios of FDCSs.

Harris, A. L.; Peacher, J. L.; Madison, D. H. [Physics Department, Missouri University of Science and Technology, Rolla, Missouri 65401 (United States)

2010-08-15

354

Orientation dependence of charge transfer for C{sub 60} on Cu(100)  

SciTech Connect

Scanning tunneling microscopy was used to characterize the lowest unoccupied molecular orbitals (LUMO), up to LUMO+3, of individual C{sub 60} molecules within monolayer films on Cu(100). On this surface C{sub 60} orients in four distinct configurations with respect to the substrate. Tunneling spectroscopy and spectroscopic imaging were used to identify the energies and spatial distributions of the molecular orbitals. We find that the LUMO shifts by {approx}200 meV depending on the orientation of the molecule, which suggests charge transfer between the surface and molecule is orientation dependent. Orientation-dependent shifts were also observed for the higher unoccupied molecular orbitals.

Daughton, D. R.; Gupta, J. A. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States)

2011-03-28

355

Effect of intramolecular charge transfer on the two-photon absorption behavior of multibranched triphenylamine derivations  

NASA Astrophysics Data System (ADS)

Solvent polarity effect on the absorption spectra and fluorescence spectra of a series of multibranched structure triphenylamine derivations (Ph-G0, Ph-G1, and Ph-G2) were analyzed to reveal the factors that determine the two-photon absorption (TPA) ability in these molecules. It was found that the dominate factor is the extent of intramolecular charge transfer upon photoexcitation, rather than coherent coupling between branches. This result suggests that it is more effective to change the electron withdrawing ability or electron giving ability of branches and core than simply increase the number of branches for enhancing the TPA ability in multibranched structure molecules.

He, Xing; Xu, Bin; Liu, Yuqiang; Yang, Yanqiang; Tian, Wenjing

2012-03-01

356

Spectroscopy of charge transfer complexes of four amino acids as organic two-dimensional conductors  

NASA Astrophysics Data System (ADS)

It is found in this study that four amino acids, namely asparagine, arginine, histidine and glutamine form two-dimensional conducting systems which are charge transfer complexes (CTCs) with organic acceptors like TCNQ, TCNE, chloranil, DDQ, TNF and iodine. It is verified using optical absorption edges that these are 2d conductors like transition metal dichalcogenides obeying absorption functions different from 1d and 3d conductors. This 2d nature is related to the network of intermolecular H-bonding in these complexes, which leads to a global H-bonded network resulting in the absence of local deformation due to the relaxation of strain.

Padhiyar, Ashvin; Patel, A. J.; Oza, A. T.

2007-12-01

357

Spontaneous charge transfer at organic-organic homointerfaces to establish thermodynamic equilibrium  

SciTech Connect

The energy level alignment of {alpha},{omega}-dihexylsexithienyl (DH6T) mono- and multilayers on tetrafluorotetracyanoquinodimethane (F4-TCNQ) precovered Ag(111) and polycrystalline Au substrates was investigated with ultraviolet photoelectron spectroscopy. For certain F4-TCNQ precoverages molecular level pinning at DH6T monolayer-multilayer homointerfaces was observed. The pinning behavior shows that thermodynamic equilibrium can be established across hexyl chains via charge transfer, indicating the limited use of these short alkyl chains for insulation in the field of molecular electronics.

Duhm, S.; Glowatzki, H.; Rabe, J. P.; Koch, N.; Johnson, R. L. [Institut fuer Physik, Humboldt-Universitaet zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany); Institut fuer Experimentalphysik, Universitaet Hamburg, D-22761 Hamburg (Germany)

2007-03-19

358

Revision of model parameters for kappa-type charge transfer salts: an ab initio study.  

PubMed

Intense experimental and theoretical studies have demonstrated that the anisotropic triangular lattice as realized in the kappa-(BEDT-TTF)2X family of organic charge transfer salts yields a complex phase diagram with magnetic, superconducting, Mott insulating, and even spin liquid phases. With extensive density functional theory calculations we refresh the link between many body theory and experiment by determining hopping parameters of the underlying Hubbard model. This leads us to revise the widely used semiempirical parameters in the direction of less frustrated, more anisotropic triangular lattices. The implications of these results on the systems' description are discussed. PMID:19792599

Kandpal, Hem C; Opahle, Ingo; Zhang, Yu-Zhong; Jeschke, Harald O; Valentí, Roser

2009-08-04

359

Theoretical evidence of photo-induced charge transfer from DNA to intercalated ruthenium (II) organometallic complexes  

NASA Astrophysics Data System (ADS)

The absorption spectrum of two ruthenium (II) organometallic complexes intercalated into DNA is studied at the quantum mechanic/molecular mechanic level. The macromolecular environment is taken into account as to include geometric, electrostatic and polarization effects that can alter the excitation energy and oscillator strength. The inclusion of DNA base pairs into the quantum mechanic partition allows us for the first time to clearly evidence the presence of charge transfer excited states involving an electron withdraw from DNA base pairs to the organometallic complex.

Chantzis, Agisilaos; Very, Thibaut; Daniel, Chantal; Monari, Antonio; Assfeld, Xavier

2013-07-01

360

Metallization and charge-transfer gap closure of transition-metal iodides under pressure  

SciTech Connect

It is shown with resistivity and near-IR absorption measurements that NiI{sub 2}, CoI{sub 2}, and FeI{sub 2} metallize under pressure by closure of the charge-transfer energy gap at pressures of 17, 10, and 23 GPa, respectively, which is close to the antiferromagnetic-diamagnetic transition in NiI{sub 2} and CoI{sub 2}. Thus, the magnetic transitions probably are caused by the metallization; in NiI{sub 2} and CoI{sub 2}, the insulator-metal transitions are first order. Moessbauer and XRD data were also collected. Figs, 46 refs.

Chen, A. Li-Chung

1993-05-01

361

Orbital Localization, Charge Transfer, and Band Gaps in Semilocal Density-Functional Theory  

NASA Astrophysics Data System (ADS)

We derive an exchange energy functional of generalized gradient form with a corresponding potential that changes discontinuously at integer particle numbers. The functional is semilocal, yet incorporates key features that are connected to the derivative discontinuity of Kohn-Sham density-functional theory. We validate our construction for several paradigm systems and explain how it addresses central well-known deficiencies of antecedent semilocal methods, i.e., the description of charge transfer, properly localized orbitals, and band gaps. We find, e.g., an improved shell structure for atoms, eigenvalues that more closely correspond to ionization energies, and an improved description of band structure where localized states are lowered in energy.

Armiento, R.; Kümmel, S.

2013-07-01

362

Metastable intermolecular charge-transfer complexes with a pentavalent carbon atom.  

PubMed

A novel type of metastable complexes of metal (such as Na) atoms with a super-fluorinated carbon molecule is investigated, with a carbon atom exhibiting a unique, pentavalent character. It is induced by the charge transfer from the alkali metal component, followed by a geometric compression of the ion pair system. Analysis of the electron-density distribution confirms the real chemical nature of the extra C-F bond. Structure and stability of the system are characterized ab initio, and a spectrum of electronic perturbations is considered. The ways of forming the systems are discussed, and the spectroscopic parameters are predicted, facilitating their detection in experiments. PMID:17020247

Naumkin, Fedor Y

2006-10-12

363

The First Molecular Charge Transfer Salt Containing Layers of an Alkali Metal  

Microsoft Academic Search

We report the first molecular charge transfer salt containing layers of Na+ within its lattice. From the crystal structure and from C=C and C-S bond lengths and Raman stretching frequencies we obtain\\u000a a formula ????-(BEDT-TTF)9[Fe(C2O4)3]8Na18(H2O)24. The structure consists of alternating layers of BEDT-TTF, and layers comprising [Fe(C2O4)3]3?, Na+ and H2O. The packing of the layers follows the sequence ABCDABCDA as

Lee Martin; Peter Day; Peter Horton; Ann Bingham; Michael B. Hursthouse

2006-01-01

364

Water structure and charge transfer phenomena at the liquid-graphene interface.  

PubMed

Physicochemical properties of the graphene-water interface have been investigated to scrutinize the perturbations with respect to the graphene-air interface, in terms of changes in optical and vibrational spectra, as well as in the 3D network of water. Experimental investigations were carried out using Raman spectroscopy and laser scanning confocal microscopy, and integrated with density functional theory (DFT) calculations. Results evidence a substantial orientation of the hydrogen-bonded water molecules at the interfacial region, which, in turn, induces disorder in the water clusters and interfacial charge transfer phenomena. PMID:23019576

D'Urso, Luisa; Satriano, Cristina; Forte, Giuseppe; Compagnini, Giuseppe; Puglisi, Orazio

2012-09-28

365

Doubly interpenetrated chiral (10,3)-a network with charge-transfer-type guest inclusion.  

PubMed

A doubly interpenetrated metal-organic framework, [Zn(3)(TATB)(2)(H(2)O)(2)](n) (2), with chiral (10,3)-a topology, has been synthesized from an achiral, trigonal-planar ligand, 4,4',4?-s-triazine-2,4,6-triyltribenzoate (TATB). The large chiral channels in 2 act as scaffolds for the inclusion of N,N-dimethylaniline (DMA) molecules by donor-acceptor interactions. The resulting host-guest composite, DMA@2, shows desirably intense luminescence, which originated from photoinduced charge-transfer interactions in excited states. PMID:23374148

Han, Lei; Qin, Lan; Xu, Lan-Ping; Zhao, Wen-Na

2013-02-01

366

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

Microsoft Academic Search

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 CH2Cl2 and CCl4. The data are discussed in terms of equilibrium constant (KCT), molar extinction coefficient (?CT), thermodynamic standard reaction quantities (?G°, ?H° and ?S°), oscillator strength (f), and transition dipole moment (?). The

Mohamed E. El-Zaria

2008-01-01

367

In situ electrochemical STM of charge-transfer complex on Cu( 1 1 1 )  

Microsoft Academic Search

Adsorption and adlayer structures of ferrite magnetic anion [Fe(C2O4)3]3?, organic ?-electron donor bis(ethylenedithio) tetrathiafulvalene (bedt-ttf) and charge-transfer complex (bedt-ttf)5(H3O)Fe(C2O4)3·CH2Cl2 have been investigated by using electrochemical scanning tunneling microscopy on Cu(111) electrode surfaces in aqueous HClO4 solution. It was found that [Fe(C2O4)3]3? formed a (4×4) structure with a characteristic propeller shape for each anion and that bedt-ttf adlayer had a (4×6)

Qing-Min Xu; Bin Zhang; Li-Jun Wan; Cheng Wang; Chun-Li Bai; Dao-Ben Zhu

2002-01-01

368

Organic Nano-transistors Wired by Oriented Charge Transfer Complex Crystal  

NASA Astrophysics Data System (ADS)

We have fabricated high conducting organic wires and self-wired nano-transistors of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) charge transfer complex using co-evaporation method with an electric field. The conducting wires which directly bridge two gold electrodes indicated high-conductive ohmic contact with the gold electrode. Self-wired organic field effect transistor was formed at the connecting point of conductive wires. Field effect transistor characteristics of nano-transistor exhibited n-channel behavior with on/off ratio of 110. The length of active layer was estimated to be approximately a few nanometer.

Sakai, Masatoshi; Yajima, Eiji; Sakuma, Hirotaka; Iizuka, Masaaki; Nakamura, Masakazu; Kudo, Kazuhiro

369

Pulse Radiolysis Study on Proton and Charge Transfer Reactions in Solid Poly(methyl methacrylate)  

NASA Astrophysics Data System (ADS)

Poly(methyl methacrylate) (PMMA) is a good matrix for a case study aimed at understanding reaction mechanisms of electron beam, X-ray and EUV resists. Radiation-induced reactions and proton dynamics of solid PMMA were studied under room temperature by pulse radiolysis. PMMA samples were doped with pyrene (Py), crystal violet lactone (CVL) or an anion scavenger to observe charge and proton transfer reactions in the solid matrix. The time-dependent behavior of ionic radicals was observed with the time resolution of 10 ns. The electron transfer from PMMA anion radicals to the anion scavenger or Py was observed in the time range of several hundred nanoseconds. The dynamics of protons generated in irradiated PMMA was traced using CVL. The growth of optical absorbance attributed to proton adducts of CVL was observed in the time range of several hundreds minutes. Protons derived from PMMA cation radicals have a long lifetime and migrated in the solid PMMA matrix.

Nakano, Atsuro; Okamoto, Kazumasa; Kozawa, Takahiro; Tagawa, Seiichi

2004-07-01

370

Photo-induced charge-transfer processes in fullerene-containing dyad and triad molecules  

NASA Astrophysics Data System (ADS)

We report on pulsed electron-spin-resonance (ESR) investigations of novel model systems for photo-induced electron-transfer processes. The schematic structures of the molecules are T5-C60 and A-T5-C60, i.e., the fullerene C60 is used as the acceptor, and quinquethiophene (T5) or anthracene (A) act as a donor. In frozen solutions of both the dyad and triad, we find rather long-lived radical signals (lifetime ~2 ?s) after laser-pulse excitation. The observed signals can be assigned by the g factor and the linewidth to the anion C60- and the cation T5+. We have examined the influence of the solvent polarity (toluene or benzonitrile) and of the excitation wavelength (355 nm or 532 nm) on the efficiency of the charge transfer.

Knorr, S.; Grupp, A.; Mehring, M.; Grube, G.; Effenberger, F.

1999-09-01

371

Charge transfer in porphyrin-calixarene complexes: ultrafast kinetics, cyclic voltammetry, and DFT calculations.  

PubMed

Transient absorption spectroscopy, cyclic voltammetry, and DFT calculations were used to describe charge transfer processes in a series of 5,10,15,20-tetrakis(N-methylpyridinium-n-yl) porphyrins (TMPyPn, n = 4,3,2) and TMPyPn/p-sulfonatocalix[m]arene (clxm, m = 4,6,8) complexes. Excitation of TMPyPn is accompanied by an increasing electron density at the methylpyridinium substituents in the order TMPyP2 < TMPyP3 < TMPyP4. The quenching of the excited singlet states of the complexes increases with the number of ionized phenolic groups of clxm and can be correlated with the partial transfer of the electron density from O(-) to the peripheral methylpyridinium substituents rather than to the porphyrin ring. PMID:21399801

Kubát, Pavel; Šebera, Jakub; Záliš, Stanislav; Langmaier, Jan; Fuciman, Marcel; Polívka, Tomáš; Lang, Kamil

2011-03-11

372

Intra- and intermolecular charge transfer in aggregates of tetrathiafulvalene-triphenylmethyl radical derivatives in solution.  

PubMed

An extensive investigation of aggregation phenomena occurring in solution for a family of electron donor-acceptor derivatives, based on polychlorotriphenylmethyl radicals (PTM) linked via a vinylene-bridge to tetrathiafulvalene (TTF) units, is presented. A large set of temperature and/or concentration dependent optical absorption and electron spin resonance (ESR) spectra in a solution of dyads bearing different number of electrons and/or with a hydrogenated PTM residue offer reliable information on the formation of homo dimers and mixed valence dimers. The results shed light on the reciprocal influence of intramolecular electron transfer (IET) within a dyad and the intermolecular charge transfer (CT) occurring in a dimer between the TTF residues and are rationalized based on a theoretical model that describes both interactions. PMID:23517105

Guasch, Judith; Grisanti, Luca; Souto, Manuel; Lloveras, Vega; Vidal-Gancedo, José; Ratera, Imma; Painelli, Anna; Rovira, Concepció; Veciana, Jaume

2013-04-22

373

Charge Transfer Processes in Collisions of Si4+ Ions with He Atoms at Intermediate Energies  

NASA Astrophysics Data System (ADS)

Charge transfer in collisions of Si4+ ions with He atoms below 100 keV/u is studied by using a molecular orbital representation within both the semiclassical and quantal representations. Single transfer reaction Si4++He ?Si3++He+ has been studied by a number of theoretical investigations. In addition to the reaction (1), the first semiclassical MOCC calculations are performed for the double transfer channel Si4++HE?Si2++He2+ Nine molecular states that connect both with single and double electron transfer processes are considered in the present model. Electronic states and corresponding couplings are determined by the multireference single- and double- excitation configuration interaction method. The present cross sections tie well with the earlier calculations of Stancil et al., Phys. Rev. A 55, 1064 (1997) at lower energies, but show a rather different magnitude from those of Bacchus-Montabonel and Ceyzeriat, Phys. Rev. A 58, 1162 (1998). The present rate constant is found to be significantly different from the experimental finding of Fang and Kwong, Phys. Rev. A 59, 342 (1996) at 4,600 K, and hence does not support the experiment.

Suzuki, R.; Watanabe, A.; Sato, H.; Gu, J. P.; Hirsch, G.; Buenker, R. J.; Kimura, M.; Stancil, P. C.

374

Lowest Energy Electronic Transition in Aqueous Cl- Salts: Cl-->(H2O)6 Charge Transfer Transition  

PubMed Central

We use UV resonance Raman spectroscopy to probe the lowest energy allowed electronic transitions of aqueous solutions containing Cl- salts. We show that the waters hydrating the Cl- are involved in charge transfer transitions that transfer electron density from Cl- to the water molecules. These charge transfer transitions cause significant change in the H-O-H bond angle in the excited states, which results in a strong enhancement of the preresonance Raman intensity of the water bending modes. Our work gives the first insight into the lowest allowed electronic transition of hydrated Cl-.

Xiong, Kan; Asher, Sanford A.

2011-01-01

375

Dependence of the direct electron transfer activity and adsorption kinetics of cytochrome c on interfacial charge properties.  

PubMed

With the advantages of in situ analysis and high surface sensitivity, surface-enhanced infrared absorption spectroscopy in attenuated total reflection mode (ATR-SEIRAS) combined with electrochemical methods has been employed to examine the interfacial direct electron transfer activity and adsorption kinetics of cytochrome c (cyt c). This work presents data on cyt c adsorption onto negatively charged mercaptohexanoic acid (MHA) and positively charged 6-amino-1-hexanethiol (MHN) self-assembled monolayers (SAMs) on gold nanofilm surfaces. The adsorbed cyt c displays a higher apparent electron transfer rate constant (33.5 ± 2.4 s(-1)) and apparent binding rate constant (73.1 ± 5.2 M(-1) s(-1)) at the MHA SAMs surface than those on the MHN SAMs surface. The results demonstrate that the surface charge density determines the protein adsorption kinetics, while the surface charge character determines the conformation and orientation of proteins assembled which in turn affects the direct electron transfer activity. PMID:23912152

Wang, Gui-Xia; Wang, Min; Wu, Zeng-Qiang; Bao, Wen-Jing; Zhou, Yue; Xia, Xing-Hua

2013-10-01

376

Charge transfer satellite in Pr@C82 metallofullerene observed using resonant x-ray emission spectroscopy  

NASA Astrophysics Data System (ADS)

Resonant x-ray emission spectroscopy (RXES) was performed on the metallofullerene Pr@C82 at the PrL3 absorption edge. We verify not only nearly three-electron charge transfers from the metal to the cage but also back-electron transfer observed as a charge transfer satellite. The results are compared to theoretical calculations with a single-impurity Anderson model. Theory shows that the electronic structure of endohedral atom in the cage is atomiclike. The satellite structure originates from the charge transfer, i.e., dynamical screening effect, induced by the core-hole potential in the final state rather than from the valence fluctuation of the rare-earth metal in the ground state. We also performed the RXES measurement of Pr2O3 for comparison.

Yamaoka, H.; Sugiyama, H.; Kubozono, Y.; Kotani, A.; Nouchi, R.; Vlaicu, A. M.; Oohashi, H.; Tochio, T.; Ito, Y.; Yoshikawa, H.

2009-11-01

377

Excited State Structural Dynamics of Carotenoids and ChargeTransfer Systems  

SciTech Connect

This dissertation describes the development andimplementation of a visible/near infrared pump/mid-infrared probeapparatus. Chapter 1 describes the background and motivation ofinvestigating optically induced structural dynamics, paying specificattention to solvation and the excitation selection rules of highlysymmetric molecules such as carotenoids. Chapter 2 describes thedevelopment and construction of the experimental apparatus usedthroughout the remainder of this dissertation. Chapter 3 will discuss theinvestigation of DCM, a laser dye with a fluorescence signal resultingfrom a charge transfer state. By studying the dynamics of DCM and of itsmethyl deuterated isotopomer (an otherwise identical molecule), we areable to investigate the origins of the charge transfer state and provideevidence that it is of the controversial twisted intramolecular (TICT)type. Chapter 4 introduces the use of two-photon excitation to the S1state, combined with one-photon excitation to the S2 state of thecarotenoid beta-apo-8'-carotenal. These 2 investigations show evidencefor the formation of solitons, previously unobserved in molecular systemsand found only in conducting polymers Chapter 5 presents an investigationof the excited state dynamics of peridinin, the carotenoid responsiblefor the light harvesting of dinoflagellates. This investigation allowsfor a more detailed understanding of the importance of structuraldynamics of carotenoids in light harvesting.

Van Tassle, Aaron Justin

2006-09-01

378

Observation of excited state charge transfer with fs/ps-CARS  

SciTech Connect

Excited state charge transfer processes are studied using the fs/ps-CARS probe technique. This probe allows for multiplexed detection of Raman active vibrational modes. Systems studied include Michler's Ketone, Coumarin 120, 4-dimethylamino-4{prime}-nitrostilbene, and several others. The vibrational spectrum of the para di-substituted benzophenone Michler's Ketone in the first excited singlet state is studied for the first time. It is found that there are several vibrational modes indicative of structural changes of the excited molecule. A combined experimental and theoretical approach is used to study the simplest 7-amino-4-methylcoumarin, Coumarin 120. Vibrations observed in FTIR and spontaneous Raman spectra are assigned using density functional calculations and a continuum solvation model is used to predict how observed modes are affected upon inclusion of a solvent. The low frequency modes of the excited state charge transfer species 4-dimethylamino-4{prime}-nitrostilbene are studied in acetonitrile. Results are compared to previous work on this molecule in the fingerprint region. Finally, several partially completed projects and their implications are discussed. These include the two photon absorption of Coumarin 120, nanoconfinement in cyclodextrin cavities and sensitization of titania nanoparticles.

Blom, Alex Jason

2009-08-01

379

Spectroscopic study of polyphenylquinolines—materials with efficient intramolecular charge transfer  

NASA Astrophysics Data System (ADS)

The energy structure and nature of intramolecular charge transfer have been determined for a series of synthesized 2,6-polyphenylquinolines (PPQs) containing resorcinol, oxygen, and phenylamine bridging groups between phenylquinoline cycles and possessing an arylene radical in the form of alkylated derivatives of carbazole or indolo[3,2-b]carbazole, as well as arylated derivatives of carbazole with nitro- and fluorine substituents. The analysis was based on data on their absorption spectra, photosensitivity, carrier photogeneration quantum efficiency, and luminescence. It is shown that the PPQ monomeric unit is a composite intramolecular charge-transfer complex (ICTC) between the donor arylene fragment and the acceptor quinoline cycle; the latter, in turn, is an ICTC between the donor bridging group and quinoline ring (when acceptor fluorine or nitro substituents are introduced into the carbazole structure, the complex becomes ternary), and the narrowest band gap (2.3 eV) corresponds to the PPQ having a phenylamine bridging group and a fragment of indolo[3,2-b]carbazole.

Aleksandrova, E. L.; Svetlichnyi, V. M.; Myagkova, L. A.; Matyushina, N. V.; Nekrasova, T. N.; Smyslov, R. Yu.; Pautov, V. D.; Tameev, A. R.; Vannikov, A. V.; Kudryavtsev, V. V.

2013-05-01

380

Spectroscopic evidence for charge-transfer complexation in monoclonal antibodies that bind opiates.  

PubMed

Molecular complexes of four monoclonal anti-morphine antibodies (mAb) with the opiate ligands morphine, oxymorphone, and naloxone were studied using UV-VIS absorption spectroscopy. Although strong overlaps in the absorption spectra of the antibodies, ligands, and complexes were observed, a curve-fitting method was developed to correlate the absorbance with the concentration of the ligand-antibody complex. Using this technique, we determined the intrinsic association constants for the mAb with morphine to be in the nanomolar range, while association constants for oxymorphone and naloxone were in the micromolar range. These values were found to be in agreement with previous radioimmunoassay determinations. We also observed different changes in the absorbancy of the mAb upon complexation with different ligands and such changes were found to be different for all four mAb examined. Upon complexation with the ligand morphine, two of the mAb (clone numbers MOR368-21 and MOR10.5) displayed distinct charge-transfer spectral bands in the 320-nm region. These observations suggest that mAb binding site tryptophans may participate in the formation of the antibody-ligand complex and such complexation involves a charge-transfer interaction. PMID:7945792

Droupadi, P R; Meyers, E A; Linthicum, D S

1994-04-01

381

A two-state model of twisted intramolecular charge-transfer in monomethine dyes  

NASA Astrophysics Data System (ADS)

A two-state model Hamiltonian is proposed, which can describe the coupling of twisting displacements to charge-transfer behavior in the ground and excited states of a general monomethine dye molecule. This coupling may be relevant to the molecular mechanism of environment-dependent fluorescence yield enhancement. The model is parameterized against quantum chemical calculations on different protonation states of the green fluorescent protein chromophore, which are chosen to sample different regimes of detuning from the cyanine (resonant) limit. The model provides a simple yet realistic description of the charge transfer character along two possible excited state twisting channels associated with the methine bridge. It describes qualitatively different behavior in three regions that can be classified by their relationship to the resonant (cyanine) limit. The regimes differ by the presence or absence of twist-dependent polarization reversal and the occurrence of conical intersections. We find that selective biasing of one twisting channel over another by an applied diabatic biasing potential can only be achieved in a finite range of parameters near the cyanine limit.

Olsen, Seth; McKenzie, Ross H.

2012-10-01

382

Label-Free Acetylcholine Image Sensor Based on Charge Transfer Technology for Biological Phenomenon Tracking  

NASA Astrophysics Data System (ADS)

A 32 × 32 charge-transfer enzyme-type acetylcholine (ACh) image sensor array was produced for label-free tracking of images of ACh distribution and its performance in repeatable measurements without enzyme deactivation was examined. The proposed sensor was based on a charge-transfer-type pH image sensor, which was modified using an enzyme membrane (acetylcholine esterase, AChE) for each pixel. The ACh image sensor detected hydrogen ions generated by the ACh--AChE reaction. A polyion complex membrane composed of poly(L-lysine) and poly(4-styrenesulfonate) was used to immobilize the enzyme on the sensor. The improved uniformity and adhesion of the polyion complex membrane were evaluated in this study. As a result, temporal and spatial fluctuations of the ACh image sensor were successfully minimized using this approach. The sensitivity of the sensor was 4.2 mV/mM, and its detection limit was 20 ?M. In five repeated measurements, the repeatability was 8.8%.

Takenaga, Shoko; Tamai, Yui; Okumura, Koichi; Ishida, Makoto; Sawada, Kazuaki

2012-02-01

383

Ligand-ligand charge-transfer excited states of Os(II) complexes  

SciTech Connect

This paper examines the photophysics of metal-to-ligand charge-transfer (MLCT) and ligand-to-ligand charge-transfer (LLCT) excited states in a series of ((bpy){sub 2}Os{sup II}(CO)L){sup 2+} (Os-L) complexes. For each of the complexes studied, the d{pi}(Os) {yields} {pi}*(bpy) absorption band is the lowest energy transition that is apparent. For L = pyridine and benzonitrile, only long-lived, highly luminescent MLCT states are observed. However, when L = an electron-donor aminobenzonitrile (ABN) species (DMABN, TMABN, or CMI; see text), MLCT emission is quenched and in < 30 ps LLCT excited states are formed, *((bpy{sup {sm bullet}{minus}})-(bpy)OS{sup II}(CO)ABN{sup {sm bullet}+}){sup 2+}. The observed, weight-average radiationless decays of the LLCT excited states in acetonitrile and dichloromethane follow the squence Os-DMABN < Os-TMABN < Os-CMI in each solvent, and the calculated energies of the LLCT states for these complexes are in inverse order to the decay rates as expected if an energy gap law is followed. Finally, multiexponential relaxations of the LLCT states are pronounced in the nonpolar solvent dichloromethane. The dependence of these relaxations on the concentration of added electrolyte suggests that they may be due to ion-pair structure and dynamics.

Perkins, T.A.; Schanze, K.S. (Univ. of Florida, Gainesville (USA)); Pourreau, D.B.; Netzel, T.L. (Amoco Research Corp., Naperville, IL (USA))

1989-06-01

384

The role of solvation effects in the growth of TCNQ-based charge-transfer salts  

NASA Astrophysics Data System (ADS)

Combining various microscopic techniques (VLM, SEM, STXM) we were able to investigate the growth TCNQ-based charge transfer salts nanocrystals in the wet chemical route. The results unambiguously show the impact of diffusion processes on the formation of Ag-TCNQ nanocrystals to support a modified mechanism for crystal formation. TCNQ-based charge transfer salts represent an attractive class of materials for utilisation in nanoscaled electronic devices. Detailed knowledge about the formation of metal-TCNQ salts is essential to control the growth of well-defined nanostructures. Silver template patterns were used to define well-ordered Ag-TCNQ structures. A comprehensive microscopic and spectroscopic investigation was conducted to examine the growth mechanism in wet-chemical environment in detail. Scanning electron microscopy (SEM) disclosed the overall morphology of the fabricated nanostructures while Scanning Transmission X-Ray Microscopy (STXM) provided insight into the chemical behaviour of the metal cation during the growth. The experimental results give clear evidence that solvation and diffusion of the metal counter ions controls the growth of well-defined metal-TCNQ nanocrystals.

Rösner, Benedikt; Späth, Andreas; Fink, Rainer H.

2013-10-01

385

Utilizing Metal to Ligand Charge Transfer States of MM Quadruply Bonded Complexes for Photovoltaic Applications  

NASA Astrophysics Data System (ADS)

In this contribution, we report two examples of our efforts to develop MM quadruply bonded complexes for photovoltaic applications. In the first example, evidence, based on femtosecond transient absorption and time resolved infrared spectroscopy, is presented for photoinduced charge transfer from the Mo_{2}? orbital of the quadruply bonded molecule trans-Mo_{2}(TiPB)_{2}BTh)_{2}, where TiPB = 2,4,6-triisopropyl benzoate and BTh = 2,2'-bithienylcarboxylate, to di-n-octyl perylene diimide and di-n-hexylheptyl perylene diimide in thin films and solutions of the mixtures. In the second example, the structural and photophysical properties of the new compounds trans-M_{2}(TiPB)_{2}(L)_{2} and trans-M_{2}(TiPB)_{2}(L')_{2}, where M=Mo or W and L and L' are triphenylamine-cyanoacrylate ligands are presented. These ligands promote intense metal to ligand charge transfer transitions that span the range 550 to 1100 nm. The excited states have been studied by transient absorption and time resolved infrared spectroscopy

Lewis, Sharlene A.; Brown-Xu, Samantha E.; Chisholm, Malcolm H.; Epstein, Arthur J.

2013-06-01

386

Radiative charge transfer and radiative association in He{sup +}+ Ne collisions  

SciTech Connect

A fully quantum-mechanical approach is utilized to study the collision process of He{sup +} with neutral neon, and the radiative charge transfer (RCT) and radiative association (RA) cross sections are presented in the energy range from 0.08 meV to 1 eV, while the optical potential and semiclassical methods are adopted to calculate the total radiative decay cross sections for energies from 0.08 meV to 5 keV. The potential energy curves and dipole transition matrix elements are obtained by an ab initio multireference configuration interaction package. For the related three lowest X {sup 2{Sigma}+}, A {sup 2{Pi}}, and B {sup 2{Sigma}+} states, the spectroscopic data are in good agreement with other theoretical calculations and experimental measurements. Our results indicate that the RCT cross section is much larger than the nonradiative charge transfer cross section for collision energy E < 20 eV, and when E > 40 eV, the nonradiative process becomes dominant. Especially, we found that in the present collision system the RA process is more important than the RCT process when E < 1 meV. The RCT and RA rate coefficients are also given for temperatures from 1 to 4 x10{sup 3} K.

Liu, X. J.; Xiao, B. J. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Qu, Y. Z.; Zhou, Y. [College of Material Sciences and Optoelectronic Technology, Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Liu, C. H.; Wang, J. G. [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Buenker, R. J. [Fachbereich C-Mathematik und Naturwissenschaften, Bergische Universitaet Wuppertal, D-42097 Wuppertal (Germany)

2010-02-15

387

Energy and Charge State Dependencies of Transfer Ionization and Single Capture  

NASA Astrophysics Data System (ADS)

Investigation of the charge state and energy dependencies of Transfer Ionization (TI) and Single Capture (SC) processes are being completed for Fluorine ions and are being extended to Silicon ions. The collision systems reported here are F^(4-9)+ and Si^(12-14)+ ions interacting with Helium. The measurements are being made for beam energies between 0.5 to 2.5 MeV/u and using a supersonic He jet with two-stage collimation. A recoil ion momentum spectrometer is used to separate TI and SC by recording the longitudinal momentum transfer and time-of-flight of each recoil ion. A magnetic field is used to control the position of the recoil ions on the detector. The ratios of TI to SC are determined with high accuracy. Furthermore, total cross-sections for the bare and hydrogen like Fluorine ions are determined by using previously measured charge exchange cross-sections.^1 SC and TI for higher Z-ions are also under investigation. This work is supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Research, Office of Science, U.S. Department of Energy. *Present address: Institute for Plasma Research, Bhat, Gandhinagar 382428 India [1] T. R. Dillingham, J. R. Macdonald, and P. Richard, Phys. Rev. A 24, 1237 (1981)

Ünal, R.; Richard, P.; Ben-Itzhak, I.; Cocke, C. L.; Singh, M. J.; Tawara, H.; Woody, N.

2001-05-01

388

Synthesis and characterization of highly conductive charge-transfer complexes using positron annihilation spectroscopy  

NASA Astrophysics Data System (ADS)

Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid (Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl4), iodine, bromine, and zinc chloride (ZnCl2) have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihilation lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors ?-acceptors (Pi-OH and QL), ?-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl4 and ZnCl2) were covered. The results of elemental analysis indicated that the CT complexes were formed with ratios 1:1 and 1:2 for QL, SnCl4, and ZnCl2 acceptors and iodine, Pi-OH, and Br2 acceptors, respectively. The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behavior of both items. The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, and the power of acceptors. The correlation between these parameters and the molecular weight and biological activities of studied complexes was also observed. Regarding the electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal (Aspergillus flavus and Candida albicans) activities.

Adam, Abdel Majid A.; Refat, Moamen S.; Sharshar, T.; Heiba, Z. K.

389

Resolving photo-induced twisted intramolecular charge transfer with vibrational anisotropy and TDDFT.  

PubMed

The interplay between reaction environment and photochemical outcome has wide ranging implications for designing and directing light driven chemical conversions. We present a detailed mechanistic description of photoisomerization in julolidine malononitrile (JDMN) as the first step to characterizing this interplay between reaction pathways and reaction environment. We have used polarization resolved UV pump-mid-IR probe spectroscopy and time dependent DFT calculations to investigate the dynamics of charge transfer induced intramolecular rotation in JDMN. We have probed the mechanism and dynamics of photoisomerization with the symmetric and antisymmetric CN-stretch of the malononitrile group. These measurements show the S1 electronic excited state relaxes with a 12.3 ps time constant by isomerizing around both the C-C single and C-C double bond of the malononitrile group with a branching ratio of 1:5. Isomerization around the single bond leads to the formation of a metastable twisted excited state, while isomerization around the double bond leads to excited state quenching via a conical intersection between the S1 and S0 electronic states. We have characterized the electronic and nuclear structure of the long-lived excited state with pump-probe anisotropy measurements and time dependent DFT calculations using the CAM-B3LYP functional and the 6-31G(d,p) basis set. These calculations further confirm that isomerization around the malononitrile single bond forms a twisted intermolecular charge transfer excited state. PMID:22934677

Zhang, Wenkai; Lan, Zhenggang; Sun, Zheng; Gaffney, Kelly J

2012-09-12

390

Charge transfer and mixed-valence behavior in phtalocyanine-dimer cations.  

PubMed

Phtalocyanine compounds deserved a considerable interest in recent times, particularly because of their possible use in the field of nanoelectronics. In particular, the charge mobility (of both electrons and holes) in phtalocyanine stacked arrangements has been recently extensively investigated. The present work focuses on the study of the hole-transfer mechanism between two phtalocyanine monomers. For an interdisk distance larger than 4.5 bohrs, the eclipsed dimer exhibits a mixed-valence behavior, with a saddle point transition state separating two equivalent minima. This behavior, however, is strongly dependent on the relative angle between the disks. In particular, the mixed-valence character of the compound is strongly enhanced for arrangements that are far from the eclipsed geometry. Moreover, for values of the angle close to ?/8 and 3?/8, the ground and excited transition states have exactly the same energy, thus implying the presence of a conical intersection. These results can have deep implication in the charge transfer along phtalocyanine chains. PMID:20886926

Monari, Antonio; Evangelisti, Stefano; Leininger, Thierry

2010-09-28

391

Interplay between excited-state intramolecular proton transfer and charge transfer in flavonols and their use as protein-binding-site fluorescence probes.  

PubMed Central

A comparative study is presented of competitive fluorescences of three flavonols, 3-hydroxyflavone, 3,3',4',7-tetrahydroxyflavone (fisetin), and 4'-diethylamino-3-hydroxyflavone (DHF). The normal fluorescence S1-->S0 (400-nm region) is largely replaced by the proton-transfer tautomer fluorescence S'1-->S'0 in the 550-nm region for all three of the flavonols in aprotic solvents at room temperature. For DHF in polar solvents the normal fluorescence becomes a charge-transfer fluorescence (460-500 nm) which competes strongly with the still dominant proton-transfer fluorescence (at 570 nm). In protic solvents, and at 77 K, the interference with intramolecular hydrogen bonding gives rise to greatly enhanced normal fluorescence, lowering the quantum yield of proton-transfer fluorescence. The utility of DHF as a discriminating fluorescence probe for protein binding sites is suggested by the strong dependence of the charge-transfer fluorescence on polarity of the environment and by various static and dynamic parameters of the charge-transfer and proton-transfer fluorescence which can be determined.

Sytnik, A; Gormin, D; Kasha, M

1994-01-01

392

Unified approach to multipolar polarisation and charge transfer for ions: microhydrated Na(+).  

PubMed

Electrostatic effects play a large part in determining the properties of chemical systems. In addition, a treatment of the polarisation of the electron distribution is important for many systems, including solutions of monatomic ions. Typically employed methods for describing polarisable electrostatics use a number of approximations, including atom-centred point charges and polarisation methods that require iterative calculation on the fly. We present a method that treats charge transfer and polarisation on an equal footing. Atom-centred multipole moments describe the charge distribution of a chemical system. The variation of these multipole moments with the geometry of the surrounding atoms is captured by the machine learning method kriging. The interatomic electrostatic interaction can be computed using the resulting predicted multipole moments. This allows the treatment of both intra- and interatomic polarisation with the same method. The proposed method does not return explicit polarisabilities but instead, predicts the result of the polarisation process. An application of this new method to the sodium cation in a water environment is described. The performance of the method is assessed by comparison of its predictions of atomic multipole moments and atom-atom electrostatic interaction energies to exact results. The kriging models are able to predict the electrostatic interaction energy between the ion and all water atoms within 4 kJ mol(-1) for any of the external test set Na(+)(H2O)6 configurations. PMID:24064799

Mills, Matthew J L; Hawe, Glenn I; Handley, Christopher M; Popelier, Paul L A

2013-10-01

393

Spontaneous redox synthesis of the charge transfer material TTF4[SVMo11O40].  

PubMed

The charge-transfer material TTF-SV(IV)Mo(11)O(40) (TTF = tetrathiafulvalene) was prepared by a spontaneous redox reaction between TTF and the vanadium-substituted polyoxometalate (n-Bu(4)N)(3)[SV(V)Mo(11)O(40)] in both solution and solid state phases. Single crystal X-ray diffraction gave the stoichiometry TTF(4)[SVMo(11)O(40)]·2H(2)O·2CH(2)Cl(2), with the single V atom positionally disordered with eight Mo atoms over the whole ?-Keggin polyanion [SVMo(11)O(40)](4-). Raman spectra support the 1+ charge assigned to the oxidized TTF deduced from bond lengths, and elemental and voltammetric analysis also are consistent with this formulation. Scanning electron microscopy images showed a rod-type morphology for the new charge-transfer material. The conductivity of the solid at room temperature is in the semiconducting range. The TTF and (n-Bu(4)N)(3)[SV(V)Mo(11)O(40)] solids also undergo a rapid interfacial reaction, as is the case with TTF and TCNQ (TCNQ = tetracyanoquinodimethane) solids. EPR spectra at temperatures down to 2.6 K confirm the presence of two paramagnetic species, V(IV) and the oxidized TTF radical. Spectral evidence shows that the TTF-SV(IV)Mo(11)O(40) materials prepared from either solution or solid state reactions are equivalent. The newly isolated TTF-SV(IV)Mo(11)O(40) material represents a new class of TTF-polyoxometalate compound having dual electrical and magnetic functionality derived from both the cationic and anionic components. PMID:23146046

Li, Qi; Lu, Jinzhen; Boas, John F; Traore, Daouda A K; Wilce, Matthew C J; Huang, Fuzhi; Martin, Lisandra L; Ueda, Tadaharu; Bond, Alan M

2012-11-12

394

Photophysical investigations on supramolecular fullerene/phthalocyanine charge transfer interactions in solution.  

PubMed

The photophysical features of non-covalently linked fullerenes C60 and C70 with a designed free-base phthalocyanine, namely, 2,3,9,10,16,17,23,24-octakis-(octyloxy)-29H,31H-phthalocyanine (1) have been investigated employing various spectroscopic tools like UV-vis absorption spectrophotometry, steady state and time resolved fluorescence along with proton NMR measurements in toluene. The ground state interaction between fullerenes and 1 is nicely demonstrated with the appearance of well defined charge transfer absorption bands in the visible region of the electronic spectra. Steady state fluorescence experiment reveals efficient quenching of the excited singlet state of 1 in presence of both C60 and C70. The average values of binding constants for the non-covalent complexes of C60 and C70 with 1 are determined to be ?18,150 and ?32,000dm(3)mol(-1), respectively. The magnitude of K suggests that 1 preferentially binds C70 in comparison to C60 although average value of selectivity in binding is measured to be low (?1.75). Time resolved emission measurements establish photoinduced energy transfer from the excited singlet state of 1 to fullerene in toluene. Measurements of free energy of electron transfer and free energy of radical ion-pair formation elicit that C70/1 complex is stabilized more in comparison to C60/1 complex regarding generation of charge-separated state. Proton NMR studies provide very good support in favor of effective ground state complexation between fullerenes and 1. Semi empirical theoretical calculations on fullerene/1 systems in vacuo substantiate the stronger binding between C70 and 1 in comparison to C60/1 system in terms of heat of formation value of the respective complexes, and determine the orientation of bound guest (here C70) towards the plane of 1 during complexation. PMID:24128922

Ray, Anamika; Pal, Haridas; Bhattacharya, Sumanta

2013-08-31

395

Influences of molecular packing on the charge mobility of organic semiconductors: from quantum charge transfer rate theory beyond the first-order perturbation.  

PubMed

The electronic coupling between adjacent molecules is an important parameter for the charge transport properties of organic semiconductors. In a previous paper, a semiclassical generalized nonadiabatic transition state theory was used to investigate the nonperturbative effect of the electronic coupling on the charge transport properties, but it is not applicable at low temperatures due to the presence of high-frequency modes from the intramolecular conjugated carbon-carbon stretching vibrations [G. J. Nan et al., J. Chem. Phys., 2009, 130, 024704]. In the present paper, we apply a quantum charge transfer rate formula based on the imaginary-time flux-flux correlation function without the weak electronic coupling approximation. The imaginary-time flux-flux correlation function is then expressed in terms of the vibrational-mode path average and is evaluated by the path integral approach. All parameters are computed by quantum chemical approaches, and the mobility is obtained by kinetic Monte-Carlo simulation. We evaluate the intra-layer mobility of sexithiophene crystal structures in high- and low-temperature phases for a wide range of temperatures. In the case of strong coupling, the quantum charge transfer rates were found to be significantly smaller than those calculated using the weak electronic coupling approximation, which leads to reduced mobility especially at low temperatures. As a consequence, the mobility becomes less dependent on temperature when the molecular packing leads to strong electronic coupling in some charge transport directions. The temperature-independent charge mobility in organic thin-film transistors from experimental measurements may be explained from the present model with the grain boundaries considered. In addition, we point out that the widely used Marcus equation is invalid in calculating charge carrier transfer rates in sexithiophene crystals. PMID:21503350

Nan, Guangjun; Shi, Qiang; Shuai, Zhigang; Li, Zesheng

2011-04-18

396

Characterization of charge transfer processes inself-assembled monolayers by high-pressure electrochemical techniques  

SciTech Connect

Here we report the first high-pressure investigation of redox processes in surface-confined monolayers. We have explored the electrochemical behavior of ferrocene-terminated self-assembled monolayers (SAMs) on gold electrodes immersed in aqueous solutions containing 1M NaClO{sub 4}. Electron-transfer reaction for ferrocene in the monolayer is restricted with the application of pressure, whereas the same reaction for ferrocene in solution is not. The dependence of the cyclic voltammetric peak redox potentials on pressure reveals that the oxidation of the ferrocene within the monolayer becomes thermodynamically and kinetically more difficult at high pressures. At pressures above 1-2 kbar, positive volumes of reaction are associated with the oxidation process, indicating that the oxidation step involves an increase in volume. Different monolayer samples, exhibiting different voltammetric responses, appear to impose different volume constraints on the charge transfer reaction and, therefore, present different pressure responses within a general common trend. These results point out the importance of structural and environmental effects, via steric constraints, on electron transfer processes in surface-confined monolayer assemblies. 36 refs., 7 figs., 6 tabs.

Cruanes, M.T.; Drickamer, H.G.; Faulkner, L.R. [Univ. of Illinois, Urbana, IL (United States)

1995-10-01

397

Photoinduced charge transfer properties of bolaamphiphile membrane-gramicidrin diad composites  

NASA Astrophysics Data System (ADS)

Ether-linked bolaform amphiphiles (Langmuir 1992 8, 637; J. Am. Chem. Soc. 1992, 9035) and novel gramicidin-porphyrin `diads' (MRS Symposium Series, Vol. 277, 1992, 93) have been synthesized. Protocols for vectorial insertion of the derivatized gramicidins into bolaform lipid vesicles have been developed and the photochemical behavior of these proteinaceous composite membranes probed in the presence of electron donors and acceptors. Photoinduced electron transfer properties of the gramicidin-porphyrin conjugates were compared in TRIS- buffered dihexadecyl-phosphate bilayer (DHP) and bolaform monolayer membrane vesicles containing dithiothreitol as sacrificial donor and methyl viologen as electron acceptor on both the inner and outer vesicle surfaces. Although the rates of methyl viologen photoreduction varied depending on the mode of diad orientation within DHP bilayer membranes, photoreduction rates were not orientation- dependent in bolaform membrane vesicles containing the gramicidin-porphyrin diad. The relevance of these results on vectorial electron transfer processes in lamellar systems and the design of integrated charge transfer components is discussed.

Thompson, David H.; Kim, Jong-Mok; di Meglio, Ciro

1993-04-01

398

Coarse-grained time-dependent density functional simulation of charge transfer in complex systems: application to hole transfer in DNA.  

PubMed

We present a coarse-grained tight-binding method based on density functional theory (DFT) for the simulation of charge transfer in complex materials. The charge-transfer parameters are computed using a fragment-orbital approach combined with the approximative DFT method self-consistent charge density functional tight binding (SCC-DFTB), which allows to follow the dynamics of excess charge along nanosecond MD trajectories, still accounting for the important impact of structural fluctuations and solvent effects. Since DFT suffers from the self-interaction error, which would lead to a delocalization of the hole charge over the entire system, we study the effect of an empirical self-interaction correction in detail. The wave function of the excess charge is propagated within the framework of time-dependent DFT, where the electron (hole) and the atomic system are propagated simultaneously according to the derived coupled equations of motion. In the case of DNA, the solvent polarization effects are a dominant factor affecting the hole transport. The hole charge polarizes the surrounding water, which in turn supports a localization of the hole charge--a water polaron is formed, extended dynamically over several nucleobases. As this polarization of water accompanies the migrating hole, the motion of hole is significantly slowed down due to the solvent reorganization energy involved. The estimated hopping rate between neighboring adenines in poly(A)-DNA is in the order of 100 ns(-1), and our simulations clearly show that the charge transfer occurs in a nonadiabatic fashion, due to the small average electronic coupling of around 0.06 eV. PMID:20687528

Kubar, Tomás; Elstner, Marcus

2010-09-01

399

Magneto-Dielectric Effects Induced by Optically-Generated Intermolecular Charge-Transfer States in Organic Semiconducting Materials  

PubMed Central

Traditionally, magneto-dielectric effects have been developed by combining ferroelectric and magnetic materials. Here, we show a magneto-dielectric effect from optically-generated intermolecular charge-transfer states in an organic semiconducting donor:acceptor (PVK:TCNB) system. We observe in magnetic field effects of photoluminescence that a magnetic field can change singlet/triplet population ratio in intermolecular charge-transfer states. Furthermore, our theoretical analysis and experimental evidence indicate that the singlets and triplets in charge-transfer states have stronger and weaker electrical polarizations, respectively. Therefore, the observed magneto-dielectric effect can be attributed to magnetically-dependent singlet/triplet ratio in intermolecular charge-transfer states. In principle, a magneto-dielectric effect can be generated through two different channels based on magneto-polarization and magneto-current effects when the singlet/triplet ratio in intermolecular charge-transfer states is changed by a magnetic field. We find, from the simulation of dielectric effects, that magneto-polarization and magneto-current effects play primary and secondary roles in the generation of magneto-dielectric effect.

Zang, Huidong; Yan, Liang; Li, Mingxing; He, Lei; Gai, Zheng; Ivanov, Ilia; Wang, Min; Chiang, Long; Urbas, Augustine; Hu, Bin

2013-01-01

400

Direct observation and control of ultrafast photoinduced twisted intramolecular charge transfer (TICT) in triphenyl-methane dyes.  

PubMed

Femtosecond time-resolved infrared spectroscopy was employed to study intramolecular charge transfer in triphenylmethane dyes, including malachite green (MG), malachite green carbinol base (MGCB), and leucomalachite green (LMG). A local excited state (LE) and a twisted intramolecular charge-transfer (TICT) state have been observed directly in MG. Furthermore, solvent-controlled TICT measurements in a series of linear alcohols indicate that the transition time (4-11 ps) from LE to TICT is strongly dependent on alcohol viscosity, which is due to rotational hindrance of dimethylaniline in high-viscosity solvents. For LMG, no TICT is observed due to steric hindrance caused by the sp(3)-hybridized central carbon atom. However, for MGCB, TICT is rescued by the addition of the electron-donating hydroxyl group to the bridge. These results for MG and its analogues provide new insight regarding the dynamics and mechanism of twisted intramolecular charge transfer (TICT) in triphenylmethane dyes. PMID:23009668

Li, Guifeng; Magana, Donny; Dyer, R Brian

2012-10-09

401

Direct Observation and Control of Ultrafast Photoinduced Twisted Intramolecular Charge Transfer (TICT) in Triphenyl-Methane Dyes  

PubMed Central

Femtosecond time-resolved infrared spectroscopy was employed to study intramolecular charge transfer in triphenylmethane dyes, including malachite green (MG), malachite green carbinol base (MGCB), and leucomalachite green (LMG). A local excited state (LE) and a twisted intramolecular charge-transfer (TICT) state have been observed directly in MG. Furthermore, solvent-controlled TICT measurements in a series of linear alcohols indicate that the transition time (4–11 ps) from LE to TICT is strongly dependent on alcohol viscosity, which is due to rotational hindrance of dimethylaniline in high-viscosity solvents. For LMG, no TICT is observed due to steric hindrance caused by the sp3-hybridized central carbon atom. However, for MGCB, TICT is rescued by the addition of the electron-donating hydroxyl group to the bridge. These results for MG and its analogues provide new insight regarding the dynamics and mechanism of twisted intramolecular charge transfer (TICT) in triphenylmethane dyes.

Li, Guifeng; Magana, Donny; Dyer, R. Brian

2012-01-01

402

Charge transfer and weak chemisorption of oxygen molecules in nanoporous carbon consisting of a disordered network of nanographene sheets  

NASA Astrophysics Data System (ADS)

The adsorption/desorption processes of oxygen are investigated in nanoporous carbon (activated carbon fiber (ACF)) consisting of a disordered network of nanographene sheets. The heat-induced desorption at 200 °C shows the decomposition of oxygen-including functional groups weakly bonded to nanographene edges. The removal of these oxygen-including negatively charged functional groups brings about a change in the type of majority carriers, from holes to electrons, through charge transfer from the functional groups to the interior of nanographene sheets. The oxygen adsorption brings ACF back to the electronic state with holes being majority carriers. In this process, a large concentration of negatively charged O2? - molecules with ? ~ 0.1 are created through charge transfer from nanographene sheets to the adsorbed oxygen molecules. The changes in the thermoelectric power and the electrical resistance in the oxygen desorption process is steeper than that in the oxygen adsorption process. This suggests the irreversibility between the two processes.

Sumanasekera, G. U.; Chen, G.; Takai, K.; Joly, J.; Kobayashi, N.; Enoki, T.; Eklund, P. C.

2010-08-01

403

Charge transfer and weak chemisorption of oxygen molecules in nanoporous carbon consisting of a disordered network of nanographene sheets.  

PubMed

The adsorption/desorption processes of oxygen are investigated in nanoporous carbon (activated carbon fiber (ACF)) consisting of a disordered network of nanographene sheets. The heat-induced desorption at 200?°C shows the decomposition of oxygen-including functional groups weakly bonded to nanographene edges. The removal of these oxygen-including negatively charged functional groups brings about a change in the type of majority carriers, from holes to electrons, through charge transfer from the functional groups to the interior of nanographene sheets. The oxygen adsorption brings ACF back to the electronic state with holes being majority carriers. In this process, a large concentration of negatively charged O(2)(?-) molecules with ? ? 0.1 are created through charge transfer from nanographene sheets to the adsorbed oxygen molecules. The changes in the thermoelectric power and the electrical resistance in the oxygen desorption process is steeper than that in the oxygen adsorption process. This suggests the irreversibility between the two processes. PMID:21386498

Sumanasekera, G U; Chen, G; Takai, K; Joly, J; Kobayashi, N; Enoki, T; Eklund, P C

2010-08-04

404

Atomic data for neutron-capture elements. III. Charge transfer rate coefficients for low-charge ions of Ge, Se, Br, Kr, Rb, and Xe  

NASA Astrophysics Data System (ADS)

We present total and final-state resolved charge transfer (CT) rate coefficients for low-charge Ge, Se, Br, Kr, Rb, and Xe ions reacting with neutral hydrogen over the temperature range 102-106 K. Each of these elements has been detected in ionized astrophysical nebulae, particularly planetary nebulae. CT rate coefficients are a key ingredient for the ionization equilibrium solutions needed to determine total elemental abundances from those of the observed ions. A multi-channel Landau Zener approach was used to compute rate coefficients for projectile ions with charges q = 2-5, and for singly-charged ions the Demkov approximation was utilized. Our results for five-times ionized species are lower limits, due to the incompleteness of level energies in the NIST database. In addition, we computed rate coefficients for charge transfer ionization reactions between the neutral species of the above six elements and ionized hydrogen. The resulting total and state-resolved CT rate coefficients are tabulated and available at the CDS. In tandem with our concurrent investigations of other important atomic processes in photoionized nebulae, this work will enable robust investigations of neutron-capture element abundances and nucleosynthesis via nebular spectroscopy. Tables 4 and 5 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/535/A117

Sterling, N. C.; Stancil, P. C.

2011-11-01

405

Ultrafast intramolecular charge transfer and dual fluorescence of dimethylamino-substituted triphenylphosphines in polar solvents  

SciTech Connect

Dimethylamino-substituted triphenylphosphines show a dual fluorescence in polar solvents. The strong red-shift of the new fluorescence band in solvents of increasing polarity indicates emission from a species of charge transfer character, by analogy with dimethylaminobenzonitrile. In this study, we give evidence for the fast formation of a polar transient species in the first excited state of substituted triphenylphosphines, by picosecond time-resolved fluorescence and transient absorption spectroscopy. The risetime of the long wavelength fluorescence band is slowed down in solvents of decreasing polarity, and when the number of dimethylamino substituents increases. Furthermore, time-resolved transient absorption spectra show the rise of a new transient absorption band in polar solvents which has a profile similar to that of the dimethylaniline cation radical.

Changenet, P.; Plaza, P.; Martin, M. M.; Meyer, Y. H.; Rettig, W. [Laboratoire de Photophysique Moleculaire du CNRS (UPR 3361), Bat 213, universite Paris-Sud, 91405 Orsay (France); Institute fuer Physikalische und Theoretische Chemie der Humboldt-Universitaet Berlin, Bunsenstr. 1, D-10117 Berlin (Germany)

1996-04-01

406

Strong intramolecular charge transfer emission in benzobisoxazole cruciforms: solvatochromic dyes as polarity indicators.  

PubMed

A photophysical study was carried out on a series of nine X-shaped cross-conjugated compounds based on the benzobisoxazole nucleus. These "molecular cruciforms" were terminally substituted with electron-rich 4-(N,N-dimethylamino)phenyl, electron-neutral phenyl or electron-poor 4-pyridyl groups. Intramolecular charge transfer (ICT) transitions in molecular cruciforms were shown to be activated to a different extent by the combinations of these substituents located in different positions along vertical and/or horizontal axes of the molecules, showing strong emission throughout the visible spectrum. The high fluorescence efficiency and bathochromic shifts associated with the increasing polarity of the solvent make these cruciforms interesting candidates for use as fluorescence polarity indicators operating in a broad solvatochromic range. PMID:24061066

Martínez-Martínez, Virginia; Lim, Jaebum; Bañuelos, Jorge; López-Arbeloa, Iñigo; Miljani?, Ognjen Š

2013-10-01

407

Modulating Charge Transfer Through Cyclic D,L ?-Peptide Self-Assembly  

PubMed Central

We describe a concise solid support-based synthetic method for the preparation of cyclic D,L ?-peptides bearing 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) side chains. Studies of the structural and photoluminescence properties of these molecules in solution show that the hydrogen bond directed self-assembly of the cyclic D,L ?-peptide backbone promotes intermolecular NDI excimer formation. The efficiency of NDI charge transfer in the resulting supramolecular assemblies is shown to depend on the length of the linker between the NDI and the peptide backbone, the distal NDI substituent, and the number of NDIs incorporated in a given structure. The design rationale and synthetic strategies described here should provide a basic blueprint for a series of self-assembling cyclic D,L ?-peptide nanotubes with interesting optical and electronic properties.

Horne, W. Seth; Ashkenasy, Nurit; Ghadiri, M. Reza

2007-01-01

408

Multifaceted ultrafast intramolecular charge transfer dynamics of 4-(dimethylamino)benzonitrile (DMABN).  

PubMed

Intramolecular charge transfer (ICT) of DMABN has been the subject of extensive investigations. Through the measurements of highly time-resolved fluorescence spectra (TRFS) over the whole emission region, we have examined the ICT dynamics of DMABN in acetonitrile free from the solvation dynamics and vibronic relaxation. The ICT dynamics was found to be characterized by a broad range of time scales; nearly instantaneous (<30 fs), 160 fs, and 3.3 ps. TRFS revealed that an ICT state with partially twisted geometry, ICT(P), is formed within a few hundred femtoseconds either directly from the initial photoexcited state or via the locally excited (LE) state. The ICT(P) state undergoes further relaxation along the intramolecular nuclear coordinate to reach the twisted ICT (TICT) state with the time constant of 4.8 ps. A conformational diversity along the rotation of the dimethylamino group was speculated to account for the observed diffusive dynamics. PMID:23249244

Park, Myeongkee; Kim, Chul Hoon; Joo, Taiha

2013-01-03

409

Spectrophotometric determination of bisoprolol in pharmaceutical preparations by charge transfer reactions  

NASA Astrophysics Data System (ADS)

A simple, rapid and sensitive method for the spectrophotometric determination, of bisoprolol was developed. The proposed methods were based on the charge-transfer reactions of bisoprolol, as n-electron donor, with 7,7,8,8-tetracyanoqumodimethane (TCNQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as ?-acceptors to give highly colored complexes. The proposed methods were validated according to the ICH guidelines with respect to linearity, limit of detection, limit of quantification, accuracy, precision, recovery and specificity. Beer's law is obeyed over the concentration ranges of 10-60 and 10-80 ?g/mL bisoprolol with TCNQ and DDQ, respectively. The proposed methods were successfully applied to the assay of bisoprolol in pharmaceutical preparations.

Ulu, Sevgi Tatar; Kel, Elif

2012-06-01

410

Site-dependent donation/backdonation charge transfer at the CoPc/Ag(111) interface.  

PubMed

The organic/metal interface formed upon adsorption of cobalt(II) phthalocyanine (CoPc) molecules on a flat Ag(111) single crystal was investigated using a combination of scanning tunneling microscopy (STM) and photoemission spectroscopy (PES). A flat-lying molecular adsorption with the ? conjugated phthalocyanine ligand parallel to the substrate was found to lead to an effective molecule-substrate coupling which governs a template-guided molecular growth. A voltage polarity dependence at the cobalt ion site was emphasized and correlated with the Co 2p core level spectra evolution which sustains an interface-confined reduction effect of the cobalt oxidation state. The formation of interface dipoles was observed via monitoring the changes in the work function (WF) upon deposition. The observations are discussed on the basis of a site-dependent donation/backdonation charge transfer at the molecule-substrate interface. PMID:22931485

Toader, Marius; Shukrynau, Pavel; Knupfer, Martin; Zahn, Dietrich R T; Hietschold, Michael

2012-09-07

411

Experimental study of the asymmetric charge transfer reaction between Ar+ ions and Fe atoms.  

PubMed

We investigate the Ar(+)-Fe asymmetric charge transfer (ACT) reaction using a combination of plasma diagnostics methods and a kinetic model of the afterglow plasma, which allow monitoring of the temporal evolution of the densities of different species. The iron vapor is created inside a discharge cell by cathode sputtering; its density is measured by atomic absorption spectroscopy. The rate coefficient of the reaction is evaluated from the emission intensity decay of Fe(+)? lines pumped by the ACT process in the He-Ar-Fe and Ar-Fe afterglow plasmas. The measurements yield a rate coefficient k = 7.6( ± 3.0) × 10(-9) cm(3) s(-1) at T = 300 K. PMID:21322681

Korolov, I; Bánó, G; Donkó, Z; Derzsi, A; Hartmann, P

2011-02-14

412

[Study on fluorescence characteristics of pefloxacin based on charge transfer reaction].  

PubMed

The charge transfer complex formed between pefloxacin mesylate (PM) as the donor and tetrachlorobenzoquinone (TCQ) as the acceptor has been studied by fluorimetry. Experiment shows that PM reacted with TCQ in methanol with light and the complex was formed. Its fluorimetric intensity was stronger than that of PM and the excitation and emission peaks of the complex were red shifted to 80 nm and 60 nm, respectively. A linear calibration graph was obtained over the PM concentration from 0.05 micromol x L(-1) to 10 micromol x L(-1) with the detection limit of 0.004 micromol x L(-1) of PM. The proposed method and UV-Vis photometric method were both applied to determining the pefloxacin in the same capsules with satisfactory results. PMID:15769057

Li, Gui-zhi; Liu, Yong-ming

2004-05-01

413

Electronic absorption spectra of charge-transfer complexes based on ferrocene and polyhalohydrocarbons  

SciTech Connect

Polyhalomethanes, being as a rule strong electron acceptors, can play the role of photosensitizers of various classes of compounds including organometallic donors such as ferrocene, benchrotrene, etc. The authors found that polyhalohydrocarbons containing CHHal/sub 2/ and CHal/sub 3/ groups from with ferrocene charge-transfer complexes (CTC). Polyhalomethanes and polyhalo-2-pentenes show the highest activity in the reaction of complex formation with ferrocene. The compounds with the CBr/sub 3/ group in CTC have the highest extinction. An elongation of the alkyl chain in the molecule of polyhalogen derivatives and the presence of an additional halogen atom in the gamma position with respect to the CHal/sub 3/ group do not exert any significant influence on their CTC spectra with ferrocene.

Germanova, L.F.; Balabanova, L.V.; Kochetkova, N.S.; Nelyubin, B.V.; Shuekhgeimer, M.G.; Vasil'eva, T.T.

1986-01-10

414

Optical switching of electric charge transfer pathways in porphyrin: a light-controlled nanoscale current router.  

PubMed

We introduce a novel molecular junction based on a thiol-functionalized porphyrin derivative with two almost energetically degenerate equilibrium configurations. We show that each equilibrium structure defines a pathway of maximal electric charge transfer through the molecular junction and that these two conduction pathways are spatially orthogonal. We further demonstrate computationally how to switch between the two equilibrium structures of the compound by coherent light. The optical switching mechanism is presented in the relevant configuration subspace of the compound, and the corresponding potential and electric dipole surfaces are obtained by ab initio methods. The laser-induced isomerization takes place in two steps in tandem, while each step is induced by a two-photon process. The effect of metallic electrodes on the electromagnetic irradiation driving the optical switching is also investigated. Our study demonstrates the potential for using thiol-functionalized porphyrin derivatives for the development of a light-controlled nanoscale current router. PMID:21832723

Thanopulos, Ioannis; Paspalakis, Emmanuel; Yannopapas, Vassilios

2008-09-26

415

Second harmonic generation by charge-transfer excitons interacting with phonons  

SciTech Connect

Effects of exciton-phonon interaction on the nonlinear optical response of charge-transfer excitons (CTE) are studied in the framework of an exactly solvable model. It is found that the second order excitonic optical polarizability {beta} is modified due to the CTE-phonon interaction. For a nonresonant frequency range, where {beta} is relatively small, the change is not significant. On the contrary, in the vicinity of resonances (when the light frequency {omega}{approximately}{omega}{sub 0} or {omega}{approximately}{omega}{sub 0}/2, {omega}{sub 0} is the CTE transition frequency), the CTE-phonon interaction may remarkably diminish the value of {beta}. This should be taken into account when considering CTE systems in nonlinear optics.

Reineker, P.; Yudson, V. I.

2001-06-15

416

The effect of interfacial charge transfer on ferromagnetism in perovskite oxide superlattices  

SciTech Connect

The structural, magnetic, and electrical properties of superlattices composed of the ferromagnetic/metal La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and non-magnetic/metal La{sub 0.5}Sr{sub 0.5}TiO{sub 3} grown on (001)-oriented SrTiO{sub 3} substrates have been investigated. Using a combination of bulk magnetometry, soft x-ray magnetic spectroscopy, and scanning transmission electron microscopy, we demonstrate that robust ferromagnetic properties can be maintained in this superlattice system where charge transfer at the interfaces is minimized. Therefore, ferromagnetism can be controlled effectively through the chemical identity and the thickness of the individual superlattice layers.

Yang, F.; Gu, M.; Takamura, Y. [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, California 95616 (United States); Arenholz, E. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Browning, N. D. [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, California 95616 (United States); 3Department of Molecular and Cellular Biology, University of California, Davis, Davis, California 95616 (United States)

2012-01-01

417

Charge Transfer in Saturation Doping of Double-Wall Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Recent experimental evidences suggest that the outer tube of a double-wall carbon nanotube (DWCNT) may serve as a 'Faraday' cage (G. Chen, et al., Phys. Rev. Lett., 90, 257403 (2003)). In this presentation, we report the result of our systematic study of the effect of saturation doping of a (10,10) single-wall carbon nanotube, a (5,5)@(10,10) DWCNT, and a C_60@(10,10) peapod using DFT-based VASP computational package (G. Kresse and J. Hafner, Phys. Rev. B, 47, 558 (1993)). By comparing the resulting charge transfer of the above mentioned cases we shall provide the physics underlying the Faraday cage behavior of DWCNTs. Acknowledgments: This work was supported by the NSF (DMR-0112824) and the U.S.DOE (DE-FG02-00ER45832).

Tchernatinsky, Alexander; Jayanthi, Chakram; Sumanasekera, Gamini; Wu, Shi-Yu

2004-03-01

418

Molecular structure and vibrational spectral investigation of charge transfer NLO crystal Naphthalene Picrate for THz application  

NASA Astrophysics Data System (ADS)

Molecular structure and the vibrational spectra of Naphthalene Picrate have been calculated using density functional theoretical computation and compared with the experimental. The dipole moments (?), polarizability (?), first hyperpolarizabilities (?) second hyperpolarizability (?) and frontier molecular orbital energies are computed at the DFT level. The frontier molecular orbital calculation shows the inverse relationship of HOMO-LUMO gap with the total static hyperpolarizability. The hyperpolarizability value reveals that these classes of organic compounds show very large non-linear optical properties. Natural Bond Orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. Terahertz time-domain spectroscopy has been used to detect the absorption spectra in the frequency range from 0.2 to 1.5 THz.

Amalanathan, M.; Hubert Joe, I.; Rastogi, V. K.

2013-05-01

419

Continuous control of third-order optical nonlinearity in charge-transfer-type conjugated polymers  

NASA Astrophysics Data System (ADS)

Third-order optical nonlinearity was investigated in two charge-transfer (CT)-type conjugated polymers, poly(aryleneethynylene) and poly(thiophene-alt-thiazole), using the third-harmonic generation (THG) method. Comparison of the results with previously obtained THG data for polythiophene and the strong CT polymer poly(thiophene-alt-quinoxaline) revealed that the ratio of the maximum value of third-order nonlinear susceptibility and the absorption coefficient max|?(3)|/?max increased as the degree of CT character increased for the four polymers. This variation in max|?(3)|/?max is discussed based on the magnitude of the transition dipole moment between the one-photon-allowed and the one-photon-forbidden excited states.

Kishida, Hideo; Hirota, Keisuke; Okamoto, Hiroshi; Kokubo, Hisashi; Yamamoto, Takakazu

2008-01-01

420

Orbital localization, charge transfer, and band gaps in semilocal density-functional theory.  

PubMed

We derive an exchange energy functional of generalized gradient form with a corresponding potential that changes discontinuously at integer particle numbers. The functional is semilocal, yet incorporates key features that are connected to the derivative discontinuity of Kohn-Sham density-functional theory. We validate our construction for several paradigm systems and explain how it addresses central well-known deficiencies of antecedent semilocal methods, i.e., the description of charge transfer, properly localized orbitals, and band gaps. We find, e.g., an improved shell structure for atoms, eigenvalues that more closely correspond to ionization energies, and an improved description of band structure where localized states are lowered in energy. PMID:23909345

Armiento, R; Kümmel, S

2013-07-17

421

Quenching mechanisms of the optical centers in Eu3+-doped nanophosphors under charge transfer excitation  

NASA Astrophysics Data System (ADS)

As the size of Eu3+-doped phosphors decreases in nanoscale, the top of the valance band is elevated and the zero-phonon charge transfer (CT) energy is decreased; the rigidity of the lattice environment is decreased and the CT state (CTS) coordinate offset is enlarged. The decrease in zero-phonon CT energy and the enlargement of CTS coordinate offset mean the displacement of CTS in the configurational coordinate diagram (CCD). The CTS displacement in CCD results in the decrease in CTS feeding to the emitting 5D states and the increase in transition probability from the CTS to the 7F states, the excitation of the optical centers tends to be relaxed by sending phonons to the host lattice. Based on the quenching mechanisms of the optical centers progressively clarified in this paper, a feasible coating method is proposed to improve the luminescence efficiency for Eu3+-doped nanophosphors under CT excitation.

Shang, Chunyu; Shang, Xiaohong; Qu, Yuqiu; Li, Meicheng

2010-11-01

422

Effect of. gamma. -cyclodextrin on the intramolecular charge transfer processes in aminocoumarin laser dyes  

SciTech Connect

Steady-state and time-resolved studies on the emission properties of three 7-(diethylamino)coumarin laser dyes (I-III) in aqueous {gamma}-cyclodextrin ({gamma}-CD) solutions are reported. On addition of {gamma}-CD, fluorescence maxima of all the three dyes shift to higher energy, with a huge enhancement of the yield of intramolecular charge transfer (ICT) emission for the flexible ones (I and II) and a very slight enhancement for the rigid analogue III. The results are explained in terms of the concept of polarity-dependent twisted ICT rates. It is proposed that twisted ICT, the main nonradiative process in the excited ICT states of these dyes, is severely restricted inside the {gamma}-cyclodextrin cavity because of the reduced polarity. This is responsible for the enhancement of fluorescence from the ICT state.

Nag, A.; Chakrabarty, T.; Bhattacharyya, K. (Indian Association for the cultivation of Science, Calcutta (India))

1990-05-17

423

Dynamics of charge-transfer excited states relevant to photochemical energy conversion  

SciTech Connect

A systematic study of intramolecular photoassociation and photoinduced charge transfer (CT) was initiated in bichromophoric systems of M-X-M, where two identical aromatic hydrocarbons M are joined by X=CH[sub 2], O, NH, etc. Dinaphthylamines, dinaphthylethers, and dinaphthylmethanes in nonpolar solvents form triplet excimers, following inter system crossing of singlets to the triplet manifold; in polar solvents, the molecule forms an intramolecular CT state. The interchromophore interaction study was extended to N-phenyl-2-naphthylamine. The lowest excited singlet states of the dinaphthylamines were studied by semiempirical quantum chemical methods. Exciplex formation was studied in excited states of jet-cooled van der Waals complexes, such as fluorene/substituted benzenes and 1-cyanonaphthalene-aliphatic amines.

Lim, E.C.

1993-01-01

424

Charge-transfer luminescence and spectroscopic properties of Yb3+ in aluminium and gallium garnets  

NASA Astrophysics Data System (ADS)

Luminescence of Yb3+ from the charge-transfer state with broad emission bands and short radiative lifetimes (few to tens of nanoseconds depending on the host lattice and the temperature) is attractive for the development of fast scintillators capable of discriminating very short events. The most important currently considered application is that in solar neutrino (?e) real-time spectroscopy, since the ?e capture by 176Yb is followed by a specific emission signature which can accordingly excite the Yb3+ fluorescence. Studies on scintillation and luminescence in aluminium garnets containing Yb3+ have shown that these materials meet some of the required properties for such scintillators. In defining our priorities, the best compromise between host crystal, Yb3+ concentration, production method, post-growth treatment and performance is to be considered based on the studies of charge-transfer luminescence and quenching mechanisms. The experiments have been extended to a large number of compounds: YAG:Yb-YbAG, YGG:Yb-YbGG, YAP:Yb-YbAP, LaYbO3 in the form of single crystals and/or powders. In garnets, the temperature-dependent fluorescence intensity and decay time under X-ray and VUV excitations decrease at low temperatures (T<100K) and demonstrate the important role played by the traps. The thermoluminescence peaks show a strong dependence on the crystal history, composition and impurities introduced intentionally. The fluorescence intensity and decay time are also dependent on Yb3+ concentration and the presence of Yb2+. The results trace the major directions to optimised scintillators in terms of their efficiency and lifetime.

Guerassimova, N.; Dujardin, C.; Garnier, N.; Pédrini, C.; Petrosyan, A. G.; Kamenskikh, I. A.; Mikhailin, V. V.; Shpinkov, I. N.; Spassky, D. A.; Ovanesyan, K. L.; Shirinyan, G. O.; Chipaux, R.; Cribier, M.; Mallet, J.; Meyer, J.-P.

2002-06-01

425

Modulation of charge transfer rate in (N,N'-dimethylamino)benzonitrile liquid solutions  

NASA Astrophysics Data System (ADS)

We studied the properties of the emission, absorption and excitation of dual fluorescence of (N,N'-dimethylamino)benzonitrile in a polar aprotic solvent acetonitrile under selective irradiation of solutions by light with different energies of quanta to elucidate mechanisms of dual fluorescence arising in this solvent at different temperatures in the range 274-313 K. In all cases, dual fluorescence of the solute in acetonitrile was observed, which is caused by emission from locally excited Franck-Condon and charge-transfer states. A change in the energy of excitation quanta has a weak effect on the position of the fluorescence bands; however, the intensity ratio between the bands noticeably changes in favour of the intensity of the long-wavelength band at excitation in the range of the long-wavelength absorption band. An interesting and unusual fact is that solution heating is accompanied by essential growth of quantum yield of dual fluorescence at all wavelengths of the excitation. To explain the observed effects, the same dependences were measured and analysed for DMABN in neutral solvent n-hexane in the same conditions. We involve also the data of quantum-mechanical calculations, which show that there is a considerable probability of occurrence in solutions of DMABN rotational isomers with differing orientation of the dimethylamino group with respect to the benzonitrile. In the excited state, these have different charge-transfer rates, resulting in a modulation in the intensity ratio of the observed fluorescence bands with change excitation energy quanta on the red wing of the absorption band, doi: 10.1134/S0030400X12050219.

Tomin, V. I.; W?odarkiewicz, A.

2013-10-01

426

The charge-transfer states in a stacked nucleobase dimer complex: a benchmark study.  

PubMed

Electronic singlet excitations of stacked adenine-thymine (AT) and guanine-cytosine (GC) complexes have been investigated with respect to local excitation and charge-transfer (CT) characters. Potential energy curves for rigid displacement of the nucleobases have been computed to establish the distance dependence of the CT states. The second-order algebraic diagrammatic construction [ADC(2)] method served as reference approach for comparison to a selected set of density functionals used within the time-dependent density functional theory (TD-DFT). Particular attention was dedicated to the performance of the recently developed family of M06 functionals. The calculations for the stacked complexes show that at the ADC(2) level, the lowest CT state is S(6) for the AT and as S(4) for the GC pair. At the reference geometry, the actual charge transferred is found to be 0.73 e for AT. In case of GC, this amount is much smaller (0.17 e). With increasing separation of the two nucleobases, the CT state is strongly destabilized. The M06-2X version provides a relatively good reproduction of the ADC(2) results. It avoids the serious overstabilization and overcrowding of the spectrum found with the B3LYP functional. On the other hand, M06-HF destabilizes the CT state too strongly. TD-DFT/M06-2X calculations in solution (heptane, isoquinoline, and water) using the polarizable continuum model show a stabilization of the CT state and an increase in CT character with increasing polarity of the solvent. PMID:21425279

Aquino, Adélia J A; Nachtigallova, Dana; Hobza, Pavel; Truhlar, Donald G; Hättig, Christof; Lischka, Hans

2010-11-29

427

Supported oxides as combustion catalysts and as humidity sensors. Tuning the surface behavior by inter-phase charge transfer  

Microsoft Academic Search

The changes of the electrical properties of semiconductor oxide catalysts, when measured in situ provide useful information about surface processes as adsorption\\/desorption\\/reaction occur with charge transfer. The electrical properties of polycrystalline powders, mainly controlled by inter-grain Schottky-type barriers, are sensible to the “quality” of the surface\\/inter-grain domains, to sample morphology and to changes in charge and coverage of the surface

Monica Caldararu; Cornel Munteanu; Paul Chesler; Mariana Carata; Cristian Hornoiu; Niculae I. Ionescu; Georgeta Postole; Veronica Bratan

2007-01-01

428

Photoinitiated charge separation in a carotenoid-porphyrin-diquinone tetra: enhanced quantum yields via multistep electron transfers  

SciTech Connect

Photosynthesis converts light to chemical potential energy in the form of long-lived charge separation across a bilayer membrane. Recombination of the charge-separated state is prevented by the large distance between the final electron donor and acceptor. Because the quantum yield of a single long-range electron transfer across the bilayer would be vanishingly small, reaction centers employ a series of electron-transfer steps, each of which occurs over a short distance with high yield. Synthetic carotenoid-porphyrin-quinone triad molecules and other molecular systems which begin to model this approach have recently been reported. In photosynthetic bacteria, the charge separation sequence includes electron donation from a bacteriopheophytin to a quinone which then transfers an electron to a second quinone. An elegant molecule that models such electron transfer has been prepared, although it did not reproduce the long-lived charge separation characteristic of the natural system. The authors now report the synthesis of a tetrachromophoric molecule 1 consisting of a porphyrin (P) covalently linked to both a carotenoid polyene (C) and a rigid diquinone moiety (Q/sub A/-Q/sub B/), excitation of which produces a long-lived (460 ns in dichloromethane, 4 ..mu..s in acetonitrile charge-separated state C/sup .+/-P-Q/sub A/-Q/sub B//sup 0 -/ with a quantum yield of 0.23 at ambient temperatures and 0.50 at 240 K.

Gust, D.; Moore, T.A.; Moore, A.L.; Barrett, D.; Harding, L.O.; Makings, L.R.; Liddell, P.A.; De Schryver, F.C.; Van der Auweraer, M.; Bensasson, R.; Rougee, M.

1988-01-06

429

Pseudocapacitive Hausmannite Nanoparticles with (101) Facets: Synthesis, Characterization, and Charge-Transfer Mechanism.  

PubMed

Hausmannite Mn3 O4 octahedral nanoparticles of 18.3±7.0?nm with (101) facets have been prepared by an oxygen-mediated growth. The electrochemical properties of the Mn3 O4 particles as pseudocapacitive cathode materials were characterized both in half-cells and in button-cells. The Mn3 O4 nanoparticles exhibited a high mass-specific capacitance of 261?F?g(-1) , which was calculated from cyclic voltammetry analyses, and a capacitive retention of 78?% after 10?000 galvanostatic charge-discharge cycles. The charge-transfer mechanisms of the Mn3 O4 nanoparticles were further studied by using synchrotron-based in?situ X-ray absorption near edge spectroscopy and XRD. Both measurements showed concurrently that throughout the potential window of 0-1.2?V (vs. Ag/AgCl), a stable spinel structure of Mn3 O4 remained, and a reversible electrochemical conversion between tetrahedral [Mn(II) O4 ] and octahedral [Mn(III) O6 ] units accounted for the redox activity. Density functional theory calculations further corroborated this mechanism by confirming the enhanced redox stability afforded by the abundant and exposed (101) facets of Mn3 O4 octahedra. PMID:23650213

Yeager, Matthew P; Du, Wenxin; Wang, Qi; Deskins, N Aaron; Sullivan, Matthew; Bishop, Brendan; Su, Dong; Xu, Wenqian; Senanayake, Sanjaya D; Si, Rui; Hanson, Jonathan; Teng, Xiaowei

2013-05-01

430

Skeletal relaxation effect on the charge transfer state formation of 4-dimethylamino,4'-cyanostilbene.  

PubMed

Ab initio complete active space self-consistent field (CASSCF) calculations combined with polarized continuum model (PCM) have been performed to examine the charge transfer (CT) state formation of trans-4-dimethylamino,4'-cyanostilbene (DCS) in a solvent. In a polar solvent, the globally stable geometry in S1 takes a twisted conformation where the electron-donating dimethylanilino group is highly twisted against the other part of the electron-withdrawing 4-cyanostyryl group. In addition, skeletal relaxation where the aromatic benzene rings turn to be a nonaromatic quinoid structure is essential to stabilize the CT state. In a nonpolar solvent, the stable geometry in S1 takes a nontwisted conformation, though the skeletal relaxation is also an essential factor. By means of the free energy decomposition analysis, it is found that the stable CT geometry which depends on solvent polarity mainly comes from two factors: the linkage bond between the dimethylanilino and the 4-cyanostyryl group and the electrostatic interaction. In a polar solvent, the linkage bond has a single bond character to slightly prevent the torsional motion. This twist geometrically assists the charge separation so as to reinforce the electrostatic interaction. In consequence, the twisted internal CT (TICT) conformation is stable. In a nonpolar solvent, on the other hand, a nontwisted CT state is stable because the linkage bonds greatly increase a double bond character so as to prevent the torsional motion, while the electrostatic interaction is not so enhanced even by the geometrical twist. PMID:16836435

Amatatsu, Yoshiaki

2006-07-20

431

Charge and momentum transfer in supercooled melts: why should their relaxation times differ?  

PubMed

The steady-state values of the viscosity and the intrinsic ionic conductivity of quenched melts are computed, in terms of independently measurable quantities. The frequency dependence of the ac dielectric response is estimated. The discrepancy between the corresponding characteristic relaxation times is only apparent; it does not imply distinct mechanisms, but stems from the intrinsic barrier distribution for alpha-relaxation in supercooled fluids and glasses. This type of intrinsic "decoupling" is argued not to exceed four orders in magnitude for known glassformers. The origin of the discrepancy between the stretching exponent beta, as extracted from epsilon(omega) and the dielectric modulus data, is explained. The actual width of the barrier distribution always grows with lowering the temperature. The contrary is an artifact of the large contribution of the dc-conductivity component to the modulus data. The methodology allows one to single out other contributions to the conductivity, as in "superionic" liquids or when charge carriers are delocalized, implying that in those systems, charge transfer does not require structural reconfiguration. PMID:17492870

Lubchenko, Vassiliy

2007-05-01

432

Charge-Transfer Satellite in Ce@C82 Probed by Resonant X-ray Emission Spectroscopy  

NASA Astrophysics Data System (ADS)

The electronic structure of metallofullerene Ce@C82 is probed by resonant x-ray emission spectroscopy at the Ce L3 absorption edge. We observed a satellite structure in x-ray absorption and resonant emission spectra for Ce@C82, which, we show, corresponds to the charge transfer induced by the core--hole potential in the final state, similarly to Pr@C82. This charge-transfer satellite may be a common feature in metallofullerenes. The temperature dependence of the electronic structure is also investigated.

Yamaoka, Hitoshi; Kotani, Akio; Kubozono, Yoshihiro; Vlaicu, Aurel Mihai; Oohashi, Hirofumi; Tochio, Tatsuki; Ito, Yoshiaki; Yoshikawa, Hideki

2011-01-01

433

Double-ionization energies of CCl4 by double-charge-transfer and x-ray Auger-electron spectroscopies  

Microsoft Academic Search

The CCl2+4 ion has been studied using charge-transfer spectroscopy and x-ray-induced Auger-electron spectroscopy. From the kinetic energy distribution of H- ions arising from double charge transfer of protons impinging on CCl4 gas, three singlet-state energies of CCl2+4 have been measured at 30.4+\\/-0.2, 33.0+\\/-0.2, and 35.8+\\/-0.2 eV. The experimental peaks are narrow, indicating that these doubly ionized states are presumably stable

P. G. Fournier; G. Comtet; J. Fournier; S. Svensson; L. Karlsson; M. P. Keane; A. Naves de Brito

1989-01-01

434

Ab initio molecular treatment for charge transfer by P{sup 3+} ions on hydrogen and helium  

SciTech Connect

A theoretical treatment of charge-transfer processes induced by collision of phosphorus P{sup 3+}(3s{sup 2}){sup 1}S ions on atomic hydrogen and helium has been carried out using ab initio potential-energy curves and couplings at the multireference configuration interaction level of theory. The cross sections calculated by means of semiclassical collision methods show the existence of a significant charge transfer in the 0.1-700-keV laboratory energy range. Radial and rotational coupling interactions were analyzed for both collision systems.

Moussa, A.; Zaidi, A.; Lahmar, S. [Laboratoire de Spectrosopie Atomique, Moleculaire et Applications (LSAMA), Faculte des Sciences de Tunis, Universite Tunis El Manar, Campus Universitaire, TN-1060 Tunis (Tunisia); Bacchus-Montabonel, M.-C. [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR 5579, CNRS et Universite Lyon I, 43 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France)

2010-02-15

435

Charge-transfer complexes of nitrones—IV. Molecular complexes of N-alkyl nitrones with ?-acceptors  

NASA Astrophysics Data System (ADS)

Charge-transfer complexes between C-phenyl- N-alkyl nitrones and tetracyanoethylene, 2,3-dichloro-5,6-dicyanobenzoquinone, 7,7,8,8-tetracyanoquinodimethane, tetrafluorocyclohexa-2,5-diene-1,4-dione and tetrachlorocyclohexa-2,5-diene-1,4-dione were studied spectrophotometrically in methylene chloride at 25°C. The spectroscopic data indicate that the complexes are weak in nature and the Ph?CH? ?N ? 0 group is responsible for the complexation with ?-acceptors. Job's method shows that the stoichiometric ratio of the complexes is 1 : 1. The effect of temperature and solvents on the stability of the charge-transfer complexes is discussed.

Nour El-Din, Ahmed M.

436

Raman spectroscopy of intermolecular charge transfer complex between a conjugated polymer and an organic acceptor molecule  

NASA Astrophysics Data System (ADS)

Intermolecular donor-acceptor charge transfer complex (CTC) formed in the electronic groundstate between poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and 2,4,7-trinitrofluorenone (TNF) has been investigated by Raman and optical absorption spectroscopies. Blending of MEH-PPV and TNF results in appearance of the CTC absorption band in the optical gap of the both components and in change