International Nuclear Information System (INIS)
Kaliambos, L.A.
2008-01-01
Fundamental interactions of spinning electrons at an interelectron separation less than 578.8 fm yield attractive electromagnetic forces with S = 0 creating vibrations under a motional emf. They explain the indistinguishability of electrons and give a vibration energy able for calculating the ground-state energies of many-electron atoms without using any perturbative approximation. Such forces create two-electron orbitals able to account for the exclusion principal and the mechanism of covalent bonds. In the outer subshells of atoms the penetrating orbitals interact also as pair-pair systems and deform drastically the probability densities of the quantum mechanical electron clouds. Such a dynamics of deformation removes the degeneracy and leads to the deviation from the shell scheme. However in the interior of atoms the large nuclear charge leads to a spherically symmetric potential with non-interacting pairs for creating shells of degenerate states giving an accurate explanation of the X-ray lines. On the other hand, considerable charge distributions in nucleons as multiples of 2e/3 and - e/3 determined by the magnetic moments, interact for creating the nuclear structure with p-n bonds. Such spin-spin interactions show that the dominant concept of the untisymmetric wave function for fermions is inapplicable not only in the simple p-n, p-p, and n-n systems but also in the LS coupling of atoms in which the electrons interact from different quantum states giving either S = 0 or S = l. (author)
Lukas, Aaron S; Bushard, Patrick J; Weiss, Emily A; Wasielewski, Michael R
2003-04-02
The spin-spin exchange interaction, 2J, in a radical ion pair produced by a photoinduced electron transfer reaction can provide a direct measure of the electronic coupling matrix element, V, for the subsequent charge recombination reaction. We have developed a series of dyad and triad donor-acceptor molecules in which 2J is measured directly as a function of incremental changes in their structures. In the dyads the chromophoric electron donors 4-(N-pyrrolidinyl)- and 4-(N-piperidinyl)naphthalene-1,8-dicarboximide, 5ANI and 6ANI, respectively, and a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor are linked to the meta positions of a phenyl spacer to yield 5ANI-Ph-NI and 6ANI-Ph-NI. In the triads the same structure is used, except that the piperidine in 6ANI is replaced by a piperazine in which a para-X-phenyl, where X = H, F, Cl, MeO, and Me(2)N, is attached to the N' nitrogen to form a para-X-aniline (XAn) donor to give XAn-6ANI-Ph-NI. Photoexcitation yields the respective 5ANI(+)-Ph-NI(-), 6ANI(+)-Ph-NI(-), and XAn(+)-6ANI-Ph-NI(-) singlet radical ion pair states, which undergo subsequent radical pair intersystem crossing followed by charge recombination to yield (3)NI. The radical ion pair distances within the dyads are about 11-12 A, whereas those in the triads are about approximately 16-19 A. The degree of delocalization of charge (and spin) density onto the aniline, and therefore the average distance between the radical ion pairs, is modulated by the para substituent. The (3)NI yields monitored spectroscopically exhibit resonances as a function of magnetic field, which directly yield 2J for the radical ion pairs. A plot of ln 2J versus r(DA), the distance between the centroids of the spin distributions of the two radicals that comprise the pair, yields a slope of -0.5 +/- 0.1. Since both 2J and k(CR), the rate of radical ion pair recombination, are directly proportional to V(2), the observed distance dependence of 2J shows directly that the recombination
International Nuclear Information System (INIS)
Hong Fenglei; Zhang Yun; Ishikawa, Jun; Onae, Atsushi; Matsumoto, Hirokazu
2002-01-01
Hyperfine structures of the R(87)33-0, R(145)37-0, and P(132)36-0 transitions of molecular iodine near 532 nm are measured by observing the heterodyne beat-note signal of two I 2 -stabilized lasers, whose frequencies are bridged by an optical frequency comb generator. The measured hyperfine splittings are fit to a four-term Hamiltonian, which includes the electric quadrupole, spin-rotation, tensor spin-spin, and scalar spin-spin interactions, with an accuracy of ∼720 Hz. High-accurate hyperfine constants are obtained from this fit. Vibration dependences of the tensor spin-spin and scalar spin-spin hyperfine constants are determined for molecular iodine, for the first time to our knowledge. The observed hyperfine transitions are good optical frequency references in the 532-nm region
Energy Technology Data Exchange (ETDEWEB)
Krivdin, L.B.; Shcherbakov, V.V.; Glukhikh, N.G.; Sigalov, V.M.; Kalabin, G.A.
1987-07-10
Vinyl ethers were prepared by the well-known Favorskii-Shostakovskii method. The purity of the compounds was controlled by GLC and by the PMR and /sup 13/C NMR spectra. The proximity of sp/sup 7/-hybridized unshared pair of oxygen atoms result in a secondary, positive contribution in the constant of spin-spin interaction between neighboring carbon nuclei in the aromatic ring.
Čenčariková, Hana; Strečka, Jozef; Gendiar, Andrej; Tomašovičová, Natália
2018-05-01
An exhaustive ground-state analysis of extended two-dimensional (2D) correlated spin-electron model consisting of the Ising spins localized on nodal lattice sites and mobile electrons delocalized over pairs of decorating sites is performed within the framework of rigorous analytical calculations. The investigated model, defined on an arbitrary 2D doubly decorated lattice, takes into account the kinetic energy of mobile electrons, the nearest-neighbor Ising coupling between the localized spins and mobile electrons, the further-neighbor Ising coupling between the localized spins and the Zeeman energy. The ground-state phase diagrams are examined for a wide range of model parameters for both ferromagnetic as well as antiferromagnetic interaction between the nodal Ising spins and non-zero value of external magnetic field. It is found that non-zero values of further-neighbor interaction leads to a formation of new quantum states as a consequence of competition between all considered interaction terms. Moreover, the new quantum states are accompanied with different magnetic features and thus, several kinds of field-driven phase transitions are observed.
Isoscalar spin-spin interaction within the quasiparticle-phonon nuclear model
International Nuclear Information System (INIS)
Dao Tien Khoa; Ponomarev, V.Yu.; Vdovin, A.I.
1986-01-01
The isoscalar spin-spin interaction constant in the quasiparticle-phonon nuclear model (QPM) has been determined from the available experimental data on the isoscalar 1 + state (E x =5.846 MeV) in 208 Pb. The isoscalar spin-spin interaction turns out to be weaker than the isovector one by an order of magnitude. The cross sections of (e, e') and (p, p') reactions with the excitation of this 1 + -state have been calculated. The QPM gives a good description of the behaviour of (e, e')-cross section at q eff -1 and reproduces absolute value of this cross section with the effective g s -factors weaker than the g s -factors for free nucleon by 20%. The description of the (p, p')-angular distribution of 201 MeV photon inelastic scattering is poorer. The absolute value of the calculated (p, p') cross section overestimates the experimental data by a factor of about 1.4. This is consistent with the quenching factor for (e, e') cross section. The interaction with two-phonon configurations influences very weakly the isoscalar 1 + -level
Leibfried, D.; Wineland, D. J.
2018-03-01
Effective spin-spin interactions between ? qubits enable the determination of the eigenvalue of an arbitrary Pauli product of dimension N with a constant, small number of multi-qubit gates that is independent of N and encodes the eigenvalue in the measurement basis states of an extra ancilla qubit. Such interactions are available whenever qubits can be coupled to a shared harmonic oscillator, a situation that can be realized in many physical qubit implementations. For example, suitable interactions have already been realized for up to 14 qubits in ion traps. It should be possible to implement stabilizer codes for quantum error correction with a constant number of multi-qubit gates, in contrast to typical constructions with a number of two-qubit gates that increases as a function of N. The special case of finding the parity of N qubits only requires a small number of operations that is independent of N. This compares favorably to algorithms for computing the parity on conventional machines, which implies a genuine quantum advantage.
International Nuclear Information System (INIS)
Nagadi, M.M.; Weisel, G.J.; Walter, R.L.; Delaroche, J.P.; Romain, P.
2004-01-01
Coupled-channel and dispersive-optical model analyses of published neutron scattering and reaction data for 27 Al, 59 Co, and 93 Nb at incident energies between 0.1 and 80 MeV have been performed. The resulting potentials are used to place constraints on the determination of the spin-spin interaction from published spin-spin cross-section measurements. For the three nuclei, the strength of the central real spin-spin potential, which was taken to have a surface plus volume shape, was found to be small. Volume integrals for this central potential component were determined to be in the 4-7 MeV fm 3 range and to decrease somewhat as mass number increases
Biktagirov, Timur; Schmidt, Wolf Gero; Gerstmann, Uwe
2018-03-01
For high-spin centers, one of the key spectroscopic fingerprints is the zero-field splitting (ZFS) addressable by electron paramagnetic resonance. In this paper, an implementation of the spin-spin contribution to the ZFS tensor within the projector augmented-wave (PAW) formalism is reported. We use a single-determinant approach proposed by M. J. Rayson and P. R. Briddon [Phys. Rev. B 77, 035119 (2008), 10.1103/PhysRevB.77.035119], and complete it by adding a PAW reconstruction term which has not been taken into account before. We benchmark the PAW approach against a well-established all-electron method for a series of diatomic radicals and defects in diamond and cubic silicon carbide. While for some of the defect centers the PAW reconstruction is found to be almost negligible, in agreement with the common assumption, we show that in general it significantly improves the calculated ZFS towards the all-electron results.
McAneny, M.; Freericks, J. K.
2014-11-01
The Coulomb repulsion between ions in a linear Paul trap gives rise to anharmonic terms in the potential energy when expanded about the equilibrium positions. We examine the effect of these anharmonic terms on the accuracy of a quantum simulator made from trapped ions. To be concrete, we consider a linear chain of Yb171+ ions stabilized close to the zigzag transition. We find that for typical experimental temperatures, frequencies change by no more than a factor of 0.01 % due to the anharmonic couplings. Furthermore, shifts in the effective spin-spin interactions (driven by a spin-dependent optical dipole force) are also, in general, less than 0.01 % for detunings to the blue of the transverse center-of-mass frequency. However, detuning the spin interactions near other frequencies can lead to non-negligible anharmonic contributions to the effective spin-spin interactions. We also examine an odd behavior exhibited by the harmonic spin-spin interactions for a range of intermediate detunings, where nearest-neighbor spins with a larger spatial separation on the ion chain interact more strongly than nearest neighbors with a smaller spatial separation.
Czech Academy of Sciences Publication Activity Database
Vavrinská, A.; Zelinka, J.; Šebera, Jakub; Sychrovský, Vladimír; Fiala, R.; Boelens, R.; Sklenář, V.; Trantírek, L.
2016-01-01
Roč. 64, č. 1 (2016), s. 53-62 ISSN 0925-2738 R&D Projects: GA ČR GA13-27676S Grant - others:AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : NMR * DFT calculations * spin-spin interactions * magnetic field Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.410, year: 2016 http://link.springer.com/article/10.1007/s10858-015-0005-x
Energy Technology Data Exchange (ETDEWEB)
Kalabin, G.A.; Kushnarev, D.F.; Valeev, R.B. (Irkutskij Gosudarstvennyj Univ. (USSR))
1981-06-01
On the basis of /sup 13/C NMR spectra of a series of unsaturated and aromatic tellurium compounds the constants of spin-spin interaction (SSIC) (sup(1.2)J(Te, C)) are measured. A reliable linear relation between /sup 1/J(Te, C) and s-character of a carbon orbitale forming bond with tellurium is found. Correlation of straight SSIC of carbon with selenium and tellurium in isological compounds is established.
QED approach to the nuclear spin-spin coupling tensor
International Nuclear Information System (INIS)
Romero, Rodolfo H.; Aucar, Gustavo A.
2002-01-01
A quantum electrodynamical approach for the calculation of the nuclear spin-spin coupling tensor of nuclear-magnetic-resonance spectroscopy is given. Quantization of radiation fields within the molecule is considered and expressions for the magnetic field in the neighborhood of a nucleus are calculated. Using a generalization of time-dependent response theory, an effective spin-spin interaction is obtained from the coupling of nuclear magnetic moments to a virtual quantized magnetic field. The energy-dependent operators obtained reduce to usual classical-field expressions at suitable limits
Spin-spin correlations in the tt'-Hubbard model
International Nuclear Information System (INIS)
Husslein, T.; Newns, D.M.; Mattutis, H.G.; Pattnaik, P.C.; Morgenstern, I.; Singer, J.M.; Fettes, W.; Baur, C.
1994-01-01
We present calculations of the tt'-Hubbard model using Quantum Monte Carlo techniques. The parameters are chosen so that the van Hove Singularity in the density of states and the Fermi level coincide. We study the behaviour of the system with increasing Hubbard interaction U. Special emphasis is on the spin-spin correlation (SSC). Unusual behaviour for large U is observed there and in the momentum distribution function (n(q)). (orig.)
Calculation of nuclear spin-spin coupling constants using frozen density embedding
Energy Technology Data Exchange (ETDEWEB)
Götz, Andreas W., E-mail: agoetz@sdsc.edu [San Diego Supercomputer Center, University of California San Diego, 9500 Gilman Dr MC 0505, La Jolla, California 92093-0505 (United States); Autschbach, Jochen [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States); Visscher, Lucas, E-mail: visscher@chem.vu.nl [Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, Theoretical Chemistry, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)
2014-03-14
We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between {sup 199}Hg and {sup 13}C upon coordination of dimethylsulfoxide solvent molecules.
Energy Technology Data Exchange (ETDEWEB)
Shcherbakov, V.V.; Krivdin, L.B.; Kalabin, G.A.; Trofimov, B.A.
1986-11-20
The authors have previously established that the direct /sup 13/C-/sup 13/C coupling constants are stereospecific relative to the orientation of unshared electron pairs (UEP) of nitrogen and oxygen atoms. Here they show that the nitrogen UEP produces a positive contribution to the direct /sup 13/C-/sup 13/C coupling constant of an adjacent syn-periplanar carbon-carbon bond and not to a negative contribution of the corresponding constant of the anti-periplanar bond. Thus, the observed effect is not a consequence of the interaction of the heteroatom UEP with the anti-bonding orbital of the adjacent anti-periplanar bond (n/sub o-o/* interaction) as in the case of anomeric and related effects.
Spin-Spin Cross Relaxation in Single-Molecule Magnets
Wernsdorfer, W.; Bhaduri, S.; Tiron, R.; Hendrickson, D. N.; Christou, G.
2002-10-01
The one-body tunnel picture of single-molecule magnets (SMMs) is not always sufficient to explain the measured tunnel transitions. An improvement to the picture is proposed by including also two-body tunnel transitions such as spin-spin cross relaxation (SSCR) which are mediated by dipolar and weak superexchange interactions between molecules. A Mn4 SMM is used as a model system. At certain external fields, SSCRs lead to additional quantum resonances which show up in hysteresis loop measurements as well-defined steps. A simple model is used to explain quantitatively all observed transitions.
Energy Technology Data Exchange (ETDEWEB)
Zarycz, M. Natalia C., E-mail: mnzarycz@gmail.com; Provasi, Patricio F., E-mail: patricio@unne.edu.ar [Department of Physics, University of Northeastern - CONICET, Av. Libertad 5500, Corrientes W3404AAS (Argentina); Sauer, Stephan P. A., E-mail: sauer@kiku.dk [Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø (Denmark)
2014-10-21
We discuss the effect of electron correlation on the unexpected differential sensitivity (UDS) in the {sup 1}J(C–H) coupling constant of CH{sub 4} using a decomposition into contributions from localized molecular orbitals and compare with the {sup 1}J(N–H) coupling constant in NH{sub 3}. In particular, we discuss the well known fact that uncorrelated coupled Hartree-Fock (CHF) calculations are not able to reproduce the UDS in methane. For this purpose we have implemented for the first time a localized molecular orbital analysis for the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes—SOPPA(CCSD) in the DALTON program. Comparing the changes in the localized orbital contributions at the correlated SOPPA and SOPPA(CCSD) levels and at the uncorrelated CHF level, we find that the latter overestimates the effect of stretching the bond between the coupled atoms on the contribution to the coupling from the localized bonding orbital between these atoms. This disturbs the subtle balance between the molecular orbital contributions, which lead to the UDS in methane.
EPR Studies of Spin-Spin Exchange Processes: A Physical Chemistry Experiment.
Eastman, Michael P.
1982-01-01
Theoretical background, experimental procedures, and analysis of experimental results are provided for an undergraduate physical chemistry experiment on electron paramagnetic resonance (EPR) linewidths. Source of line broadening observed in a spin-spin exchange process between radicals formed in aqueous solutions of potassium peroxylamine…
The susceptibilities in the spin-S Ising model
International Nuclear Information System (INIS)
Ainane, A.; Saber, M.
1995-08-01
The susceptibilities of the spin-S Ising model are evaluated using the effective field theory introduced by Tucker et al. for studying general spin-S Ising model. The susceptibilities are studied for all spin values from S = 1/2 to S = 5/2. (author). 12 refs, 4 figs
Compound nucleus effects in spin-spin cross sections
International Nuclear Information System (INIS)
Thompson, W.J.
1976-01-01
By comparison with recent data, it is shown that spin-spin cross sections for low-energy neutrons may be dominated by a simple compound-elastic level-density effect, independent of spin-spin terms in the nucleon-nucleus optical-model potential. (Auth.)
Magnetocaloric effect in quantum spin-s chains
Directory of Open Access Journals (Sweden)
A. Honecker
2009-01-01
Full Text Available We compute the entropy of antiferromagnetic quantum spin-s chains in an external magnetic field using exact diagonalization and Quantum Monte Carlo simulations. The magnetocaloric effect, i. e., temperature variations during adiabatic field changes, can be derived from the isentropes. First, we focus on the example of the spin-s=1 chain and show that one can cool by closing the Haldane gap with a magnetic field. We then move to quantum spin-s chains and demonstrate linear scaling with s close to the saturation field. In passing, we propose a new method to compute many low-lying excited states using the Lanczos recursion.
Rotational Invariance of the 2d Spin - Spin Correlation Function
Pinson, Haru
2012-09-01
At the critical temperature in the 2d Ising model on the square lattice, we establish the rotational invariance of the spin-spin correlation function using the asymptotics of the spin-spin correlation function along special directions (McCoy and Wu in the two dimensional Ising model. Harvard University Press, Cambridge, 1973) and the finite difference Hirota equation for which the spin-spin correlation function is shown to satisfy (Perk in Phys Lett A 79:3-5, 1980; Perk in Proceedings of III international symposium on selected topics in statistical mechanics, Dubna, August 22-26, 1984, JINR, vol II, pp 138-151, 1985).
DEFF Research Database (Denmark)
Rusakov, Yury Yu; Krivdin, Leonid B.; Østerstrøm, Freja From
2013-01-01
This paper documents a very first example of a high-level correlated calculation of spin-spin coupling constants involving tellurium taking into account relativistic effects, vibrational corrections and solvent effects for the medium sized organotellurium molecules. The 125Te-1H spin-spin coupling...... constants of tellurophene and divinyl telluride were calculated at the SOPPA and DFT levels in a good agreement with experiment. A new full-electron basis set av3z-J for tellurium derived from the "relativistic" Dyall's basis set, dyall.av3z, and specifically optimized for the correlated calculations...... of spin-spin coupling constants involving tellurium, was developed. The SOPPA methods show much better performance as compared to 15 those of DFT, if relativistic effects calculated within the ZORA scheme are taken into account. Vibrational and solvent corrections are next to negligible, while...
Energy Technology Data Exchange (ETDEWEB)
Krivdin, L.B.; Shcherbakov, V.V.; Kalabin, G.A.
1986-07-10
It was shown that the direct /sup 13/C-/sup 13/C spin-spin coupling constants can be used for the unambiguous identification of the configurational isomers of oximes and their derivatives. The stereospecificity of the constants is explained by the additional contribution from the unshared electron pair of the nitrogen atom to the spin-spin coupling constant between the adjacent carbon nuclei in the cis position.
Critical behaviour of magnetic thin film with Heisenberg spin-S model
International Nuclear Information System (INIS)
Masrour, R.; Hamedoun, M.; Bouslykhane, K.; Hourmatallah, A.; Benzakour, N.; Benyoussef, A.
2009-01-01
The magnetic properties of a ferromagnetic thin film of face centered cubic (FCC) lattice with Heisenberg spin-S are examined using the high-temperature series expansions technique extrapolated with Pade approximations method. The critical reduced temperature of the system τ c is studied as function of thickness of the film and the exchange interactions in the bulk, and within the surfaces J b , J s and J perpendicular respectively. A critical value of surface exchange interaction above which surface magnetism appears is obtained. The dependence of the reduced critical temperature on the film thickness L has been investigated.
A low-temperature derivation of spin-spin exchange in Kondo lattice model
International Nuclear Information System (INIS)
Feng Szeshiang; Mochena, Mogus
2005-01-01
Using Hubbard-Stratonovich transformation and drone-fermion representations for spin-12 and for spin-32, which is presented for the first time, we make a path-integral formulation of the Kondo lattice model. In the case of weak coupling and low temperature, the functional integral over conduction fermions can be approximated to the quadratic order and this gives the well-known RKKY interaction. In the case of strong coupling, the same quadratic approximation leads to an effective local spin-spin interaction linear in hopping energy t
A low-temperature derivation of spin-spin exchange in Kondo lattice model
Energy Technology Data Exchange (ETDEWEB)
Feng Szeshiang [Physics Department, Florida A and M University, Tallahassee, FL 32307 (United States)]. E-mail: shixiang.feng@famu.edu; Mochena, Mogus [Physics Department, Florida A and M University, Tallahassee, FL 32307 (United States)
2005-11-01
Using Hubbard-Stratonovich transformation and drone-fermion representations for spin-12 and for spin-32, which is presented for the first time, we make a path-integral formulation of the Kondo lattice model. In the case of weak coupling and low temperature, the functional integral over conduction fermions can be approximated to the quadratic order and this gives the well-known RKKY interaction. In the case of strong coupling, the same quadratic approximation leads to an effective local spin-spin interaction linear in hopping energy t.
Hardy's argument and successive spin-s measurements
International Nuclear Information System (INIS)
Ahanj, Ali
2010-01-01
We consider a hidden-variable theoretic description of successive measurements of noncommuting spin observables on an input spin-s state. In this scenario, the hidden-variable theory leads to a Hardy-type argument that quantum predictions violate it. We show that the maximum probability of success of Hardy's argument in quantum theory is ((1/2)) 4s , which is more than in the spatial case.
Nuclear spin-spin coupling in a van der Waals-bonded system: xenon dimer.
Vaara, Juha; Hanni, Matti; Jokisaari, Jukka
2013-03-14
Nuclear spin-spin coupling over van der Waals bond has recently been observed via the frequency shift of solute protons in a solution containing optically hyperpolarized (129)Xe nuclei. We carry out a first-principles computational study of the prototypic van der Waals-bonded xenon dimer, where the spin-spin coupling between two magnetically non-equivalent isotopes, J((129)Xe - (131)Xe), is observable. We use relativistic theory at the four-component Dirac-Hartree-Fock and Dirac-density-functional theory levels using novel completeness-optimized Gaussian basis sets and choosing the functional based on a comparison with correlated ab initio methods at the nonrelativistic level. J-coupling curves are provided at different levels of theory as functions of the internuclear distance in the xenon dimer, demonstrating cross-coupling effects between relativity and electron correlation for this property. Calculations on small Xe clusters are used to estimate the importance of many-atom effects on J((129)Xe - (131)Xe). Possibilities of observing J((129)Xe - (131)Xe) in liquid xenon are critically examined, based on molecular dynamics simulation. A simplistic spherical model is set up for the xenon dimer confined in a cavity, such as in microporous materials. It is shown that the on the average shorter internuclear distance enforced by the confinement increases the magnitude of the coupling as compared to the bulk liquid case, rendering J((129)Xe - (131)Xe) in a cavity a feasible target for experimental investigation.
Czech Academy of Sciences Publication Activity Database
Azamat, Dmitry; Dejneka, Alexandr; Lančok, Ján; Trepakov, Vladimír; Jastrabík, Lubomír; Badalyan, A. G.
2012-01-01
Roč. 111, č. 10 (2012), "104119-1"-"104119-6" ISSN 0021-8979. [International Symposium on Integrated Functionalities (ISIF) /22./. San Juan, Puerto Rico , 13.06.2010-16.06.2010] R&D Projects: GA TA ČR TA01010517; GA MŠk(CZ) LM2011029; GA ČR GAP108/12/1941 Grant - others:SAFMAT(CZ) CZ.2.16/3.1.00/22132 Institutional research plan: CEZ:AV0Z10100522 Keywords : electron paramagnetic resonance * X- and Q-band * SrTiO 3 doped with Mn Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.210, year: 2012
Energy Technology Data Exchange (ETDEWEB)
Kalabin, G.A. (Siberian Branch of the Academy of Sciences of the USSR); Krivdin, L.B.; Trofimov, B.A.
1982-07-20
In order to elucidate the /sup 13/C-/sup 13/-C SSCC (spin-spin coupling constants) segment with the electronic excitations induced by the R group, a series of phenyl alkyl ethers, PhOAlk, where Alk = Me(I), Et(II), i-Pr(III), and t-Bu(IV), were studied. This series was chosen because in studying the /sup 13/C CS in monosubstituted benzenes it was observed that the intensity of the ..pi..-electron interaction of the unshared electron pairs of oxygen with the ..pi.. system of the benzene ring was practically the same in some compounds, but increased by 30% in others. This is related to the fact that the latter is characterized by an average noncoplanar conformation, with a dihedral angle between the benzene-ring plane and the C-O-C bond of approx. 45/sup 0/, whereas some compounds have an angle < 20/sup 0/. The reason for the difference is significant steric interaction of the alkyl hydrogens with the o-position of the ring. Thus, consideration of the /sup 13/C-/sup 13/C SSCC of a series of quite similar compounds, especially when compared to the whole set of such SSCC for other monosubstituted benzenes, shows that their relationship to the structure of the substituent R is extremely complex.
Electron: Cluster interactions
International Nuclear Information System (INIS)
Scheidemann, A.A.; Knight, W.D.
1994-02-01
Beam depletion spectroscopy has been used to measure absolute total inelastic electron-sodium cluster collision cross sections in the energy range from E ∼ 0.1 to E ∼ 6 eV. The investigation focused on the closed shell clusters Na 8 , Na 20 , Na 40 . The measured cross sections show an increase for the lowest collision energies where electron attachment is the primary scattering channel. The electron attachment cross section can be understood in terms of Langevin scattering, connecting this measurement with the polarizability of the cluster. For energies above the dissociation energy the measured electron-cluster cross section is energy independent, thus defining an electron-cluster interaction range. This interaction range increases with the cluster size
International Nuclear Information System (INIS)
Pavlov, R.L.; Pavlov, L.I.; Raychev, P.P.; Garistov, V.P.; Dimitrova-Ivanovich, M.
2002-01-01
The matrix elements and expectation values of the hyperfine interaction operators are presented in a form suitable for numerical implementation in density matrix methods. The electron-nuclear spin-spin (dipolar and contact) interactions are considered, as well as the interaction between nuclear spin and electron-orbital motions. These interactions from the effective Breit-Pauli Hamiltonian determine the hyperfine structure in ESR spectra and contribute to chemical shifts in NMR. Applying the Wigner-Eckart theorem in the irreducible tensor-operator technique and the spin-space separation scheme, the matrix elements and expectation values of these relativistic corrections are expressed in analytical form. The final results are presented as products, or sums of products, of factors determined by the spin and (or) angular momentum symmetry and a spatial part determined by the action of the symmetrized tensor-operators on the normalized matrix or function of the spin or charge distribution.
Energy Technology Data Exchange (ETDEWEB)
Krivdin, L.B.; Shcherbakov, V.V.; Bzhezovskii, V.M.; Kalabin, G.A.
1986-10-10
The /sup 13/C-/sup 13/C spin-spin coupling constants between the carbon nuclei of the vinyl group were measured for a series of vinyl ethers. It was established that the unshared electron pairs of the oxygen atom can make a substantial stereospecific contribution to the direct /sup 13/C-/sup 13/C constants of the adjacent nuclei. The observed effect was used to establish the conformational structure of the compounds.
Energy Technology Data Exchange (ETDEWEB)
Krivdin, L.B.; Shcherbakov, V.V.; Kalabin, G.A.
1988-03-10
The direct spin-spin coupling constants in the vinyl group were measured in 100 mono-substituted ethylene derivatives. The inductive effect of the substituent was found to be the major factor in the variation of this constant and, in some cases, the stereospecific effect of the unshared electron pairs of heteratoms makes a significant contribution to the /sup 13/C-/sup 13/C coupling constants.
Electron structure of molecules with very heavy atoms using effective core potentials
International Nuclear Information System (INIS)
Pitzer, K.S.
1982-01-01
Topics covered include effective potential, Hamiltonian for valence-electron motion, molecular calculations, spin-spin coupling, L-S coupling, numerical results of molecular calculations, and results of configuration-interaction Slater-orbital calculations in L-S coupling
International Nuclear Information System (INIS)
Andreev, Pavel A.
2015-01-01
We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction
Electron-positron interactions
International Nuclear Information System (INIS)
Wiik, B.; Wolf, G.
1979-01-01
This book is an introduction into the physics of electron-positron interactions. After a description of electron-positron storage rings pure electromagnetic e + e - interactions, and the total cross section are considered. Then low energy processes, the production of the J/psi and psi' particles including their radiative decay as well as the search for other narrow vector states are described. Then after the quark model interpretation of J/psi and psi' charmed mesons, the heavy lepton t, and the upsilon resonances are described. Thereafter inclusive hadron production and jet formation is discussed. Finally the next generation of e + e - colliding rings is described, and the first results from PETRA are presented. This book is suited for all physicists, who want to get a general review about e + e - physics. (HSI) 891 HSI/HSI 892 RKD
International Nuclear Information System (INIS)
Loeh, H.
1981-01-01
For the study of the spin-spin interactions in the optical potential the depolarization in the elastic scattering of polarized protons was measured. The double-scattering experiments were performed in the angular range 40 0 -110 0 at an incident energy of 10.35 MeV at the Erlangen QD magnetic spectrometer. The determination of the optical model parameters independent from the spin-spin potentials resulted by the fit of those to the observables and sigmasup(di). These were obtained from a measurement of the angular distribution of the analyzing power and the differential cross section in the 4π-scattering chamber for the reaction 27 Al (p vector,psub(o)) at the same energy. The compound contributions present at this energy, which can also influence the depolarization, were regarded by the calculation of the compound-elastic non-spin-flip respectively spin-flip subcross sections by means of the formalism of Hofmann, Richard, Tepel, and Weidenmueller. Because of the target nucleus 27 Al posesses in the ground state a spin I=5/2 also the possible quadrupole spin flip had to be included in the analysis. This was performed by coupled channel calculations. The depolarization data corrected according to compound contributions and quadrupole effects could now be applied to the study of the spin-spin potentials by means of DWBA calculations. As result it turned out that for the description of the experimental data a spherical spin-spin potential of the strength Vsub(SS)=1.5+-0.3 MeV had to be assumed. For the addition of a tensor term however no necessity resulted. (orig.) [de
International Nuclear Information System (INIS)
Loeh, H.
1981-01-01
For the study of the spin-spin interaction in the optical potential the depolarisation in the elastic scattering of polarized protons was measured. The double-scattering experiments were performed in the angular range 40 0 -110 0 at an incident energy of 10.35 MeV at the Erlangen QD-magnetic spectrometer. The determination of the optical model parameters independent from the spin-spin potentials was performed by the fitting of these to the observables and sigmasup(di). These were obtained from a measurement of the angular distribution of the analyzing power and the differential cross section in the 4π-scattering chamber for the reaction 27 Al(p vector,p 0 ) at the same energy. The compound contributions present at this energy, which can also influence the depolarization, were regarded by the calculation of the compound-elastic non-spin-flip respectively spin-flip subcross sections by means of the formalism of Hofmann, Richert, Tepel and Weidenmueller. Because the target nucleus 27 Al possesses in the ground state a spin I=5/2, also the possible quadrupole spin flip had to be included. This was performed by coupled-channel calculations. The respecting compound contributions and quadrupole effects corrected depolarization data could by used for the study of the spin-spin potentials by means of DWBA calculations. As result it was shown that for the description of the experimental data a spherical spin-spin potential of the strength Vsub(SS)=1.5+-0.3 MeV had to be assumed. (orig.) [de
Magnetic properties of a ferromagnet spin-S, Ising, XY and Heisenberg models semi-infinites systems
International Nuclear Information System (INIS)
Masrour, R.; Hamedoun, M.; Hourmatallah, A.; Bouslykhane, K.; Benzakour, N.
2008-01-01
The magnetic properties of a ferromagnet spin-S a disordered semi-infinite system with a face-centered cubic lattice are investigated using the high-temperature series expansions technique extrapolated with Pade approximants method for Heisenberg, XY and Ising models. The reduced critical temperature of the system τ c =(k B T c )/(2S(S+1)J b ) is studied as function of the thickness of the film and the exchange interactions in the bulk, and within the surfaces J b ,J s and J perpendicular , respectively. It is found that τ c increases with the exchange interactions of surface. The magnetic phase diagrams (τ c versus the dilution x) and the percolation threshold are obtained
Electron-electron interactions in disordered systems
Efros, AL
1985-01-01
``Electron-Electron Interactions in Disordered Systems'' deals with the interplay of disorder and the Coulomb interaction. Prominent experts give state-of-the-art reviews of the theoretical and experimental work in this field and make it clear that the interplay of the two effects is essential, especially in low-dimensional systems.
DEFF Research Database (Denmark)
Faber, Rasmus; Sauer, Stephan P. A.
2015-01-01
We present zero-point vibrational corrections to the indirect nuclear spin-spin coupling constants in ethyne, ethene, cyclopropene and allene. The calculations have been carried out both at the level of the second order polarization propagator approximation (SOPPA) employing a new implementation ...
The spin-spin effect in the total neutron cross section of polarized neutrons on polarized 165Ho
International Nuclear Information System (INIS)
Fasoli, U.; Galeazzi, G.; Pavan, P.; Toniolo, D.; Zago, G.; Zannoni, R.
1978-01-01
The spin-spin effect in the total neutron cross section of polarized neutrons on polarized 165 Ho has been measured in the energy interval 0.4 to 2.5 MeV, in perpendicular geometry. The results are consistent with zero effect. The spin-spin cross section sigmasub(ss) has been theoretically evaluated by a non-adiabatic coupled-channel calculation. From the comparison between the experimental and theoretical results a value Vsub(ss) = 9+-77 keV for the strength of the spin-spin potential has been obtained. Compound-nucleus effects do not seem to be relevant. (Auth.)
Electron-electron interactions in artificial graphene
Rasanen, Esa
2013-03-01
Recent advances in the creation and modulation of graphenelike systems are introducing a science of ``designer Dirac materials.'' In its original definition, artificial graphene is a man-made nanostructure that consists of identical potential wells (quantum dots) arranged in an adjustable honeycomb lattice in the two-dimensional electron gas. As our ability to control the quality of artificial graphene samples improves, so grows the need for an accurate theory of its electronic properties, including the effects of electron-electron interactions. Here we determine those effects on the band structure and on the emergence of Dirac points, and discuss future investigations and challenges in this field.
Ovchinnikov, Sergey G.; Makarov, Ilya A.; Kozlov, Peter A.
2017-03-01
In this work dependences of the electron band structure and spectral function in the HTSC cuprates on magnitude of electron-phonon interaction (EPI) and temperature are investigated. We use three-band p-d model with diagonal and offdiagonal EPI with breathing and buckling phonon mode in the frameworks of polaronic version of the generalized tight binding (GTB) method. The polaronic quasiparticle excitation in the system with EPI within this approach is formed by a hybridization of the local multiphonon Franck-Condon excitations with lower and upper Hubbard bands. Increasing EPI leads to transfer of spectral weight to high-energy multiphonon excitations and broadening of the spectral function. Temperature effects are taken into account by occupation numbers of local excited polaronic states and variations in the magnitude of spin-spin correlation functions. Increasing the temperature results in band structure reconstruction, spectral weight redistribution, broadening of the spectral function peak at the top of the valence band and the decreasing of the peak intensity. The effect of EPI with two phonon modes on the polaron spectral function is discussed.
The spin-s quantum Heisenberg ferromagnetic models in the physical magnon theory
International Nuclear Information System (INIS)
Liu, B.-G.; Pu, F.-C.
2001-01-01
The spin-s quantum Heisenberg ferromagnetic model is investigated in the physical magnon theory. The effect of the extra unphysical magnon states on every site is completely removed in the magnon Hamiltonian and during approximation procedure so that the condition †n i a n i >=0(n≥2s+1) is rigorously satisfied. The physical multi-magnon occupancy †n i a n i >(1≤n≤2s) is proportional to T 3n/2 at low temperature and is equivalent to 1/(2s+1) at the Curie temperature. The magnetization not only unified but also well-behaved from zero temperature to Curie temperature is obtained in the framework of the magnon theory for the spin-s quantum Heisenberg ferromagnetic model. The ill-behaved magnetizations at high temperature in earlier magnon theories are completely corrected. The relation of magnon (spin wave) theory with spin-operator decoupling theory is clearly understood
Electron-excited molecule interactions
International Nuclear Information System (INIS)
Christophorou, L.G.; Tennessee Univ., Knoxville, TN
1991-01-01
In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10 6 to 10 7 times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs
International Nuclear Information System (INIS)
Oliveira, Joao Paulo Cavalcante; Mota, F. de Brito; Rivelino, Roberto
2011-01-01
Full text. Carbon nano wires made of long linear atomic chains have attracted considerable interest due to their potential applications in nano electronics. We report a density-functional-theory study of the nuclear spin-spin coupling constants for nano assemblies made of two coronene molecules bridged by carbon linear chains, considering distinct sizes and spin multiplicities. Also, we examine the effects of two terminal conformations (syn and anti) of the terminal anchor pieces on the magnetic properties of the carbon chains via 13 C NMR calculations. Our results reveal that simplified chemical models such as those based on cumulenes or polyynes are not appropriate to describe the linear chains with sp 2 terminations. For these types of atomic chains, the electronic ground state of the even-numbered chains can be singlet or triplet, whereas the ground state of the odd-numbered chains can be doublet or quartet. We discuss how the 13 C NMR chemical shift absorption is affected by increasing the size and changing the parity of the linear carbon chains. We have found that the J coupling constants between the carbon atoms in the linear chains present a well-defined pattern, in good accordance with our electronic structure calculations. For example, in the -C 4 - units we obtain couplings of 43.8, 114.5, 84.6, 114.5, and 43.8 Hz from one end to the other
Energy Technology Data Exchange (ETDEWEB)
Křístková, Anežka; Malkin, Vladimir G. [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava (Slovakia); Komorovsky, Stanislav; Repisky, Michal [Centre for Theoretical and Computational Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø (Norway); Malkina, Olga L., E-mail: olga.malkin@savba.sk [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava (Slovakia); Department of Inorganic Chemistry, Comenius University, Bratislava (Slovakia)
2015-03-21
In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density fitting approach for the rapid evaluation of density functional theory exchange-correlation response kernels. The new approach is aimed to speedup the bottleneck in the solution of the coupled perturbed equations: evaluation of the matrix elements of the kernel of the exchange-correlation potential. The performance of the new scheme has been tested on a representative set of indirect nuclear spin-spin couplings. The obtained results have been compared with the corresponding results of the reference method with traditional evaluation of the exchange-correlation kernel, i.e., without employing the fitted electron densities. Overall good agreement between both methods was observed, though the new approach tends to give values by about 4%-5% higher than the reference method. On the average, the solution of the coupled perturbed equations with the new scheme is about 8.5 times faster compared to the reference method.
International Nuclear Information System (INIS)
Křístková, Anežka; Malkin, Vladimir G.; Komorovsky, Stanislav; Repisky, Michal; Malkina, Olga L.
2015-01-01
In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density fitting approach for the rapid evaluation of density functional theory exchange-correlation response kernels. The new approach is aimed to speedup the bottleneck in the solution of the coupled perturbed equations: evaluation of the matrix elements of the kernel of the exchange-correlation potential. The performance of the new scheme has been tested on a representative set of indirect nuclear spin-spin couplings. The obtained results have been compared with the corresponding results of the reference method with traditional evaluation of the exchange-correlation kernel, i.e., without employing the fitted electron densities. Overall good agreement between both methods was observed, though the new approach tends to give values by about 4%-5% higher than the reference method. On the average, the solution of the coupled perturbed equations with the new scheme is about 8.5 times faster compared to the reference method
Interplay between electron-phonon and electron-electron interactions
International Nuclear Information System (INIS)
Roesch, O.; Gunnarsson, O.; Han, J.E.; Crespi, V.H.
2005-01-01
We discuss the interplay between electron-electron and electron-phonon interactions for alkali-doped fullerides and high temperature superconductors. Due to the similarity of the electron and phonon energy scales, retardation effects are small for fullerides. This raises questions about the origin of superconductivity, since retardation effects are believed to be crucial for reducing effects of the Coulomb repulsion in conventional superconductors. We demonstrate that by treating the electron-electron and electron-phonon interactions on an equal footing, superconductivity can be understood in terms of a local pairing. The Jahn-Teller character of the important phonons in fullerides plays a crucial role for this result. To describe effects of phonons in cuprates, we derive a t-J model with phonons from the three-band model. Using exact diagonalization for small clusters, we find that the anomalous softening of the half-breathing phonon as well as its doping dependence can be explained. By comparing the solution of the t-J model with the Hartree-Fock approximation for the three-band model, we address results obtained in the local-density approximation for cuprates. We find that genuine many-body results, due to the interplay between the electron-electron and electron-phonon interactions, play an important role for the the results in the t-J model. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Rigorous spin-spin correlation function of Ising model on a special kind of Sierpinski Carpets
International Nuclear Information System (INIS)
Yang, Z.R.
1993-10-01
We have exactly calculated the rigorous spin-spin correlation function of Ising model on a special kind of Sierpinski Carpets (SC's) by means of graph expansion and a combinatorial approach and investigated the asymptotic behaviour in the limit of long distance. The result show there is no long range correlation between spins at any finite temperature which indicates no existence of phase transition and thus finally confirms the conclusion produced by the renormalization group method and other physical arguments. (author). 7 refs, 6 figs
Symmetry rules for the indirect nuclear spin-spin coupling tensor revisited
Buckingham, A. D.; Pyykkö, P.; Robert, J. B.; Wiesenfeld, L.
The symmetry rules of Buckingham and Love (1970), relating the number of independent components of the indirect spin-spin coupling tensor J to the symmetry of the nuclear sites, are shown to require modification if the two nuclei are exchanged by a symmetry operation. In that case, the anti-symmetric part of J does not transform as a second-rank polar tensor under symmetry operations that interchange the coupled nuclei and may be called an anti-tensor. New rules are derived and illustrated by simple molecular models.
Energy Technology Data Exchange (ETDEWEB)
San Fabián, J.; Omar, S.; García de la Vega, J. M., E-mail: garcia.delavega@uam.es [Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid (Spain)
2016-08-28
The effect of a fraction of Hartree-Fock exchange on the calculated spin-spin coupling constants involving fluorine through a hydrogen bond is analyzed in detail. Coupling constants calculated using wavefunction methods are revisited in order to get high-level calculations using the same basis set. Accurate MCSCF results are obtained using an additive approach. These constants and their contributions are used as a reference for density functional calculations. Within the density functional theory, the Hartree-Fock exchange functional is split in short- and long-range using a modified version of the Coulomb-attenuating method with the SLYP functional as well as with the original B3LYP. Results support the difficulties for calculating hydrogen bond coupling constants using density functional methods when fluorine nuclei are involved. Coupling constants are very sensitive to the Hartree-Fock exchange and it seems that, contrary to other properties, it is important to include this exchange for short-range interactions. Best functionals are tested in two different groups of complexes: those related with anionic clusters of type [F(HF){sub n}]{sup −} and those formed by difluoroacetylene and either one or two hydrogen fluoride molecules.
Electron spin from self interaction
International Nuclear Information System (INIS)
Spavieri, G.
1992-01-01
The author explores the possibility that the electron self-interaction is the origin of the spin and of the radiative effects of QED. The electron is conceived as a charged, massless, point particle with a quantum or stochastic, internal motion about its center of mass and bound by a self-interaction potential. The hydrodynamic equations of motion describing the electron in its center of mass frame are related to non-Markovian stochastic equations recently used to derive the Schroedinger equation. By averaging over this stochastic internal motion and identifying the energy with the rest mass energy, the angular momentum exhibits properties characteristic of spin. The electromagnetic self-interactions added to the Hamiltonian of the particle correct the g factor to yield the anomalous value (g-2)/2 ∼ 1159.7(2.3) X 10 -6 in agreement with experiment. Calculations of other open-quotes radiativeclose quotes effects including the Lamb shift are presented. The results obtained are finite and suggest that the QED corrections attributed to radiative effects could be obtained classically, i.e., without second quantization and renormalization, by complementing the Dirac theory with this self-interaction mechanism. The g factor dependence on the external magnetic field of this and other spin models is compared with that of QED, showing that these theories can be tested by the present precision measurements of the g factor. 33 refs., 2 tabs
Sunahori, Fumie X.; Nagarajan, Ramya; Clouthier, Dennis J.
2015-12-01
The cold boron carbide free radical (BC X 4Σ-) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescence spectra have been obtained for the B 4Σ--X 4Σ- and E 4Π-X 4Σ- band systems of both 11BC and 10BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then recording the various allowed transitions from the intermediate B state to the final E state with a second laser by monitoring the subsequent E-X ultraviolet fluorescence. In this fashion, we were able to prove unambiguously that, contrary to previous studies, the spin-spin constant λ is negative in the ground state and positive in the B 4Σ- excited state. It has been shown that λ″ expected based on a semiempirical second order perturbation theory calculation of the magnitude of the spin-spin constant. The OODR spectra have also been used to validate our assignments of the complex and badly overlapped E 4Π-X 4Σ- 0-0 and 1-0 bands of 11BC. The E-X 0-0 band of 10BC was found to be severely perturbed. The ground state main electron configuration is …3σ24σ25σ11π22π0 and the derived bond lengths show that there is a 0.03 Å contraction in the B state, due to the promotion of an electron from the 4σ antibonding orbital to the 5σ bonding orbital. In contrast, the bond length elongates by 0.15 Å in the E state, a result of promoting an electron from the 5σ bonding orbital to the 2π antibonding orbitals.
Electron interactions with polar molecules
International Nuclear Information System (INIS)
Garrett, W.R.
1981-01-01
A description is given of a number of the features of discrete and continuous spectra of electrons interacting with polar molecules. Attention is focused on the extent to which theoretical predictions concerning cross sections, resonances, and bound states are strongly influenced by the various approximations that are so ubiquitous in the treatment of such problems. Similarly, threshold scattering and photodetachment processes are examined for the case of weakly bound dipole states whose higher members overlap the continuum
Electronic conduction in doped multiferroic BiFeO3
Yang, Chan-Ho; Seidel, Jan; Kim, Sang-Yong; Gajek, M.; Yu, P.; Holcomb, M. B.; Martin, L. W.; Ramesh, R.; Chu, Y. H.
2009-03-01
Competition between multiple ground states, that are energetically similar, plays a key role in many interesting material properties and physical phenomena as for example in high-Tc superconductors (electron kinetic energy vs. electron-electron repulsion), colossal magnetoresistance (metallic state vs. charge ordered insulating state), and magnetically frustrated systems (spin-spin interactions). We are exploring the idea of similar competing phenomena in doped multiferroics by control of band-filling. In this paper we present systematic investigations of divalent Ca doping of ferroelectric BiFeO3 in terms of structural and electronic conduction properties as well as diffusion properties of oxygen vacancies.
Spin-Spin Relaxation and Karyagin-Gol'danskii Effect in FeCl3·6H2O
DEFF Research Database (Denmark)
Thrane, N.; Trumpy, Georg
1970-01-01
. Qualitatively, the experimental results can be explained by a combination of a temperature-and magnetic-field-dependent spin-spin relaxation and the Karyagin-Gol'danskii effect. This implies that the zero-field splitting is about 20°K between the lowest-lying Kramers doublet, found to be the |±1 / 2...
Electron-molecule interactions and their applications
Christophorou, L G
1984-01-01
Electron-Molecule Interactions and Their Applications, Volume 2 provides a balanced and comprehensive account of electron-molecule interactions in dilute and dense gases and liquid media. This book consists of six chapters. Chapter 1 deals with electron transfer reactions, while Chapter 2 discusses electron-molecular positive-ion recombination. The electron motion in high-pressure gases and electron-molecule interactions from single- to multiple-collision conditions is deliberated in Chapter 3. In Chapter 4, knowledge on electron-molecule interactions in gases is linked to that on similar proc
Energy Technology Data Exchange (ETDEWEB)
Krivdin, L.B.; Proidakov, A.G.; Bazhenov, B.N.; Zinchenko, S.V.; Kalabin, G.A.
1989-01-10
The effects of substitution on the direct /sup 13/C-/sup 13/C spin-spin coupling constants of the triple bond were studied in 100 derivatives of acetylene. It was established that these parameters exhibit increased sensitivity to the effect of substituents compared with other types of compounds. The main factor which determines their variation is the electronegativity of the substituting groups, and in individual cases the /pi/-electronic effects are appreciable. The effect of the substituents with an element of the silicon subgroup at the /alpha/ position simultaneously at the triple bond or substituent of the above-mentioned type and a halogen atom.
International Nuclear Information System (INIS)
Goepfert, A.
1994-01-01
This thesis develops a new model, and related numerical methods, to describe classical time-dependent many-body systems interacting through central forces, spin-orbit forces and spin-spin forces. The model is based on two-particle interactions. The two-body forces consist of attractive and repulsive parts. In this model the investigated multi-particle systems are self-bound. Also the total potential of the whole ensemble is derived from the two-particle potential and is not imposed 'from outside'. Each particle has the three degrees of freedom of its centre-of-mass motion and the spin degree of freedom. The model allows for the particles to be either charged or uncharged. Furthermore, each particle has an angular momentum, an intrinsic spin, and a magnetic dipole moment. Through the electromagnetic forces between these charges and moments there arise dynamical couplings between them. The internal interactions between the charges and moments are well described by electromagnetic coupling mechanisms. In fact, compared to conventional classical molecular dynamics calculations in van der Waals clusters, which have no spin degrees of freedom, or for Heisenberg spin Systems, which have no orbital degrees of freedom, the model presented here contains both types of degrees of freedom with a highly non-trivial coupling. The model allows to study the fundamental effects resulting from the dynamical coupling of the spin and the orbital-motion sub-systems. In particular, the dynamics of the particle mass points show a behaviour basically different from the one of particles in a potential with only central forces. Furthermore, a special type of quenching procedure was invented, which tends to drive the multi-particle Systems into states with highly periodic, non-ergodic behaviour. Application of the model to cluster simulations has provided evidence that the model can also be used to investigate items like solid-to-liquid phase transitions (melting), isomerism and specific heat
Measurement of the spin-spin correlation parameter C/sub LL/(THETA) in proton-proton scattering
International Nuclear Information System (INIS)
Stuart, S.J.
1982-08-01
The experimental procedures and methods of data analysis used to measure the spin-spin correlation parameter C/sub LL/(THETA) in proton-proton scattering at thirteen different energies in the range 300 to 800 MeV are presented. The results compare favorably with previous data. Good agreement is found with phase shift predictions at energies below 500 MeV
Energy Technology Data Exchange (ETDEWEB)
Faber, Rasmus; Sauer, Stephan P. A. [Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø (Denmark)
2015-12-31
We present zero-point vibrational corrections to the indirect nuclear spin-spin coupling constants in ethyne, ethene, cyclopropene and allene. The calculations have been carried out both at the level of the second order polarization propagator approximation (SOPPA) employing a new implementation in the DALTON program, at the density functional theory level with the B3LYP functional employing also the Dalton program and at the level of coupled cluster singles and doubles (CCSD) theory employing the implementation in the CFOUR program. Specialized coupling constant basis sets, aug-cc-pVTZ-J, have been employed in the calculations. We find that on average the SOPPA results for both the equilibrium geometry values and the zero-point vibrational corrections are in better agreement with the CCSD results than the corresponding B3LYP results. Furthermore we observed that the vibrational corrections are in the order of 5 Hz for the one-bond carbon-hydrogen couplings and about 1 Hz or smaller for the other couplings apart from the one-bond carbon-carbon coupling (11 Hz) and the two-bond carbon-hydrogen coupling (4 Hz) in ethyne. However, not for all couplings lead the inclusion of zero-point vibrational corrections to better agreement with experiment.
Phase diagram study of a dimerized spin-S zig–zag ladder
International Nuclear Information System (INIS)
Matera, J M; Lamas, C A
2014-01-01
The phase diagram of a frustrated spin-S zig–zag ladder is studied through different numerical and analytical methods. We show that for arbitrary S, there is a family of Hamiltonians for which a fully-dimerized state is an exact ground state, being the Majumdar–Ghosh point for a particular member of the family. We show that the system presents a transition between a dimerized phase to a Néel-like phase for S = 1/2, and spiral phases can appear for large S. The phase diagram is characterized by means of a generalization of the usual mean field approximation. The novelty in the present implementation is to consider the strongest coupled sites as the unit cell. The gap and the excitation spectrum is analyzed through the random phase approximation. Also, a perturbative treatment to obtain the critical points is discussed. Comparisons of the results with numerical methods like the Density Matrix Renormalization Group are also presented. (paper)
Electron paramagnetic resonance of transition ions
Abragam, Anatole
1970-01-01
This book is a reissue of a classic Oxford text, and provides a comprehensive treatment of electron paramagnetic resonance of ions of the transition groups. The emphasis is on basic principles, with numerous references to publications containing further experimental results and more detailed developments of the theory. An introductory survey gives a general understanding, and a general survey presents such topics as the classical and quantum resonance equations, thespin-Hamiltonian, Endor, spin-spin and spin-lattice interactions, together with an outline of the known behaviour of ions of each
Energy Technology Data Exchange (ETDEWEB)
Sunahori, Fumie X. [Department of Chemistry and Physics, Franklin College, Franklin, Indiana 46131 (United States); Nagarajan, Ramya; Clouthier, Dennis J., E-mail: dclaser@uky.edu [Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)
2015-12-14
The cold boron carbide free radical (BC X {sup 4}Σ{sup −}) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescence spectra have been obtained for the B {sup 4}Σ{sup −}–X {sup 4}Σ{sup −} and E {sup 4}Π–X {sup 4}Σ{sup −} band systems of both {sup 11}BC and {sup 10}BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then recording the various allowed transitions from the intermediate B state to the final E state with a second laser by monitoring the subsequent E–X ultraviolet fluorescence. In this fashion, we were able to prove unambiguously that, contrary to previous studies, the spin-spin constant λ is negative in the ground state and positive in the B {sup 4}Σ{sup −} excited state. It has been shown that λ″ < 0 is in fact expected based on a semiempirical second order perturbation theory calculation of the magnitude of the spin-spin constant. The OODR spectra have also been used to validate our assignments of the complex and badly overlapped E {sup 4}Π–X {sup 4}Σ{sup −} 0-0 and 1-0 bands of {sup 11}BC. The E–X 0-0 band of {sup 10}BC was found to be severely perturbed. The ground state main electron configuration is …3σ{sup 2}4σ{sup 2}5σ{sup 1}1π{sup 2}2π{sup 0} and the derived bond lengths show that there is a 0.03 Å contraction in the B state, due to the promotion of an electron from the 4σ antibonding orbital to the 5σ bonding orbital. In contrast, the bond length elongates by 0.15 Å in the E state, a result of promoting an electron from the 5σ bonding orbital to the 2π antibonding orbitals.
Dynamics of the two-spin spin-boson model with a common bath
Energy Technology Data Exchange (ETDEWEB)
Deng, Tianrui [Division of Materials Science, Nanyang Technological University, Singapore 639798 (Singapore); Centre for Optical and Electromagnetic Research, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Hangzhou 310058 (China); Yan, Yiying; Chen, Lipeng; Zhao, Yang, E-mail: YZhao@ntu.edu.sg [Division of Materials Science, Nanyang Technological University, Singapore 639798 (Singapore)
2016-04-14
Dynamics of the two-spin spin-boson model in the presence of Ohmic and sub-Ohmic baths is investigated by employing a multitude of the Davydov D{sub 1} trial states, also known as the multi-D{sub 1} Ansatz. Its accuracy in dynamics simulations of the two-spin SBM is improved significantly over the single D{sub 1} Ansatz, especially in the weak to moderately strong coupling regime. Validity of the multi-D{sub 1} Ansatz for various coupling strengths is also systematically examined by making use of the deviation vector which quantifies how faithfully the trial state obeys the Schrödinger equation. The time evolution of population difference and entanglement has been studied for various initial conditions and coupling strengths. Careful comparisons are carried out between our approach and three other methods, i.e., the time-dependent numerical renormalization group (TD-NRG) approach, the Bloch-Redfield theory, and a method based on a variational master equation. For strong coupling, the multi-D{sub 1} trial state yields consistent results as the TD-NRG approach in the Ohmic regime while the two disagree in the sub-Ohmic regime, where the multi-D{sub 1} trial state is shown to be more accurate. For weak coupling, the multi-D{sub 1} trial state agrees with the two master-equation methods in the presence of both Ohmic and sub-Ohmic baths, but shows considerable differences with the TD-NRG approach in the presence of a sub-Ohmic bath, calling into question the validity of the TD-NRG results at long times in the literature.
Electron interactions with nuclei: Progress report
International Nuclear Information System (INIS)
1988-08-01
This paper contains information on the following topics: inclusive electron scattering; electroexcitation of Δ in nuclei; longitudinal and transverse response in the quasi-elastic region; electron scattering at MIT-Bates; detector development at LEGS; electron scattering at Saclay; intermediate energy nuclear interactions; research and development at CEBAF; and computing facilities
The 40th anniversary of the discovery of NMR-chemical shift and nuclear spin-spin coupling
International Nuclear Information System (INIS)
Zhu Zhenghe; Gou Qingquan
1989-01-01
After the discovery of NMR Phenomenon in the physics laboratories of E.M.Purcell at Harvard and F.Bloch at Stanford in 1946, W.G.Proctor and F.C.Yu made the successful discovery of NMR-chemical shift and nuclear spin-spin coupling at Stanford in 1950, Which brought NMR spectroscopy from the physics laboratory to the laboratories of many different fields. This is worth memorizing. Retrospecting the past 40 years, it is sure that chemical shift theory will be much more prosperous prospects
International Nuclear Information System (INIS)
Zarycz, M. Natalia C.; Provasi, Patricio F.; Sauer, Stephan P. A.
2015-01-01
It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH 4 , NH 3 , H 2 O, SiH 4 , PH 3 , SH 2 , C 2 H 2 , C 2 H 4 , and C 2 H 6 . The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states
Energy Technology Data Exchange (ETDEWEB)
Zarycz, M. Natalia C., E-mail: mnzarycz@gmail.com; Provasi, Patricio F., E-mail: patricio@unne.edu.ar [Department of Physics, University of Northeastern - CONICET, Av. Libertad 5500, Corrientes W3404AAS (Argentina); Sauer, Stephan P. A., E-mail: sauer@kiku.dk [Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø (Denmark)
2015-12-28
It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH{sub 4}, NH{sub 3}, H{sub 2}O, SiH{sub 4}, PH{sub 3}, SH{sub 2}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, and C{sub 2}H{sub 6}. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.
Electron scattering in the interacting boson model
Dieperink, AEL; Iachello, F; Rinat, A; Creswell, C
1978-01-01
It is suggested that the interacting boson model be used in the analysis of electron scattering data. Qualitative features of the expected behavior of the inelastic excitation of some 2 ÷ states inthe transitional Sm-Nd region are discussed
Noncovalent Interactions in Organic Electronic Materials
Ravva, Mahesh Kumar; Risko, Chad; Bredas, Jean-Luc
2017-01-01
In this chapter, we provide an overview of how noncovalent interactions, determined by the chemical structure of π-conjugated molecules and polymers, govern essential aspects of the electronic, optical, and mechanical characteristics of organic
Photon-Electron Interaction and Condense Beams
International Nuclear Information System (INIS)
Chattopadhyay, S.
1998-01-01
We discuss beams of charged particles and radiation from multiple perspectives. These include fundamental acceleration and radiation mechanisms, underlying electron-photon interaction, various classical and quantum phase-space concepts and fluctuational interpretations
The Electron Transport Chain: An Interactive Simulation
Romero, Chris; Choun, James
2014-01-01
This activity provides students an interactive demonstration of the electron transport chain and chemiosmosis during aerobic respiration. Students use simple, everyday objects as hydrogen ions and electrons and play the roles of the various proteins embedded in the inner mitochondrial membrane to show how this specific process in cellular…
International Nuclear Information System (INIS)
Repisky, Michal; Komorovsky, Stanislav; Malkina, Olga L.; Malkin, Vladimir G.
2009-01-01
The relativistic four-component density functional approach based on the use of restricted magnetically balanced basis (mDKS-RMB), applied recently for calculations of NMR shielding, was extended for calculations of NMR indirect nuclear spin-spin coupling constants. The unperturbed equations are solved with the use of a restricted kinetically balanced basis set for the small component while to solve the second-order coupled perturbed DKS equations a restricted magnetically balanced basis set for the small component was applied. Benchmark relativistic calculations have been carried out for the X-H and H-H spin-spin coupling constants in the XH 4 series (X = C, Si, Ge, Sn and Pb). The method provides an attractive alternative to existing approximate two-component methods with transformed Hamiltonians for relativistic calculations of spin-spin coupling constants of heavy-atom systems. In particular, no picture-change effects arise in our method for property calculations
García de la Vega, J M; Omar, S; San Fabián, J
2017-04-01
Spin-spin coupling constants in water monomer and dimer have been calculated using several wave function and density functional-based methods. CCSD, MCSCF, and SOPPA wave functions methods yield similar results, specially when an additive approach is used with the MCSCF. Several functionals have been used to analyze their performance with the Jacob's ladder and a set of functionals with different HF exchange were tested. Functionals with large HF exchange appropriately predict 1 J O H , 2 J H H and 2h J O O couplings, while 1h J O H is better calculated with functionals that include a reduced fraction of HF exchange. Accurate functionals for 1 J O H and 2 J H H have been tested in a tetramer water model. The hydrogen bond effects on these intramolecular couplings are additive when they are calculated by SOPPA(CCSD) wave function and DFT methods. Graphical Abstract Evaluation of the additive effect of the hydrogen bond on spin-spin coupling constants of water using WF and DFT methods.
Noncovalent Interactions in Organic Electronic Materials
Ravva, Mahesh Kumar
2017-06-29
In this chapter, we provide an overview of how noncovalent interactions, determined by the chemical structure of π-conjugated molecules and polymers, govern essential aspects of the electronic, optical, and mechanical characteristics of organic semiconductors. We begin by describing general aspects of materials design, including the wide variety of chemistries exploited to control the electronic and optical properties of these materials. We then discuss explicit examples of how the study of noncovalent interactions can provide deeper chemical insights that can improve the design of new generations of organic electronic materials.
Localization of electrons by electron-electron interaction in an Anderson model
International Nuclear Information System (INIS)
Ritala, R.K.; Kurkijaervi, J.
1981-01-01
We study the effect of attractive Hubbard interaction on disordered electron system. We map the interacting system back to noninteracting one and determine self-consistently the disorder change due to interaction in the system. (author)
Energy Technology Data Exchange (ETDEWEB)
Kahnoj, Sina Soleimani; Touski, Shoeib Babaee [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Pourfath, Mahdi, E-mail: pourfath@ut.ac.ir, E-mail: pourfath@iue.tuwien.ac.at [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Institute for Microelectronics, TU Wien, Gusshausstrasse 27–29/E360, 1040 Vienna (Austria)
2014-09-08
The effect of dephasing induced by electron-electron interaction on electronic transport in graphene nanoribbons is theoretically investigated. In the presence of disorder in graphene nanoribbons, wavefunction of electrons can set up standing waves along the channel and the conductance exponentially decreases with the ribbon's length. Employing the non-equilibrium Green's function formalism along with an accurate model for describing the dephasing induced by electron-electron interaction, we show that this kind of interaction prevents localization and transport of electrons remains in the diffusive regime where the conductance is inversely proportional to the ribbon's length.
Analytical local electron-electron interaction model potentials for atoms
International Nuclear Information System (INIS)
Neugebauer, Johannes; Reiher, Markus; Hinze, Juergen
2002-01-01
Analytical local potentials for modeling the electron-electron interaction in an atom reduce significantly the computational effort in electronic structure calculations. The development of such potentials has a long history, but some promising ideas have not yet been taken into account for further improvements. We determine a local electron-electron interaction potential akin to those suggested by Green et al. [Phys. Rev. 184, 1 (1969)], which are widely used in atom-ion scattering calculations, electron-capture processes, and electronic structure calculations. Generalized Yukawa-type model potentials are introduced. This leads, however, to shell-dependent local potentials, because the origin behavior of such potentials is different for different shells as has been explicated analytically [J. Neugebauer, M. Reiher, and J. Hinze, Phys. Rev. A 65, 032518 (2002)]. It is found that the parameters that characterize these local potentials can be interpolated and extrapolated reliably for different nuclear charges and different numbers of electrons. The analytical behavior of the corresponding localized Hartree-Fock potentials at the origin and at long distances is utilized in order to reduce the number of fit parameters. It turns out that the shell-dependent form of Green's potential, which we also derive, yields results of comparable accuracy using only one shell-dependent parameter
Interactions of electrons with biologically important molecules
International Nuclear Information System (INIS)
Pisklova, K.; Papp, P.; Stano, M.
2012-01-01
For the study of interactions of low-energy electrons with the molecules in the gas phase, the authors used electron-molecule cross-beam apparatus. The experiment is carried out in high vacuum, where molecules of the tested compound are inducted through a capillary. For purposes of this experiment the sample was electrically heated to 180 Deg C., giving a bundle of GlyGly molecules into the gas phase. The resulting signals can be evaluated in two different modes: mass spectrum - at continuous electron energy (e.g. 100 eV) they obtained the signal of intensity of the ions according to their mass to charge ratio; ionization and resonance spectra - for selected ion mass when the authors received the signal of intensity of the ions, depending on the energy of interacting electron.
Electron-electron interaction in Multiple Quantum Wells
Zybert, M.; Marchewka, M.; Tomaka, G.; Sheregii, E. M.
2012-07-01
The complex investigation of the magneto-transport effects in structures containing multiple quantum well (MQWs) based on the GaAs/AlGaAs-heterostructures has been performed. The MQWs investigated have different electron densities in QWs. The parameters of 2DEG in MQWs were determined from the data of the Integer Quantum Hall Effect (IQHE) and Shubnikov-de Haas oscillations (SdH) observed at low temperatures (0.6-4.2 K). The method of calculation of the electron states energies in MQWs has been developed which is based on the splitting of these states due to the exchange interaction (SAS-splitting, see D. Płoch et al., Phys. Rev. B 79 (2009) 195434) including the screening of this interaction. The IQHE and SdH observed in these multilayer structures with the third degree of freedom for electrons are interpreted from this.
Studying electron-PAG interactions using electron-induced fluorescence
Narasimhan, Amrit; Grzeskowiak, Steven; Ostrander, Jonathan; Schad, Jonathon; Rebeyev, Eliran; Neisser, Mark; Ocola, Leonidas E.; Denbeaux, Gregory; Brainard, Robert L.
2016-03-01
In extreme ultraviolet (EUV) lithography, 92 eV photons are used to expose photoresists. Typical EUV resists are organic-based and chemically amplified using photoacid generators (PAGs). Upon exposure, PAGs produce acids which catalyze reactions that result in changes in solubility. In EUV lithography, photo- and secondary electrons (energies of 10- 80 eV) play a large role in PAG acid-production. Several mechanisms for electron-PAG interactions (e.g. electron trapping, and hole-initiated chemistry) have been proposed. The aim of this study is to explore another mechanism - internal excitation - in which a bound PAG electron can be excited by receiving energy from another energetic electron, causing a reaction that produces acid. This paper explores the mechanism of internal excitation through the analogous process of electron-induced fluorescence, in which an electron loses energy by transferring that energy to a molecule and that molecule emits a photon rather than decomposing. We will show and quantify electron-induced fluorescence of several fluorophores in polymer films to mimic resist materials, and use this information to refine our proposed mechanism. Relationships between the molecular structure of fluorophores and fluorescent quantum yield may aid in the development of novel PAGs for EUV lithography.
Electron-phonon interactions in correlated systems
International Nuclear Information System (INIS)
Wysokinski, K.I.
1996-01-01
There exist attempts to describe the superconducting mechanism operating in HTS as based on antiferromagnetic fluctuations. It is not our intention to dwell on the superconducting mechanism, even though this is very a important issue. The main aim is to discuss the problem of interplay between electron-phonon and electron-electron interactions in correlated systems. We believe such analysis can be of importance for various materials and not only HTS'S. We shall however mainly refer to experiments on this last class of superconductors. Severe complications are to be expected by studying the problem. As is well known electron correlations are very important in narrow band systems, where the relevant electronic scale E F is quite small. In those circumstances, the phonon energy scale ω D is of comparable magnitude, with the ratio ω D /E F of order 1 signalling a possible break down of the Migdal - Eliashberg description of the electron-phonon interaction in metals. Here we shall assume the validity of the Migdal-Eliashberg approximation and concentrate on the mutual influence of electron and phonon subsystems. In the next section we shall discuss experimental motivation for and theoretical work related to the present problem. Section 3 contains a brief discussion of our theory. It is a self-consistent theory a la Migdal with strong correlations treated with an auxiliary boson technique. We conclude with results and their discussion. (orig.)
DEFF Research Database (Denmark)
Faber, Rasmus; Sauer, Stephan P. A.
2018-01-01
The basis set convergence of nuclear spin-spin coupling constants (SSCC) calculated at the coupled cluster singles and doubles (CCSD) level has been investigated for ten difficult molecules. Eight of the molecules contain fluorine atoms and nine contain double or triple bonds. Results obtained...
Czech Academy of Sciences Publication Activity Database
Sychrovský, Vladimír; Vacek, Jaroslav; Hobza, Pavel; Žídek, L.; Sklenář, V.; Cremer, D.
2002-01-01
Roč. 106, - (2002), s. 10242-10250 ISSN 1089-5639 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : DNA * help of NMR spin-spin coupling constants * quantum chemical investigation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.765, year: 2002
DEFF Research Database (Denmark)
Enevoldsen, Thomas; Oddershede, Jens; Sauer, Stephan P. A.
1998-01-01
We present correlated calculations of the indirect nuclear spin-spin coupling constants of HD, HF, H2O, CH4, C2H2, BH, AlH, CO and N2 at the level of the second-order polarization propagator approximation (SOPPA) and the second-order polarization propagator approximation with coupled-cluster sing...
International Nuclear Information System (INIS)
Ardehali, M.
1990-01-01
Some simple inequalities which demonstrate the incompatibility of local realism with quantum theory are derived. They establish, for the first time, necessary conditions for violation of the generalized spin-s Bell inequalities for a set of three distinct noncoplanar axes. For s=1/2, however, these inequalities are equivalent to Wigner's results, thus giving necessary and sufficient conditions
Measurement of np elastic scattering spin-spin correlation parameters at 484, 634, and 788 MeV
International Nuclear Information System (INIS)
Garnett, R.W.
1989-03-01
The spin-spin correlation parameters C/sub LL/ and C/sub SL/ were measured for np elastic scattering at the incident neutron kinetic energy of 634 MeV. Good agreement was obtained with previously measured data. Additionally, the first measurement of the correlation parameter C/sub SS/ was made at the three energies, 484, 634, and 788 MeV. It was found that the new values, in general, do not agree well with phase shift predictions. A study was carried out to determine which of the isospin-0 partial waves will be affected by this new data. It was found that the 1 P 1 partial wave will be affected significantly at all three measurement energies. At 634 and 788 MeV, the 3 S 1 phase shifts will also change. 29 refs., 21 figs., 16 tabs
Electron scattering in the interacting boson model
International Nuclear Information System (INIS)
Dieperink, A.E.L.; Iachello, F.; Creswell, C.
1978-01-01
It is suggested that the interacting boson model be used in the analysis of electron scattering data. Qualitative features of the expected behavior of the inelastic excitation of some 2 + states in the transitional Sm-Nd region are discussed. (Auth.)
Electron Beam interaction with an inhomogeneous
Energy Technology Data Exchange (ETDEWEB)
Zaki, N G; El-Shorbagy, Kh H [Plasma physics and Nuclear Fusion Dept. Nuclear Research Centre Atomic Energy Authority, Cairo, (Egypt)
1997-12-31
The linear and nonlinear interaction of an electron beam with an inhomogeneous semi bounded warm plasma is investigated. The amount of energy absorbed by the plasma is obtained. The formation of waves at double frequency at the inlet of the beam into the plasma is also considered.
Electron Donor Acceptor Interactions. Final Progress Report
Energy Technology Data Exchange (ETDEWEB)
Moore, Ana L. [Arizona State Univ., Tempe, AZ (United States)
2002-08-16
The Gordon Research Conference (GRC) on Electron Donor Acceptor Interactions was held at Salve Regina University, Newport, Rhode Island, 8/11-16/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.
Analysis of electron interactions in dielectric gases
International Nuclear Information System (INIS)
Olivet, Aurelio; Duque, Daniel; Vega, Lourdes F.
2007-01-01
We present and discuss results concerning electron interactions processes of dielectric gases and their relationship with the macroscopic behavior of these gases, in particular, with their dielectric strength. Such analysis is based on calculating energies of reactions for molecular ionization, dissociative ionization, parent negative ion formation, and dissociative electron attachment processes. We hypothesize that the estimation of the required energy for a reduced number of processes that take place in electrically stressed gases could be related to the gas' capability to manage the electron flow during an electrical discharge. All calculations were done with semiempirical quantum chemistry methods, including an initial optimization of molecular geometry and heat of formation of the dielectric gases and all of species that appear during electron interaction reactions. The performance of semiempirical methods Austin model 1 and Parametric model 3 (PM3) was compared for several compounds, PM3 being superior in most cases. Calculations performed for a sample of nine dielectric gases show that electron attachment and detachment processes occur in different energy bands that do not overlap for any value of the dielectric strength. We have also analyzed the relationship between dielectric strength and two physical properties: electron affinity and ionization energy. Calculations performed for 43 dielectric gases show no clear correlation between them, although certain guidelines for the qualitative estimation of dielectric strength can still be assessed
Magnetic impurity coupled to interacting conduction electrons
International Nuclear Information System (INIS)
Schork, T.
1996-01-01
We consider a magnetic impurity which interacts by hybridization with a system of weakly correlated electrons and determine the energy of the ground state by means of a 1/N f expansion. The correlations among the conduction electrons are described by a Hubbard Hamiltonian and are treated to the lowest order in the interaction strength. We find that their effect on the Kondo temperature, T K , in the Kondo limit is twofold: first, the position of the impurity level is shifted due to the reduction of charge fluctuations, which reduces T K . Secondly, the bare Kondo exchange coupling is enhanced as spin fluctuations are enlarged. In total, T K increases. Both corrections require intermediate states beyond the standard Varma-Yafet ansatz. This shows that the Hubbard interaction does not just provide quasiparticles, which hybridize with the impurity, but also renormalizes the Kondo coupling. copyright 1996 The American Physical Society
Electron beam interaction with space plasmas
International Nuclear Information System (INIS)
Krafft, C.; Volokitin, A.S.
1999-01-01
Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification. Recently, theoretical studies of the nonlinear evolution of a thin monoenergetic electron beam injected in a magnetized plasma and interacting with a whistler wave packet have led to new results. The influence of an effective dissipation process connected with whistler wave field leakage out of the beam volume to infinity (that is, effective radiation outside the beam) on the nonlinear evolution of beam electrons distribution in phase space has been studied under conditions relevant to active space experiments and related laboratory modelling. The beam-waves system's evolution reveals the formation of stable nonlinear structures continuously decelerated due to the effective friction imposed by the strongly dissipated waves. The nonlinear interaction between the electron bunches and the wave packet are discussed in terms of dynamic energy exchange, particle trapping, slowing down of the beam, wave dissipation and quasi-linear diffusion. (author)
Electron beam interaction with space plasmas.
Krafft, C.; Bolokitin, A. S.
1999-12-01
Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification.
High-field electron-photon interactions
International Nuclear Information System (INIS)
Hartemann, F V.
1999-01-01
Recent advances in novel technologies (including chirped-pulse amplification, femtosecond laser systems operating in the TW-PW range, high-gradient rf photoinjectors, and synchronized relativistic electron bunches with subpicosecond durations and THz bandwidths) allow experimentalists to study the interaction of relativistic electrons with ultrahigh-intensity photon fields. Ponderomotive scattering can accelerate these electrons with extremely high gradients in a three-dimensional vacuum laser focus. The nonlinear Doppler shift induced by relativistic radiation pressure in Compton backscattering is shown to yield complex nonlinear spectra which can be modified by using temporal laser pulse shaping techniques. Colliding laser pulses, where ponderomotive acceleration and Compton backscattering are combined, could also yield extremely short wavelength photons. Finally, one expects strong radiative corrections when the Doppler-upshifted laser wavelength approaches the Compton scale. These are discussed within the context of high-field classical electrodynamics, a new discipline borne out of the aforementioned innovations
Effective electron-electron and electron-phonon interactions in the Hubbard-Holstein model
International Nuclear Information System (INIS)
Aprea, G.; Di Castro, C.; Grilli, M. . E-mail marco.grilli@roma1.infn.it; Lorenzana, J.
2006-01-01
We investigate the interplay between the electron-electron and the electron-phonon interaction in the Hubbard-Holstein model. We implement the flow-equation method to investigate within this model the effect of correlation on the electron-phonon effective coupling and, conversely, the effect of phonons in the effective electron-electron interaction. Using this technique we obtain analytical momentum-dependent expressions for the effective couplings and we study their behavior for different physical regimes. In agreement with other works on this subject, we find that the electron-electron attraction mediated by phonons in the presence of Hubbard repulsion is peaked at low transferred momenta. The role of the characteristic energies involved is also analyzed
Runaway-electron-materials interaction studies
International Nuclear Information System (INIS)
Bolt, H.; Miyahara, A.
1990-03-01
During the operation of magnetic fusion devices it has been frequently observed that runaway electrons can cause severe damage to plasma facing components. The energy of the runaway electrons could possibly reach several 100 MeV in a next generation device with an energy content in the plasma in the order of 100 MJ. In this study effects of high energy electron - materials interaction were determined by laboratory experiments using particle beam facilities, i.e. the Electron Linear Accelerator of the Institute of Scientific and Industrial Research of Osaka University and the 10 MW Neutral Beam Injection Test Stand of the National Institute for Fusion Science. The experiments and further analyses lead to a first assessment of the damage thresholds of plasma facing materials and components under runaway electron impact. It was found that metals (stainless steel, molybdenum, tungsten) showed grain growth, crack formation and/or melting already below the threshold for crack initiation on graphite (14-33 MJ/m 2 ). Strong erosion of carbon materials would occur above 100 MJ/m 2 . Damage to metal coolant channels can occur already below an energy deposition of 100 MJ/m 2 . The energy deposited in the metal coolant channels depends on the thickness of the plasma facing carbon material D, with the shielding efficiency S of carbon approximately as S∼D 1.15 . (author) 304 refs. 12 tabs. 59 figs
Topics in electron-positron interactions
International Nuclear Information System (INIS)
Soeding, P.
1983-01-01
This chapter investigates the collision of an electron and a positron in a high energy storage ring in which a large energy Q=W=√s=2 E /SUB beam/ is dumped into a tiny region of space-time. If the electron and positron annihilate each other almost all of this energy becomes concentrated in a single field quantum. Points out 3 consequences: 1) all flavored particles existing in nature are expected to be pair-produced provided their mass is not larger than W/2; 2) the pair production process acts as an effective ''filter'' for fundamental (i.e. pointlike) particles; and 3) particles without flavor (i.e. the gluons) are not directly pair-produced in e - e + interactions. Discusses basic processes; probing QED and lepton structure; hadron production at high energies; resonances; e - e + storage rings; detectors; electroweak interaction and new particles (leptons, quarks); restrictions on a more general weak interaction scenario; limits on pair production of scalar particles; and jets and QCD tests
Gas–Electron Interaction in the ETEM
DEFF Research Database (Denmark)
Wagner, Jakob Birkedal; Beleggia, Marco
2016-01-01
Imaging in a differential pumped environmental TEM (ETEM) results in general in a degradation of the image quality. Scattering of electrons by gas molecules in the pressurized volume between the pole pieces blurs the image and decreases the signal-to-noise ratio of the acquired images. The somewhat...... simple picture of a plane wave interacting with the sample of interest is no longer valid. Furthermore, the exit wave from the sample is altered by scattering events taking place after the sample in the direction of propagation. In this chapter, the effect of the increased gas pressure between the pole...... pieces in an aberration-corrected highresolution transmission electron microscope is discussed in order to shine some light on the additional phenomena occurring in ETEM compared to conventional HRTEM. Both direct effects on the image quality and more indirect effects rising from gas ionization...
Interaction of electron neutrino with LSD detector
Ryazhskaya, O. G.; Semenov, S. V.
2016-06-01
The interaction of electron neutrino flux, originating in the rotational collapse mechanism on the first stage of Supernova burst, with the LSD detector components, such as 56Fe (a large amount of this metal is included in as shielding material) and liquid scintillator barNnH2n+2, is being investigated. Both charged and neutral channels of neutrino reaction with 12barN and 56Fe are considered. Experimental data, giving the possibility to extract information for nuclear matrix elements calculation are used. The number of signals, produced in LSD by the neutrino pulse of Supernova 1987A is determined. The obtained results are in good agreement with experimental data.
Attractive electron-electron interactions within robust local fitting approximations.
Merlot, Patrick; Kjærgaard, Thomas; Helgaker, Trygve; Lindh, Roland; Aquilante, Francesco; Reine, Simen; Pedersen, Thomas Bondo
2013-06-30
An analysis of Dunlap's robust fitting approach reveals that the resulting two-electron integral matrix is not manifestly positive semidefinite when local fitting domains or non-Coulomb fitting metrics are used. We present a highly local approximate method for evaluating four-center two-electron integrals based on the resolution-of-the-identity (RI) approximation and apply it to the construction of the Coulomb and exchange contributions to the Fock matrix. In this pair-atomic resolution-of-the-identity (PARI) approach, atomic-orbital (AO) products are expanded in auxiliary functions centered on the two atoms associated with each product. Numerical tests indicate that in 1% or less of all Hartree-Fock and Kohn-Sham calculations, the indefinite integral matrix causes nonconvergence in the self-consistent-field iterations. In these cases, the two-electron contribution to the total energy becomes negative, meaning that the electronic interaction is effectively attractive, and the total energy is dramatically lower than that obtained with exact integrals. In the vast majority of our test cases, however, the indefiniteness does not interfere with convergence. The total energy accuracy is comparable to that of the standard Coulomb-metric RI method. The speed-up compared with conventional algorithms is similar to the RI method for Coulomb contributions; exchange contributions are accelerated by a factor of up to eight with a triple-zeta quality basis set. A positive semidefinite integral matrix is recovered within PARI by introducing local auxiliary basis functions spanning the full AO product space, as may be achieved by using Cholesky-decomposition techniques. Local completion, however, slows down the algorithm to a level comparable with or below conventional calculations. Copyright © 2013 Wiley Periodicals, Inc.
Anisotropic exchange interaction for magnetic ion pairs in insulators
International Nuclear Information System (INIS)
Passeggi, M.C.G.
1975-12-01
The sources of possible contributions to the magnetic anisotropy for a pair of orbitally non degenerate magnetic ions are investigated. The problem being formulated with the help of the operator form of perturbation theory and irreducible tensor operators. Apart from the usual dipole-dipole effective interaction, mainly induced by the electronic spin-spin dipole coupling corrected by covalency, other mechanisms mediated by the spin-orbit coupling appear. These are a consequence of an appropriate description of the spin-orbit operators for a system which allows for delocalization of the magnetic electrons. A process similar to that known as pseudodipolar appears from contributions in which spin orbit combined with the Coulomb repulsion and with one-electron interactions (acting analogously as for the ''kinetic exchange'') produce compensating effects in third and fourth order, respectively. However, this effect does not appear to be describable in terms of the phenomenological exchange, as is usually assumed. (Passeggi, M.C.G.)
Exact solution of the mixed spin-1/2 and spin-S Ising-Heisenberg diamond chain
Directory of Open Access Journals (Sweden)
L. Čanová
2009-01-01
Full Text Available The geometric frustration in a class of the mixed spin-1/2 and spin-S Ising-Heisenberg diamond chains is investigated by combining three exact analytical techniques: Kambe projection method, decoration-iteration transformation and transfer-matrix method. The ground state, the magnetization process and the specific heat as a function of the external magnetic field are particularly examined for different strengths of the geometric frustration. It is shown that the increase of the Heisenberg spin value S raises the number of intermediate magnetization plateaux, which emerge in magnetization curves provided that the ground state is highly degenerate on behalf of a sufficiently strong geometric frustration. On the other hand, all intermediate magnetization plateaux merge into a linear magnetization versus magnetic field dependence in the limit of classical Heisenberg spin S → ∞. The enhanced magnetocaloric effect with cooling rate exceeding the one of paramagnetic salts is also detected when the disordered frustrated phase constitutes the ground state and the external magnetic field is small enough.
Born-Oppenheimer Dynamics, Electronic Friction, and the Inclusion of Electron-Electron Interactions
Dou, Wenjie; Miao, Gaohan; Subotnik, Joseph E.
2017-07-01
We present a universal expression for the electronic friction as felt by a set of classical nuclear degrees of freedom (DOFs) coupled to a manifold of quantum electronic DOFs; no assumptions are made regarding the nature of the electronic Hamiltonian and electron-electron repulsions are allowed. Our derivation is based on a quantum-classical Liouville equation for the coupled electronic-nuclear motion, followed by an adiabatic approximation whereby electronic transitions are assumed to equilibrate faster than nuclear movement. The resulting form of friction is completely general, but does reduce to previously published expressions for the quadratic Hamiltonian (i.e., Hamiltonians without electronic correlation). At equilibrium, the second fluctuation-dissipation theorem is satisfied and the frictional matrix is symmetric. To demonstrate the importance of electron-electron correlation, we study electronic friction within the Anderson-Holstein model, where a proper treatment of electron-electron interactions shows signatures of a Kondo resonance and a mean-field treatment is completely inadequate.
Interaction of Schroedinger electrons and photons
International Nuclear Information System (INIS)
Haller, K.; Sohn, R.B.
1979-01-01
The effect of transformations carried out on the Hamiltonian for the Schroedinger electron-photon system is studied. These transformations include gauge transformations and certain similarity and ''hybrid'' transformations. The last named involve unitary transformations of either operators or states, but not both. Unitary and hybrid transformation are discussed, which affect the transverse components of the electromagnetic vector potentials and therefore are distinct from gauge transformations. A hybrid transformation is identified which leads to a form of the Hamiltonian that contains no reference to the transverse vector potential and includes electric and magnetic fields as well as nonlocal interactions of charges and currents. The behavior of the scattering matrix under the influence of these hybrid transformations is discussed. Comments are made on two-photon absorption calculations
Attractive electron correlation in wide band gap semiconductors by electron-photon interaction
International Nuclear Information System (INIS)
Takeda, Hiroyuki; Yoshino, Katsumi
2004-01-01
We theoretically demonstrate attractive electron correlation in wide band gap semiconductors by electron-photon interaction. At low temperature, wavevectors of electromagnetic waves absorbed in wide band gap semiconductors cannot be neglected for wavevectors of electron waves; that is, electromagnetic waves affect the movements of electrons. In particular, attractive interaction occurs between two electrons when one electron changes from a valence band to a conduction band and the other electron changes from a conduction band to a valence band
Study of electron-positron interactions
International Nuclear Information System (INIS)
Abashian, A.; Gotow, K.; Philonen, L.
1990-01-01
For the past seven years, this group has been interested in the study of tests of the Standard Model of Electroweak interactions. The program has centered about the AMY experiment which examines the nature of the final state products in electron-positron collisions in the center of mass energy range near 60 GeV. Results of these measurements have shown a remarkable consistency with the predictions of the minimal model of 3 quark and lepton generations and single charged and neutral intermediate bosons. No new particles or excited states have been observed nor has any evidence for departures in cross sections or angular asymmetries from expectations been observed. These conclusions have been even more firmly established by the higher energy results from the LEP and SLC colliders at center of mass energies of about 90 GeV. Our focus is shifting to the neutrino as a probe to electroweak interactions. The relative merit of attempting to observe neutrinos from point sources versus observing neutrinos generally is not easy to predict. The improved ability to interpret is offset by the probably episodic nature of the emission and irreproducibility of the results. In this phase of development, it is best to be sensitive to both sources of neutrinos. As a second phase of our program at Virginia Tech, we are studying the feasibility of detecting cosmic ray neutrinos in a proposed experiment which we have called NOVA. the results of the test setup will be instrumental in developing an optimum design. A third program we are involved in is the MEGA experiment at Los Alamos, an experiment to place a limit on the rate of muon decay to electron plus photon which is forbidden by the Standard Model
Spin-spin cross-relaxation of optically-excited rare-earth ions in crystals
International Nuclear Information System (INIS)
Otto, F.W.; D'Amato, F.X.; Hahn, E.L.; Lukas, M.
1986-01-01
A laser saturation grating experiment is applied for the measurement of electron hyperfine state spin orientation diffusion among Tm +2 impurity ion hyperfine ground states in SrF 2 . A strong laser pulse at λ 1 produces a spatial grating of excited spin states followed by a probe at λ 2 . The probe transmission intensity is to assess diffusion of non-equilibrium spin population into regions not excited by the pulse at λ 1 . In a second experiment, a field sweep laser hole burning method enables measurement of Pr +3 optical ion hyperfine coupling of optical ground states to the reservoir of F nuclear moments in LaF 3 by level crossing. A related procedure with external RF resonance sweep excitation maps out the nuclear Zeeman-electric quadrupole coupled spectrum of Pr +3 over a wide range by monitoring laser beam transmission absorption
The electrical conductivity of an interacting electron gas
International Nuclear Information System (INIS)
Kojima, D.Y.
1977-01-01
A manybody theory by the propagator method developed by Montroll and Ward for the equilibrium statistical mechanics, is reformulated to describe the electrical conductivity for an electron gas system containing impurity. The theory includes electron-impurity interaction to the infinite order and electron-electron interaction to the first order exchange effect. The propagator used by Montroll and Ward is separated into two propagators, each of which satisfies either Bloch or Schroedinger equation, to utilize the perturbation method. Correct counting of graphs are presented. Change in the relaxation time due to the electron-electron interaction is explicity shown and compared with recent works [pt
Energy Technology Data Exchange (ETDEWEB)
Szczesniak, R. [Institute of Physics, Czestochowa University of Technology (Poland); Institute of Physics, Jan Dlugosz University in Czestochowa (Poland); Durajski, A.P.; Duda, A.M. [Institute of Physics, Czestochowa University of Technology (Poland)
2017-04-15
The properties of the superconducting and the anomalous normal state were described by using the Eliashberg method. The pairing mechanism was reproduced with the help of the Hamiltonian, which models the electron-phonon and the electron-electron-phonon interaction (EEPh). The set of the Eliashberg equations, which determines the order parameter function (φ), the wave function renormalization factor (Z), and the energy shift function (χ), was derived. It was proven that for the sufficiently large values of the EEPh potential, the doping dependence of the order parameter (φ/Z) has the analogous course to that observed experimentally in cuprates. The energy gap in the electron density of states is induced by Z and χ - the contribution from φ is negligible. The electron density of states possesses the characteristic asymmetric form and the pseudogap is observed above the critical temperature. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Interaction effects in liquids with low electron densities
International Nuclear Information System (INIS)
Warren, W.W. Jr.
1987-01-01
The author discusses two complementary classes of systems in which strong electron-electron or electron-ion interactions appear at low electron densities. The first are the expanded liquid alkali metals (cesium) in which electron correlation effects have a profound effect on the magnetic properties on the metallic side of the metal-nonmetal transition. The second group are molten alkali halides containing low densities of localized electrons introduced, say, by dissolution of small amounts of excess metal. (Auth.)
Study of electron and neutrino interactions
International Nuclear Information System (INIS)
Abashian, A.
1997-01-01
This is the final report for the DOE-sponsored experimental particle physics program at Virginia Tech to study the properties of the Standard Model of strong and electroweak interactions. This contract (DE-AS05-80ER10713) covers the period from August 1, 1980 to January 31, 1993. Task B of this contract, headed by Professor Alexander Abashian, is described in this final report. This program has been pursued on many fronts by the researchers-in a search for axions at SLAC, in electron-positron collisions in the AMY experiment at the TRISTAN collider in Japan, in measurements of muon decay properties in the MEGA and RHO experiments at the LAMPF accelerator, in a detailed analysis of scattering effects in the purported observation of a 17 keV neutrino at Oxford, in a search for a disoriented chiral condensate with the MiniMax experiment at Fermilab, and in an R ampersand D program on resistive plate counters that could find use in low-cost high-quality charged particle detection at low rates
Effect of electron-photon interaction on the knight shift
International Nuclear Information System (INIS)
Tripathi, G.S.; Misra, C.M.; Tripathi, P.; Misra, P.K.
1990-01-01
The effect of electron-phonon interaction is considered on the spin (K s ), orbital (K o ) and spin-orbit (K so ) contributions to the Knight shift. In case of K s , it is found that the modifications caused due to the magnetic field dependence of electron self-energy in the presence of electron-phonon interaction is cancelled by the electron-phonon mass enhancement. However, in the presence of both electron-electron and electron-phonon interactions, the exchange enhancement parameter α is modified to α(1+γ) -1 where γ is the electron-phonon mass enhancement parameter. The orbital and spin-orbital contributions are mainly modified through the changes in the one-electron energies and wave functions. (orig.)
Inelastic interactions of swift electrons in solids
International Nuclear Information System (INIS)
Tung, C.J.; Ritchie, R.H.; Ashley, J.C.; Anderson, V.E.
1976-01-01
Theoretical calculations of electron mean free paths and electron slowing-down spectra in solids are described. These calculations involve (a) the use of an electron gas model to approximate the response of conduction band electrons in metals, (b) the application of a statistical model for the calculation of electron mean free paths in metals, (c) the development of an insulator model to describe valence band electrons in insulators and semiconductors, and (d) the use of data on atomic generalized oscillator strengths to describe the excitation of the ion cores. Exchange effects are included in the calculations through a semi-empirical procedure. Detailed results are presented for electron mean free paths in Ag, Au, Al, and Al 2 O 3 , and on the stopping power of Al and Al 2 O 3 , for electrons with energies at a few eV to 10 keV. The agreement of these calculations with experimental measurements is quite reasonable over a wide range of electron energies. A detailed description of the calculation of electron slowing-down spectra in solids is presented. Low energy electron slowing-down spectra of monoenergetic electron sources in Al and Al 2 O 3 are calculated. Calculations of electron slowing-down spectra in Al 2 O 3 are made using differential cross sections obtained employing an insulator model and from GOS functions for ion core electrons. Auger electron contributions to the slowing-down spectrum are discussed. Results for the slowing-down spectrum are compared with the experimental data measured by Birkhoff and coworkers. Generally good agreement is found over a wide range of electron energies
Energy Technology Data Exchange (ETDEWEB)
Krividin, L.B.; Kalabin, G.A.
1985-08-10
The authors measure the direct geminal and vicinal spinspin coupling constants between the C-13 nuclei of the phenyl group in the series of alkyl phenyl sulfides C/sub 6/H/sub 5/SR. It was shown that the variation in most of the discussed constants is determined by the ratio of the planar and orthogonal conformers. Linear relationships were obtained between the C-13-C-13 constants and the fractions of the planar conformer. The C-13-C-13 spin-spin coupling constants in the planar and orthogonal conformers of the compounds were calculated by means of empirical relationships.
Electron emission during multicharged ion-metal surface interactions
International Nuclear Information System (INIS)
Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Hughes, I.G.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M.; Meyer, F.W.
1992-01-01
The electron emission during multicharged ion-metal surface interactions will be discussed. The interactions lead to the emission of a significant number of electrons. Most of these electrons have energies below 30 eV. For incident ions with innershell vacancies the emission of Auger electrons that fill these vacancies has been found to occur mainly below the surface. We will present recently measured electron energy distributions which will be used to discuss the mechanisms that lead to the emission of Auger and of low-energy electrons
Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field
DEFF Research Database (Denmark)
Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.
2015-01-01
We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...... of compressible strips in the potential profile and the electron density. We numerically solve the Dirac equations describing the electron dynamics in quantum dots, and we demonstrate that compressible strips lead to the appearance of plateaus in the electron energies as a function of the magnetic field. Finally...
Theoretical study of the interplay of electron-electron interaction and disorder
International Nuclear Information System (INIS)
Brezini, A.; Behilil, S.
1988-10-01
A disordered Hubbard model with diagonal disorder is used to investigate the electron localization effects associated with both disorder and electron-electron interaction. Extensive results are reported on the ground state properties and compared to other theories. Two regimes have been found: when the electron-electron interaction u is greater than the disorder parameter w and when u < w. (author). 18 refs, 4 figs
Effects of electron-electron interactions on electronic transport in disordered systems
International Nuclear Information System (INIS)
Foley, Simon Timothy
2002-01-01
This thesis is concerned with the role of electron-electron interactions on electronic transport in disordered systems. We first consider a novel non-linear sigma model in order to microscopically treat the effects of disorder and electronic interaction. We successfully reproduce the perturbative results for the zero-bias anomaly and the interaction correction to the conductivity in a weakly disordered system, and discuss possible directions for future work. Secondly we consider the fluctuations of the dephasing rate for a closed diffusive and quantum dot system. Using the Keldysh technique we derive an expression for the inelastic scattering rate with which we self-consistently obtain the fluctuations in the dephasing rate. For the diffusive regime we find the relative fluctuations is given by F ∼ (L φ /L) 2 /g 2 , where g is the dimensionless conductance, L φ is the dephasing length and L is the sample size. For the quantum dot regime we find a perturbative divergence due to the presence of the zero mode. By mapping divergent diagrams to those for the two-level correlation function, we conjecture the existence of an exact relation between the two. Finally we discuss the consequences of this relation. (author)
Contreras, Rubén H; dos Santos, Francisco P; Ducati, Lucas C; Tormena, Cláudio F
2010-12-01
Adequate analyses of canonical molecular orbitals (CMOs) can provide rather detailed information on the importance of different σ-Fermi contact (FC) coupling pathways (FC term transmitted through the σ-skeleton). Knowledge of the spatial distribution of CMOs is obtained by expanding them in terms of natural bond orbitals (NBOs). Their relative importance for transmitting the σ-FC contribution to a given spin-spin coupling constants (SSCCs) is estimated by resorting to the expression of the FC term given by the polarisation propagator formalism. In this way, it is possible to classify the effects affecting such couplings in two different ways: delocalisation interactions taking place in the neighbourhood of the coupling nuclei and 'round the ring' effects. The latter, associated with σ-ring currents, are observed to yield significant differences between the FC terms of (2)J(C2H3) and (2)J(C3H2) SSCCs which, consequently, are taken as probes to gauge the differences in σ-ring currents for the five-membered rings (furan, thiophene, selenophene and pyrrol) and also for the six-membered rings (benzene, pyridine, protonated pyridine and N-oxide pyridine) used in the present study. Copyright © 2010 John Wiley & Sons, Ltd.
Electron interactions with nuclei. Progress report
International Nuclear Information System (INIS)
1986-07-01
Research includes work at SLAC, Bates, and Saclay research facilities. The high energy program at SLAC concerns inclusive electron scattering from nuclei, electroexcitation of the delta in nuclei, and the design of an electron detection system for the SLAC 1.6 GeV/c magnetic spectrometer. The high energy program at Bates includes quasielastic electron scattering from 1 H, 2 H, 3 He, and 4 He, and electron scattering from 3 H and 3 He. Nuclear structure studies are based on high resolution inelastic electron scattering and include electron scattering from 208 Pb and mercury isotopes, charge densities from low lying states in 86 Sr, and magnetization densities of 205 Tl and 207 Pb. (DWL) 72 refs., 29 figs., 1 tab
Modeling microwave/electron-cloud interaction
International Nuclear Information System (INIS)
Mattes, M; Sorolla, E; Zimmermann, F
2013-01-01
Starting from the separate codes BI-RME and ECLOUD or PyECLOUD, we are developing a novel joint simulation tool, which models the combined effect of a charged particle beam and of microwaves on an electron cloud. Possible applications include the degradation of microwave transmission in telecommunication satellites by electron clouds; the microwave-transmission techniques being used in particle accelerators for the purpose of electroncloud diagnostics; the microwave emission by the electron cloud itself in the presence of a magnetic field; and the possible suppression of electron-cloud formation in an accelerator by injecting microwaves of suitable amplitude and frequency. A few early simulation results are presented. (author)
Electron-electron interaction in p-SiGe/Ge quantum wells
International Nuclear Information System (INIS)
Roessner, Benjamin; Kaenel, Hans von; Chrastina, Daniel; Isella, Giovanni; Batlogg, Bertram
2005-01-01
The temperature dependent magnetoresistance of high mobility p-SiGe/Ge quantum wells is studied with hole densities ranging from 1.7 to 5.9 x 10 11 cm -2 . At magnetic fields below the onset of quantum oscillations that reflect the high mobility values (up to 75000 cm 2 /Vs), we observe the clear signatures of electron-electron interaction. We compare our experiment with the theory of electron-electron interaction including the Zeeman band splitting. The observed magnetoresistance is well explained as a superposition of band structure induced positive magnetoresistance and the negative magntoresistance due to the electron-electron interaction effect
Spin-spin cross relaxation and spin-Hamiltonian spectroscopy by optical pumping of Pr/sup 3+/:LaF3
International Nuclear Information System (INIS)
Lukac, M.; Otto, F.W.; Hahn, E.L.
1989-01-01
We report the observation of an anticrossing in solid-state laser spectroscopy produced by cross relaxation. Spin-spin cross relaxation between the /sup 141/Pr- and /sup 19/F-spin reservoirs in Pr/sup 3+/:LaF 3 and its influence on the /sup 141/Pr NMR spectrum is detected by means of optical pumping. The technique employed combines optical pumping and hole burning with either external magnetic field sweep or rf resonance saturation in order to produce slow transient changes in resonant laser transmission. At a certain value of the external Zeeman field, where the energy-level splittings of Pr and F spins match, a level repulsion and discontinuity of the Pr/sup 3+/ NMR lines is observed. This effect is interpreted as the ''anticrossing'' of the combined Pr-F spin-spin reservoir energy states. The Zeeman-quadrupole-Hamiltonian spectrum of the hyperfine optical ground states of Pr/sup 3+/:LaF 3 is mapped out over a wide range of Zeeman magnetic fields. A new scheme is proposed for dynamic polarization of nuclei by means of optical pumping, based on resonant cross relaxation between rare spins and spin reservoirs
Electron-photon and electron-electron interactions in the presence of strong electromagnetic fields
International Nuclear Information System (INIS)
Surzhykov, A.; Fritzsche, S.; Stoehlker, Th.
2010-01-01
During the last decade, photon emission from highly-charged, heavy ions has been in the focus of intense studies at the GSI accelerator and storage ring facility in Darmstadt. These studies have revealed unique information about the electron-electron and electron-photon interactions in the presence of extremely strong nuclear fields. Apart from the radiative electron capture processes, characteristic photon emission following collisional excitation of projectile ions has also attracted much interest. In this contribution, we summarize the recent theoretical studies on the production of excited ionic states and their subsequent radiative decay. We will pay special attention to the angular and polarization properties of Kα emission from helium-like ions produced by means of dielectronic recombination. The results obtained for this (resonant) capture process will be compared with the theoretical predictions for the characteristic X-rays following Coulomb excitation and radiative recombination of few-electron, heavy ions. Work is supported by Helmholtz Association and GSl under the project VH-NG--421. (author)
The interaction of low-energy electrons with fructose molecules
Chernyshova, I. V.; Kontrosh, E. E.; Markush, P. P.; Shpenik, O. B.
2017-11-01
Using a hypocycloidal electronic spectrometer, the interactions of low energy electrons (0-8.50 eV) with fructose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of fructose molecules occurs effectively even at an electron energy close to zero. In the total electron-scattering cross section by molecules, resonance features (at energies 3.10 and 5.00 eV) were first observed near the formation thresholds of light ion fragments OH- and H-. The correlation of the features observed in the cross sections of electron scattering and dissociative attachment is analyzed.
Interaction Between Electrons, Magnons and Phonons in Nickel. RCN Report
International Nuclear Information System (INIS)
Frikkee, E.
1971-02-01
By means of inelastic neutron scattering, a localized electron excitation was observed in Ni and (4% Fe). The excitation interacts with magnons and phonons, and is assumed to correspond with transitions between the nearly-degenerate electronstates Δ 6 ↑ and Δ 7 ↑ near X, which are situated just below the Fermi level.Selection rules for electron-phonon and electronmagnon scattering are determined by means of group theory. It is found that in particular the transverse (Δ 5 ) phonons in the [100] direction are perturbed. The observed neutron-electron scattering turns out to be an indirect process, which is only possible due to the interaction between the (Δ 6 , Δ 7 ) electrons and the lattice. The basic mechanism for the observed effects is the electron spin-orbit coupling, which establishes the interaction between the electron spin system and the lattice. (author)
Light propagation and interaction observed with electrons
Energy Technology Data Exchange (ETDEWEB)
Word, Robert C.; Fitzgerald, J.P.S.; Könenkamp, R., E-mail: rkoe@pdx.edu
2016-01-15
We discuss possibilities for a microscopic optical characterization of thin films and surfaces based on photoemission electron microscopy. We show that propagating light with wavelengths across the visible range can readily be visualized, and linear and non-linear materials properties can be evaluated non-invasively with nanometer spatial resolution. While femtosecond temporal resolution can be achieved in pump-probe-type experiments, the interferometric approach presented here has typical image frame times of ~200 fs. - Highlights: • Non-linear photoemission electron micrographs are analyzed. • Optical properties of transparent and metallic thin films are determined. • Light propagation, surface plasmon resonances and energy transfer are discussed.
Writing an Electronic Astronomy Book with Interactive Curricular Material
Thompson, Kristen L.; Belloni, Mario; Christian, Wolfgang
2015-01-01
With the rise of tablets, the past few years have seen an increase in the demand for quality electronic textbooks. Unfortunately, most of the current offerings do not exploit the accessibility and interactivity that electronic books can deliver. In this poster, we discuss how we are merging our curriculum development projects (Physlets, Easy Java/JavaScript Simulations, and Open Source Physics) with the EPUB electronic book format to develop an interactive textbook for use in a one-semester introductory astronomy course. The book, Astronomy: An Interactive Introduction, combines the narrative, equations, and images of a traditional astronomy text with new JavaScript simulations.
Inter-atomic interaction between electrons, 2
International Nuclear Information System (INIS)
Haga, Eijiro; Kato, Tomohiko; Aisaka, Tsuyoshi.
1978-01-01
Intra- and inter-atomic interactions in the exchange process are defined with respect to the Wannier function rather than the atomic function. In relation to the neutron scattering data for nickel, the behavior for the effective exchange parameter I(q) in the q-dependent susceptibility is, in RPA, investigated by taking into account the main types of the nearest neighbor interactions and by extending our previous treatment. The different types of interactions lead to different behavior for the q-dependence of I(q). The contribution to I(q) from inter-atomic interactions other than the exchange type decreases as the surface area of the Fermi surface becomes large. For the exchange type, the l-th neighbor interaction with l<=4 is taken into account, and, from the comparison with the empirical result for I(q), it is found that the inter-atomic contribution to I(0) is about thirty percent with a reasonable decrease against l. (author)
Electronic structures in ion-surface interactions
International Nuclear Information System (INIS)
Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.
1997-01-01
A chemical bond generated by the interaction between low energy ion and base was investigated by ab initio molecular orbital method. The effects of ion charge were studied by calculation of this method. When carbon ion approached to graphite base (C 24 H 12 ), the positive ion and the neutral atom covalently bonded, but the negative ion did not combine with it. When carbon ion was injected into h-BN base (B 12 N 12 H 12 , hexagonal system boron nitride), the positive ion and the neutron atom formed covalent bond and the van der Waals binding, and the negative ion interacted statically with it. (S.Y.)
Electron interactions with nuclei: Progress report
International Nuclear Information System (INIS)
McCarthy, J.S.
1987-08-01
High energy is being conducted at the Stanford Linear Accelerator Center. This includes inclusive electron scattering, electroexcitation of the delta in nuclei, longitudinal and transverse response in the quasi-elastic region, the q 2 dependence of 4 He(e,e'p), deep inelastic scattering from nuclei, transverse and longitudinal response in the resonance region, nuclear physics at PEP and 1.6 GeV spectrometer properties. Additional high energy research on electron scattering on 3 H and 3 He and the nuclear structure of 205 Tl and 206 Pb are being conducted at MIT-Bates. Other activities are being carried out at Saclay and research and development for Monte Carlo studies of Hall A spectrometers for CEBAF is being conducted
The Electron-Phonon Interaction as Studied by Photoelectron Spectroscopy
International Nuclear Information System (INIS)
Lynch, D.W.
2004-01-01
With recent advances in energy and angle resolution, the effects of electron-phonon interactions are manifest in many valence-band photoelectron spectra (PES) for states near the Fermi level in metals
Research and Development Issues for Interactive Electronic Technical Manuals
National Research Council Canada - National Science Library
Ricci, Katrina
2002-01-01
... technologies to support Interactive Electronic Technical Manuals (IETMs). A workshop was conducted at the NAVAIR Orlando, Training Systems Division to discuss the domain and to present current research in this area...
Electron acceleration via high contrast laser interacting with submicron clusters
International Nuclear Information System (INIS)
Zhang Lu; Chen Liming; Wang Weiming; Yan Wenchao; Yuan Dawei; Mao Jingyi; Wang Zhaohua; Liu Cheng; Shen Zhongwei; Li Yutong; Dong Quanli; Lu Xin; Ma Jinglong; Wei Zhiyi; Faenov, Anatoly; Pikuz, Tatiana; Li Dazhang; Sheng Zhengming; Zhang Jie
2012-01-01
We experimentally investigated electron acceleration from submicron size argon clusters-gas target irradiated by a 100 fs, 10 TW laser pulses having a high-contrast. Electron beams are observed in the longitudinal and transverse directions to the laser propagation. The measured energy of the longitudinal electron reaches 600 MeV and the charge of the electron beam in the transverse direction is more than 3 nC. A two-dimensional particle-in-cell simulation of the interaction has been performed and it shows an enhancement of electron charge by using the cluster-gas target.
Wang, Hongyue; Lhuillier, Emmanuel; Yu, Qian; Mottaghizadeh, Alireza; Ulysse, Christian; Zimmers, Alexandre; Dubertret, Benoit; Aubin, Herve
2015-03-01
We present a tunnel spectroscopy study of the electronic spectrum of single PbS Quantum Dots (QDs) trapped between nanometer-spaced electrodes, measured at low temperature T=5 K. The carrier filling of the QD can be controlled either by the drain voltage in the shell filling regime or by a gate voltage. In the empty QD, the tunnel spectrum presents the expected signature of the 8x degenerated excited levels. In the drain controlled shell filling regime, the levels degeneracies are lifted by the global electrostatic Coulomb energy of the QD; in the gate controlled shell filling regime, the levels degeneracies are lifted by the intra-Coulomb interactions. In the charged quantum dot, electron-phonons interactions lead to the apparition of Franck-Condon side bands on the single excited levels and possibly Franck Condon blockade at low energy. The sharpening of excited levels at higher gate voltage suggests that the magnitude of electron-phonon interactions is decreased upon increasing the electron filling in the quantum dot. This work was supported by the French ANR Grants 10-BLAN-0409-01, 09-BLAN-0388-01, by the Region Ile-de-France in the framework of DIM Nano-K and by China Scholarship Council.
Electron–electron interactions and the electrical resistivity of lithium
Indian Academy of Sciences (India)
The electron–electron interactions in lithium metal have been examined keeping in view the recent developments. The contribution of the electron–electron Umklapp scattering processes in the electrical resistivity of lithium at low temperatures has been evaluated using a simplified spherical Fermi surface model with ...
Role of electron-electron interactions in the RKKY theory of magnetism
International Nuclear Information System (INIS)
Cooke, J.F.
1978-10-01
The theory of magnetism in heavy rare earth metals is based on the RKKY theory. In this formalism the indirect exchange interaction between the local 4f spins is mediated by the conduction electrons. When carried to second order in the 4f-conduction electron interaction, traditional perturbation theory leads to a Heisenberg-like interaction between the local spins which depends on the electronic energy bands and 4f-conduction electron exchange matrix elements. This derivation neglects the detailed behavior of electron-electron interaction within the conduction band, which is known to be important in metallic systems. By using an equation of motion method, an expression for the inelastic neutron scattering cross-section has been derived which includes, in an approximate way, this electron-electron interaction. The results of this calculation indicate that spin-wave peaks can be broadened and shifted if the spin-wave band lies near the conduction electron Stoner continuum. The origin of this effect is similar to that found in itinerant electron systems where the spin-wave band actually intersects the Stoner continuum, resulting in the disappearance of the spin-wave mode
Role of electron-electron interactions in the RKKY theory of magnetism
International Nuclear Information System (INIS)
Cooke, J.F.
1979-01-01
The theory of magnetism in heavy rare earth metals is based on the RKKY theory. In this formalism the indirect exchange interaction between the local 4f spins is mediated by the conduction electrons. When carried to second order in the 4f-conduction electron interaction, traditional pertubation theory leads to a Heisenberg-like interaction between the local spins which depends on the electronic energy bands and 4f-conduction electron exchange matrix elements. This derivation neglects the detailed behavior of electron-electron interaction within the conduction band, which is known to be important in metallic systems. By using an equation of motion method, an expression for the inelastic neutron scattering cross-section has been derived which includes, in an approximate way, this electron-electron interaction. The results of this calculation indicate that spin-wave peaks can be broadened and shifted if the spin-wave band lies near the conduction electron Stoner continuum. The origin of this effect is similar to that found in itinerant electron systems where the spin-wave band actually intersects the Stoner continuum, resulting in the disappearance of the spin-wave mode
Interacting electrons theory and computational approaches
Martin, Richard M; Ceperley, David M
2016-01-01
Recent progress in the theory and computation of electronic structure is bringing an unprecedented level of capability for research. Many-body methods are becoming essential tools vital for quantitative calculations and understanding materials phenomena in physics, chemistry, materials science and other fields. This book provides a unified exposition of the most-used tools: many-body perturbation theory, dynamical mean field theory and quantum Monte Carlo simulations. Each topic is introduced with a less technical overview for a broad readership, followed by in-depth descriptions and mathematical formulation. Practical guidelines, illustrations and exercises are chosen to enable readers to appreciate the complementary approaches, their relationships, and the advantages and disadvantages of each method. This book is designed for graduate students and researchers who want to use and understand these advanced computational tools, get a broad overview, and acquire a basis for participating in new developments.
Interaction of slow electrons with surfaces. II
International Nuclear Information System (INIS)
Komolov, S.A.; Chadderton, L.T.
1976-01-01
Total current spectroscopy (TCS) has been used to study the growth of films of gold and silver on (100) vanadium surfaces. A slow transition from TCS curves characteristic of vanadium to curves characteristic of the noble metals is observed, accompanied by an increase in the net work function - more rapid for silver than for gold. Vanadium characteristics are lost from the TCS curves for mean overlayer thicknesses > approximately 15A, and a simple analysis shows that the thickness of the surface zone from which TCS signals originate is approximately given by the electron mean free path. Observations of progressive attenuation of a characteristic vanadium feature with increasing mean thickness of overlayer permits separation into stages of nucleation and growth. There is a critical nucleus size of approximately 2A for silver and approximately 4A for gold. (Auth.)
Interaction between Electron Holes in a Strongly Magnetized Plasma
DEFF Research Database (Denmark)
Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans
1980-01-01
The interaction between electron holes in a strongly magnetized, plasma-filled waveguide is investigated by means of computer simulation. Two holes may or may not coalesce, depending on their amplitudes and velocities. The interaction between holes and Trivelpiece-Gould solitons is demonstrated...
Electron-dislocation interaction at low temperatures. Progress report
International Nuclear Information System (INIS)
1976-01-01
Studies of the interaction of mobile dislocations with electrons have shown that dislocation motion can be, in part, described by treating the dislocation as an underdamped oscillator. In particular, studies in lead alloys have shown tht dislocation motion can be considered as the motion of string, slightly damped by electrons, without regard for any other lattice friction. In addition we have shown that silver solutes, in lead crystals, occupy, partially, interstitial sites. Finally, we have shown that dislocations in copper interact, unexpectedly, with electrons. This is shown by measuring the influence of a magnetic field on the flow stress of copper crystals at 4.2 0 K
Electron-phonon interaction in Chevrel-phase compounds
International Nuclear Information System (INIS)
Rainer, D.; Pobell, F.
1981-03-01
Experiments on the electron-phonon interaction in Chevrel-phase compounds (CPC) and a theoretical discussion of their results are presented. The authors particularly discuss measurements of the isotope effect of the transition temperature in Mo 6 Se 8 and SnMo 6 S 8 and tunneling spectroscopy experiments on Cu 1 . 8 Mo 6 S 8 and PbMo 6 S 8 . These investigations have been performed to get information about the strength of the electron-phonon interaction in CPC, and about the question whether there are phonon modes which couple particularly strongly to the electrons in these compounds. (orig./GSCH)
The Electron-Phonon Interaction in Strongly Correlated Systems
International Nuclear Information System (INIS)
Castellani, C.; Grilli, M.
1995-01-01
We analyze the effect of strong electron-electron repulsion on the electron-phonon interaction from a Fermi-liquid point of view and show that the electron-electron interaction is responsible for vertex corrections, which generically lead to a strong suppression of the electron-phonon coupling in the v F q/ω >>1 region, while such effect is not present when v F q/ω F is the Fermi velocity and q and ω are the transferred momentum and frequency respectively. In particular the e-ph scattering is suppressed in transport properties which are dominated by low-energy-high-momentum processes. On the other hand, analyzing the stability criterion for the compressibility, which involves the effective interactions in the dynamical limit, we show that a sizable electron-phonon interaction can push the system towards a phase-separation instability. Finally a detailed analysis of these ideas is carried out using a slave-boson approach for the infinite-U three-band Hubbard model in the presence of a coupling between the local hole density and a dispersionless optical phonon. (author)
Designing Interactive Electronic Module in Chemistry Lessons
Irwansyah, F. S.; Lubab, I.; Farida, I.; Ramdhani, M. A.
2017-09-01
This research aims to design electronic module (e-module) oriented to the development of students’ chemical literacy on the solution colligative properties material. This research undergoes some stages including concept analysis, discourse analysis, storyboard design, design development, product packaging, validation, and feasibility test. Overall, this research undertakes three main stages, namely, Define (in the form of preliminary studies); Design (designing e-module); Develop (including validation and model trial). The concept presentation and visualization used in this e-module is oriented to chemical literacy skills. The presentation order carries aspects of scientific context, process, content, and attitude. Chemists and multi media experts have done the validation to test the initial quality of the products and give a feedback for the product improvement. The feasibility test results stated that the content presentation and display are valid and feasible to be used with the value of 85.77% and 87.94%. These values indicate that this e-module oriented to students’ chemical literacy skills for the solution colligative properties material is feasible to be used.
Microwave interaction with hot electron plasmas
International Nuclear Information System (INIS)
Tanaka, M.; Fujiwara, M.; Ikegami, H.
1980-01-01
A numerical calculation is presented of ray trajectories and cyclotron damping for toroidal plasmas using geometrical optics. In the absorption region, group velocity does not always coincide with the velocity of energy flow, therefore it should be careful to apply the geometrical optics to finite temperature plasmas. In these calculations, attention is paid mainly to the finite temperature effect on ray tracing. Some numerical results for ordinary waves are presented. Second, new cutoff and resonance appear in the plasmas with anisotropic electron temperature. This resonance frequency is shifted from the usual cyclotron resonance by an amount proportional to T 11 /mc 2 , so that one can determine T 11 when this resonance frequency is measured. A simple discussion is given. The results are presented of recent density measurement on Nagoya Bumpy Torus obtained by interferometer system with different frequencies, 35 GHz and 55 GHz. The results are different than each other in T-mode. The possible reasons for these differences are enumerated in this section
Multiply excited molecules produced by photon and electron interactions
International Nuclear Information System (INIS)
Odagiri, T.; Kouchi, N.
2006-01-01
The photon and electron interactions with molecules resulting in the formation of multiply excited molecules and the subsequent decay are subjects of great interest because the independent electron model and Born-Oppenheimer approximation are much less reliable for the multiply excited states of molecules than for the ground and lower excited electronic states. We have three methods to observe and investigate multiply excited molecules: 1) Measurements of the cross sections for the emission of fluorescence emitted by neutral fragments in the photoexcitation of molecules as a function of incident photon energy [1-3], 2) Measurements of the electron energy-loss spectra tagged with the fluorescence photons emitted by neutral fragments [4], 3) Measurements of the cross sections for generating a pair of photons in absorption of a single photon by a molecule as a function of incident photon energy [5-7]. Multiply excited states degenerate with ionization continua, which make a large contribution in the cross section curve involving ionization processes. The key point of our methods is hence that we measure cross sections free from ionization. The feature of multiply excited states is noticeable in such a cross section curve. Recently we have measured: i) the cross sections for the emission of the Lyman- fluorescence in the photoexcitation of CH 4 as a function of incident photon energy in the range 18-51 eV, ii) the electron energy-loss spectrum of CH 4 tagged with the Lyman-photons at 80 eV incident electron energy and 10 electron scattering angle in the range of the energy loss 20-45 eV, in order to understand the formation and decay of the doubly excited methane in photon and electron interactions. [8] The results are summarized in this paper and the simultaneous excitation of two electrons by electron interaction is compared with that by photon interaction in terms of the oscillator strength. (authors)
Impact of electron-electron Coulomb interaction on the high harmonic generation process in graphene
Avetissian, H. K.; Mkrtchian, G. F.
2018-03-01
Generation of high harmonics in a monolayer graphene initiated by a strong coherent radiation field, taking into account electron-electron Coulomb interaction, is investigated. A microscopic theory describing the nonlinear optical response of graphene is developed. The Coulomb interaction of electrons is treated in the scope of dynamic Hartree-Fock approximation. The closed set of integrodifferential equations for the single-particle density matrix of a graphene quantum structure is solved numerically. The obtained solutions show the significance of many-body Coulomb interaction on the high harmonic generation process in graphene.
Spin Relaxation in GaAs: Importance of Electron-Electron Interactions
Directory of Open Access Journals (Sweden)
Gionni Marchetti
2014-04-01
Full Text Available We study spin relaxation in n-type bulk GaAs, due to the Dyakonov–Perel mechanism, using ensemble Monte Carlo methods. Our results confirm that spin relaxation time increases with the electronic density in the regime of moderate electronic concentrations and high temperature. We show that the electron-electron scattering in the non-degenerate regime significantly slows down spin relaxation. This result supports predictions by Glazov and Ivchenko. Most importantly, our findings highlight the importance of many-body interactions for spin dynamics: we show that only by properly taking into account electron-electron interactions within the simulations, results for the spin relaxation time—with respect to both electron density and temperature—will reach good quantitative agreement with corresponding experimental data. Our calculations contain no fitting parameters.
Interaction of electrons with light metal hydrides in the transmission electron microscope.
Wang, Yongming; Wakasugi, Takenobu; Isobe, Shigehito; Hashimoto, Naoyuki; Ohnuki, Somei
2014-12-01
Transmission electron microscope (TEM) observation of light metal hydrides is complicated by the instability of these materials under electron irradiation. In this study, the electron kinetic energy dependences of the interactions of incident electrons with lithium, sodium and magnesium hydrides, as well as the constituting element effect on the interactions, were theoretically discussed, and electron irradiation damage to these hydrides was examined using in situ TEM. The results indicate that high incident electron kinetic energy helps alleviate the irradiation damage resulting from inelastic or elastic scattering of the incident electrons in the TEM. Therefore, observations and characterizations of these materials would benefit from increased, instead decreased, TEM operating voltage. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Trapped electron losses by interactions with coherent VLF waves
International Nuclear Information System (INIS)
Walt, M.; Inan, U.S.; Voss, H.D.
1996-01-01
VLF whistler waves from lightning enter the magnetosphere and cause the precipitation of energetic trapped electrons by pitch angle scattering. These events, known as Lightning-induced Electron Precipitation (LEP) have been detected by satellite and rocket instruments and by perturbations of VLF waves traveling in the earth-ionosphere waveguide. Detailed comparison of precipitating electron energy spectra and time dependence are in general agreement with calculations of trapped electron interactions with ducted whistler waves. In particular the temporal structure of the precipitation and the dynamic energy spectra of the electrons confirm this interpretation of the phenomena. There are discrepancies between observed and measured electron flux intensities and pitch angle distributions, but these quantities are sensitive to unknown wave intensities and trapped particle fluxes near the loss cone angle. The overall effect of lightning generated VLF waves on the lifetime of trapped electrons is still uncertain. The flux of electrons deflected into the bounce loss cone by a discrete whistler wave has been measured in a few cases. However, the area of the precipitation region is not known, and thus the total number of electrons lost in an LEP event can only be estimated. While the LEP events are dramatic, more important effects on trapped electrons may arise from the small but numerous deflections which increase the pitch angle diffusion rate of the electron population. copyright 1996 American Institute of Physics
Trapped electron losses by interactions with coherent VLF waves
Walt, M.; Inan, U. S.; Voss, H. D.
1996-07-01
VLF whistler waves from lightning enter the magnetosphere and cause the precipitation of energetic trapped electrons by pitch angle scattering. These events, known as Lightning-induced Electron Precipitation (LEP) have been detected by satellite and rocket instruments and by perturbations of VLF waves traveling in the earth-ionosphere waveguide. Detailed comparison of precipitating electron energy spectra and time dependence are in general agreement with calculations of trapped electron interactions with ducted whistler waves. In particular the temporal structure of the precipitation and the dynamic energy spectra of the electrons confirm this interpretation of the phenomena. There are discrepancies between observed and measured electron flux intensities and pitch angle distributions, but these quantities are sensitive to unknown wave intensities and trapped particle fluxes near the loss cone angle. The overall effect of lightning generated VLF waves on the lifetime of trapped electrons is still uncertain. The flux of electrons deflected into the bounce loss cone by a discrete whistler wave has been measured in a few cases. However, the area of the precipitation region is not known, and thus the total number of electrons lost in an LEP event can only be estimated. While the LEP events are dramatic, more important effects on trapped electrons may arise from the small but numerous deflections which increase the pitch angle diffusion rate of the electron population.
Stochastic Coulomb interactions in space charge limited electron emission
International Nuclear Information System (INIS)
Nijkerk, M.D.; Kruit, P.
2004-01-01
Emission models that form the basis of self-consistent field computations make use of the approximation that emitted electrons form a smooth space charge jelly. In reality, electrons are discrete particles that are subject to statistical Coulomb interactions. A Monte Carlo simulation tool is used to evaluate the influence of discrete space charge effects on self-consistent calculations of cathode-ray tube optics. We find that interactions in the space charge cloud affect the electron trajectories such that the velocity distribution is Maxwellian, regardless of the current density. Interactions near the emitter effectively conserve the Maxwellian distribution. The surprising result is that the width of the distribution of transversal velocities does not change. The distribution of longitudinal velocities does broaden, as expected from existing theories
Effects of electrostatic interactions on electron transfer reactions
International Nuclear Information System (INIS)
Hickel, B.
1987-01-01
The fast reactions of electron transfer are studied by pulse radiolysis. This technique allows the creation in about 10 -8 second radicals and radical ions with high redox potentials. For solvated electrons electrostatic interaction on the kinetics of reactions limited by diffusion is described by Debye's equation when ion mobility is known. Deviation from theory can occur in ion pairs formation. This is evidenced experimentally for anions by cation complexation with a cryptate. Relatively slow reactions are more sensitive to electrostatic interactions than limited by diffusion. If ion pairs are not formed kinetics constant depends on dielectric constant of solvent and reaction radius. Experimentally is studied the effect of electrostatic interaction on the rate constants of solvated electrons with anions and cations in water-ethanol mixtures where the dielectric constant change from 80 to 25 at room temperature. 17 refs
Scanning Tunneling Spectroscopy on Electron-Boson Interactions in Superconductors
Schackert, Michael Peter
2014-01-01
This thesis describes the experimental study of electron-boson interactions in superconductors by means of inelastic electron tunneling spectroscopy performed with a scanning tunneling microscope (STM) at temperatures below 1 K. This new approach allows the direct measurement of the Eliashberg function of conventional superconductors as demonstrated on lead (Pb) and niobium (Nb). Preparative experiments on unconventional iron-pnictides are presented in the end.
Scanning tunneling spectroscopy on electron-boson interactions in superconductors
Energy Technology Data Exchange (ETDEWEB)
Schackert, Michael Peter
2014-07-01
This work describes the experimental study of electron-boson interactions in superconductors by means of inelastic electron tunneling spectroscopy performed with a scanning tunneling microscope (STM) at temperatures below 1 K. This new approach allows the direct measurement of the Eliashberg function of conventional superconductors as demonstrated on lead (Pb) and niobium (Nb). Preparative experiments on unconventional iron-pnictides are presented in the end.
Scanning tunneling spectroscopy on electron-boson interactions in superconductors
Schackert, Michael Peter
2015-01-01
This work describes the experimental study of electron-boson interactions in superconductors by means of inelastic electron tunneling spectroscopy performed with a scanning tunneling microscope (STM) at temperatures below 1 K. This new approach allows the direct measurement of the Eliashberg function of conventional superconductors as demonstrated on lead (Pb) and niobium (Nb). Preparative experiments on unconventional iron-pnictides are presented in the end.
Dose calculation due to electrons interaction with DNA
Energy Technology Data Exchange (ETDEWEB)
Mark, S; Orion, I; Shani, G [Ben-Gurion Univ. of the Negev, Beersheba (Israel). Dept. of Nuclear Engineering; Laster, B [Brookhaven National Lab., Upton, NY (United States)
1996-12-01
Experiments done with gadolinium loaded V79 Chinese Hamster cells, irradiated with thermal neutrons, showed that cells lethality increased by a factor of 1.8 compared to the case where the Gd atoms were located outside the cell.(l) It was obvious that the dramatic increase in cell lethality is due to the emission of Auger electrons following the {sup 157}Gd(n,{gamma}){sup 158}Gd reaction. Electrons of various energies from about 40 keV (very few) to less than 1 keV, are emitted. In the present work, energy absorbed in DNA was calculated, due to interaction of electron of different energies: 30, 15, 10, 8, 5 and 2 keV. The Monte Carlo code EGS4(2) was used for the calculations. The DNA was modeled as a series of alternative layers of sugar (phosphate - C{sub 5}O{sub 5}H{sub 7}P p=1.39gr cm{sup -1}) and water. The sugar layer thickness was assumed 2.5nm and the water layer thickness 10nm. An isotropic electron source was assumed to be located in a water layer and the electrons interactions (absorption and scattering) were calculated in the forward hemisphere. The energy absorbed in a group of 8 layers, (4 sugar and 4 water) was calculated for each one of the electron energies. An interesting fact found in those calculations; when the source electrons energy is 10 keV or more, most of the electrons are absorbed in the DNA-water system, are at energy about 2keV. There is no good explanation for this phenomenon except for assuming that when the electron`s energy reaches a low point of about 2keV, it cannot escape absorption in the medium. 10% of the 10 keV electrons deposit their entire energy in the 8 layers range (authors).
Magnetic impurity in a system of interacting electrons
International Nuclear Information System (INIS)
Huynh Thanh Duc; Nguyen Toan Thang
1999-04-01
The Kondo effect of the Anderson impurity in a correlated conduction electron system is studied within the slave boson mean-field theory. The interacting conduction electrons are described by a Hubbard model with an interaction of strength U. It is shown that the Kondo temperature T K decreases with an increase of U. In the intermediate regime at half-filling the exponential scale of the Kondo temperature T K is lost already at the saddle-point level of slave boson formulation. (author)
Relativistic electron beam interaction with a thin target
International Nuclear Information System (INIS)
Gazaix, M.
1981-03-01
This study is concerned with the increasing possibilities of electron energy deposition in thin targets. The thesis theoretical part studies the relativistic electron beam-plasma instability; the Buneman-Pierce instability in limited medium is also studied. In the experimental part, several questions are tentatively answered: - what is the spatial and temporal evolution of the anode material, in temperature and in density. - What sort of interaction is the beam-target interaction; more particularly questions about focusing and energy deposition are studied [fr
Electron-phonon interaction on an Al(001) surface
International Nuclear Information System (INIS)
Sklyadneva, I Yu; Chulkov, E V; Echenique, P M
2008-01-01
We report an ab initio study of the electron-phonon (e-ph) interaction and its contribution to the lifetime broadening of excited hole (electron) surface states on Al(001). The calculations based on density-functional theory were carried out using a linear response approach in the plane-wave pseudopotential representation. The obtained results show that both the electron-phonon coupling and the linewidth experience a weak variation with the energy and momentum position of a hole (electron) surface state in the energy band. An analysis of different contributions to the e-ph coupling reveals that bulk phonon modes turn out to be more involved in the scattering processes of excited electrons and holes than surface phonon modes. It is also shown that the role of the e-ph coupling in the broadening of the Rayleigh surface phonon mode is insignificant compared to anharmonic effects
Energy Technology Data Exchange (ETDEWEB)
Golowacz, H; Degras, D A [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires, Deptartement de Physique des Plasmas et de la Fusion Controlee, Service de Physique Appliquee, Service de Physique des Interractions Electroniques, Section d' Etude des Interactions Gaz-Solides
1967-07-01
The geometry and the technology of a cell used for investigations on electron-adsorbed gas interactions are described. The resonance frequencies of the surface ions which are created by the electron impact on the adsorbed gas are predicted by simplified calculations. The experimental data relative to carbon monoxide and neon are in good agreement with these predictions. (authors) [French] Les caracteristiques geometriques et technologiques generales d'une cellule d'etude des interactions entre un faisceau d'electrons et un gaz adsorbe sont donnees. Un calcul simplifie permet de prevoir les frequences de resonance des ions de surface crees par l'impact des electrons sur le gaz adsorbe. Les donnees experimentales sur l'oxyde de carbone et le neon confirment les previsions du calcul. (auteurs)
Coulomb Interactions in Hanbury Brown-Twiss Experiments with Electrons
Shen, Kan
2009-01-01
This dissertation examines the effect of Coulomb interactions in Hanbury Brown-Twiss (HBT) type experiments with electrons. HBT experiments deal with intensity interference, which is related to the second-order correlation function of the particle field. This is an extension of the usual amplitude interference experiment, such as Young's…
Stochastic Coulomb interactions in space charge limited electron emission
Nijkerk, M.D.; Kruit, P.
2004-01-01
A Monte Carlo simulation tool, which was used to evaluate the influence of discrete space charge effects on self-consistent calculations of cathode-ray tube optics, was discussed. It was found that interactions in the space charge cloud affect the electron trajectories such that the velocity
Electron-dislocation interaction at low temperatures. Progress report
International Nuclear Information System (INIS)
1978-01-01
The interaction of mobile dislocations with electrons in copper and copper alloys has shown that dislocation motion in copper, at low temperature, can be treated as an analog of an underdamped oscillator. We have also shown that the viscous drag on mobile dislocations in type II superconductors can be treated as an acoustic attenuation of an elastic wave
Interaction of ultrarelativistic electron and proton bunches with dense plasmas
Rukhadze, A A
2012-01-01
Here we discuss the possibility of employment of ultrarelativistic electron and proton bunches for generation of high plasma wakefields in dense plasmas due to the Cherenkov resonance plasma-bunch interaction. We estimate the maximum amplitude of such a wake and minimum system length at which the maximum amplitude can be generated at the given bunch parameters.
Electron–electron interactions and the electrical resistivity of lithium ...
Indian Academy of Sciences (India)
is governed mainly by electron–electron and electron–phonon interactions. ... This phase change is the root cause of lithium for its abnormal behavior as .... rule. The range of g has been taken from 0 to 2 in the units of kF, the Fermi wave vector. By varying g we are varying the angle between the incident and the scat-.
Interactions between electrons in the field of a positive ion
International Nuclear Information System (INIS)
Heideman, A.G.M.; Eck, J. van.
1976-01-01
Recent studies on the (auto)ionization of atoms by means of electron-atom collisions reveal the existence of phenomena probably brought about by post-collision interactions in the vicinity of a positive ion. In this article, a review of the subject is given in relation to the research program of the Utrecht atomic physics group
ENERGETIC PHOTON AND ELECTRON INTERACTIONS WITH POSITIVE IONS
Energy Technology Data Exchange (ETDEWEB)
Phaneuf, Ronald A. [UNR
2013-07-01
The objective of this research is a deeper understanding of the complex multi-electron interactions that govern inelastic processes involving positive ions in plasma environments, such as those occurring in stellar cares and atmospheres, x-ray lasers, thermonuclear fusion reactors and materials-processing discharges. In addition to precision data on ionic structure and transition probabilities, high resolution quantitative measurements of ionization test the theoretical methods that provide critical input to computer codes used for plasma modeling and photon opacity calculations. Steadily increasing computational power and a corresponding emphasis on simulations gives heightened relevance to precise and accurate benchmark data. Photons provide a highly selective probe of the internal electronic structure of atomic and molecular systems, and a powerful means to better understand more complex electron-ion interactions.
Electromagnetic Structure and Electron Acceleration in Shock–Shock Interaction
Energy Technology Data Exchange (ETDEWEB)
Nakanotani, Masaru [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-Koen, Kasuga, Fukuoka, 816-8580 (Japan); Matsukiyo, Shuichi; Hada, Tohru [Faculty of Engineering Sciences, Kyushu University, 6-1 Kasuga-Koen, Kasuga, Fukuoka, 816-8580 (Japan); Mazelle, Christian X., E-mail: nakanot@esst.kyushu-u.ac.jp [IRAP, Université Paul Sabatier Toulouse III-CNRS, F-31028 Toulouse Cedex 4 (France)
2017-09-10
A shock–shock interaction is investigated by using a one-dimensional full particle-in-cell simulation. The simulation reproduces the collision of two symmetrical high Mach number quasi-perpendicular shocks. The basic structure of the shocks and ion dynamics is similar to that obtained by previous hybrid simulations. The new aspects obtained here are as follows. Electrons are already strongly accelerated before the two shocks collide through multiple reflection. The reflected electrons self-generate waves upstream between the two shocks before they collide. The waves far upstream are generated through the right-hand resonant instability with the anomalous Doppler effect. The waves generated near the shock are due to firehose instability and have much larger amplitudes than those due to the resonant instability. The high-energy electrons are efficiently scattered by the waves so that some of them gain large pitch angles. Those electrons can be easily reflected at the shock of the other side. The accelerated electrons form a power-law energy spectrum. Due to the accelerated electrons, the pressure of upstream electrons increases with time. This appears to cause the deceleration of the approaching shock speed. The accelerated electrons having sufficiently large Larmor radii are further accelerated through the similar mechanism working for ions when the two shocks are colliding.
Experimental investigation of electron beam wave interactions utilising short pulses
International Nuclear Information System (INIS)
Wiggins, Samuel Mark
2000-01-01
Experiments have investigated the production of ultra-short electromagnetic pulses and their interaction with electrons in various resonant structures. Diagnostic systems used in the measurements included large bandwidth detection systems for capturing the short pulses. Deconvolution techniques have been applied to account for bandwidth limitation of the detection systems and to extract the actual pulse amplitudes and durations from the data. A Martin-Puplett interferometer has been constructed for use as a Fourier transform spectrometer. The growth of superradiant electromagnetic spikes from short duration (0.5-1.0 ns), high current (0.6-2.0 kA) electron pulses has been investigated in a Ka-band Cherenkov maser and Ka- and W-band backward wave oscillators (BWO). In the Cherenkov maser, radiation spikes were produced with a peak power ≤ 3 MW, a duration ≥ 70 ps and a bandwidth ≤ 19 %. It is shown that coherent spontaneous emission from the leading edge of the electron pulse drives these interactions, giving rise to self-amplified coherent spontaneous emission (SACSE). BWO spikes were produced with a peak power ≤ 63 MW and a pulse duration ∼ 250 ps in the Ka-band and ≤ 12 MW and ∼ 170 ps in the W-band. Evidence of superradiant evolution has been observed in the measurements of scaling laws such as power scaling with the current squared and duration scaling inversely with the fourth root of the power. An X-band free-electron maser amplifier, in which a short (1.0ns) injected radiation pulse interacts with a long (∼ 140 ns) electron beam, has been investigated. The interaction is shown to evolve in the linear regime. The peak output power was 320 kW, which corresponded to a gain, approximately constant across the band, of 42 dB. Changes to the spectrum, that occur when the input radiation pulse is injected into electrons with an energy gradient, have been analysed. (author)
Tunable Electron-Electron Interactions in LaAlO_{3}/SrTiO_{3} Nanostructures
Directory of Open Access Journals (Sweden)
Guanglei Cheng
2016-12-01
Full Text Available The interface between the two complex oxides LaAlO_{3} and SrTiO_{3} has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of “sketched” quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a single-electron (Andreev bound state tunneling regime where the interactions become repulsive. The electron-electron interaction sign change is associated with a Lifshitz transition where the d_{xz} and d_{yz} bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.
Electron-electron interaction and transfer ionization in fast ion-atom collisions
International Nuclear Information System (INIS)
Voitkiv, A B
2008-01-01
Recently it was pointed out that electron capture occurring in fast ion-atom collisions can proceed via a mechanism which earlier was not considered. In the present paper we study this mechanism in more detail. Similarly as in radiative capture, where the electron transfer occurs due to the interaction with the radiation field and proceeds via emission of a photon, within this mechanism the electron capture is caused by the interaction with another atomic electron leading mainly to the emission of the latter. In contrast to the electron-electron Thomas capture, this electron-electron (E-E) mechanism is basically a first-order one having similarities to the kinematic and radiative capture channels. It also possesses important differences with the latter two. Leading to transfer ionization, this first-order capture mechanism results in the electron emission mainly in the direction opposite to the motion of the projectile ion. The same, although less pronounced, feature is also characteristic for the momenta of the target recoil ions produced via this mechanism. It is also shown that the action of the E-E mechanism is clearly seen in recent experimental data on the transfer ionization in fast proton-helium collisions.
Dogan, Fatih; Kesserwan, Hasan; Manchon, Aurelien
2015-03-01
In spintronics, most of the phenomena that we are interested happen at very fast time scales and are rich in structure in time domain. Our understanding, on the other hand, is mostly based on energy domain calculations. Many of the theoretical tools use approximations and simplifications that can be perceived as oversimplifications. We compare the structure, material, carrier density and temperature dependence of spin relaxation time in n-doped III-V semiconductors using Elliot-Yafet (EY) and D'yakanov-Perel'(DP) with real time analysis using kinetic spin Bloch equations (KSBE). The EY and DP theories fail to capture details as the system investigated is varied. KSBE, on the other hand, incorporates all relaxation sources as well as electron-electron interaction which modifies the spin relaxation time in a non-linear way. Since el-el interaction is very fast (~ fs) and spin-conserving, it is usually ignored in the analysis of spin relaxation. Our results indicate that electron-electron interaction cannot be neglected and its interplay with the other (spin and momentum) relaxation mechanisms (electron-impurity and electron-phonon scattering) dramatically alters the resulting spin dynamics. We use each interaction explicitly to investigate how, in the presence of others, each relaxation source behaves. We use GaAs and GaN for zinc-blend structure, and GaN and AlN for the wurtzite structure.
Spin Interactions and Cross-checks of Polarization in NH$_{3}$ Target
Kiselev, Yu; Doshita, N; Gautheron, F; Hess, Ch; Iwata, T; Koivuniemi, J; Kondo, K; Magnon, A; Mallot, G; Michigami, T; Meyer, W; Reicherz, G
2008-01-01
We study the magnetic structure of irradiated ammonia (NH$_{3}$) polarized by Dynamic Nuclear Polarization method at 0.2 K and at 2.5 T field. In this material, the electron spins, induced by ionizing radiation, couple $^{14}$N and $^{1}$H spins by the indirect spin-spin interaction. As a result, the local frequencies of $^{1}$H-spins are varied depending on $^{14}$N spin polarizations and lead to an asymmetry in the proton signal. This asymmetry allowes a good detection of $^{14}$N spins directly on the proton Larmor frequency. In the long COMPASS target at CERN, we use the cross-checks between spectral asymmetries and integral polarizations to decrease the relative error for longitudinal target polarizations up to $\\pm$2.0%.
Simulation of Coulomb interaction effects in electron sources
International Nuclear Information System (INIS)
Rouse, John; Zhu Xieqing; Liu Haoning; Munro, Eric
2011-01-01
Over many years, we have developed electron source simulation software that has been used widely in the electron optics community to aid the development of rotationally symmetric electron and ion guns. The simulation includes the modelling of cathode emission and the effects of volumetric space charge. In the present paper we describe the existing software and explain how we have extended this software to include the effects of discrete Coulomb interactions between the electrons as they travel from the cathode surface to the exit of the gun. In the paper, we will describe the numerical models we have employed, the techniques we have used to maximize the speed of the Coulomb force computation and present several illustrative examples of cases analyzed using the new software, including thermal field emitters, LaB 6 guns and flat dispenser-type cathodes.
International Nuclear Information System (INIS)
Popelis, Yu.Yu.; Liepin'sh, E.E.; Lukevits, E.Ya.
1986-01-01
The 1 H, 13 C, and 15 N NMR spectra of 15 N-enriched 5-substituted furfural oximes were investigated. It was shown that the chemical shifts of the ring atoms and the oxime group correlate satisfactorily with the F and R substituent constants, whereas their sensitivity to the effect of the substituents is lower than in monosubstituted furan derivatives. The constants of spin-spin coupling between the ring protons and the oxime group were determined. An analysis of the 1 H- 1 H spin-spin coupling constants (SSCC) on the basis of their stereospecificity indicates that the E isomers have primarily an s-trans conformation in polar dimethyl sulfoxide, whereas the Z isomers, on the other hand, have an s-cis conformation. The signs of the direct and geminal 13 C- 15 N SSCC were determined for 5-trimethylsilylfurfural oxime
INTERACTION OF SEARCH CAPABILITIES OF ELECTRONIC AND TRADITIONAL (CARD CATALOGS
Directory of Open Access Journals (Sweden)
Л. В. Головко
2017-10-01
Full Text Available Purpose. Interaction of search capabilities of electronic and traditional (card catalogs. Subject: search capabilities of electronic and traditional (card catalogs and their interaction. Goal: Creating efficient search system for library information services, updating and improving the information retrieval system. To reach this goal, following tasks are set: – to determine the possibility of parallel functioning of electronic and traditional card catalogs, and to reveal the interaction of their search capabilities by conducting a survey via questionnaire titled «Interaction of search capabilities of electronic and traditional (card catalogs»; – to find out which search systems are preferred by users; – to estimate the actual condition of search capabilities of electronic and traditional (card catalogs in the library. Methodology. On various stages of the survey the following methods were used: analysis and synthesis, comparison, generalization, primary sources search; sociological method (survey. These methods allowed determining, processing and ana lyzing the whole complex of available sources, which became an important factor of research objectivity. Finding. Survey results allowed us to analyze the dynamics of changes, new needs of the readers, and to make a decision regarding the quality improvement of information search services. Practical value. Creating a theoretical foundation for implementation of set tasks is the practical value of the acquired findings. Conclusions and results of the research can be used in university students’, postgraduates’ and professors’ information search activities. Certain results of the research are used and implemented in practice of the library of Kryvyi Rih State Pedagogical University, namely at workshops on the basics of information culture (using bibliographic reference unit, information search by key words, authors and titles via electronic catalogue. Guides for users were created. Duty
Electron beam emission and interaction of double-beam gyrotron
International Nuclear Information System (INIS)
Singh, Udaybir; Kumar, Anil; Kumar, Nitin; Kumar, Narendra; Pratap, Bhanu; Purohit, L.P.; Sinha, A.K.
2012-01-01
Highlights: ► The complete electrical design of electron gun and interaction structure of double-beam gyrotron. ► EGUN code is used for the simulation of electron gun of double-beam gyrotron. ► MAGIC code is used for the simulation of interaction structure of double-beam gyrotron. ► Design validations with other codes. - Abstract: This paper presents the numerical simulation of a double-beam magnetron injection gun (DB-MIG) and beam-wave interaction for 60 GHz, 500 kW gyrotron. The beam-wave interaction calculations, power and frequency growth estimation are performed by using PIC code MAGIC. The maximum output power of 510 kW at 41.5% efficiency, beam currents of 6 A and 12 A, electron beam velocity ratios of 1.41 and 1.25 and beam voltage of 69 kV are estimated. To obtain the design parameters, the DB-MIG with maximum transverse velocity spread less than 5% is designed. The computer simulations are performed by using the commercially available code EGUN and the in-house developed code MIGANS. The simulated results of DB-MIG design obtained by using the EGUN code are also validated with another trajectory code TRAK, which are in good agreement.
Electron beam emission and interaction of double-beam gyrotron
Energy Technology Data Exchange (ETDEWEB)
Singh, Udaybir, E-mail: uday.ceeri@gmail.com [Gyrotron Laboratory, Microwave Tube Area, Central Electronics Engineering Research Institute (CEERI), Council of Scientific and Industrial Research (CSIR), Pilani, Rajasthan 333031 (India); Department of Physics, Gurukul Kangri University, Haridwar 249404 (India); Kumar, Anil [Gyrotron Laboratory, Microwave Tube Area, Central Electronics Engineering Research Institute (CEERI), Council of Scientific and Industrial Research (CSIR), Pilani, Rajasthan 333031 (India); Kumar, Nitin, E-mail: nitin_physika@rediffmail.com [Gyrotron Laboratory, Microwave Tube Area, Central Electronics Engineering Research Institute (CEERI), Council of Scientific and Industrial Research (CSIR), Pilani, Rajasthan 333031 (India); Kumar, Narendra; Pratap, Bhanu [Gyrotron Laboratory, Microwave Tube Area, Central Electronics Engineering Research Institute (CEERI), Council of Scientific and Industrial Research (CSIR), Pilani, Rajasthan 333031 (India); Purohit, L.P. [Department of Physics, Gurukul Kangri University, Haridwar 249404 (India); Sinha, A.K., E-mail: aksinha@ceeri.ernet.in [Gyrotron Laboratory, Microwave Tube Area, Central Electronics Engineering Research Institute (CEERI), Council of Scientific and Industrial Research (CSIR), Pilani, Rajasthan 333031 (India)
2012-09-15
Highlights: Black-Right-Pointing-Pointer The complete electrical design of electron gun and interaction structure of double-beam gyrotron. Black-Right-Pointing-Pointer EGUN code is used for the simulation of electron gun of double-beam gyrotron. Black-Right-Pointing-Pointer MAGIC code is used for the simulation of interaction structure of double-beam gyrotron. Black-Right-Pointing-Pointer Design validations with other codes. - Abstract: This paper presents the numerical simulation of a double-beam magnetron injection gun (DB-MIG) and beam-wave interaction for 60 GHz, 500 kW gyrotron. The beam-wave interaction calculations, power and frequency growth estimation are performed by using PIC code MAGIC. The maximum output power of 510 kW at 41.5% efficiency, beam currents of 6 A and 12 A, electron beam velocity ratios of 1.41 and 1.25 and beam voltage of 69 kV are estimated. To obtain the design parameters, the DB-MIG with maximum transverse velocity spread less than 5% is designed. The computer simulations are performed by using the commercially available code EGUN and the in-house developed code MIGANS. The simulated results of DB-MIG design obtained by using the EGUN code are also validated with another trajectory code TRAK, which are in good agreement.
Controlling electron quantum dot qubits by spin-orbit interactions
International Nuclear Information System (INIS)
Stano, P.
2007-01-01
Single electron confined in a quantum dot is studied. A special emphasis is laid on the spin properties and the influence of spin-orbit interactions on the system. The study is motivated by a perspective exploitation of the spin of the confined electron as a qubit, a basic building block of in a foreseen quantum computer. The electron is described using the single band effective mass approximation, with parameters typical for a lateral electrostatically defined quantum dot in a GaAs/AlGaAs heterostructure. The stemming data for the analysis are obtained by numerical methods of exact diagonalization, however, all important conclusions are explained analytically. The work focuses on three main areas -- electron spectrum, phonon induced relaxation and electrically and magnetically induced Rabi oscillations. It is shown, how spin-orbit interactions influence the energy spectrum, cause finite spin relaxation and allow for all-electrical manipulation of the spin qubit. Among the main results is the discovery of easy passages, where the spin relaxation is unusually slow and the qubit is protected against parasitic electrical fields connected with manipulation by resonant electromagnetic fields. The results provide direct guide for manufacturing quantum dots with much improved properties, suitable for realizing single electron spin qubits. (orig.)
Controlling electron quantum dot qubits by spin-orbit interactions
Energy Technology Data Exchange (ETDEWEB)
Stano, P.
2007-01-15
Single electron confined in a quantum dot is studied. A special emphasis is laid on the spin properties and the influence of spin-orbit interactions on the system. The study is motivated by a perspective exploitation of the spin of the confined electron as a qubit, a basic building block of in a foreseen quantum computer. The electron is described using the single band effective mass approximation, with parameters typical for a lateral electrostatically defined quantum dot in a GaAs/AlGaAs heterostructure. The stemming data for the analysis are obtained by numerical methods of exact diagonalization, however, all important conclusions are explained analytically. The work focuses on three main areas -- electron spectrum, phonon induced relaxation and electrically and magnetically induced Rabi oscillations. It is shown, how spin-orbit interactions influence the energy spectrum, cause finite spin relaxation and allow for all-electrical manipulation of the spin qubit. Among the main results is the discovery of easy passages, where the spin relaxation is unusually slow and the qubit is protected against parasitic electrical fields connected with manipulation by resonant electromagnetic fields. The results provide direct guide for manufacturing quantum dots with much improved properties, suitable for realizing single electron spin qubits. (orig.)
Secondary electron interactions in materials with environmental and radiological interest
International Nuclear Information System (INIS)
Garcia, G.; Blanco, F.; Pablos, J.L. de; Perez, J.M.; Williart, A.
2003-01-01
Important environmental and radiological applications require energy deposition models including the interactions between secondary electrons and the atoms or molecules of the medium. In this work we propose a method to obtain reliable cross-section data to be used in these models by combining total and ionization cross-section measurements with simple calculations of the differential and integral elastic cross-sections. The energy loss spectra obtained in this experiment have been also used to drive stopping power of the considered materials for electrons. Some examples of results for atomic (Xe) and molecular (CF 4 ) targets are presented and discussed in this paper. (author)
Spin interactions of light quarks
International Nuclear Information System (INIS)
Simonov, Yu.A.
1989-01-01
Spin-spin and spin-orbit interactions of light quarks is calculated exactly, i.e. without use of perturbation expansion in (mass) -1 . Vacuum gluonic fields are represented by bilocal correlators and higher order correlators are neglected. Perturbative contribution is reproduced in lowest order by a simple modification of the bilocal correlator, and the smearing of the function in the hyperfine term is discussed. 12 refs
Probing Nanoscale Electronic and Magnetic Interaction with Scanning Tunneling Spectroscopy
DEFF Research Database (Denmark)
Bork, Jakob
tunneling microscope (STM). Especially at low temperatures the Kondo resonance is used to probe magnetic interaction with ferromagnetic islands and between two atoms. The latter showing a crossover between Kondo screened atoms and antiferromagnetically coupled atoms close to the quantum critical point....... This is related to research in correlated electron materials such as studies of phase transitions in heavy fermion compounds and magnetic interaction in spintronic research. The capping of cobalt islands on Cu(111) with silver is investigated with STM and photoemission spectroscopy. It is shown that at low...
The impact parameter dependence of swift electron-matter interactions
International Nuclear Information System (INIS)
Ritchie, R.H.
1988-01-01
In quantal collision theories, momentum and energy are usually taken to be good quantal variables. Classical collision theory, on the other hand, uses position and time to describe interactions between a probe and a target. In modern physics one may wish to express quantal theories in terms of spacelike variables. For example, experiments are now common in which one measures, by means of a narrowly focused beam of swift electrons, the distribution in energy of losses experienced in a very small region of space. Also, in experiments with channeled ions, and in microdosimetry, one is interested in the spatial coherence of unlocalized excitations created by swift ions and electrons, and their ultimate localization through transfer of energy to, e.g., single-particle excitations. In this lecture the author describes work, done in part in collaboration with Professor Howie, on some aspects of the spatial dependence of inelastic interactions between a charged particle and a condensed matter target. 6 refs., 1 fig
Effect of electrostatic interactions on electron-transfer reactions
International Nuclear Information System (INIS)
Hickel, B.
1987-01-01
Fast reactions of electron transfer are studied by pulsed radiolysis. By this technique radicals and ionic radicals with high redox potentials are created homogeneously in the solution in about 10 -8 second. For solvated electron effect of electrostatic interaction on kinetics of reactions limited by diffusion is obtained with a good approximation by the Debye equation when ion mobility is known. Deviation from the theory occurs in ion pair formation, which is evidenced experimentally in reactions between anions when cations are complexed by a cryptate. Slow reactions k 8 M -1 s -1 are more sensitive to electrostatic interactions than reactions limited by diffusion. When there is no ion pair formation the velocity constant depends upon dielectric constant of the solvent and reaction distance. 17 refs
Electron correlation effects on the N2--N2 interaction
International Nuclear Information System (INIS)
Hay, P.J.; Pack, R.T.; Martin, R.L.
1984-01-01
Ab initio self-consistent field, configuration interaction, and many-body perturbation theory methods are used to calculate the intermolecular potential between two nitrogen molecules. The emphasis is placed on the repulsive region important at the temperatures and pressures encountered in detonations. In addition, electron gas calculations are employed to fit and extend the ab initio data. We also generate effective spherical potentials which fit dilute gas virial, viscosity, and differential scattering data while being constrained by Hugoniot or ab initio data in the repulsive region. Finally, we discuss the roles of electron correlation and of many-body effects on the N 2 --N 2 interaction. Comparisons are also made to the Ar 2 potential where similar ab initio calculations are compared to an accurate empirical potential
Electron-lattice Interaction and Nonlinear Excitations in Cuprate Structures
International Nuclear Information System (INIS)
Paulsen, J.; Eschrig, H.; Drechsler, S.L.; Malek, J.
1995-01-01
A low temperature lattice modulation of the chains of the YBa 2 Cu 3 O 7 is considered by deriving a Hamiltonian of electron-lattice interaction from density-functional calculations for deformed lattice and solving it for the groundstate. Hubbard-type Coulomb interaction is included. The obtained groundstate is a charge-density-wave state with a pereodicity of four lattice constants and a gap for one-electron excitations of about 1eV, sensitively depending on parameters of the Hamiltonian. There are lots of polaronic and solitonic excitations with formation energies deep in the gap, which can pin the Fermi level and thus produce again metallicity of the chain. They might also contribute to pairing of holes in adjacent CuO 2 -planes. (author)
Anomalous transport of magnetized electrons interacting with EC waves
Energy Technology Data Exchange (ETDEWEB)
Tsironis, C; Vlahos, L [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)
2005-01-01
We consider the nonlinear interaction of magnetized electrons with an oblique narrow-band electromagnetic wave-packet. The interaction is analysed over and near the local threshold to chaos. The statistical character of the forcing that controls the trajectories of the particles is also studied. We focus our analysis on issues related to energy and spatial diffusion across the magnetic field by following the evolution of the ensemble mean squares (({gamma} - {gamma}{sub 0}){sup 2}) and ((r{sub perpendicular}-r{sub perpendicular0}){sup 2}) for various values of the wave amplitude and angle of wave propagation. We study, in particular, the interaction of magnetized electrons with waves having strong and moderate amplitudes, near the transition to chaos, where the dynamics is complex and a mixture of periodic and stochastic orbits coexist. The electron diffusions in real and energy spaces are found to obey simple power laws in time, and the scaling exponents are indicative of sub-diffusion. This is a direct consequence of the effect of the resonant phase-space islands in the particle motion.
Relativistic electron beam - plasma interaction with intense self-fields
International Nuclear Information System (INIS)
Davidson, R.C.
1984-01-01
The major interest in the equilibrium, stability and radiation properties of relativistic electron beams and in beam-plasma interactions originates from several diverse research areas. It is well known that a many-body collection of charged particles in which there is not overall charge neutrality and/or current neutrality can be characterized by intense self-electric fields and/or self-magnetic fields. Moreover, the intense equilibrium self-fields associated with the lack of charge neutrality and/or current neutrality can have a large effect on particle trajectories and on detailed equilibrium and stability behavior. The main emphasis in Sections 9.1.2-9.1.5 of this chapter is placed on investigations of the important influence of self-fields on the equilibrium and stability properties of magnetically confined electron beam-plasma systems. Atomic processes and discrete particle interactions (binary collisions) are omitted from the analysis, and collective processes are assumed to dominate on the time and length scales of interest. Moreover, both macroscopic (Section 9.1.2) and kinetic (Sections 9.1.3-9.1.5) theoretical models are developed and used to investigate equilibrium and stability properties in straight cylindrical geometry. Several of the classical waves and instabilities characteristic of nonneutral plasmas and beam-plasma systems are analyzed in Sections 9.1.2-9.1.5, including stable surface oscillation on a nonneutral electron beam, the ion resonance instability, the diocotron instability, two-stream instabilities between beam electrons and plasma electrons and between beam electrons and plasma ions, the filamentation instability, the modified two-stream instability, etc
Relativistic electron mirrors from high intensity laser nanofoil interactions
International Nuclear Information System (INIS)
Kiefer, Daniel
2012-01-01
The reflection of a laser pulse from a mirror moving close to the speed of light could in principle create an X-ray pulse with unprecedented high brightness owing to the increase in photon energy and accompanying temporal compression by a factor of 4γ 2 , where γ is the Lorentz factor of the mirror. While this scheme is theoretically intriguingly simple and was first discussed by A. Einstein more than a century ago, the generation of a relativistic structure which acts as a mirror is demanding in many different aspects. Recently, the interaction of a high intensity laser pulse with a nanometer thin foil has raised great interest as it promises the creation of a dense, attosecond short, relativistic electron bunch capable of forming a mirror structure that scatters counter-propagating light coherently and shifts its frequency to higher photon energies. However, so far, this novel concept has been discussed only in theoretical studies using highly idealized interaction parameters. This thesis investigates the generation of a relativistic electron mirror from a nanometer foil with current state-of-the-art high intensity laser pulses and demonstrates for the first time the reflection from those structures in an experiment. To achieve this result, the electron acceleration from high intensity laser nanometer foil interactions was studied in a series of experiments using three inherently different high power laser systems and free-standing foils as thin as 3nm. A drastic increase in the electron energies was observed when reducing the target thickness from the micrometer to the nanometer scale. Quasi-monoenergetic electron beams were measured for the first time from ultrathin (≤5nm) foils, reaching energies up to ∝35MeV. The acceleration process was studied in simulations well-adapted to the experiments, indicating the transition from plasma to free electron dynamics as the target thickness is reduced to the few nanometer range. The experience gained from those
Relativistic electron mirrors from high intensity laser nanofoil interactions
Energy Technology Data Exchange (ETDEWEB)
Kiefer, Daniel
2012-12-21
The reflection of a laser pulse from a mirror moving close to the speed of light could in principle create an X-ray pulse with unprecedented high brightness owing to the increase in photon energy and accompanying temporal compression by a factor of 4γ{sup 2}, where γ is the Lorentz factor of the mirror. While this scheme is theoretically intriguingly simple and was first discussed by A. Einstein more than a century ago, the generation of a relativistic structure which acts as a mirror is demanding in many different aspects. Recently, the interaction of a high intensity laser pulse with a nanometer thin foil has raised great interest as it promises the creation of a dense, attosecond short, relativistic electron bunch capable of forming a mirror structure that scatters counter-propagating light coherently and shifts its frequency to higher photon energies. However, so far, this novel concept has been discussed only in theoretical studies using highly idealized interaction parameters. This thesis investigates the generation of a relativistic electron mirror from a nanometer foil with current state-of-the-art high intensity laser pulses and demonstrates for the first time the reflection from those structures in an experiment. To achieve this result, the electron acceleration from high intensity laser nanometer foil interactions was studied in a series of experiments using three inherently different high power laser systems and free-standing foils as thin as 3nm. A drastic increase in the electron energies was observed when reducing the target thickness from the micrometer to the nanometer scale. Quasi-monoenergetic electron beams were measured for the first time from ultrathin (≤5nm) foils, reaching energies up to ∝35MeV. The acceleration process was studied in simulations well-adapted to the experiments, indicating the transition from plasma to free electron dynamics as the target thickness is reduced to the few nanometer range. The experience gained from those
Terahertz electron cyclotron maser interactions with an axis-encircling electron beam
Li, G. D.; Kao, S. H.; Chang, P. C.; Chu, K. R.
2015-04-01
To generate terahertz radiation via the electron cyclotron maser instability, harmonic interactions are essential in order to reduce the required magnetic field to a practical value. Also, high-order mode operation is required to avoid excessive Ohmic losses. The weaker harmonic interaction and mode competition associated with an over-moded structure present challenging problems to overcome. The axis-encircling electron beam is a well-known recipe for both problems. It strengthens the harmonic interaction, as well as minimizing the competing modes. Here, we examine these advantages through a broad data base obtained for a low-power, step-tunable, gyrotron oscillator. Linear results indicate far more higher-harmonic modes can be excited with an axis-encircling electron beam than with an off-axis electron beam. However, multi-mode, time-dependent simulations reveal an intrinsic tendency for a higher-harmonic mode to switch over to a lower-harmonic mode at a high beam current or upon a rapid current rise. Methods are presented to identify the narrow windows in the parameter space for stable harmonic interactions.
Terahertz electron cyclotron maser interactions with an axis-encircling electron beam
International Nuclear Information System (INIS)
Li, G. D.; Kao, S. H.; Chang, P. C.; Chu, K. R.
2015-01-01
To generate terahertz radiation via the electron cyclotron maser instability, harmonic interactions are essential in order to reduce the required magnetic field to a practical value. Also, high-order mode operation is required to avoid excessive Ohmic losses. The weaker harmonic interaction and mode competition associated with an over-moded structure present challenging problems to overcome. The axis-encircling electron beam is a well-known recipe for both problems. It strengthens the harmonic interaction, as well as minimizing the competing modes. Here, we examine these advantages through a broad data base obtained for a low-power, step-tunable, gyrotron oscillator. Linear results indicate far more higher-harmonic modes can be excited with an axis-encircling electron beam than with an off-axis electron beam. However, multi-mode, time-dependent simulations reveal an intrinsic tendency for a higher-harmonic mode to switch over to a lower-harmonic mode at a high beam current or upon a rapid current rise. Methods are presented to identify the narrow windows in the parameter space for stable harmonic interactions
DEFF Research Database (Denmark)
Faber, Rasmus; Sauer, Stephan P. A.
2012-01-01
on the choice of one-electron basis set, the choice of correlated wave function method and the inclusion of zero-point vibrational and temperature corrections. All terms of the SSCC have been evaluated at the second-order polarization propagator, SOPPA and SOPPA(CCSD), and coupled cluster singles and doubles...... (CCSD) levels of theory and for the most correlation dependent term, the paramagnetic spin-orbit contribution (PSO), also at the very accurate CC3 level. We ¿nd that in order to get results that are well converged with respect to the basis set, one needs to use special SSCC optimized basis sets...
Radiative interaction of electrons in a short electron bunch moving in an undulator
International Nuclear Information System (INIS)
Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.
1999-01-01
This paper presents investigations of the longitudinal radiative force in an electron bunch. The model of the electron bunch assumes line density distribution. General formulas are presented for the calculation of the radiative force in the bunch moving along an arbitrary small-angle trajectory. The case of a motion in an undulator (wiggler) has been studied in detail. Analytical solutions are obtained for a rectangular and for a Gaussian bunch shape. It is shown that the rate of the bunch energy loss due to the radiative interaction is equal to the power of the coherent radiation in the far zone. Numerical estimations presented in the paper show that the effects of induced energy spread due to the radiative interaction can be important for free electron lasers operating in the infrared wavelength range
D-state Rydberg electrons interacting with ultracold atoms
Energy Technology Data Exchange (ETDEWEB)
Krupp, Alexander Thorsten
2014-10-02
This thesis was established in the field of ultracold atoms where the interaction of highly excited D-state electrons with rubidium atoms was examined. This work is divided into two main parts: In the first part we study D-state Rydberg molecules resulting from the binding of a D-state Rydberg electron to a ground state rubidium atom. We show that we can address specific rovibrational molecular states by changing our laser detuning and thus create perfectly aligned axial or antialigned toroidal molecules, in good agreement with our theoretical calculations. Furthermore the influence of the electric field on the Rydberg molecules was investigated, creating novel states which show a different angular dependence and alignment. In the second part of this thesis we excite single D-state Rydberg electrons in a Bose-Einstein condensate. We study the lifetime of these Rydberg electrons, the change of the shape of our condensate and the atom losses in the condensate due to this process. Moreover, we observe quadrupolar shape oscillations of the whole condensate created by the consecutive excitation of Rydberg atoms and compare all results to previous S-state measurements. In the outlook we propose a wide range of further experiments including the proposal of imaging a single electron wavefunction by the imprint of its orbit into the Bose-Einstein condensate.
Design of the large hadron electron collider interaction region
Cruz-Alaniz, E.; Newton, D.; Tomás, R.; Korostelev, M.
2015-11-01
The large hadron electron collider (LHeC) is a proposed upgrade of the Large Hadron Collider (LHC) within the high luminosity LHC (HL-LHC) project, to provide electron-nucleon collisions and explore a new regime of energy and luminosity for deep inelastic scattering. The design of an interaction region for any collider is always a challenging task given that the beams are brought into crossing with the smallest beam sizes in a region where there are tight detector constraints. In this case integrating the LHeC into the existing HL-LHC lattice, to allow simultaneous proton-proton and electron-proton collisions, increases the difficulty of the task. A nominal design was presented in the the LHeC conceptual design report in 2012 featuring an optical configuration that focuses one of the proton beams of the LHC to β*=10 cm in the LHeC interaction point to reach the desired luminosity of L =1033 cm-2 s-1 . This value is achieved with the aid of a new inner triplet of quadrupoles at a distance L*=10 m from the interaction point. However the chromatic beta beating was found intolerable regarding machine protection issues. An advanced chromatic correction scheme was required. This paper explores the feasibility of the extension of a novel optical technique called the achromatic telescopic squeezing scheme and the flexibility of the interaction region design, in order to find the optimal solution that would produce the highest luminosity while controlling the chromaticity, minimizing the synchrotron radiation power and maintaining the dynamic aperture required for stability.
Design of the large hadron electron collider interaction region
Directory of Open Access Journals (Sweden)
E. Cruz-Alaniz
2015-11-01
Full Text Available The large hadron electron collider (LHeC is a proposed upgrade of the Large Hadron Collider (LHC within the high luminosity LHC (HL-LHC project, to provide electron-nucleon collisions and explore a new regime of energy and luminosity for deep inelastic scattering. The design of an interaction region for any collider is always a challenging task given that the beams are brought into crossing with the smallest beam sizes in a region where there are tight detector constraints. In this case integrating the LHeC into the existing HL-LHC lattice, to allow simultaneous proton-proton and electron-proton collisions, increases the difficulty of the task. A nominal design was presented in the the LHeC conceptual design report in 2012 featuring an optical configuration that focuses one of the proton beams of the LHC to β^{*}=10 cm in the LHeC interaction point to reach the desired luminosity of L=10^{33} cm^{-2} s^{-1}. This value is achieved with the aid of a new inner triplet of quadrupoles at a distance L^{*}=10 m from the interaction point. However the chromatic beta beating was found intolerable regarding machine protection issues. An advanced chromatic correction scheme was required. This paper explores the feasibility of the extension of a novel optical technique called the achromatic telescopic squeezing scheme and the flexibility of the interaction region design, in order to find the optimal solution that would produce the highest luminosity while controlling the chromaticity, minimizing the synchrotron radiation power and maintaining the dynamic aperture required for stability.
Electron microscopy study of antioxidant interaction with bacterial cells
Plotnikov, Oleg P.; Novikova, Olga V.; Konnov, Nikolai P.; Korsukov, Vladimir N.; Gunkin, Ivan F.; Volkov, Uryi P.
2000-10-01
To maintain native microorganisms genotype and phenotype features a lyophylization technique is widely used. However in this case cells are affected by influences of vacuum and low temperature that cause a part of the cells population to be destruction. Another factor reduced microorganisms vitality is formation of reactive oxygen forms that damage certain biological targets (such as DNA, membranes etc.) Recently to raise microorganism's resistance against adverse condition natural and synthetic antioxidants are used. Antioxidant- are antagonists of free radicals. Introduction of antioxidants in protective medium for lyophylization increase bacteria storage life about 2,0-4,8 fold in comparison with reference samples. In the article the main results of our investigation of antioxidants interaction with microorganism cells is described. As bacteria cells we use vaccine strain yersinia pestis EV, that were grown for 48 h at 28 degree(s)C on the Hottinger agar (pH 7,2). Antioxidants are inserted on the agar surface in specimen under test. To investigate a localization of antioxidants for electron microscopy investigation, thallium organic antioxidants were used. The thallium organic compounds have an antioxidant features if thallium is in low concentration (about 1(mu) g/ml). The localization of the thallium organic antioxidants on bacteria Y. pestis EV is visible in electron microscopy images, thallium being heavy metal with high electron density. The negatively stained bacteria and bacteria thin sections with thallium organic compounds were investigated by means of transmission electron microscopy. The localization of the thallium organic compounds is clearly visible in electron micrographs as small dark spots with size about 10-80nm. Probably mechanisms of interaction of antioxidants with bacteria cells are discussed.
Exact diagonalization library for quantum electron models
Iskakov, Sergei; Danilov, Michael
2018-04-01
We present an exact diagonalization C++ template library (EDLib) for solving quantum electron models, including the single-band finite Hubbard cluster and the multi-orbital impurity Anderson model. The observables that can be computed using EDLib are single particle Green's functions and spin-spin correlation functions. This code provides three different types of Hamiltonian matrix storage that can be chosen based on the model.
Relativistic spin-orbit interactions of photons and electrons
Smirnova, D. A.; Travin, V. M.; Bliokh, K. Y.; Nori, F.
2018-04-01
Laboratory optics, typically dealing with monochromatic light beams in a single reference frame, exhibits numerous spin-orbit interaction phenomena due to the coupling between the spin and orbital degrees of freedom of light. Similar phenomena appear for electrons and other spinning particles. Here we examine transformations of paraxial photon and relativistic-electron states carrying the spin and orbital angular momenta (AM) under the Lorentz boosts between different reference frames. We show that transverse boosts inevitably produce a rather nontrivial conversion from spin to orbital AM. The converted part is then separated between the intrinsic (vortex) and extrinsic (transverse shift or Hall effect) contributions. Although the spin, intrinsic-orbital, and extrinsic-orbital parts all point in different directions, such complex behavior is necessary for the proper Lorentz transformation of the total AM of the particle. Relativistic spin-orbit interactions can be important in scattering processes involving photons, electrons, and other relativistic spinning particles, as well as when studying light emitted by fast-moving bodies.
Misra, Sushil K.
The measurement of very short spin-lattice, or longitudinal, relaxation (SLR) times (i.e., 10-10 Misra, 1998), and polymer resins doped with rare-earth ions (Pescia et al., 1999a; Pescia et al. 1999b). The ability to measure such fast SLR data on amorphous Si and copper-chromium-tin spinel led to an understanding of the role of exchange interaction in affecting spin-lattice relaxation, while the data on polymer resins doped with rare-earth ions provided evidence of spin-fracton relaxation (Pescia et al., 1999a, b). But such fast SLR times are not measurable by the most commonly used techniques of saturation- and inversion-recovery (Poole, 1982; Alger, 1968), which only measure spin-lattice relaxation times longer than 10-6 s. A summary of relevant experimental data is presented in Table 1.
Electronic structure of MnSi : The role of electron-electron interactions
Carbone, F; Zangrando, M; Brinkman, A; Nicolaou, A; Bondino, F; Magnano, E; Nugroho, A. A.; Parmigiani, F; Jarlborg, T; van der Marel, D
We present an experimental study of the electronic structure of MnSi. Using x-ray absorption spectroscopy (XAS), x-ray photoemission, and x-ray fluorescence, we provide experimental evidence that MnSi has a mixed valence ground state. We show that self-consistent local density approximation
Electronic structure of MnSi: The role of electron-electron interactions
Carbone, F.; Zangrando, M.; Brinkman, Alexander; Nicolaou, A.; Bondino, F.; Magnano, E.; Nugroho, A.A.; Parmigiani, F.; Jarlborg, Th.; van der Marel, D.
2006-01-01
We present an experimental study of the electronic structure of MnSi. Using x-ray absorption spectroscopy (XAS), x-ray photoemission, and x-ray fluorescence, we provide experimental evidence that MnSi has a mixed valence ground state. We show that self-consistent local density approximation
Laser-electron Compton interaction in plasma channels
International Nuclear Information System (INIS)
Pogorelsky, I.V.; Ben-Zvi, I.; Hirose, T.
1998-10-01
A concept of high intensity femtosecond laser synchrotron source (LSS) is based on Compton backscattering of focused electron and laser beams. The short Rayleigh length of the focused laser beam limits the length of interaction to a few picoseconds. However, the technology of the high repetition rate high-average power picosecond lasers required for high put through LSS applications is not developed yet. Another problem associated with the picosecond laser pulses is undesirable nonlinear effects occurring when the laser photons are concentrated in a short time interval. To avoid the nonlinear Compton scattering, the laser beam has to be split, and the required hard radiation flux is accumulated over a number of consecutive interactions that complicates the LSS design. In order to relieve the technological constraints and achieve a practically feasible high-power laser synchrotron source, the authors propose to confine the laser-electron interaction region in the extended plasma channel. This approach permits to use nanosecond laser pulses instead of the picosecond pulses. That helps to avoid the nonlinear Compton scattering regime and allows to utilize already existing technology of the high-repetition rate TEA CO 2 lasers operating at the atmospheric pressure. They demonstrate the advantages of the channeled LSS approach by the example of the prospective polarized positron source for Japan Linear Collider
Signature of electron-phonon interaction in high temperature superconductors
Directory of Open Access Journals (Sweden)
Vinod Ashokan
2011-09-01
Full Text Available The theory of thermal conductivity of high temperature superconductors (HTS based on electron and phonon line width (life times formulation is developed with Quantum dynamical approach of Green's function. The frequency line width is observed as an extremely sensitive quantity in the transport phenomena of HTS as a collection of large number of scattering processes. The role of resonance scattering and electron-phonon interaction processes is found to be most prominent near critical temperature. The theory successfully explains the spectacular behaviour of high Tc superconductors in the vicinity of transition temperature. A successful agreement between theory and experiment has been obtained by analyzing the thermal conductivity data for the sample La1.8Sr0.2CuO4 in the temperature range 0 − 200K. The theory is equally and successfully applicable to all other high Tc superconductors.
International Nuclear Information System (INIS)
Babinski, A; Korkusinski, M; Hawrylak, P; Wasilewski, Z R; Potemski, M
2013-01-01
Magnetic-field dispersion of the multiexcitons related to the p shell of a single quantum dot (QD) is analysed in this work. The reduced cyclotron effective mass of carriers is determined from the energy splitting between the p + - and p − - related multiexcitonic emission lines. The reduced mass in the occupied QD was found to be larger than the mass related to the QD's single particle structure. The apparent increase of the reduced mass with increasing excitonic occupation of the dot is related to the mass renoralization due to electron-electron interactions within a multiexcitonic droplet
Interactions of free electrons with an electromagnetic radiation
Energy Technology Data Exchange (ETDEWEB)
Zel' dovich, Ya B [AN SSSR, Moscow. Inst. Prikladnoj Matematiki
1975-02-01
The interaction of a chaotic field of electromagnetic radiation with free electrons in plasma is considered as applied to astrophysical problems, in particular, to the theory of establishing thermodynamic equilibrium of radiation in the hot universe. The kinetic equation describes a change in the spectrum; particular attention is paid to the induced scattering and to the classical interpretation of the induced transfer of energy and momentum. In spectra of radiosources with a high brightness temperature the induced scattering may lead to the Bose condensation of photons, shock wave and appearance of solutions. The scattering of strong low-frequency waves is considered as applied to pulsars and laboratory coherent generators.
Cherenkov interaction of hollow electron beam with a dielectric waveguide
International Nuclear Information System (INIS)
Karbushev, N.I.; Shlapakovskij, A.S.
1989-01-01
The waveguide excitation methods are used to study magnetized hollow electron beam interaction with electromagnetic waves of a waveguide with a dielectric bush. Characteristic equation with explicit presentation of depression coefficients and the beam coupling with the synchronous wave is derived. Dependences of depression and coupling coefficients on the beam and waveguide parameters are studied. the current limiting values of small and large space charge regimes are determined. Coefficients of synchronous wave amplification by a beam and oscillation set up conditions in the considered finite length system are determined
The theory of coherent resonance tunneling of interacting electrons
International Nuclear Information System (INIS)
Elesin, V. F.
2001-01-01
Analytical solutions of the Schrödinger equation for a two-barrier structure (resonance-tunnel diode) with open boundary conditions are found within the model of coherent tunneling of interacting electrons. Simple expressions for resonance current are derived which enable one to analyze the current-voltage characteristics, the conditions of emergence of hysteresis, and singularities of the latter depending on the parameters of resonance-tunnel diode. It is demonstrated that the hysteresis is realized if the current exceeds some critical value proportional to the square of resonance level width.
International Nuclear Information System (INIS)
Molinari, V.G.; Pizzio, F.; Spiga, G.
1979-01-01
The electron distribution function, the electron temperature and some transport parameters (electrical conductivity and energy flow coefficient) are obtained starting from the nonlinear Boltzmann equation for a plasma under the action of an external electric field. The Fokker-Planck approximation is used for electron-electron and electron-ion interactions. The effects of electron-electron collisions are studied for different values of collision frequencies and electric field. (author)
Electron beam interactions with CO on W[100] studied by Auger electron spectroscopy
International Nuclear Information System (INIS)
Housley, M.; King, D.A.
1977-01-01
The interaction of 2500 eV electrons with carbon monoxide chemisorbed on tungsten [100] was investigated by rapid-scan Auger electron spectroscopy. When no α state was present the O and C signals from the β state of CO were invariant during electron bombardment, giving an upper limit estimate for the electron stimulated desorption cross section, Qsub(β), of 2 x 10 -21 cm 2 . With the crystal at room temperature and saturated with CO, however, electron-beam induced accumulation of carbon was observed and characterised, the rate of the process being independent of CO pressure at pressures above 2 x 10 -8 Torr. At 450 K the rate was found to be pressure dependent up to at least 6 x 10 -7 Torr. A model is proposed for the accumulation process, which is based on electron beam dissociation of α 2 -CO to form adsorbed carbon and gaseous O and the creation of new sites for further α 2 -CO adsorption; it is in quantitative agreement with the results and yields a cross section for ESD of α 2 -CO (Qsub(α 2 )=1.55 X 10 -18 cm 2 ) in clo 2 e agreement with direct measurements. (Auth.)
2012 Gordon Research Conference, Electron donor-acceptor interactions, August 5-10 2012
Energy Technology Data Exchange (ETDEWEB)
McCusker, James [Michigan State Univ., East Lansing, MI (United States)
2012-08-10
The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.
Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek
2017-07-01
Standard computational methods used to take account of the Pauli Exclusion Principle into Monte Carlo (MC) simulations of electron transport in semiconductors may give unphysical results in low field regime, where obtained electron distribution function takes values exceeding unity. Modified algorithms were already proposed and allow to correctly account for electron scattering on phonons or impurities. Present paper extends this approach and proposes improved simulation scheme allowing including Pauli exclusion principle for electron-electron (e-e) scattering into MC simulations. Simulations with significantly reduced computational cost recreate correct values of the electron distribution function. Proposed algorithm is applied to study transport properties of degenerate electrons in graphene with e-e interactions. This required adapting the treatment of e-e scattering in the case of linear band dispersion relation. Hence, this part of the simulation algorithm is described in details.
Photon and electron interaction properties of ICRP reference man
International Nuclear Information System (INIS)
White, D.R.; Fitzgerald, M.; Ingram, D.
1977-01-01
The latest report of the Task Group of Committee 2 on Reference Man contains a comprehensive tabulation of the concentrations of 51 elements in 81 organs, tissues and tissue components. A comparison of the summation of the masses of the elements present in the tissue to the quoted total masses, has indicated discrepancies in excess of 20% for 12 tissues. The errors were generally due to data relating to the elements C, H, N or O being omitted, but certain skeletal systems were without calcium. Consequently, calculations were performed on 69 organs and tissues. Partial and total mass attenuation and energy absorption coefficients for 33 energies within the range 10 keV - 100 MeV, have been calculated using published elemental cross sections. Data were derived by the use of the conventional 'mixture rule', by summing over 51 elements. Photoelectric K, L 1 , L 2 and L 3 absorption edges for the high atomic number elements present were also considered in the analysis. Electron collision and radiation mass stopping powers, angular scattering powers and ranges have also been calculated for the same 33 energies from 10 keV - 100 MeV and for the same 69 tissues and organs. All of the tissues and organs have been categorised according to the basic fat/water/protein compositions and the magnitudes of the derived photon and electron data. The analysis has indicated a number of results of importance in radiation dosimetry. These include differences in excess of 30% in the photon interaction data at low energies for cortical bone compared to similar data for an earlier published formulation and significant K-edge discontinuities from iodine present in the thyroid. A review of this work will be given and comparisons made with interaction data derived from the previous reference Man document that was published in 1959. The implications of both the photon and the electron results in radiation dosimetry will be discussed
Rusakov, Yury Yu; Rusakova, Irina L; Krivdin, Leonid B
2014-05-01
Four-component relativistic calculations of (77)Se-(13)C spin-spin coupling constants have been performed in the series of selenium heterocycles and their parent open-chain selenides. It has been found that relativistic effects play an essential role in the selenium-carbon coupling mechanism and could result in a contribution of as much as 15-25% of the total values of the one-bond selenium-carbon spin-spin coupling constants. In the overall contribution of the relativistic effects to the total values of (1)J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spin-orbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic second-order polarization propagator approach (CC2) with the four-component relativistic density functional theory scheme is recommended as a versatile tool for the calculation of (1)J(Se,C). Solvent effects in the values of (1)J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.2-78.4) are next to negligible decreasing negative (1)J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of (77)Se-(13)C spin-spin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.1-0.2-Hz loss of accuracy. Copyright © 2014 John Wiley & Sons, Ltd.
Nonlinear dynamics of resonant electrons interacting with coherent Langmuir waves
Tobita, Miwa; Omura, Yoshiharu
2018-03-01
We study the nonlinear dynamics of resonant particles interacting with coherent waves in space plasmas. Magnetospheric plasma waves such as whistler-mode chorus, electromagnetic ion cyclotron waves, and hiss emissions contain coherent wave structures with various discrete frequencies. Although these waves are electromagnetic, their interaction with resonant particles can be approximated by equations of motion for a charged particle in a one-dimensional electrostatic wave. The equations are expressed in the form of nonlinear pendulum equations. We perform test particle simulations of electrons in an electrostatic model with Langmuir waves and a non-oscillatory electric field. We solve equations of motion and study the dynamics of particles with different values of inhomogeneity factor S defined as a ratio of the non-oscillatory electric field intensity to the wave amplitude. The simulation results demonstrate deceleration/acceleration, thermalization, and trapping of particles through resonance with a single wave, two waves, and multiple waves. For two-wave and multiple-wave cases, we describe the wave-particle interaction as either coherent or incoherent based on the probability of nonlinear trapping.
Photon-Electron Interactions in Dirac Quantum Materials
Energy Technology Data Exchange (ETDEWEB)
Xu, Xiaodong [Univ. of Washington, Seattle, WA (United States). Dept. of Material Science and Engineering
2017-11-10
The objective of this proposal was to explore the fundamental light-matter interactions in a new class of Dirac quantum materials, atomically thin transition metal dichalcogenides (TMDs). Monolayer TMDs are newly discovered two-dimensional semiconductors with direct bandgap. Due to their hexagonal lattice structure, the band edge localizes at corner of Brillouin zone, i.e. “Dirac valleys”. This gives the corresponding electron states a “valley index” (or pseudospin) in addition to the real spin. Remarkably, the valley pseudospins have circularly polarized optical selection rules, providing the first solid state system for dynamic control of the valley degree of freedom. During this award, we have developed a suite of advanced nano-optical spectroscopy tools in the investigation and manipulation of charge, spin, and valley degrees of freedom in monolayer semiconductors. Emerging physical phenomena, such as quantum coherence between valley pseudospins, have been demonstrated for the first time in solids. In addition to monolayers, we have developed a framework in engineering, formulating, and understanding valley pseudospin physics in 2D heterostructures formed by different monolayer semiconductors. We demonstrated long-lived valley-polarized interlayer excitons with valley-dependent many-body interaction effects. These works push the research frontier in understanding the light-matter interactions in atomically-thin quantum materials for protentional transformative energy technologies.
Electromagnetic interactions in an electron-hole plasma
International Nuclear Information System (INIS)
1977-01-01
Certain problems electromagnetic interactions both of external SHF radiation with an electron-hole (eh) plasma and in the plasma itself are considered. The production and properties of a non-equilibrium eh plasma in semiconductors, pinch effect in a plasma of solids, strong electric fields in a plasma of inhomogeneous semiconductors and heat effects in a semiconductor plasma are discussed. The influence of a surface, kinetics of recombination processes in the semiconductor volume and the plasma statistics the spatial distribution of carriers, current characteristics and plasma recombination radiation under the conditions of pinch effect is described. The diagnostics methods of the phenomena are presented. The behaviour of diode structures with pn transitions in strong SHF fields is discussed. Special attention is paid to collective phenomena in the plasma of semiconductor devices and the variation of carrier density in strong fields. The appearance of electromotive force in inhomogeneous diode structures placed in strong SHF fields is considered
Interactive, Inter-organizational Innovations in Electronic Commerce
DEFF Research Database (Denmark)
Elliot, Steve; Loebbecke, Claudia
2000-01-01
Electronic commerce has been recognised as a source of fundamental change to the conduct of business. Exploitation by business of this innovative approach to payments will necessitate wide‐scale adoption of new processes and technologies and may require new thinking on how organizations adopt...... innovations. Primarily, these innovations will be interactive and inter‐organizational, i.e. a successful cash substitute will require the concurrent participation of many different organizations, as well as consumers. Current theoretical models of adoption may not cater for this type of innovation....... This paper compares four diverse pilot implementations of smart‐card payment systems with Rogers’ (1995) attributes of innovations, adoption processes and adoption decision approaches for organizations. In general, Rogers’ models do not reflect the levels of complexity and diversity found in practice...
Electron density interferometry measurement in laser-matter interaction
International Nuclear Information System (INIS)
Popovics-Chenais, C.
1981-05-01
This work is concerned with the laser-interferometry measurement of the electronic density in the corona and the conduction zone external part. Particularly, it is aimed at showing up density gradients and at their space-time localization. The first chapter recalls the density profile influence on the absorption principal mechanisms and the laser energy transport. In chapter two, the numerical and analytical hydrodynamic models describing the density profile are analysed. The influence on the density profile of the ponderomotive force associated to high oscillating electric fields is studied, together with the limited thermal conduction and suprathermal electron population. The mechanism action, in our measurement conditions, is numerically simulated. Calculations are made with experimental parameters. The measurement interaction conditions, together with the diagnostic method by high resolution laser interferometry are detailed. The results are analysed with the help of numerical simulation which is the experiment modeling. An overview of the mechanisms shown up by interferometric measurements and their correlation with other diagnostics is the conclusion of this work [fr
Maeda, Kiminori; Lodge, Matthew T.J.; Harmer, Jeffrey; Freed, Jack H.; Edwards, Peter P.
2012-01-01
Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T1) and spin-spin (T2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multi-exponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1–10)×10−12 s over a temperature range 230–290K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a timescale of ca. 10−13 s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential
Maeda, Kiminori; Lodge, Matthew T J; Harmer, Jeffrey; Freed, Jack H; Edwards, Peter P
2012-06-06
Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T(1)) and spin-spin (T(2)) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multiexponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1-10) × 10(-12) s over a temperature range 230-290 K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a time scale of ∼10(-13) s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great
Escaping Electrons from Intense Laser-Solid Interactions as a Function of Laser Spot Size
Rusby, Dean; Gray, Ross; Butler, Nick; Dance, Rachel; Scott, Graeme; Bagnoud, Vincent; Zielbauer, Bernhard; McKenna, Paul; Neely, David
2018-01-01
The interaction of a high-intensity laser with a solid target produces an energetic distribution of electrons that pass into the target. These electrons reach the rear surface of the target creating strong electric potentials that act to restrict the further escape of additional electrons. The measurement of the angle, flux and spectra of the electrons that do escape gives insights to the initial interaction. Here, the escaping electrons have been measured using a differentially filtered imag...
Kraayvanger, Ryan J; Bidinosti, Christopher P; Dominguez-Viqueira, William; Parra-Robles, Juan; Fox, Matthew; Lam, Wilfred W; Santyr, Giles E
2010-11-01
Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, (3) He and (129) Xe, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin-spin relaxation rate (R(2) ) of (3) He at low magnetic field strengths (oxygen partial pressure measurements based on Carr-Purcell-Meiboom-Gill R(2) values of hyperpolarized (3) He and (129) Xe in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin-spin relaxivity constants for (3) He and (129) Xe were determined to be (5.2 ± 0.6) × 10(-6) Pa(-1) sec(-1) and (7.3 ± 0.4) × 10(-6) Pa(-1) s(-1) compared with spin-lattice relaxivity constants of (4.0 ± 0.4) × 10(-6) Pa(-1) s(-1) and (4.3 ± 1.3) × 10(-6) Pa(-1) s(-1), respectively. In vivo experimental measurements of alveolar oxygen partial pressure using (3) He in whole rat lung show good agreement (r(2) = 0.973) with predictions based on lung volumes and ventilation parameters. For (129) Xe, multicomponent relaxation was observed with one component exhibiting an increase in R(2) with decreasing alveolar oxygen partial pressure. Copyright © 2010 Wiley-Liss, Inc.
Energy Technology Data Exchange (ETDEWEB)
Niki, Haruo; Okuda, Hiroyuki; Oshiro, Morihito; Yogi, Mamoru [Department of Physics, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213 (Japan); Seki, Ichiro; Fukuhara, Mikio [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)
2012-06-15
Using the Fourier transform of the echo envelope, the proton line shapes, spin-lattice relaxation time, and spin-spin relaxation time have been measured in a (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} glassy alloy at 1.83 T ({approx}78 MHz) and at temperatures between 1.8 and 300 K. First, the spectral line width decreases abruptly between 1.8 and 2.1 K. Next, it remains almost constant at 13 kHz up to {approx}150 K. Finally, the line width decreases as the temperature increases from {approx}150 to 300 K. The initial decrease in the spectral line width is ascribed to the distribution of the external field, which is caused by the penetration of vortices in the superconducting state. The subsequent leveling off in the spectral line width is ascribed to the dipole-dipole interaction between protons when hydrogen atoms are trapped into vacancies among the Zr-centered icosahedral Zr{sub 5}Ni{sub 5}Nb{sub 3} clusters. The final decrease in the spectral line width is ascribed to the motional narrowing of the width that is caused by the movement of hydrogen atoms. The temperature dependences of the spin-lattice and spin-spin relaxation time showed that at temperature above 150 K and the activation energy of 8.7 kJ/mol allowed the hydrogen atoms to migrate among the clusters. The distance between the hydrogen atoms is estimated to be 2.75 A. Hydrogen occupancies among clusters in the (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} glassy alloy play an important role in the diffusion behavior and in the electronic properties of this alloy.
Coulomb drag: a probe of electron interactions in coupled quantum wells
DEFF Research Database (Denmark)
Jauho, Antti-Pekka
1996-01-01
As semiconductor devices shrink in size and in dimensionality, interactions between charge carriers become more and more important. There is a simple physical reason behind this behavior: fewer carriers lead to less effective screening, and hence stronger effective interactions. A point in case...... are one-dimensional systems (quantum wires): there electron-electron interactions may lead to a behavior, which is qualitatively different from the standard Fermi liquid picture (Luttinger liquids). Electron-electron interactions also play a central role in the fractional quantum Hall effect, which...... be the study of quantum wires: there the interactions may lead to even more dramatic effects...
Anisotropic Electron-Photon and Electron-Phonon Interactions in Black Phosphorus.
Ling, Xi; Huang, Shengxi; Hasdeo, Eddwi H; Liang, Liangbo; Parkin, William M; Tatsumi, Yuki; Nugraha, Ahmad R T; Puretzky, Alexander A; Das, Paul Masih; Sumpter, Bobby G; Geohegan, David B; Kong, Jing; Saito, Riichiro; Drndic, Marija; Meunier, Vincent; Dresselhaus, Mildred S
2016-04-13
Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) and tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to date, as shown by a number of inconsistencies in the recent literature. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight, both experimentally and theoretically, a nontrivial dependence between anisotropy and flake thickness and photon and phonon energies. We show that once understood, the anisotropic optical absorption appears to be a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness, as commonly used previously.
Büyükyıldız, M.
2017-09-01
The radiological properties of some vitamins such as Retinol, Beta-carotene, Riboflavin, Niacin, Niacinamide, Pantothenic acid, Pyridoxine, Pyridoxamine, Pyridoxal, Biotin, Folic acid, Ascorbic acid, Cholecalciferol, Alpha-tocopherol, Gamma-tocopherol, Phylloquinone have been investigated with respect to total electron interaction and some heavy charged particle interaction as means of effective atomic numbers (Z_{eff}) and electron densities (N_{eff}) for the first time. Calculations were performed for total electron interaction and heavy ions such as H, He and C ion interactions in the energy region 10keV-10MeV by using a logarithmic interpolation method. Variations in Z_{eff}'s and N_{eff}'s of given vitamins have been studied according to the energy of electron or heavy charged particles, and significant variations have been observed for all types of interaction in the given energy region. The maximum values of Z_{eff} have been found in the different energy regions for different interactions remarkably and variations in N_{eff} seem approximately to be the same with variation in Z_{eff} for the given vitamins as expected. Z_{eff} values of some vitamins were plotted together and compared with each other for electron, H, He and C interactions and the ratios of Z_{eff}/ have been changed in the range of 0.25-0.36, 0.20-0.36, 0.22-0.35 and 0.20-0.35 for electron, H, He and C interactions, respectively.
Study of electron and neutrino interactions. Final report
International Nuclear Information System (INIS)
Abashian, A.
1997-01-01
This is the final report for the DOE-sponsored experimental particle physics program at Virginia Tech to study the properties of the Standard Model of strong and electroweak interactions. This contract (DE-AS05-80ER10713) covers the period from August 1, 1980 to January 31, 1993. Task B of this contract, headed by Professor Alexander Abashian, is described in this final report. This program has been pursued on many fronts by the researchers in a search for axions at SLAC, in electron-positron collisions in the AMY experiment at the TRISTAN collider in Japan, in measurements of muon decay properties in the MEGA and RHO experiments at the LAMPF accelerator, in a detailed analysis of scattering effects in the purported observation of a 17 keV neutrino at Oxford, in a search for a disoriented chiral condensate with the MiniMax experiment at Fermilab, and in an R ampersand D program on resistive plate counters that could find use in low-cost high-quality charged particle detection at low rates
Seth, Priyanka; Hansmann, Philipp; van Roekeghem, Ambroise; Vaugier, Loig; Biermann, Silke
2017-08-04
The determination of the effective Coulomb interactions to be used in low-energy Hamiltonians for materials with strong electronic correlations remains one of the bottlenecks for parameter-free electronic structure calculations. We propose and benchmark a scheme for determining the effective local Coulomb interactions for charge-transfer oxides and related compounds. Intershell interactions between electrons in the correlated shell and ligand orbitals are taken into account in an effective manner, leading to a reduction of the effective local interactions on the correlated shell. Our scheme resolves inconsistencies in the determination of effective interactions as obtained by standard methods for a wide range of materials, and allows for a conceptual understanding of the relation of cluster model and dynamical mean field-based electronic structure calculations.
Electron and VLF travel time differences for wave-particle interactions at L=4: Pt. 2
International Nuclear Information System (INIS)
Rash, J.P.S.; Scourfield, M.W.J.; Dougherty, M.K.
1984-01-01
The cyclotron resonance or gyroresonance interaction has been widely invoked as a generation mechanism for discrete VLF emissions and plasmaspheric hiss. This interaction involves electrons and VLF waves travelling in opposite directions along a geomagnetic field line. We examine, for an interaction region in the equatorial plane at L=4, the energy of the resonant electrons as a function of VLF wave frequency and ambient equatorial electron density. Then for two different spatial configurations of the interaction and two standard plasma distribution models we examine the difference in travel times to a ground-based observer in the Southern hemisphere for the electrons and waves taking part in the interaction. This difference in travel times is shown as a function of VLF wave frequency and equatorial electron density. The results, and their significance for observations of auroral electrons and VLF at Sanae, Antarctica, are discussed and compared with similar results for the Cerenkov interaction discussed in an earlier paper
Irregular Aharonov–Bohm effect for interacting electrons in a ZnO quantum ring
International Nuclear Information System (INIS)
Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk
2017-01-01
The electronic states and optical transitions of a ZnO quantum ring containing few interacting electrons in an applied magnetic field are found to be very different from those in a conventional semiconductor system, such as a GaAs ring. The strong Zeeman interaction and the Coulomb interaction of the ZnO system, two important characteristics of the electron system in ZnO, exert a profound influence on the electron states and on the optical properties of the ring. In particular, our results indicate that the Aharonov–Bohm (AB) effect in a ZnO quantum ring strongly depends on the electron number. In fact, for two electrons in the ZnO ring, the AB oscillations become aperiodic, while for three electrons (interacting) the AB oscillations completely disappear. Therefore, unlike in conventional quantum ring topology, here the AB effect (and the resulting persistent current) can be controlled by varying the electron number. (paper)
Interaction of the Modulated Electron Beam with Plasma: Kinetic Effects
International Nuclear Information System (INIS)
Anisimov, I.O.; Kiyanchuk, M.J.; Soroka, S.V.; Velikanets', D.M.
2006-01-01
Evolution of the velocity distribution functions of plasma and beam electrons during modulated electron beam propagation in homogeneous and inhomogeneous plasmas was studied numerically. Velocity distribution function of plasma electrons at the late time moments strongly differs from the initially Maxwellian one. In the regions of strong electric field plasma electrons' bunches are formed. Comparison of distribution functions of beam electrons for modulated and non-modulated beams shows that deep initial modulation suppresses resonant instability development. In the inhomogeneous plasma acceleration of electrons in the plasma resonance point can be observed
Sutton, Christopher; Risko, Chad; Bredas, Jean-Luc
2015-01-01
Noncovalent intermolecular interactions, which can be tuned through the toolbox of synthetic chemistry, determine not only the molecular packing but also the resulting electronic, optical, and mechanical properties of materials derived from π
Bond of donor-acceptor interaction in metal-ligand system with energies of Fermi electrons
International Nuclear Information System (INIS)
Vlasov, Yu.V.; Khentov, V.Ya.; Velikanova, L.N.; Semchenko, V.V.
1993-01-01
Role of quantum nature of metal (W, Mo and others) in donor-acceptor interaction of metal salicylalaniline - aprotic solvent was discussed. The dependence of dissolution rate and activation energy of donor-acceptor interaction on electron energy was established
Coulomb interactions in dense two-dimensional electron systems in a magnetic field
International Nuclear Information System (INIS)
Cheng, Szucheng.
1988-01-01
The simplest model of a two-dimensional system ignores the Coulomb interactions between the electrons. In this approximation, the electrons occupy the Landau levels, broadened by impurities and irregularities in the lattice. This independent electron approximation has usually been used to discuss observations for electron densities ρ and magnetic fields B where bar ν > 1 (bar ν triple-bond the number of Landau levels occupied). The most famous example is the theory of the integral Quantum Hall effect. However, when bar ν 1, electron-electron interactions should become important through the mixing of Landau levels. This thesis describes calculations for bar ν > 1 on phenomena which should be sensitive to electron-electron interactions: Wigner crystallization, the stability of the Landau levels under electron-electron interactions, the existence of quasiparticles and quasiholes, and the densities of states. The main results obtained concern: (1) The values of ρ and B where crystallization should occur when bar ν > 1. (2) The effect of electron-electron interactions in broadening the individual Landau levels, and in distributing the amplitudes for the excitation of independent electrons over many Landau levels. (3) The existence of quasiparticles and quasiholes whose lifetime is infinite near the Fermi level
Sutton, Christopher
2015-10-30
Noncovalent intermolecular interactions, which can be tuned through the toolbox of synthetic chemistry, determine not only the molecular packing but also the resulting electronic, optical, and mechanical properties of materials derived from π-conjugated molecules, oligomers, and polymers. Here, we provide an overview of the theoretical underpinnings of noncovalent intermolecular interactions and briefly discuss the computational chemistry approaches used to understand the magnitude of these interactions. These methodologies are then exploited to illustrate how noncovalent intermolecular interactions impact important electronic properties-such as the electronic coupling between adjacent molecules, a key parameter for charge-carrier transport-through a comparison between the prototype organic semiconductor pentacene with a series of N-substituted heteropentacenes. Incorporating an understanding of these interactions into the design of organic semiconductors can assist in developing novel materials systems from this fascinating molecular class. © 2015 American Chemical Society.
Attractive electron-electron interactions at the LaAlO3/SrTiO3 Interface
DEFF Research Database (Denmark)
Prawiroatmodjo, Guenevere E D K
state is found, and transport characteristics are described to originate from attractive electron-electron interactions that result in a negative effective charging energy U. Further, the excitation spectrum is explored and compared to calculations based on a single-orbital Anderson model with negative...
Experiments on the nuclear interactions of pions and electrons
International Nuclear Information System (INIS)
Minehart, R.C.; Ziock, K.O.H.
1992-08-01
The analysis of the deuterium content in the CD target used in an experiment to study the π + d → 2p reaction at incident pion energies from 4 to 20 MeV was completed. The final paper describing this experiment will be submitted for publication this summer. Analysis of LAMPF Exp. on pion absorption in 4 He is continuing. In 1991, we collaborated with D. Pocanic from the Univ. of Virginia on a measurement at LAMPF of the π 0 production in π + p interactions. This run proved the validity of the method and additional data were obtained in a second run during the summer of 1992, using a new target. Current collaborations at LAMPF include the search for the decay μ + → e + + γ(MEGA) and a measurement of the Michel ρ parameter in the decay μ → e + v + v. A U.Va.--PSI collaboration is measuring pion beta decay to an accuracy of less than 1%, using a large acceptance CsI detector to measure the π 0 following decay of stopped π + mesons. Most of the U.Va. effort is devoted to the CEBAF Large Acceptance Spectrometer (CLAS) program to the construction of the CLAS forward calorimeter. An apparatus to measure the properties of the scintillators with light from a N 2 laser was built in the spring of 1992. The electronic circuitry for the energy signal from the EGN detector and the circuitry needed to route the signals from the all the photomultipliers to the TDC and ADC circuits are being developed. Experimental proposals for the study of electroproduction of nucleon resonances at CEBAF, including measurements with polarized beam and targets, are being developed
International Nuclear Information System (INIS)
Kato, Takashi
2010-01-01
Graphical abstract: The electron-phonon interactions destroy the electron pairs formed by Coulomb interactions, and at the same time, form the energy gap by which the electron pairs become stable. - Abstract: In order to discuss how the nondissipative delocalized diamagnetic currents in the microscopic sized materials are closely related to the conventional superconductivity in the macroscopic sized materials, the unified theory, by which various sized superconductivity can be explained, is suggested. It has been believed for a long time that the electron-phonon interactions play an essential role in the attractive electron-electron interactions, as described in the Bardeen-Cooper-Schrieffer (BCS) theory in the conventional superconductivity. However, it is suggested in this paper that the electron-phonon interactions do not play an essential role in the attractive electron-electron interactions but play an essential role in the forming of energy gap by which the electron pairs formed by the attractive Coulomb interactions in the conventional superconducting states become more stable than those in the normal metallic states at low temperatures.
Jobst, Johannes; van der Torren, Alexander J H; Krasovskii, Eugene E; Balgley, Jesse; Dean, Cory R; Tromp, Rudolf M; van der Molen, Sense Jan
2016-11-29
High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the 'chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of.
Leggett-Garg inequalities violation via the Fermi contact hyperfine interaction
Energy Technology Data Exchange (ETDEWEB)
Lobejko, Marcin; Dajka, Jerzy [Institute of Physics, University of Silesia, Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, University of Silesia, Chorzow (Poland)
2017-06-15
In this paper we examine theoretically how the spin-spin interaction between a nuclei and an electron in the atom affects violation of the Leggett-Garg inequalities. We consider the simplest case of atoms in the {sup 2}S{sub 1/2} state that in the valence shell have just a single electron and the evolution in time of the spin is dictated only by the Fermi contact hyperfine interaction. We found that for special initial conditions and a particular measured observable the high spin nucleus couple to the valence electron such that violation of Leggett-Garg inequalities increases with total spin of states. Consequently, our results show that for the Hydrogen, the smallest atom in Nature, the violation of the Leggett-Garg inequalities is the smallest whereas for the largest atom, the Cesium, the violation is the largest. Moreover, this violation does not depend on a principal quantum number, thus our model can be used for Rydberg atoms in order to test macrorealism for 'almost macroscopic' objects. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Electronic voting to encourage interactive lectures: a randomised trial
2007-01-01
Background Electronic Voting Systems have been used for education in a variety of disciplines. Outcomes from these studies have been mixed. Because results from these studies have been mixed, we examined whether an EVS system could enhance a lecture's effect on educational outcomes. Methods A cohort of 127 Year 5 medical students at the University of Adelaide was stratified by gender, residency status and academic record then randomised into 2 groups of 64 and 63 students. Each group received consecutive 40-minute lectures on two clinical topics. One group received the EVS for both topics. The other group received traditional teaching only. Evaluation was undertaken with two, 15-question multiple-choice questionnaires (MCQ) assessing knowledge and problem solving and undertaken as a written paper immediately before and after the lectures and repeated online 8–12 weeks later. Standardised institutional student questionnaires were completed for each lecture and independent observers assessed student behaviour during the lectures. Lecturer's opinions were assessed by a questionnaire developed for this study. Results Two-thirds of students randomised to EVS and 59% of students randomised to traditional lectures attended. One-half of the students in the EVS group and 41% in the traditional group completed all questionnaires. There was no difference in MCQ scores between EVS and traditional lectures (p = 0.785). The cervical cancer lectures showed higher student ranking in favour of EVS in all parameters. The breast cancer lectures showed higher ranking in favour of traditional lectures in 5 of 7 parameters (p lecturer-students interactions were increased in the EVS lecture for one lecturer and reduced for the other. Both lecturers felt that the EVS lectures were difficult to prepare, that they were able to keep to time in the traditional lectures, that the educational value of both lecture styles was similar, and that they were neutral-to-slightly favourably disposed
Magnetic interactions and electronic structure of Ni–Mn–In
Energy Technology Data Exchange (ETDEWEB)
D' Souza, Sunil Wilfred [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India); Chakrabarti, Aparna [Raja Ramanna Centre for Advanced Technology, Indore 452013, Madhya Pradesh (India); Barman, Sudipta Roy, E-mail: barmansr@gmail.com [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India)
2016-04-15
Highlights: • The ground state of Ni{sub 2}Mn{sub 1.4}In{sub 0.6} is ferromagnetic. • The magnetic moments of Ni–Mn–In are in good agreement with the magnetization measurements. • Exchange coupling parameters exhibit a strong competition between ferromagnetic and antiferromagnetic configurations. • Jahn–Teller splitting of the Ni 3d e{sub g} states drives the martensite transformation. - Abstract: The electronic structure and magnetic properties of a magnetic shape memory alloy Ni–Mn–In have been studied using spin polarized fully relativistic Korringa–Kohn–Rostoker (SPRKKR) method. The total energy calculations with different starting magnetic spin configurations show that the ground state of Ni{sub 2}Mn{sub 1.4}In{sub 0.6} is ferromagnetic. The spin and orbital magnetic moments of Ni{sub 2}Mn{sub 1.4}In{sub 0.6} and Ni{sub 2}MnIn are in good agreement with the magnetization measurements. The exchange coupling parameters of the different sublattice interactions exhibit a strong competition between ferromagnetic and antiferromagnetic configurations, due to the substitution of excess Mn atoms at the In site in Ni{sub 2}Mn{sub 1.4}In{sub 0.6}. The Curie temperature of Ni{sub 2}MnIn, calculated under a mean field approximation, is found to be in relatively good agreement with the experimental values. While Ni{sub 2}MnIn does not undergo martensite transition, it is shown that a Jahn–Teller splitting of the Ni 3d e{sub g} states plays an important role in driving the martensite transformation in Ni{sub 2}Mn{sub 1.4}In{sub 0.6}. We find that both the calculated ultra-violet photoemission spectra and the inverse photoemission spectra are in good agreement with the existing experimental data.
Investigation of electron heating in laser-plasma interaction
Directory of Open Access Journals (Sweden)
A Parvazian
2013-03-01
Full Text Available In this paper, stimulated Raman scattering (SRS and electron heating in laser plasma propagating along the plasma fusion is investigated by particle-in cell simulation. Applying an external magnetic field to plasma, production of whistler waves and electron heating associated with whistler waves in the direction perpendicular to external magnetic field was observed in this simulation. The plasma waves with low phase velocities, generated in backward-SRS and dominateing initially in time and space, accelerated the backward electrons by trapping them. Then these electrons promoted to higher energies by the forward-SRS plasma waves with high phase velocities. This tow-stage electron acceleration is more efficient due to the coexistence of these two instabilities.
Investigation of electron heating in laser-plasma interaction
International Nuclear Information System (INIS)
Parvazian, A.; Haji Sharifi, K.
2013-01-01
In this paper, stimulated Raman scattering and electron heating in laser plasma propagating along the plasma fusion is investigated by particle-in cell simulation. Applying an external magnetic field to plasma, production of whistler waves and electron heating associated with whistler waves in the direction perpendicular to external magnetic field was observed in this simulation. The plasma waves with low phase velocities, generated in backward-stimulated Raman scattering and dominating initially in time and space, accelerated the backward electrons by trapping them. Then these electrons promoted to higher energies by the forward-stimulated Raman scattering plasma waves with high phase velocities. This two-stage electron acceleration is more efficient due to the coexistence of these two instabilities.
Spin effects in strong-field laser-electron interactions
International Nuclear Information System (INIS)
Ahrens, S; Bauke, H; Müller, T-O; Villalba-Chávez, S; Müller, C
2013-01-01
The electron spin degree of freedom can play a significant role in relativistic scattering processes involving intense laser fields. In this contribution we discuss the influence of the electron spin on (i) Kapitza-Dirac scattering in an x-ray laser field of high intensity, (ii) photo-induced electron-positron pair production in a strong laser wave and (iii) multiphoton electron-positron pair production on an atomic nucleus. We show that in all cases under consideration the electron spin can have a characteristic impact on the process properties and their total probabilities. To this end, spin-resolved calculations based on the Dirac equation in the presence of an intense laser field are performed. The predictions from Dirac theory are also compared with the corresponding results from the Klein-Gordon equation.
Gudmundsson, Vidar; Abdullah, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei
2018-06-01
We calculate the current correlations for the steady-state electron transport through multi-level parallel quantum dots embedded in a short quantum wire, that is placed in a non-perfect photon cavity. We account for the electron-electron Coulomb interaction, and the para- and diamagnetic electron-photon interactions with a stepwise scheme of configuration interactions and truncation of the many-body Fock spaces. In the spectral density of the temporal current-current correlations we identify all the transitions, radiative and non-radiative, active in the system in order to maintain the steady state. We observe strong signs of two types of Rabi oscillations.
On the supression of electron phase-bunching in gyroresonant interactions in the magnetosphere
International Nuclear Information System (INIS)
Serra, F.M.
1985-01-01
The gyroresonant interaction between a whistler mode monochromatic wave and energetic electrons may cause a spatial and temporal coherence of resonant electrons. It is shown using a simple test particle model that a perturbing second wave can destroy the coherence by inhibiting phase bunching of the first-wave resonant electron. (R.P.)
Playing with Technology: Mother-Toddler Interaction Scores Lower during Play with Electronic Toys
Wooldridge, Michaela B.; Shapka, Jennifer
2012-01-01
To investigate play with electronic toys (battery-operated or digital), 25 mother-toddler (16-24 months old) dyads were videotaped in their homes playing with sets of age-appropriate electronic and non-electronic toys for approximately 10 min each. Parent-child interactions were coded from recorded segments of both of the play conditions using the…
Features of electron-phonon interactions in nanotubes with chiral symmetry in magnetic field
Kibis, O V
2001-01-01
Interaction of the electrons with acoustic phonons in the nanotube with chiral symmetry by availability of the magnetic field, parallel to the nanotube axis, is considered. It is shown that the electron energy spectrum is asymmetric relative to the electron wave vector inversion and for that reason the electron-phonon interaction appears to be different for similar phonons with mutually contrary directions of the wave vector. This phenomenon leads to origination of the electromotive force by the spatially uniform electron gas heating and to appearance of the quadrupole component in the nanotube volt-ampere characteristics
Interacting Electrons and Holes in Quasi-2D Quantum Dots in Strong Magnetic Fields
Hawrylak, P.; Sheng, W.; Cheng, S.-J.
2004-09-01
Theory of optical properties of interacting electrons and holes in quasi-2D quantum dots in strong magnetic fields is discussed. In two dimensions and the lowest Landau level, hidden symmetries control the interaction of the interacting system with light. By confining electrons and holes into quantum dots hidden symmetries can be removed and the excitation spectrum of electrons and excitons can be observed. We discuss a theory electronic and of excitonic quantum Hall droplets at a filling factorν=2. For an excitonic quantum Hall droplet the characteristic emission spectra are predicted to be related to the total spin of electron and hole configurations. For the electronic droplet the excitation spectrum of the droplet can be mapped out by measuring the emission for increasing number of electrons.
Interacting electrons and holes in quasi-2D quantum dots in strong magnetic fields
International Nuclear Information System (INIS)
Hawrylak, P.; Sheng, W.; Cheng, S.-J.
2004-01-01
Theory of optical properties of interacting electrons and holes in quasi-2D quantum dots in strong magnetic fields is discussed. In two dimensions and the lowest Landau level, hidden symmetries control the interaction of the interacting system with light. By confining electrons and holes into quantum dots hidden symmetries can be removed and the excitation spectrum of electrons and excitons can be observed. We discuss a theory electronic and excitonic quantum Hall droplets at a filling factor υ = 2. For an excitonic quantum Hall droplet the characteristic emission spectra are predicted to be related to the total spin of electron and hole configurations. For the electronic droplet the excitation spectrum of the droplet can be mapped out by measuring the emission for increasing number of electrons. (author)
Calculating the radiation characteristics of accelerated electrons in laser-plasma interactions
International Nuclear Information System (INIS)
Li, X. F.; Yu, Q.; Qu, J. F.; Kong, Q.; Gu, Y. J.; Ma, Y. Y.; Kawata, S.
2016-01-01
In this paper, we studied the characteristics of radiation emitted by electrons accelerated in a laser–plasma interaction by using the Lienard–Wiechert field. In the interaction of a laser pulse with a underdense plasma, electrons are accelerated by two mechanisms: direct laser acceleration (DLA) and laser wakefield acceleration (LWFA). At the beginning of the process, the DLA electrons emit most of the radiation, and the DLA electrons emit a much higher peak photon energy than the LWFA electrons. As the laser–plasma interaction progresses, the LWFA electrons become the major radiation emitter; however, even at this stage, the contribution from DLA electrons is significant, especially to the peak photon energy.
Electron-Ion Beam Coupling Through Collective Interactions
National Research Council Canada - National Science Library
Wheelock, Adrian; Cooke, David L; Gatsonis, Nikolaos A
2006-01-01
.... It is shown that Coulomb collisions, which can act to match velocities through strong ion-electron collisions between particles with low relative velocities, are far too slow to explain the phenomenon...
Interaction of measles virus vectors with Auger electron emitting radioisotopes
International Nuclear Information System (INIS)
Dingli, David; Peng, K.-W.; Harvey, Mary E.; Vongpunsawad, Sompong; Bergert, Elizabeth R.; Kyle, Robert A.; Cattaneo, Roberto; Morris, John C.; Russell, Stephen J.
2005-01-01
A recombinant measles virus (MV) expressing the sodium iodide symporter (NIS) is being considered for therapy of advanced multiple myeloma. Auger electrons selectively damage cells in which the isotope decays. We hypothesized that the Auger electron emitting isotope 125 I can be used to control viral proliferation. MV was engineered to express both carcinoembryonic antigen and NIS (MV-NICE). Cells were infected with MV-NICE and exposed to 125 I with appropriate controls. MV-NICE replication in vitro is inhibited by the selective uptake of 125 I by cells expressing NIS. Auger electron damage is partly mediated by free radicals and abrogated by glutathione. In myeloma xenografts, control of MV-NICE with 125 I was not possible under the conditions of the experiment. MV-NICE does not replicate faster in the presence of radiation. Auger electron emitting isotopes effectively stop propagation of MV vectors expressing NIS in vitro. Additional work is necessary to translate these observations in vivo
Electron confinement in thin metal films. Structure, morphology and interactions
Energy Technology Data Exchange (ETDEWEB)
Dil, J.H.
2006-05-15
This thesis investigates the interplay between reduced dimensionality, electronic structure, and interface effects in ultrathin metal layers (Pb, In, Al) on a variety of substrates (Si, Cu, graphite). These layers can be grown with such a perfection that electron confinement in the direction normal to the film leads to the occurrence of quantum well states in their valence bands. These quantum well states are studied in detail, and their behaviour with film thickness, on different substrates, and other parameters of growth are used here to characterise a variety of physical properties of such nanoscale systems. The sections of the thesis deal with a determination of quantum well state energies for a large data set on different systems, the interplay between film morphology and electronic structure, and the influence of substrate electronic structure on their band shape; finally, new ground is broken by demonstrating electron localization and correlation effects, and the possibility to measure the influence of electron-phonon coupling in bulk bands. (orig.)
Gudmundsson, Vidar; Abdulla, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei
2018-02-01
We show that a Rabi-splitting of the states of strongly interacting electrons in parallel quantum dots embedded in a short quantum wire placed in a photon cavity can be produced by either the para- or the dia-magnetic electron-photon interactions when the geometry of the system is properly accounted for and the photon field is tuned close to a resonance with the electron system. We use these two resonances to explore the electroluminescence caused by the transport of electrons through the one- and two-electron ground states of the system and their corresponding conventional and vacuum electroluminescense as the central system is opened up by coupling it to external leads acting as electron reservoirs. Our analysis indicates that high-order electron-photon processes are necessary to adequately construct the cavity-photon dressed electron states needed to describe both types of electroluminescence.
Electron-electron attractive interaction in Maxwell-Chern-Simons QED3 at zero temperature
International Nuclear Information System (INIS)
Belich, H.; Ferreira Junior, M.M.; Helayel-Neto, J.A.; Ferreira Junior, M.M.
2001-04-01
One discusses the issue of low-energy electron-electron bound states in the Maxwell-Chern-Simons model coupled to QED 3 with spontaneous breaking of a local U(1)-symmetry. The scattering potential, in the non-relativistic limit, steaming from the electron-electron Moeller scattering, mediated by the Maxwell-Chern-Simons-Proca gauge field and the Higgs scalar, might be attractive by fine-tuning properly the physical parameters of the model. (author)
International Nuclear Information System (INIS)
Barwick, Brett; Gronniger, Glen; Yuan, Lu; Liou, Sy-Hwang; Batelaan, Herman
2006-01-01
Electron diffraction from metal coated freestanding nanofabricated gratings is presented, with a quantitative path integral analysis of the electron-grating interactions. Electron diffraction out to the 20th order was observed indicating the high quality of our nanofabricated gratings. The electron beam is collimated to its diffraction limit with ion-milled material slits. Our path integral analysis is first tested against single slit electron diffraction, and then further expanded with the same theoretical approach to describe grating diffraction. Rotation of the grating with respect to the incident electron beam varies the effective distance between the electron and grating bars. This allows the measurement of the image charge potential between the electron and the grating bars. Image charge potentials that were about 15% of the value for that of a pure electron-metal wall interaction were found. We varied the electron energy from 50 to 900 eV. The interaction time is of the order of typical metal image charge response times and in principle allows the investigation of image charge formation. In addition to the image charge interaction there is a dephasing process reducing the transverse coherence length of the electron wave. The dephasing process causes broadening of the diffraction peaks and is consistent with a model that ascribes the dephasing process to microscopic contact potentials. Surface structures with length scales of about 200 nm observed with a scanning tunneling microscope, and dephasing interaction strength typical of contact potentials of 0.35 eV support this claim. Such a dephasing model motivated the investigation of different metallic coatings, in particular Ni, Ti, Al, and different thickness Au-Pd coatings. Improved quality of diffraction patterns was found for Ni. This coating made electron diffraction possible at energies as low as 50 eV. This energy was limited by our electron gun design. These results are particularly relevant for the
Electron and positron interaction with pyrimidine: A theoretical investigation
Sinha, Nidhi; Antony, Bobby
2018-03-01
Pyrimidine (C4H4N2) is considered as the building block of nucleobases, viz., cytosine, thymine and uracil. They provide a blueprint for probing the scattering of radiation by DNA and RNA bases. In this article, we report the elastic and total scattering cross-sections for electron and positron scattering from the pyrimidine molecule, employing a spherical complex optical potential (SCOP) formalism for an extensive energy range of 10 eV to 5 keV. In the case of positron scattering, the original SCOP formalism is modified to adequately solve the positron-target dynamics. Moreover, a reasonable agreement is observed between the present results and other available datasets, for both electron and positron scattering. The cross-sections for electron and positron impact scattering by pyrimidine are necessary input data for codes that seek to simulate radiation damage, and hence are useful to model biomolecular systems.
Cavity-photon contribution to the effective interaction of electrons in parallel quantum dots
Energy Technology Data Exchange (ETDEWEB)
Gudmundsson, Vidar [Science Institute, University of Iceland, Reykjavik (Iceland); Sitek, Anna [Science Institute, University of Iceland, Reykjavik (Iceland); Department of Theoretical Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Technology (Poland); Abdullah, Nzar Rauf [Science Institute, University of Iceland, Reykjavik (Iceland); Physics Department, Faculty of Science and Science Education, School of Science, University of Sulaimani, Kurdistan Region (Iraq); Tang, Chi-Shung [Department of Mechanical Engineering, National United University, Miaoli (China); Manolescu, Andrei [School of Science and Engineering, Reykjavik University (Iceland)
2016-05-15
A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron-electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Cavity-photon contribution to the effective interaction of electrons in parallel quantum dots
Gudmundsson, Vidar; Sitek, Anna; Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei
2016-05-01
A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron-electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field.
Dzhioev, R. I.; Korenev, V. L.
2007-07-01
The nuclear quadrupole interaction eliminates the restrictions imposed by hyperfine interaction on the spin coherence of an electron and nuclei in a quantum dot. The strain-induced nuclear quadrupole interaction suppresses the nuclear spin flip and makes possible the zero-field dynamic nuclear polarization in self-organized InP/InGaP quantum dots. The direction of the effective nuclear magnetic field is fixed in space, thus quenching the magnetic depolarization of the electron spin in the quantum dot. The quadrupole interaction suppresses the zero-field electron spin decoherence also for the case of nonpolarized nuclei. These results provide a new vision of the role of the nuclear quadrupole interaction in nanostructures: it elongates the spin memory of the electron-nuclear system.
Molecular Understanding of Fullerene - Electron Donor Interactions in Organic Solar Cells
Ryno, Sean
2016-09-13
Organic solar cells hold promise of providing low-cost, renewable power generation, with current devices providing up to 13% power conversion efficiency. The rational design of more performant systems requires an in-depth understanding of the interactions between the electron donating and electron accepting materials within the active layers of these devices. Here, we explore works that give insight into the intermolecular interactions between electron donors and electron acceptors, and the impact of molecular orientations and environment on these interactions. We highlight, from a theoretical standpoint, the effects of intermolecular interactions on the stability of charge carriers at the donor/acceptor interface and in the bulk and how these interactions influence the nature of the charge transfer states as wells as the charge separation and charge transport processes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Danehkar, A.
2018-06-01
Suprathermal electrons and inertial drifting electrons, so called electron beam, are crucial to the nonlinear dynamics of electrostatic solitary waves observed in several astrophysical plasmas. In this paper, the propagation of electron-acoustic solitary waves (EAWs) is investigated in a collisionless, unmagnetized plasma consisting of cool inertial background electrons, hot suprathermal electrons (modeled by a κ-type distribution), and stationary ions. The plasma is penetrated by a cool electron beam component. A linear dispersion relation is derived to describe small-amplitude wave structures that shows a weak dependence of the phase speed on the electron beam velocity and density. A (Sagdeev-type) pseudopotential approach is employed to obtain the existence domain of large-amplitude solitary waves, and investigate how their nonlinear structures depend on the kinematic and physical properties of the electron beam and the suprathermality (described by κ) of the hot electrons. The results indicate that the electron beam can largely alter the EAWs, but can only produce negative polarity solitary waves in this model. While the electron beam co-propagates with the solitary waves, the soliton existence domain (Mach number range) becomes narrower (nearly down to nil) with increasing the beam speed and the beam-to-hot electron temperature ratio, and decreasing the beam-to-cool electron density ratio in high suprathermality (low κ). It is found that the electric potential amplitude largely declines with increasing the beam speed and the beam-to-cool electron density ratio for co-propagating solitary waves, but is slightly decreased by raising the beam-to-hot electron temperature ratio.
Interactive electronic storybooks for kindergartners to promote vocabulary growth
Smeets, Daisy J. H.; Bus, Adriana G
2012-01-01
The goals of this study were to examine (a) whether extratextual vocabulary instructions embedded in electronic storybooks facilitated word learning over reading alone and (b) whether instructional formats that required children to invest more effort were more effective than formats that required
Interaction between electrons and tunneling levels in metallic glasses
International Nuclear Information System (INIS)
Black, J.L.; Gyorffy, B.L.
1978-01-01
A simple model in which the conduction electrons of a metallic glass experience a local time-dependent potential due to two-level tunneling states is considered. The model exhibits interesting divergent behavior which is quite different from that predicted by an earlier ''s-d Kondo'' model
The interaction of swift electrons with surface excitations
International Nuclear Information System (INIS)
Ritchie, R.H.; Tennessee Univ., Knoxville, TN
1992-01-01
For many decades swift electrons have comprised a powerful tool for the study of the dynamical properties of condensed matter. The development of this technique has involved much important physics. Here we sketch the historical background of the field and some important developments in theory and experiment. Possible directions for future research are indicated
Experiments on neutron-proton and neutron-electron interaction
International Nuclear Information System (INIS)
Koester, L.
1975-01-01
The paper reports on zero-energy experiments with neutrons, protons and electrons with a wavelength that is considerably longer than the particle expansion. Scattering amplitudes are measured for the reactions n + p and n + e. A neutron gravity refractometer is used. (WL/AK) [de
International Nuclear Information System (INIS)
Krive, I.V.; Sandstroem, P.
1997-01-01
The persistent current for a one-dimensional ring with two tunneling barriers is considered in the limit of weakly interacting electrons. In addition to small off-resonance current, there are two kinds of resonant behaviour; (i) a current independent of the barrier transparency (true resonance) and (ii) a current analogous to the one for a ring with only single barrier (''semi''-resonance). For a given barrier transparency the realization of this or that type of resonant behaviour depends both on the geometrical factor (the ratio of interbarrier distance to a ring circumference) and on the strength of electron-electron interaction. It is shown that repulsive interaction favours the ''semi''-resonance behaviour. For a small barrier transparency the ''semi''-resonance peaks are easily washed out by temperature whereas the true resonance peaks survive. (author). 22 refs, 2 figs
Reversible electron heating vs. wave-particle interactions in quasi-perpendicular shocks
Veltri, P.; Mangeney, A.; Scudder, J. D.
1992-01-01
The energy necessary to explain the electron heating in quasi-perpendicular collisionless shocks can be derived either from the electron acceleration in the d.c. cross shock electric potential, or by the interactions between the electrons and the waves existing in the shock. A Monte Carlo simulation has been performed to study the electron distribution function evolution through the shock structure, with and without particle diffusion on waves. This simulation has allowed us to clarify the relative importance of the two possible energy sources; in particular it has been shown that the electron parallel temperature is determined by the d.c. electromagnetic field and not by any wave-particle-induced heating. Wave particle interactions are effective in smoothing out the large gradients in phase space produced by the 'reversible' motion of the electrons, thus producing a 'cooling' of the electrons.
Confinement of acoustical modes due to the electron-phonon interaction within 2D-electron gas
International Nuclear Information System (INIS)
Kochelap, V.A.; Gulseren, O.
1992-09-01
We study the confinement of acoustical modes within 2DEG due only to the electron-phonon interaction. The confined modes split out from the bulk phonons even at uniform lattice parameters, when the 2DEG is created by means of modulation doping. The effect is more pronounced when the wave vector q of the modes increases and is maximum at q = 2 k F (k F is the Fermi wave vector). In the case of several electron sheets the additional features of the confinement effect appear. In the limit of the strong electron-phonon coupling and high surface concentration of the electrons the considered system can suffer Peierls-type phase transition. In this case periodical deformation of the lattice and charge density wave are confined within the electron sheet. (author). 18 refs, 2 figs
RAMAN LIGHT SCATTERING IN PSEUDOSPIN-ELECTRON MODEL AT STRONG PSEUDOSPIN-ELECTRON INTERACTION
Directory of Open Access Journals (Sweden)
T.S.Mysakovych
2004-01-01
Full Text Available Anharmonic phonon contributions to Raman scattering in locally anharmonic crystal systems in the framework of the pseudospin-electron model with tunneling splitting of levels are investigated. The case of strong pseudospin-electron coupling is considered. Pseudospin and electron contributions to scattering are taken into account. Frequency dependences of Raman scattering intensity for different values of model parameters and for different polarization of scattering and incident light are investigated.
New insights in low-energy electron-fullerene interactions
Msezane, Alfred Z.; Felfli, Zineb
2018-03-01
The robust Regge-pole methodology has been used to probe for long-lived metastable anionic formation in Cn (n = 20, 24, 26, 28, 44, 70, 92 and 112) through the calculated electron elastic scattering total cross sections (TCSs). All the TCSs are found to be characterized by Ramsauer-Townsend minima, shape resonances and dramatically sharp resonances manifesting metastable anionic formation during the collisions. The energy positions of the anionic ground states resonances are found to match the measured electron affinities (EAs). We also investigated the size-effect through the correlation and polarization induced metastable resonances as the fullerene size varied from C20 through C112. The C20 TCSs exhibit atomic behavior while the C112 TCSs demonstrate strong departure from atomic behavior attributed to the size effect. Surprisingly C24 is found to have the largest EA among the investigated fullerenes making it suitable for use in organic solar cells and nanocatalysis.
Computerized creation of interactive electronic technical manuals (IETM)
International Nuclear Information System (INIS)
Galin, I.Yu.
2011-01-01
The author informs that the automated system of developing and maintaining the operational documentation (OD) (Technical Guide Builder) has been first developed and experimentally tested. The obtained result raises the competitiveness of Russian aircraft in international markets. The author offers methods and technology of OD formation, allowing to produce interactive OD for domestic aircraft industry, issued according to international standards in several languages [ru
Electron emission during multicharged ion-surface interactions
International Nuclear Information System (INIS)
Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Meyer, F.W.; Zehner, D.M.
1990-01-01
Recent measurements of electron spectra for slow multicharged N ion-surface collisions are presented. The emphasis is on potential emission, i.e. the electron emission related to the neutralization of the ions. When using N ions that carry a K shell vacancy into the collision, characteristic K Auger electron emission from the projectiles is observed, as well as, for specific surfaces, target atom Auger transitions (resulting from vacancy transfer). Measurements of the intensity of these Auger transitions as a function of the time the ions spend above the surface can serve as a useful probe of the timescales characterizing the relevant neutralization processes. This technique is elucidated with the help of some computer simulations. It is shown that neutralization timescales required in the atomic ladder picture, in which neutralization takes place by resonant capture followed by purely intra-atomic Auger transitions, are too long to explain our experimental results. The introduction of additional neutralization/de-excitation mechanisms in the simulations leads to much better agreement with the experiments
Experiments on the Nuclear Interactions of Pions and Electrons
International Nuclear Information System (INIS)
Ralph C. Minehart
2005-01-01
This is the final technical report. Yearly Progress Reports were submitted throughout the duration of the project. Along with our publications, these reports provide a detailed record of our accomplishments. This report largely consists of a summary of the technical activities carried out during last 2-1/2 years of the project, along with a list of papers published in the period from 2002-2005. Our work during this period involved the following: 1. Electro-production of excited states of the nucleon through the analysis of exclusive single pion production reactions induced by polarized electrons incident on both polarized and unpolarized nucleon targets. (JLab) 2. Measurement of proton and deuteron spin structure functions in and above the nucleon resonance region at low and moderate Q 2 , using inclusive electron-proton and electron deuteron scattering (JLAB). 3. Contributions to the PRIMEX experiment (JLab). 4. A precise measurement of the branching ratio for pion beta decay was carried out along with other members of the PIBETA collaboration (PSI). The first three, labeled JLab, were experiments made with the CLAS detector at the Thomas Jefferson Laboratory in Newport News, VA. The PIBETA experiment was carried out using a low energy pion beam at the Paul Scherrer Institute in Villigen, Switzerland
Experimental evidence for interactions between anions and electron-deficient aromatic rings.
Berryman, Orion B; Johnson, Darren W
2009-06-14
This feature article summarizes our research aimed at using electron-deficient aromatic rings to bind anions in the context of complementary research in this active field. Particular attention is paid to the different types of interactions exhibited between anions and electron-deficient arenes in solution. The 120+ references cited in this article underscore the flurry of recent activity by numerous researchers in this field, which was relatively nascent when our efforts began in 2005. While the interaction of anions with electron-deficient aromatic rings has recently garnered much attention by supramolecular chemists, the observation of these interactions is not a recent discovery. Therefore, we begin with a historical perspective on early examples of anions interacting with electron-deficient arenes. An introduction to recent (and not so recent) computational investigations concerning anions and electron-deficient aromatic rings as well as a brief structural survey of crystalline examples of this interaction are provided. Finally, the limited solution-based observations of anions interacting with electron-deficient aromatic rings are summarized to introduce our current investigations in this area. We highlight three different systems from our lab where anion-arene interactions have been investigated. First, we show that tandem hydrogen bonds and anion-arene interactions augment halide binding in solution. Second, a crystallographic and computational study highlights the multiple types of interactions possible between anions and electron-deficient arenes. Third, we summarize the first example of a class of designed receptors that emphasize the different types of anion-arene interactions possible in solution.
Sit, Cindy H P; Lam, Jessica W K; McKenzie, Thomas L
2010-07-01
Interactive electronic games have recently been popularized and are believed to help promote children's physical activity (PA). The purpose of the study was to examine preferences and PA levels during interactive and online electronic games among overweight and nonoverweight boys and girls. Using a modification of the SOFIT, we systematically observed 70 Hong Kong Chinese children (35 boys, 35 girls; 50 nonoverweight, 20 overweight), age 9 to 12 years, during 2 60-minute recreation sessions and recorded their game mode choices and PA levels. During Session One children could play either an interactive or an online electronic bowling game and during Session Two they could play an interactive or an online electronic running game. Children chose to play the games during 94% of session time and split this time between interactive (52%) and online (48%) versions. They engaged in significantly more moderate-to-vigorous physical activity (MVPA) during interactive games than their online electronic versions (70% vs. 2% of game time). Boys and nonoverweight children expended relatively more energy during the interactive games than girls and overweight children, respectively. New-generation interactive games can facilitate physical activity in children, and given the opportunity children may select them over sedentary versions.
International Nuclear Information System (INIS)
Moody, J. T.; Musumeci, P.; Scoby, C. M.; To, H.; Marcoux, C.
2010-01-01
The concept of a THz-based IFEL compressor at the UCLA Pegasus photoinjector laboratory is explored. A 3.5 MeV sub-picosecond electron beam generated in the photoinjector blowout regime can be compressed to femtosecond timescales by a THz IFEL interaction.
Yang, Shuyan; Zhou, Yanxue; Zhang, Peng; Cai, Zhuodi; Li, Yangping; Fan, Hongbo
2017-12-01
Interfacial interaction is one of the key factors to improve comprehensive properties of polymer/inorganic filler nanocomposites. In this work, a new interfacial interaction called electron transferring interaction is reported in the nitrile-butadiene rubber/halloysite nanotubes (NBR/HNTs) nanocomposites. The X-ray photoelectron spectroscopy (XPS) and in-situ controlling temperature Fourier transform infrared spectroscopy (FTIR) have confirmed that electrons of electron-rich -CN groups in NBR can transfer to the electron-deficiency aluminum atoms of HNTs, which packs a part of NBR molecules onto the surface of HNTs to form bound rubber and stabilize the homogeneous dispersion of HNTs with few agglomeration as revealed by scanning electron microscope (SEM) and dynamic mechanical analysis (DMA) performances, even at high HNTs addition, resulting in high light transmittance. The tensile strength of NBR/30wt%HNTs nanocomposites is about 291% higher than pure NBR, without sacrificing the elongation at break.
On the gyro resonance electron-whistler interaction in transition layers of near-earth plasma
International Nuclear Information System (INIS)
Erokhin, N.S.; Zol'nikova, N.N.; Mikhajlovskaya, L.A.
1996-01-01
Gyro resonance interaction of electrons with low amplitude triggered whistler in the transition layers of the ionospheric and magnetospheric plasma that correspond to the blurred jumps of the magnetic field and plasma concentration was studied
Electron trajectory evaluation in laser-plasma interaction for effective output beam
Zobdeh, P.; Sadighi-Bonabi, R.; Afarideh, H.
2010-06-01
Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and cavity electrostatic potential.
Industry interactions of the electronic structure research community in Europe
Goldbeck, Gerhard
2014-01-01
This report explores the interactions of the academic Psi-k community with industry. The evidence presented is mainly based on a semi-quantitative survey and interviews of network members. All Psi-k board, working group and advisory group members, a total of about 120 people were invited to take part in the study, and 40 people responded, representing more than 400 scientists from 33 different institutions in 12 European countries. 90% of respondents work with industry. Main industry sectors ...
International Nuclear Information System (INIS)
Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek
2017-01-01
Standard computational methods used to take account of the Pauli Exclusion Principle into Monte Carlo (MC) simulations of electron transport in semiconductors may give unphysical results in low field regime, where obtained electron distribution function takes values exceeding unity. Modified algorithms were already proposed and allow to correctly account for electron scattering on phonons or impurities. Present paper extends this approach and proposes improved simulation scheme allowing including Pauli exclusion principle for electron–electron (e–e) scattering into MC simulations. Simulations with significantly reduced computational cost recreate correct values of the electron distribution function. Proposed algorithm is applied to study transport properties of degenerate electrons in graphene with e–e interactions. This required adapting the treatment of e–e scattering in the case of linear band dispersion relation. Hence, this part of the simulation algorithm is described in details.
Energy Technology Data Exchange (ETDEWEB)
Borowik, Piotr, E-mail: pborow@poczta.onet.pl [Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa (Poland); Thobel, Jean-Luc, E-mail: jean-luc.thobel@iemn.univ-lille1.fr [Institut d' Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université Lille 1, Avenue Poincaré, CS 60069, 59652 Villeneuve d' Ascq Cédex (France); Adamowicz, Leszek, E-mail: adamo@if.pw.edu.pl [Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa (Poland)
2017-07-15
Standard computational methods used to take account of the Pauli Exclusion Principle into Monte Carlo (MC) simulations of electron transport in semiconductors may give unphysical results in low field regime, where obtained electron distribution function takes values exceeding unity. Modified algorithms were already proposed and allow to correctly account for electron scattering on phonons or impurities. Present paper extends this approach and proposes improved simulation scheme allowing including Pauli exclusion principle for electron–electron (e–e) scattering into MC simulations. Simulations with significantly reduced computational cost recreate correct values of the electron distribution function. Proposed algorithm is applied to study transport properties of degenerate electrons in graphene with e–e interactions. This required adapting the treatment of e–e scattering in the case of linear band dispersion relation. Hence, this part of the simulation algorithm is described in details.
Energy Technology Data Exchange (ETDEWEB)
Kemp, Gregory Elijah [The Ohio State Univ., Columbus, OH (United States)
2013-01-01
Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic
1991-07-01
authoring systems. Concurrently, great strides in computer-aided design and computer-aided maintenance have contributed to this capability. 12 Junod ...J.; William A. Nugent; and L. John Junod . Plan for the Navy/Air Force Test of the Interactive Electronic Technical Manual (IETM) at Cecil Field...AFHRL Logistics and Human Factors Division, WPAFB. Aug 1990. 12. Junod , John L. PY90 Interactive Electronic Technical Manual (IETM) Portable Delivery
International Nuclear Information System (INIS)
Hobert, H.; Arnold, D.
1975-01-01
The mechanism of chemisorption on the surface of iron oxide was studied by Moessbauer spectroscopy performed on samples of iron oxide finely dispersed in SiO 2 . It was found from Moessbauer spectra that the interaction of the oxide with amines resulted in a reversible electron transition from the amine to the adsorbent. The interaction with BF 3 brought about an irreversible electron transition from iron to boron. (A.K.)
Experimental investigations of interaction of supercritical electron beams with plasma
International Nuclear Information System (INIS)
Chupikov, P.T.; Medvedev, D.V.; Onishchenko, I.N.; Panasenko, B.D.; Faehl, R.J.
2002-01-01
The first section of the collective ions acceleration based on simultaneous temporal and spatial modulation of relativistic electron beam (REB) was studied experimentally. The virtual cathode was originated in the electrodynamic structure consisting of two tubes with different diameters (jump of electrodynamics) by REB, produced in magnetically insulated diode. At plasma assistance the low-frequency oscillations of REB current and the low-frequency microwave radiation were obtained due to the virtual cathode periodical relaxation in the processes of charge compensation by ionized residual gas
Unraveling the acoustic electron-phonon interaction in graphene
DEFF Research Database (Denmark)
Kaasbjerg, Kristen; Thygesen, Kristian S.; Jacobsen, Karsten W.
2012-01-01
Using a first-principles approach we calculate the electron-phonon couplings in graphene for the transverse and longitudinal acoustic phonons. Analytic forms of the coupling matrix elements valid in the long-wavelength limit are found to give an almost quantitative description of the first...... that the intrinsic effective acoustic deformation potential of graphene is Ξeff=6.8 eV and that the temperature dependence of the mobility μ~T-α in the Bloch-Gru¨neisen regime increases beyond an α=4 dependence even in the absence of screening when the true coupling matrix elements are considered. The α>4...
Electrons trajectories around a bubble regime in intense laser plasma interaction
International Nuclear Information System (INIS)
Lu, Ding; Xie, Bai-Song; Ali Bake, Muhammad; Sang, Hai-Bo; Zhao, Xue-Yan; Wu, Hai-Cheng
2013-01-01
Some typical electrons trajectories around a bubble regime in intense laser plasma interaction are investigated theoretically. By considering a modification of the fields and ellipsoid bubble shape due to the presence of residual electrons in the bubble regime, we study in detail the electrons nonlinear dynamics with or without laser pulse. To examine the electron dynamical behaviors, a set of typical electrons, which locate initially at the front of the bubble, on the transverse edge and at the bottom of the bubble respectively, are chosen for study. It is found that the range of trapped electrons in the case with laser pulse is a little narrower than that without laser pulse. The partial phase portraits for electrons around the bubble are presented numerically and their characteristic behaviors are discussed theoretically. Implication of our results on the high quality electron beam generation is also discussed briefly
Hyperfine interactions of /sup 12/B implanted in ferromagnetic nickel
Energy Technology Data Exchange (ETDEWEB)
Hamagaki, H; Nojiri, Y; Sugimoto, K [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Nakai, K
1979-12-01
Temperature dependences of hyperfine interactions of /sup 12/B implanted in Ni were investigated in the temperature range of 6 K - 730 K by the NMR method with use of polarized /sup 12/B produced in a nuclear reaction and the asymmetric ..beta.. decay. Two kinds of hyperfine fields with different signs were observed (B sub(hf)sup(+) = +4.161 +- 0.022 kG and B sub(hf)sup(-) = -1.611 +- 0.021 kG at 6 K), which indicated that the implanted /sup 12/B were trapped in two different sites (S/sup +/ and S/sup -/, respectively). The spin-lattice relaxation times T/sub 1/ and the population rates at the two sites were studied. Near the Curie temperature, an effect of critical slowing-down of the spin-spin correlation was observed as steep variation of T/sub 1/. The behavior of local field around T sub(C) was also studied by varying the external field. Results of these experiments near T sub(C) indicate itinerant nature of the electron-spin structure in nickel.
Electron-phonon interactions and intrinsic nonadiabatic state of superconductors
International Nuclear Information System (INIS)
Banacky, Pavol
2007-01-01
Study of band structure of YBa 2 Cu 3 O 7 has shown that electron coupling to A g , B 2g and B 3g modes results in fluctuation of saddle point of one of the CuO plane d-pσ band in Y point of 1st BZ across Fermi level. It represents breakdown of adiabatic Born-Oppenheimer approximation and transition of the system into intrinsic nonadiabatic state, ω > E F . Results show that system is stabilized in this state at distorted nuclear geometry. Stabilization effect is mainly due to strong dependence of the electronic motion on instantaneous nuclear momenta. On the lattice scale, the intrinsic nonadiabatic state is geometrically degenerate at broken translation symmetry - system has fluxional nuclear configuration of O2, O3 atoms in CuO planes. It enables formation of mobile bipolarons that can move in the lattice without dissipation. Described effects are absent in non-superconducting YBa 2 Cu 3 O 6
Electron phonon interactions and intrinsic nonadiabatic state of superconductors
Baňacký, Pavol
2007-09-01
Study of band structure of YBa 2Cu 3O 7 has shown that electron coupling to A g, B 2g and B 3g modes results in fluctuation of saddle point of one of the CuO plane d-pσ band in Y point of 1st BZ across Fermi level. It represents breakdown of adiabatic Born-Oppenheimer approximation and transition of the system into intrinsic nonadiabatic state, ω > EF. Results show that system is stabilized in this state at distorted nuclear geometry. Stabilization effect is mainly due to strong dependence of the electronic motion on instantaneous nuclear momenta. On the lattice scale, the intrinsic nonadiabatic state is geometrically degenerate at broken translation symmetry - system has fluxional nuclear configuration of O2, O3 atoms in CuO planes. It enables formation of mobile bipolarons that can move in the lattice without dissipation. Described effects are absent in non-superconducting YBa 2Cu 3O 6.
Direct interaction between linear electron transfer chains and solute transport systems in bacteria
Elferink, Marieke G.L.; Hellingwerf, Klaas J.; Belkum, Marco J. van; Poolman, Bert; Konings, Wil N.
1984-01-01
In studies on alanine and lactose transport in Rhodopseudomonas sphaeroides we have demonstrated that the rate of solute uptake in this phototrophic bacterium is regulated by the rate of light-induced cyclic electron transfer. In the present paper the interaction between linear electron transfer
Prediction for neutrino-electron cross-sections in Weinberg's model for weak interactions
Hooft, G. 't
1971-01-01
Weinberg's theory of purely leptonic weak interactions can be tested in neutrino-electron scattering experiments. Cross-sections must be measured as a function of the energy of the recoil electron. If Weinberg's theory is correct, then the masses of the intermediate vector bosons can be derived from
Khazanov, George V.; Sibeck, David G.
2013-01-01
The interaction of electrons with coherent chorus waves in the random phase approximation can be described as quasi-linear diffusion for waves with amplitudes below some limit. The limit is calculated for relativistic and non-relativistic electrons. For stronger waves, the friction force should be taken into account.
Electron–electron interactions in the chemical bond: “1/3” Effect in ...
Indian Academy of Sciences (India)
Unknown
Abstract. The prominent “1/3” effect observed in the Hall effect plateaus of two- dimensional electron gas (2DEG) systems has been postulated to indicating 1/3 fractional charge quasiparticle excitations arising from electron–electron interactions. Tunneling shot-noise experiments on 2DEF exhibiting fractional quantum Hall ...
International Nuclear Information System (INIS)
Pandya, Ankur; Shinde, Satyam; Jha, Prafulla K.
2015-01-01
In this paper the hot electron transport properties like carrier energy and momentum scattering rates and electron energy loss rates are calculated via interactions of electrons with polar acoustical phonons for Mn doped BN quantum well in BN nanosheets via piezoelectric scattering and deformation potential mechanisms at low temperatures with high electric field. Electron energy loss rate increases with the electric field. It is observed that at low temperatures and for low electric field the phonon absorption is taking place whereas, for sufficient large electric field, phonon emission takes place. Under the piezoelectric (polar acoustical phonon) scattering mechanism, the carrier scattering rate decreases with the reduction of electric field at low temperatures wherein, the scattering rate variation with electric field is limited by a specific temperature beyond which there is no any impact of electric field on such scattering
Experiments on the nuclear interactions of pions and electrons
International Nuclear Information System (INIS)
Minehart, R.C.; Ziock, K.O.H.
1989-07-01
We have completed the analysis of the 3 He(π + ,pp)n reaction, and are working on the analysis of data for the 3 He(π - ,pn)p reaction. An experiment to study the π + d → 2p reaction at LAMPF was successful in studying incident pion energies as low as 6 MeV. Preliminary results have been reported, and work is continuing to improve the accuracy in the calculation of the fraction of pions in the incident beam. A proposal has been accepted by LAMPF for a new experiment, scheduled to run in the summer of 1990, to study pion absorption in 3 He and 4 He using an extensive scintillator time-of-flight system capable of detecting neutrons as well as charged particles. We are continuing to analyze data obtained in PSI in the search for the admixture of massive neutrinos in pion decay and have continued the search for fractionally charged particles. We are also fully involved in some major collaborations: the search for the decay μ + → e + + γ, and the study of anti-proton absorption in heavy nuclei. We are taking part in a U.Va.-PSI collaboration to measure pion beta decay to an accuracy of about 1%, using a large acceptance CsI detector to measure the π 0 following decay of stopped π + mesons. We have also been working on experiments to study electron scattering, using the SLAC-NPAS facility for nuclear physics and the electron accelerator at SACLAY in France. Data from experiment NE-9 at SLAC are being analyzed. This experiment, which was run near the end of 1987, is intended to separate the transverse and longitudinal cross sections for inclusive electron scattering in the QFS region. Experiment NE-8 measured the cross section for photo-disintegration of the deuteron in the GeV range. Some design work was carried out this year on Experiment NE-16 at SLAC, a study of the (e,e'p) reaction in 4 He, expected to run late in 1990
Final Report on Investigation of the Electron Interactions in Graphene
Energy Technology Data Exchange (ETDEWEB)
Kim, Philip [Columbia University
2015-02-14
In graphene, combined with the real spin degree of freedom, which exhibits SU(2) symmetry, the total internal degrees of freedom of graphene carriers is thus described by a larger SU(4) symmetry, which produces a richer space for potential phenomena of emergent correlated electron phenomena. The major part of this proposal is exploring this unique multicomponent correlated system in the quantum limit. In the current period of DOE BES support we have made several key advances that will serve as a foundation for the new studies in this proposal. Employing the high-mobility encapsulated graphene heterostructures developed during the current phase of research, we have investigated spin and valley quantum Hall ferromagnetism in graphene and discovered a spin phase transition leading to a quantum spin Hall analogue. We have also observed the fractal quantum Hall effect arising from the Hofstadter’s butterfly energy spectrum. In addition, we have discovered multiband transport phenomena in bilayer graphene at high carrier densities.
Universally-Usable Interactive Electronic Physics Instructional And Educational Materials
Gardner, John
2000-03-01
Recent developments of technologies that promote full accessibility of electronic information by future generations of people with print disabilities will be described. ("Print disabilities" include low vision, blindness, and dyslexia.) The guiding philosophy of these developments is that information should be created and transmitted in a form that is as display-independent as possible, and that the user should have maximum freedom over how that information is to be displayed. This philosophy leads to maximum usability by everybody and is, in the long run, the only way to assure truly equal access. Research efforts to be described include access to mathematics and scientific notation and to graphs, tables, charts, diagrams, and general object-oriented graphics.
Theoretical investigation of electron-positive ion/atom interactions
International Nuclear Information System (INIS)
Msezane, A.Z.
1992-01-01
Very brief summaries are given on three research topics. Electron impact elastic, excitation, and total cross sections for K were investigated by using elaborate Cl target wave functions in the close-coupling approximation. Photoionization cross sections from ground-state Na were calculated near the 2s 2 2p 5 3s and 2s2p 6 3s inner-shell thresholds; also, the photoionization cross sections of excited 3p 2 P o and 3d 2 D states were calculated with the R-matrix methodology near the 2s2p 6 3s thresholds. A numerical approach was developed to calculate the charge transfer matrix elements for ion-atom(ion) collisions; this was used for the proton-hydrogen collision problem as an illustration
Measurement of the magnetic interaction between two bound electrons of two separate ions.
Kotler, Shlomi; Akerman, Nitzan; Navon, Nir; Glickman, Yinnon; Ozeri, Roee
2014-06-19
Electrons have an intrinsic, indivisible, magnetic dipole aligned with their internal angular momentum (spin). The magnetic interaction between two electronic spins can therefore impose a change in their orientation. Similar dipolar magnetic interactions exist between other spin systems and have been studied experimentally. Examples include the interaction between an electron and its nucleus and the interaction between several multi-electron spin complexes. The challenge in observing such interactions for two electrons is twofold. First, at the atomic scale, where the coupling is relatively large, it is often dominated by the much larger Coulomb exchange counterpart. Second, on scales that are substantially larger than the atomic, the magnetic coupling is very weak and can be well below the ambient magnetic noise. Here we report the measurement of the magnetic interaction between the two ground-state spin-1/2 valence electrons of two (88)Sr(+) ions, co-trapped in an electric Paul trap. We varied the ion separation, d, between 2.18 and 2.76 micrometres and measured the electrons' weak, millihertz-scale, magnetic interaction as a function of distance, in the presence of magnetic noise that was six orders of magnitude larger than the magnetic fields the electrons apply on each other. The cooperative spin dynamics was kept coherent for 15 seconds, during which spin entanglement was generated, as verified by a negative measured value of -0.16 for the swap entanglement witness. The sensitivity necessary for this measurement was provided by restricting the spin evolution to a decoherence-free subspace that is immune to collective magnetic field noise. Our measurements show a d(-3.0(4)) distance dependence for the coupling, consistent with the inverse-cube law.
Measurements of integral cross-sections of incoherent interactions of photons with L-shell electrons
Energy Technology Data Exchange (ETDEWEB)
Verma, S L; Allawadhi, K L; Sood, B S [Punjabi Univ., Patiala (India). Nuclear Science Labs.
1983-05-21
Integral cross-sections of incoherent interactions of 662 and 1250 keV gamma-rays with L-shell electrons of different elements with 74<=Z<=92 have been measured. The experimental results, when interpreted in terms of photoelectric and Compton interaction cross-sections, are found to agree with theory.
Measurement of integral cross-sections of incoherent interactions of photons with K-shell electrons
Energy Technology Data Exchange (ETDEWEB)
Verma, S L; Allawadhi, K L; Sood, B S [Punjabi Univ., Patiala (India). Dept. of Physics. Nuclear Science Labs.
1981-06-01
Integral cross-sections of incoherent interactions of 145, 279, 662 and 1250 keV gamma-rays with K-shell electrons of thirty-one different elements with 26 <= Z <= 92 have been measured. The results are interpreted in terms of the photoelectric and Compton interactions and are found to agree with theory.
Investigating the interaction of x-ray free electron laser radiation with grating structure
Gaudin, J.; Ozkan, C.; Chalupsky, J.; Bajt, S.; Burian, T.; Vysin, L.; Coppola, N.; Farahani, S. D.; Chapman, H. N.; Galasso, G.; Hajkova, V.; Harmand, M.; Juha, L.; Jurek, M.; Loch, R. A.; Möller, S.; Nagasono, M.; Stormer, M.; Sinn, H.; Saksl, K.; Sobierajski, R.; Schulz, J.; Sovak, P.; Toleikis, S.; Tiedtke, K.; Tschentscher, T.; Krzywinski, J.
2012-01-01
The interaction of free electron laser pulses with grating structure is investigated using 4.6 +/- 0.1 nm radiation at the FLASH facility in Hamburg. For fluences above 63.7 +/- 8.7 mJ/cm(2), the interaction triggers a damage process starting at the edge of the grating structure as evidenced by
Assili, Mohamed; Haddad, Sonia
2014-01-01
We derive the frequency shifts and the broadening of $\\Gamma$ point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction, in graphene under uniaxial strain as a function of the electron density and the disorder amount. We show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and TO modes which contributes to the splitting of the G Raman band. The anisotropy of the electronic...
Energy Technology Data Exchange (ETDEWEB)
Krishtopenko, S. S., E-mail: sergey.krishtopenko@mail.ru; Gavrilenko, V. I. [Institute for Physics of Microstructures, Russian Academy of Sciences, 603950 Nizhny Novgorod, GSP-105 (Russian Federation); Lobachevsky State University, 23 Prospekt Gagarina, 603950 Nizhny Novgorod (Russian Federation); Ikonnikov, A. V. [Institute for Physics of Microstructures, Russian Academy of Sciences, 603950 Nizhny Novgorod, GSP-105 (Russian Federation); Orlita, M. [Laboratoire National des Champs Magnétiques Intenses (LNCMI-G), CNRS, 25 rue des Martyrs, B.P. 166, 38042 Grenoble (France); Sadofyev, Yu. G. [P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow 119991, GSP-1, 53 Leninskiy Prospect (Russian Federation); Goiran, M. [Laboratoire National des Champs Magnétiques Intenses (LNCMI-T), CNRS, 143 Avenue de Rangueil, 31400 Toulouse (France); Teppe, F.; Knap, W. [Laboratoire Charles Coulomb (L2C), UMR CNRS 5221, GIS-TERALAB, Universite Montpellier II, 34095 Montpellier (France)
2015-03-21
We report observation of electron-electron (e-e) interaction effect on cyclotron resonance (CR) in InAs/AlSb quantum well heterostructures. High mobility values allow us to observe strongly pronounced triple splitting of CR line at noninteger filling factors of Landau levels ν. At magnetic fields, corresponding to ν > 4, experimental values of CR energies are in good agreement with single-electron calculations on the basis of eight-band k ⋅ p Hamiltonian. In the range of filling factors 3 < ν < 4 pronounced, splitting of CR line, exceeding significantly the difference in single-electron CR energies, is discovered. The strength of the splitting increases when occupation of the partially filled Landau level tends to a half, being in qualitative agreement with previous prediction by MacDonald and Kallin [Phys. Rev. B 40, 5795 (1989)]. We demonstrate that such behaviour of CR modes can be quantitatively described if one takes into account both electron correlations and the mixing between conduction and valence bands in the calculations of matrix elements of e-e interaction.
Interactions between electrons, mesoscopic Josephson effect and asymmetric current fluctuations
Huard, B.
2006-07-01
This article discusses three experiments on the properties of electronic transport at the mesoscopic scale. The first one allowed to measure the energy exchange rate between electrons in a metal contaminated by a very weak concentration of magnetic impurities. The role played by magnetic impurities in the Kondo regime on those energy exchanges is quantitatively investigated, and the global measured exchange rate is larger than expected. The second experiment is a measurement of the current-phase relation in a system made of two superconductors linked through a single atom. We thus provide quantitative support for the recent description of the mesoscopic Josephson effect. The last experiment is a measurement of the asymmetry of the current fluctuations in a mesoscopic conductor, using a Josephson junction as a threshold detector. Cet ouvrage décrit trois expériences portant sur les propriétés du transport électronique à l'échelle mésoscopique. La première a permis de mesurer le taux d'échange d'énergie entre électrons dans un métal contenant une très faible concentration d'impuretés magnétiques. Nous avons validé la description quantitative du rôle des impuretés magnétiques dans le régime Kondo sur ces échanges énergétiques et aussi montré que le taux global d'échange est plus fort que prévu. La seconde expérience est une mesure de la relation courant-phase dans un système constitué de deux supraconducteurs couplés par un seul atome. Elle nous a permis de conforter quantitativement la récente description de l'effet Josephson mésoscopique. La dernière expérience est unemesure de l'asymétrie des fluctuations du courant dans un conducteur mésoscopique en utilisant une Jonction Josephson comme détecteur de seuil.
Nguyen, Minh T; Biberdorf, Joshua D; Holliday, Bradley J; Jones, Richard A
2017-11-01
A polymer consisting of a polynorbornene backbone with perylene diimide (PDI) pendant groups on each monomeric unit is synthesized via ring opening metathesis polymerization. The PDI pendant groups along the polymer backbone, studied by UV-vis absorption, fluorescence emission, and electron paramagnetic resonance spectroscopy in addition to electrochemical methods, show evidence of molecular aggregation and corresponding electronic coupling with neighboring groups, which forms pathways for efficient electron transport from one group to another in a specific reduced form. When n-doped, the title polymer shows redox conductivity of 5.4 × 10 -3 S cm -1 , comparable with crystalline PDI materials, and is therefore a promising material for use in organic electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Effect of CDW and magnetic interactions on the eg electrons of the manganite systems
International Nuclear Information System (INIS)
Rout, G.C.; Panda, S.; Behera, S.N.
2009-01-01
We address a model study which includes the co-existence of the charge density wave (CDW) and ferromagnetic interactions in order to explain the colossal magnetoresistance (CMR) in manganites. The Hamiltonian consists of the ferromagnetic Hund's rule exchange interaction between e g and t 2g spins, Heisenberg core spin interactions and the CDW interaction present in the e g band electrons. The core electron magnetization, induced e g electron magnetization and the CDW gap are calculated using Zubarev's Green's function technique and determined self-consistently. The effect of core electron magnetization and the CDW interaction on the induced magnetization as well as on the occupation number in the different spin states of the e g band electrons are investigated by varying the model parameters of the system like the CDW coupling, the exchange coupling, the Heisenberg coupling and the external field. It is observed that the induced magnetization exhibits re-entrant behaviour and exists within a narrow temperature range just below the Curie temperature. This unusual behaviour of the e g band electrons will throw some new insights on the physical properties of the manganite systems.
Bulanov, S. S.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.
2013-06-01
The interaction of high-energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high-energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when three-dimensional effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and photons are calculated for the case of a high-energy e-beam interacting with a counterstreaming, short intense laser pulse. The energy loss of the e-beam, which requires a self-consistent quantum description, plays an important role in this process, as well as provides a clear experimental observable for the transition from the classical to quantum regime of interaction.
Electron and nuclear spin interactions in the optical spectra of single GaAs quantum dots.
Gammon, D; Efros, A L; Kennedy, T A; Rosen, M; Katzer, D S; Park, D; Brown, S W; Korenev, V L; Merkulov, I A
2001-05-28
Fine and hyperfine splittings arising from electron, hole, and nuclear spin interactions in the magneto-optical spectra of individual localized excitons are studied. We explain the magnetic field dependence of the energy splitting through competition between Zeeman, exchange, and hyperfine interactions. An unexpectedly small hyperfine contribution to the splitting close to zero applied field is described well by the interplay between fluctuations of the hyperfine field experienced by the nuclear spin and nuclear dipole/dipole interactions.
Possible interaction between thermal electrons and vibrationally excited N2 in the lower E-region
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K.-I. Oyama
2011-03-01
Full Text Available As one of the tasks to find the energy source(s of thermal electrons, which elevate(s electron temperature higher than neutral temperature in the lower ionosphere E-region, energy distribution function of thermal electron was measured with a sounding rocket at the heights of 93–131 km by the applying second harmonic method. The energy distribution function showed a clear hump at the energy of ~0.4 eV. In order to find the reason of the hump, we conducted laboratory experiment. We studied difference of the energy distribution functions of electrons in thermal energy range, which were measured with and without EUV radiation to plasma of N2/Ar and N2/O2 gas mixture respectively. For N2/Ar gas mixture plasma, the hump is not clearly identified in the energy distribution of thermal electrons. On the other hand for N2/O2 gas mixture, which contains vibrationally excited N2, a clear hump is found when irradiated by EUV. The laboratory experiment seems to suggest that the hump is produced as a result of interaction between vibrationally excited N2 and thermal electrons, and this interaction is the most probable heating source for the electrons of thermal energy range in the lower E-region. It is also suggested that energy distribution of the electrons in high energy part may not be Maxwellian, and DC probe measures the electrons which are non Maxwellian, and therefore "electron temperature" is calculated higher.
Likhtenshtein, Gertz
2016-01-01
This book presents the versatile and pivotal role of electron spin interactions in nature. It provides the background, methodologies and tools for basic areas related to spin interactions, such as spin chemistry and biology, electron transfer, light energy conversion, photochemistry, radical reactions, magneto-chemistry and magneto-biology. The book also includes an overview of designing advanced magnetic materials, optical and spintronic devices and photo catalysts. This monograph appeals to scientists and graduate students working in the areas related to spin interactions physics, biophysics, chemistry and chemical engineering.
Auger electron spectroscopy study on interaction between aluminum thin layers and uranium substrate
International Nuclear Information System (INIS)
Zhou Wei; Liu Kezhao; Yang Jiangrong; Xiao Hong; Jiang Chunli; Lu Lei
2005-01-01
Aluminum thin layers on uranium were prepared by sputter deposition at room temperature in ultra high vacuum analysis chamber. Interaction between U and Al, and growth mode were investigated by Auger electron spectroscopy (AES) and electron energy loss spectroscopy (EELS). It is shown that Al thin film growth follows the volmer-weber (VW) mode. At room temperature, Al and U interact with each other, resulting in interdiffusion action and formation of U-Al alloys at U/Al interface. Annealing promotes interaction and interdiffusion between U and Al, and UAl x maybe formed at interface. (authors)
Yavari, H.; Mokhtari, M.; Bayervand, A.
2015-03-01
Based on Kubo's linear response formalism, temperature dependence of the spin-Hall conductivity of a two-dimensional impure (magnetic and nonmagnetic impurities) Rashba electron gas in the presence of electron-electron and electron-phonon interactions is analyzed theoretically. We will show that the temperature dependence of the spin-Hall conductivity is determined by the relaxation rates due to these interactions. At low temperature, the elastic lifetimes ( and are determined by magnetic and nonmagnetic impurity concentrations which are independent of the temperature, while the inelastic lifetimes ( and related to the electron-electron and electron-phonon interactions, decrease when the temperature increases. We will also show that since the spin-Hall conductivity is sensitive to temperature, we can distinguish the intrinsic and extrinsic contributions.
Nonlinear interaction of photons and phonons in electron-positron plasmas
International Nuclear Information System (INIS)
Tajima, T.; Taniuti, T.
1990-03-01
Nonlinear interaction of electromagnetic waves and acoustic modes in an electron-positron plasma is investigated. The plasma of electrons and positrons is quite plastic so that the imposition of electromagnetic (EM) waves causes depression of the plasma and other structural imprints on it through either the nonresonant or resonant interaction. Our theory shows that the nonresonant interaction can lead to the coalescence of photons and collapse of plasma cavity in higher (≥ 2) dimensions. The resonant interaction, in which the group velocity of EM waves is equal to the phase velocity of acoustic waves, is analyzed and a set of basic equations of the system is derived via the reductive perturbation theory. We find new solutions of solitary types: bright solitons, kink solitons, and dark solitons as the solutions to these equations. Our computation hints their stability. An impact of the present theory on astrophysical plasma settings is expected, including the cosmological relativistically hot electron-positron plasma. 20 refs., 9 figs
Ab initio study of He-He interactions in homogeneous electron gas
Energy Technology Data Exchange (ETDEWEB)
Wang, Jinlong; Niu, Liang-Liang; Zhang, Ying, E-mail: zhyi@buaa.edu.cn
2017-02-15
Highlights: • Helium atoms interact via the He induced Friedel oscillations of electron densities. • He-He global binding energy minimum of ∼−0.09 eV is reached at an optimal electron density of 0.04 e/Å{sup 3}, corresponding to an optimal He-He separation of ∼1.7 Å. • The present results can qualitatively interpret the well-known He self-trapping behavior in metals. - Abstract: We have investigated the immersion energy of a single He and the He-He interactions in homogeneous electron gas using ab initio calculations. It is found that He dislikes electrons and He-He interact via the He induced Friedel oscillations of electron densities. A critical electron density at which the global binding energy extremum shifts from the first minimum to the second one is identified. We also discover that the He-He global binding energy minimum of ∼−0.09 eV is reached at an optimal electron density of 0.04 e/Å{sup 3}, corresponding to an optimal He-He separation of ∼1.7 Å. Further, the He atoms are found to gain a trivial amount of 2s and 2p states from the free electrons, inducing a hybridization between the He s- and p-states. The present results can qualitatively interpret the well-known He self-trapping behavior in metals.
Dimension-dependent stimulated radiative interaction of a single electron quantum wavepacket
Gover, Avraham; Pan, Yiming
2018-06-01
In the foundation of quantum mechanics, the spatial dimensions of electron wavepacket are understood only in terms of an expectation value - the probability distribution of the particle location. One can still inquire how the quantum electron wavepacket size affects a physical process. Here we address the fundamental physics problem of particle-wave duality and the measurability of a free electron quantum wavepacket. Our analysis of stimulated radiative interaction of an electron wavepacket, accompanied by numerical computations, reveals two limits. In the quantum regime of long wavepacket size relative to radiation wavelength, one obtains only quantum-recoil multiphoton sidebands in the electron energy spectrum. In the opposite regime, the wavepacket interaction approaches the limit of classical point-particle acceleration. The wavepacket features can be revealed in experiments carried out in the intermediate regime of wavepacket size commensurate with the radiation wavelength.
Electronic voting to encourage interactive lectures: a randomised trial
Directory of Open Access Journals (Sweden)
Palmer Edward
2007-07-01
Full Text Available Abstract Background Electronic Voting Systems have been used for education in a variety of disciplines. Outcomes from these studies have been mixed. Because results from these studies have been mixed, we examined whether an EVS system could enhance a lecture's effect on educational outcomes. Methods A cohort of 127 Year 5 medical students at the University of Adelaide was stratified by gender, residency status and academic record then randomised into 2 groups of 64 and 63 students. Each group received consecutive 40-minute lectures on two clinical topics. One group received the EVS for both topics. The other group received traditional teaching only. Evaluation was undertaken with two, 15-question multiple-choice questionnaires (MCQ assessing knowledge and problem solving and undertaken as a written paper immediately before and after the lectures and repeated online 8–12 weeks later. Standardised institutional student questionnaires were completed for each lecture and independent observers assessed student behaviour during the lectures. Lecturer's opinions were assessed by a questionnaire developed for this study. Results Two-thirds of students randomised to EVS and 59% of students randomised to traditional lectures attended. One-half of the students in the EVS group and 41% in the traditional group completed all questionnaires. There was no difference in MCQ scores between EVS and traditional lectures (p = 0.785. The cervical cancer lectures showed higher student ranking in favour of EVS in all parameters. The breast cancer lectures showed higher ranking in favour of traditional lectures in 5 of 7 parameters (p Conclusion In this setting, EVS technology used in large group lectures did not offer significant advantages over the more traditional lecture format.
Interactive stereo electron microscopy enhanced with virtual reality
International Nuclear Information System (INIS)
Bethel, E.Wes; Bastacky, S.Jacob; Schwartz, Kenneth S.
2001-01-01
An analytical system is presented that is used to take measurements of objects perceived in stereo image pairs obtained from a scanning electron microscope (SEM). Our system operates by presenting a single stereo view that contains stereo image data obtained from the SEM, along with geometric representations of two types of virtual measurement instruments, a ''protractor'' and a ''caliper''. The measurements obtained from this system are an integral part of a medical study evaluating surfactant, a liquid coating the inner surface of the lung which makes possible the process of breathing. Measurements of the curvature and contact angle of submicron diameter droplets of a fluorocarbon deposited on the surface of airways are performed in order to determine surface tension of the air/liquid interface. This approach has been extended to a microscopic level from the techniques of traditional surface science by measuring submicrometer rather than millimeter diameter droplets, as well as the lengths and curvature of cilia responsible for movement of the surfactant, the airway's protective liquid blanket. An earlier implementation of this approach for taking angle measurements from objects perceived in stereo image pairs using a virtual protractor is extended in this paper to include distance measurements and to use a unified view model. The system is built around a unified view model that is derived from microscope-specific parameters, such as focal length, visible area and magnification. The unified view model ensures that the underlying view models and resultant binocular parallax cues are consistent between synthetic and acquired imagery. When the view models are consistent, it is possible to take measurements of features that are not constrained to lie within the projection plane. The system is first calibrated using non-clinical data of known size and resolution. Using the SEM, stereo image pairs of grids and spheres of known resolution are created to calibrate the
Theoretical study of ultrarelativistic laser-electron interaction with radiation reaction
Directory of Open Access Journals (Sweden)
Seto K.
2013-11-01
Full Text Available When the laser intensity becomes higher than 1022 W/cm2, the motion of an electron becomes relativistic, and emits large amounts of radiation. This radiation energy loss transferred to the kinetic energy loss of the electron, is treated as an external force, the “radiation reaction force”. We show the new equation of motion including this radiation reaction and the simulation method, as well as results of single electron system or dual electrons system with Liénard-Wiechert field interaction.
Fast-electron-relaxation measurement for laser-solid interaction at relativistic laser intensities
International Nuclear Information System (INIS)
Chen, H.; Shepherd, R.; Chung, H. K.; Kemp, A.; Hansen, S. B.; Wilks, S. C.; Ping, Y.; Widmann, K.; Fournier, K. B.; Beiersdorfer, P.; Dyer, G.; Faenov, A.; Pikuz, T.
2007-01-01
We present measurements of the fast-electron-relaxation time in short-pulse (0.5 ps) laser-solid interactions for laser intensities of 10 17 , 10 18 , and 10 19 W/cm 2 , using a picosecond time-resolved x-ray spectrometer and a time-integrated electron spectrometer. We find that the laser coupling to hot electrons increases as the laser intensity becomes relativistic, and that the thermalization of fast electrons occurs over time scales on the order of 10 ps at all laser intensities. The experimental data are analyzed using a combination of models that include Kα generation, collisional coupling, and plasma expansion
Electron ion interactions in crystal channels: Collisions in ultra-dense electron media
International Nuclear Information System (INIS)
Datz, S.; Dittner, P.F.; Gomez del Campo, J.; Krause, H.F.; Rosseel, T.M.; Vane, C.R.
1990-01-01
Dielectronic excitation of H-like S, Ca and Ti is shown to occur in the dense electron gas of a crystal channel. Cross sections for collisional ionization of the short lived excited states can then be determined. Ionic excitation can also be achieved by resonant coherent excitation in which case specific m states can be excited for further study. 12 refs., 8 figs
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Jiguang Du
2016-04-01
Full Text Available The interaction natures between Pu and different ligands in several plutonyl (VI complexes are investigated by performing topological analyses of electron density. The geometrical structures in both gaseous and aqueous phases are obtained with B3LYP functional, and are generally in agreement with available theoretical and experimental results when combined with all-electron segmented all-electron relativistic contracted (SARC basis set. The Pu– O y l bond orders show significant linear dependence on bond length and the charge of oxygen atoms in plutonyl moiety. The closed-shell interactions were identified for Pu-Ligand bonds in most complexes with quantum theory of atoms in molecules (QTAIM analyses. Meanwhile, we found that some Pu–Ligand bonds, like Pu–OH−, show weak covalent. The interactive nature of Pu–ligand bonds were revealed based on the interaction quantum atom (IQA energy decomposition approach, and our results indicate that all Pu–Ligand interactions is dominated by the electrostatic attraction interaction as expected. Meanwhile it is also important to note that the quantum mechanical exchange-correlation contributions can not be ignored. By means of the non-covalent interaction (NCI approach it has been found that some weak and repulsion interactions existed in plutonyl(VI complexes, which can not be distinguished by QTAIM, can be successfully identified.
Final state interactions in electron induced trinucleon breakup reactions
International Nuclear Information System (INIS)
Meijgaard, E. van.
1989-01-01
This thesis presents an exact analysis of the electromagnetic breakup process of a trinucleon system. The one-photon exchange mechanism is reviewed. The relevant components of the nuclear current are discussed and the off-shell one-body current matrix elements are derived to accommodate the evaluation of the trinucleon nuclear structure functions. The Faddeev equations are introduced. To facilitate the numerical evaluations the unitary pole expansion (UPE) is employed to describe a local S-wave spin-dependent interaction in a series of separable potential terms. The UPE convergence properties for the trinucleon bound state as well as for the N-N and N-d scattering observables are investigated. In view of the electromagnetic two-body and three-body breakup analysis the half off-shell wave functions for 3N→Nd and 3N→3N scattering are calculated. The nuclear structure functions of the electromagnetic two-body breakup structure functions of the electromagnetic two-body breakup processes are derived and exactly calculated. Results are presented and discussed for several kinetamic configurations. The nuclear response functions of the trinucleon breakup processes are calculated for a momentum transfer Q = 400 MeV/c. The results are compared with recent experimental data for the longitudinal and transverse response of both trinucleon systems. The three-body contributions to the response functions result from an essentially fourfold numerical integration of the invariant electromagnetic three-body breakup amplitude. A detailed derivation of this amplitude is presented and the treatment of the subsequent integration is discussed. An extension is formulated to include D-state components in the trinucleon bound state as well as in the disconnected final state components for the two-body breakup process. One kinematic situation is studied with the D-state extension. For the three-body breakup processes only the PWIA response is determined with the D-state component in the
International Nuclear Information System (INIS)
Vugman, N.V.
1973-08-01
The radiation effects in ]Ir III (CN) 6 ] 3- diamagnetic complexe inserted in the KCl lattice and irradiated with electrons of 2MeV by electron spin resonance (ESR) are analysed. Formulas for g and A tensors in the ligand field approximation, are derivated to calculate non coupling electron density in the metal. The X polarization field of inner shells is positive, indicating a 6s function mixture in the non coupling electron molecular orbital. The observed hyperfine structure is assigned to 4 equivalent nitrogen and one non equivalent nitrogen. This hypothesis is verified by experience of isotope substitution with 15 N. The s and p spin density in ligands are calculated and discussed in terms of molecular obitals. The effects of strong quadrupole interaction into the EPR spectra of ]Ir II (CN) 5 ] 3- complex are analysed by MAGNSPEC computer program to diagonalize the Spin Hamiltonian of the system. Empiric rules for EPR espectrum interpretation with strong quadrupole interaction. A review of EPR technique and a review of main concepts of crystal-field and ligand field theories, are also presented. (M.C.K.) [pt
Interaction of electrons with biomolecules and development of a helium cluster source
International Nuclear Information System (INIS)
Denifl, S.
2004-07-01
In the main part of the present work electron interaction (attachment/ionization) with molecules of biological relevance has been studied in the electron energy range from about 0 to 70 eV. For these measurements a crossed neutral / high resolution electron beams apparatus in conjunction with a quadrupole mass spectrometer has been used. The present work should evaluate the description of the damage induced by high energy radiation since low secondary electrons with energies below 20 eV are created in a large amount in the interaction of the primary radiation with cell compounds. Thus dissociative electron attachment (DEA) and electron impact ionization near the threshold of biomulecules has been studied below 20 eV under isolated conditions. DEA to the DNA/RNA molecules thymine, cytosine and uracil has been carried out. As for most of the recently studied simple biomolecules (like isolated DNA bases, amino acids and sugars) no parent ion has been observed. It turned out that the most abundant fragment ions for DNA/RNA bases are the dehydrogenated bases. In addition to DNA/RNA bases also electron interaction with 6-Chlorouracil has been studied. Another part of this thesis is the construction of a He cluster source. Helium clusters are most difficult to produce as temperatures of about 10 K have to be reached in the stagnation chamber at the stagnation pressure of about 20 bar. The newly developed source allows achieving stagnation conditions for a helium cluster production. (author)
Escaping Electrons from Intense Laser-Solid Interactions as a Function of Laser Spot Size
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Rusby Dean
2018-01-01
Full Text Available The interaction of a high-intensity laser with a solid target produces an energetic distribution of electrons that pass into the target. These electrons reach the rear surface of the target creating strong electric potentials that act to restrict the further escape of additional electrons. The measurement of the angle, flux and spectra of the electrons that do escape gives insights to the initial interaction. Here, the escaping electrons have been measured using a differentially filtered image plate stack, from interactions with intensities from mid 1020-1017 W/cm2, where the intensity has been reduced by defocussing to increase the size of the focal spot. An increase in electron flux is initially observed as the intensity is reduced from 4x1020 to 6x1018 W/cm2. The temperature of the electron distribution is also measured and found to be relatively constant. 2D particle-in-cell modelling is used to demonstrate the importance of pre-plasma conditions in understanding these observations.
Directory of Open Access Journals (Sweden)
A. Gover
2006-06-01
Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.
Enhancement of the Number of Fast Electrons Generated in a Laser Inverse Cone Interaction
International Nuclear Information System (INIS)
Yan-Ling, Ji; Gang, Jiang; Wei-Dong, Wu; Ji-Cheng, Zhang; Yong-Jian, Tang
2010-01-01
Enhancement of the energy-conversion efficiency from laser to target electrons is demonstrated by two-dimensional particle-in-cell simulations in a laser-inverse cone interaction. When an intense short-pulse laser illuminates the inverse cone target, the electrons at the cone end are accelerated by the ponderomotive force. Then these electrons are guided and confined to transport along the inverse cone walls by the induced electromagnetic fields. A device consisting of inverse hollow-cone and multihole array plasma is proposed in order to increase the energy-conversion efficiency from laser to electrons. Particle-in-cell simulations present that the multiholes transpiercing the cone end help to enhance the number of fast electrons and the maximum electron energy significantly. (physics of gases, plasmas, and electric discharges)
Nonlinear interaction of powerful short electromagnetic pulses with an electron plasma
International Nuclear Information System (INIS)
Rao, N.N.; Yu, M.Y.; Shukla, P.K.
1990-01-01
The nonlinear interaction of powerful short electromagnetic pulses with a plasma consisting of two groups of electrons and immobile ions has been studied. It is shown that the interaction is governed by a nonlinear equation for the electromagnetic wave envelope and a driven nonlinear equation for the low-frequency electron fluctuations. The driver for the latter depends explicitly on the spatio-temporal evolution of the electromagnetic wave flux. It is found that, depending on the cold-to-hot electron density ratio, the localized pulse can propagate with sub- as well as supersonic velocities accompanied by compressional or rarefactional density perturbations. The conditions of existence for the different types of solitary pulses are obtained. The present investigation may be relevant to the study of wave-plasma interaction devices such as inertial fusion confinement as well as to ionospheric modification experiments. (author)
Competing effective interactions of Dirac electrons in the Spin–Fermion system
International Nuclear Information System (INIS)
Marino, E.C.; Nunes, Lizardo H.C.M.
2014-01-01
Recently discovered advanced materials, such as heavy fermions, frequently exhibit a rich phase diagram suggesting the presence of different competing interactions. A unified description of the origin of these multiple interactions, albeit very important for the comprehension of such materials is, in general not available. It would be therefore very useful to have a simple model where the common source of different interactions could be possibly traced back. In this work we consider a system consisting in a set of localized spins on a square lattice with antiferromagnetic nearest neighbors interactions and itinerant electrons, which are assumed to be Dirac-like and interact with the localized spins through a Kondo magnetic interaction. This system is conveniently described by the Spin–Fermion model, which we use in order to determine the effective interactions among the itinerant electrons. By integrating out the localized degrees of freedom we obtain a set of different interactions, which includes: a BCS-like superconducting term, a Nambu–Jona-Lasinio-like, excitonic term and a spin–spin magnetic term. The resulting phase diagram is investigated by evaluation of the mean-field free-energy as a function of the relevant order parameters. This shows the competition of the above interactions, depending on the temperature, chemical potential and coupling constants. -- Highlights: •Antiferromagnetic Heisenberg–Kondo lattice model with itinerant Dirac fermions. •Integrating out the spins generates competing interactions: BCS-like, excitonic and magnetic. •Novel mechanism of superconductivity from magnetic interactions between the spins and electrons. •Dome-shaped dependence of the temperature on the chemical potential in agreement with pnictides
Weak localization and electron-electron interaction in modulation doped GaAs/AlGaAs heterostructures
International Nuclear Information System (INIS)
Taboryski, R.; Lindelof, P.E.
1990-01-01
The first heterostructure wafer only had one electronic subband at the GaAs/AlGaAs interface populated. Weak localization magnetoresistance was interpreted by a theory valid to relatively high magnetic fields and also valid for electrons with a long mean free path. The adjustable parameter in fitting the magnetoresistance was in each case the phasebreaking relaxation time, which could then subsequently be plotted as a function of temperature. The temperature dependence of the phasebreaking rate could be interpreted on the basic of existing theories, but the residual relaxation rate at the lowest temperature remains so far unexplained. Already at low magnetic fields the weak localization magnetoresistance saturates, indicating a complete quench of weak localization. We find that the value of saturation (i.e. the total weak localization at the appropriate temperature) was smaller than predicted by the existing theories. At magnetic fields of the order of the inverse electron mobility, a quadratic magnetoresistance show up in our experiments. This quadratic magnetoresistance corresponds to corrections to the conductivity of the order of e 2 /h. Whereas we find that the temperature dependence of this conductivity correction is well in agreement with predicted effects of electron-electron interaction, the dependence on mobility, which we can measure via our ion implantation, is larger than any existing theory predicts, yet still in the ballpark of the conductance quantum. (orig./BHO)
Electron-phonon interaction and its manifestation in high-temperature superconductors
International Nuclear Information System (INIS)
Maksimov, E.G.
1995-01-01
Different types of band structure approaches for a description of electrons in systems with strong correlations are discussed. It is shown that all methods considered give different electron energy dispersions and Fermi surfaces. The good agreement between measured Fermi surfaces and those calculated by LDA shows that the spatial dispersion of the correlation interaction is not so important in HTSC systems. The same conclusion can be obtained from the optical and photoemission spectra. It is shown that the most important contribution beyond a band structure approach is given by an energy dependence of the electron self-energy. The most likely interaction responsible for this energy dependence is the electron-phonon one. Evidences about this fact are given
Electron self-injection and acceleration in the bubble regime of laser-plasma interaction
International Nuclear Information System (INIS)
Kostyukov, I.; Nerush, E.
2010-01-01
Complete text of publication follows. The intense laser-plasma and beam-plasma interactions are highly nonlinear-phenomena, which besides being of fundamental interest, attract a great attention due to a number of important applications. One of the key applications is particle acceleration based on excitation of the strong plasma wakefield by laser pulse. In the linear regime of interaction when the laser intensity is low the plasma wake is the linear plasma wave. Moreover, the ponderomotive force of the laser pulse pushes out the plasma electrons from high intensity region leaving behind the laser pulse the plasma cavity - bubble, which is almost free from the plasma electrons. This is the bubble the laser-plasma interaction. Although the bubble propagates with velocity, which is close to speed of light, the huge charge of unshielded ions inside the plasma cavity can trap the cold plasma electrons. Moreover, the electrons are trapped in the accelerated phase of the bubble plasma field thereby leading to efficient electron acceleration. The electron self-injection is an important advantage of the plasma-based acceleration, which allows to exclude the beam loading system requiring accurate synchronization and additional space. The recent experiments have demonstrated high efficiency of the electron self-injection. The beam quality is often of crucial importance in many applications ranging from inertial confinement fusion to the x-ray free electron lasers. Despite a great interest there is still a little theory for relativistic electron dynamics in the plasma wake in multidimensional geometry including electron self-injection. The dynamics of the self-injected electrons can be roughly divided into three stage: (i) electron scattering by the laser pulse, (ii) electron trapping by the bubble, (iii) electron acceleration in the bubble. We developed two analytical models for electron dynamics in the bubble field and verify them by direct measurements of model parameters
Hannemann, Frank; Guyot, Arnaud; Zöllner, Andy; Müller, Jürgen J; Heinemann, Udo; Bernhardt, Rita
2009-07-01
Dipole moments of proteins arise from helical dipoles, hydrogen bond networks and charged groups at the protein surface. High protein dipole moments were suggested to contribute to the electrostatic steering between redox partners in electron transport chains of respiration, photosynthesis and steroid biosynthesis, although so far experimental evidence for this hypothesis was missing. In order to probe this assumption, we changed the dipole moment of the electron transfer protein adrenodoxin and investigated the influence of this on protein-protein interactions and electron transfer. In bovine adrenodoxin, the [2Fe-2S] ferredoxin of the adrenal glands, a dipole moment of 803 Debye was calculated for a full-length adrenodoxin model based on the Adx(4-108) and the wild type adrenodoxin crystal structures. Large distances and asymmetric distribution of the charged residues in the molecule mainly determine the observed high value. In order to analyse the influence of the resulting inhomogeneous electric field on the biological function of this electron carrier the molecular dipole moment was systematically changed. Five recombinant adrenodoxin mutants with successively reduced dipole moment (from 600 to 200 Debye) were analysed for their redox properties, their binding affinities to the redox partner proteins and for their function during electron transfer-dependent steroid hydroxylation. None of the mutants, not even the quadruple mutant K6E/K22Q/K24Q/K98E with a dipole moment reduced by about 70% showed significant changes in the protein function as compared with the unmodified adrenodoxin demonstrating that neither the formation of the transient complex nor the biological activity of the electron transfer chain of the endocrine glands was affected. This is the first experimental evidence that the high dipole moment observed in electron transfer proteins is not involved in electrostatic steering among the proteins in the redox chain.
Target Surface Area Effects on Hot Electron Dynamics from High Intensity Laser-Plasma Interactions
2016-08-19
Science, University ofMichigan, AnnArbor,MI 48109-2099, USA E-mail: czulick@umich.edu Keywords: laser- plasma ,mass-limited, fast electrons , sheath...New J. Phys. 18 (2016) 063020 doi:10.1088/1367-2630/18/6/063020 PAPER Target surface area effects on hot electron dynamics from high intensity laser... plasma interactions CZulick, ARaymond,AMcKelvey, VChvykov, AMaksimchuk, AGRThomas, LWillingale, VYanovsky andKKrushelnick Center forUltrafast Optical
Interactions in 2D electron and hole systems in the intermediate and ballistic regimes
International Nuclear Information System (INIS)
Proskuryakov, Y Y; Savchenko, A K; Safonov, S S; Li, L; Pepper, M; Simmons, M Y; Ritchie, D A; Linfield, E H; Kvon, Z D
2003-01-01
In different 2D semiconductor systems we study the interaction correction to the Drude conductivity in the intermediate and ballistic regimes, where the parameter k B Tτ/ h-bar changes from 0.1 to 10 (τ is momentum relaxation time). The temperature dependence of the resistance and magnetoresistance in parallel and perpendicular magnetic fields is analysed in terms of the recent theories of electron-electron interactions in systems with different degree of disorder and different character of the fluctuation potential. Generally, good agreement is found between the experiments and the theories
Emission and electron transitions in an atom interacting with an ultrashort electromagnetic pulse
International Nuclear Information System (INIS)
Matveev, V.I.
2003-01-01
Electron transitions and emission of an atom interacting with a spatially inhomogeneous ultrashort electromagnetic pulse are considered. The excitation and ionization probabilities are obtained as well as the spectra and cross sections of the reemission of such a pulse by atoms. By way of an example, one- and two-electron inelastic processes accompanying the interaction of ultrashort pulses with hydrogen- and helium-like atoms are considered. The developed technique makes it possible to take into account exactly the spatial nonuniformity of the ultrashort pulse field and photon momenta in the course of reemission
Echterling, N.; Schriver, D.; Roeder, J. L.; Fennell, J. F.
2017-12-01
During the recovery phase of substorm plasma injections, the Van Allen Probes commonly observe events of quasi-periodic energetic electron bursts correlating with simultaneously detected upper-band, whistler-mode chorus emissions. These electron bursts exhibit narrow ranges of pitch angles (75-80° and 100-105°) and energies (20-40 keV). Electron cyclotron harmonic (ECH) emissions are also commonly detected, but typically do not display correlation with the electron bursts. To examine sources of free energy and the generation of these wave emissions, an observed electron velocity distribution on January 13, 2013 is used as the starting condition for a particle in cell (PIC) simulation. Effects of temperature anisotropy (perpendicular temperature greater than parallel temperature), the presence of a loss cone and a cold electron population on the generation of whistler and ECH waves are examined to understand wave generation and nonlinear interactions with the particle population. These nonlinear interactions produce energy diffusion along with strong pitch angle scattering into the loss cone on the order of milliseconds, which is faster than a typical bounce period of seconds. To examine the quasi-periodic nature of the electron bursts, a loss-cone recycling technique is implemented to model the effects of the periodic emptying of the loss cone and electron injection on the growth of whistler and ECH waves. The results of the simulations are compared to the Van Allen Probe observations to determine electron acceleration, heating and transport in Earth's radiation belts due to wave-particle interactions.
Ultrafast Gap Dynamics and Electronic Interactions in a Photoexcited Cuprate Superconductor
Directory of Open Access Journals (Sweden)
S. Parham
2017-10-01
Full Text Available We perform time- and angle-resolved photoemission spectroscopy (trARPES on optimally doped Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} (BSCCO-2212 using sufficient energy resolution (9 meV to resolve the k-dependent near-nodal gap structure on time scales where the concept of an electronic pseudotemperature is a useful quantity, i.e., after electronic thermalization has occurred. We study the ultrafast evolution of this gap structure, uncovering a very rich landscape of decay rates as a function of angle, temperature, and energy. We explicitly focus on the quasiparticle states at the gap edge as well as on the spectral weight inside the gap that “fills” the gap—understood as an interaction, or self-energy effect—and we also make high resolution measurements of the nodal states, enabling a direct and accurate measurement of the electronic temperature (or pseudotemperature of the electrons in the system. Rather than the standard method of interpreting these results using individual quasiparticle scattering rates that vary significantly as a function of angle, temperature, and energy, we show that the entire landscape of relaxations can be understood by modeling the system as following a nonequilibrium, electronic pseudotemperature that controls all electrons in the zone. Furthermore, this model has zero free parameters, as we obtain the crucial information of the SC gap Δ and the gap-filling strength Γ_{TDoS} by connecting to static ARPES measurements. The quantitative and qualitative agreement between data and model suggests that the critical parameters and interactions of the system, including the pairing interactions, follow parametrically from the electronic pseudotemperature. We expect that this concept will be relevant for understanding the ultrafast response of a great variety of electronic materials, even though the electronic pseudotemperature may not be directly measurable.
Model calculations of the interaction of two parallel antiaromatic 4n π-electron systems
Böhm, Michael C.; Bickert, Peter; Hafner, Klaus; Boekelheide, V.
1984-01-01
The nature of the interaction between decks of a pentalene dimer and an s-indacene dimer has been studied by semi-empirical MNDO/1 and MINDO/3 calculations for distances between decks of from 5 Å to 2 Å. In contradiction to qualitative predictions from a frontier orbital analysis, it is found that the 4n-4n π-electron interaction between decks for such dimers is destabilizing for distances exceeding about 2.5 Å. PMID:16593458
Magnetic behavior of Van Vleck ions and an electron gas interacting by exchange
International Nuclear Information System (INIS)
Palermo, L.; Silva, X.A. da.
1980-01-01
The magnetic behavior of a model in which Van Vleck ions, under the action of a crystal field, interacting by exchange with an electron gas is investigated. The condition of onset of ferromagnetism and the behavior of the critical temperature, band and ionic magnetizations (and susceptibilities) versus temperature, as a function of the band width, exchange interaction and the crystal field splitting energy parameters are obtained within an approximation equivalent to a molecular field formulation. (Author) [pt
Study of electrons distribution produced by laser-plasma interaction on x-ray generation
International Nuclear Information System (INIS)
Nikzad, L.; Sadighi-Bonabi, R.
2010-01-01
Complete text of publication follows. In the present work, X-ray beams are generated from interaction of relativistic electron beams produced by interaction of 500 mJ, 30 femtosecond Ti:sapphire laser pulses with thin solid targets such as lead, molybdenum and tungsten. After interaction of an intense pulsed laser with He gas-jet, a micron-scale laser produced plasma, creates and accelerates electron bunches, which propagate in the ion channel produced in the wake of the laser pulse. When an electron bunch is injected into the bubble in phase with its field, it will gain relativistic energies within very short distance. These accelerated electrons with Megaelectron-Volt energy and different distributions, can interact with targets to generate X-ray radiation with Kiloelectron-Volt energy, providing to be close enough to the gas-jet, where the relativistic accelerated electrons exist. Here, to determine the results, Monte Carlo simulation (MCNP-4C code) is employed to present Bremsstrahlung and characteristic X-ray production by quasi-Maxwellian and quasi-monoenergetic electron beams for three samples with different thicknesses. The outcome shows that for one specific electron spectrum and one definite target, the energy which the maximum characteristic x-ray flux takes place, varies with thickness. Also, for each material the energy which this maximum happens is constant for all thicknesses, for both produced electron spectra. For each sample, x-ray flux is calculated for different thicknesses and the thickness which the maximum characteristic x-ray flux occurs is obtained. Besides, it is concluded that by increasing the atomic number of the target, maximum X-ray flux moves towards higher energy. Also, comparison of the results for three targets and two electron distributions shows that by using quasi-monoenergetic electron spectra, more intense and narrower characteristic X-ray can be produced compared to the quasi-Maxwellian electron distribution, almost for all
Modeling the process of interaction of 10 keV electrons with a plane dielectric surface
Vokhmyanina, Kristina; Sotnikova, Valentina; Sotnikov, Alexey; Kaplii, Anna; Nikulicheva, Tatyana; Kubankin, Alexandr; Kishin, Ivan
2018-05-01
The effect of guiding of charged particles by dielectric channels is of noticeable interest at the present time. The phenomenon is widely studied experimentally and theoretically but some points still need to be clarified. A previously developed model of interaction of fast electrons with dielectric surface at grazing incidence is used to study the independence of electron deflection on the value of electron beam current. The calculations were performed assuming a smooth dependence of the surface conductivity on the beam current in the 40-3000 nA range.
Electromagnetic microwaves in metal films with electron-phonon interaction and a dc magnetic field
DEFF Research Database (Denmark)
Hasselberg, L.E.
1976-01-01
A quantum-mechanical treatment of electromagnetic microwaves is performed for a metal film. The directions of the exterior ac and dc fields are taken to be arbitrary and boundary conditions for the electrons are assumed to be specular. The relation between the current and the electromagnetic field...... in the transmission spectrum can perhaps be obtained by assuming a finite Debye temperature and specular reflections of the electrons at the boundary surfaces. A sharp peak entirely caused by the finite electron-phonon interaction is also discussed....
Electron emission induced by resonant coherent ion-surface interaction at grazing incidence
International Nuclear Information System (INIS)
Garcia de Abajo, F.J.; Ponce, V.H.; Echenique, P.M.
1992-01-01
A new spectroscopy based on the resonant coherently induced electron loss to the continuum in ion-surface scattering under grazing incidence is proposed. A series of peaks, corresponding to the energy differences determined by the resonant interaction with the rows of atoms in the surface, is predicted to appear in the energy distribution of electrons emitted from electronic states bound to the probe. Calculations for MeV He + ions scattered at a W(001) surface along the left-angle 100 right-angle direction with a glancing angle of 0--2 mrad show a total yield close to 1
NMR detects molecular interactions of graphene with aromatic and aliphatic hydrocarbons in water
Bichenkova, Elena V.; Raju, Arun P. A.; Burusco, Kepa K.; Kinloch, Ian A.; Novoselov, Kostya S.; Clarke, David J.
2018-03-01
Polyaromatic carbon is widely held to be strongly diamagnetic and hydrophobic, with textbook van der Waals and ‘π-stacked’ binding of hydrocarbons, which disrupt their self-assembled supramolecular structures. The NMR of organic molecules sequestered by polyaromatic carbon is expected to be dominated by shielding from the orbital diamagnetism of π electrons. We report the first evidence of very different polar and magnetic behavior in water, wherein graphene remained well-dispersed after extensive dialysis and behaved as a 1H-NMR-silent ghost. Magnetic effects dominated the NMR of organic structures which interacted with graphene, with changes in spin-spin coupling, vast increase in relaxation, line broadening and decrease in NMR peak heights when bound to graphene. However, the interactions were weak, reversible and did not disrupt organic self-assemblies reliant on hydrophobic ‘π-stacking’, even when substantially sequestered on the surface of graphene by the high surface area available. Interacting assemblies of aromatic molecules retained their strongly-shielded NMR signals and remained within self-assembled structures, with slower rates of diffusion from association with graphene, but with no further shielding from graphene. Binding to graphene was selective for positively-charged organic assemblies, weaker for non-aromatic and negligible for strongly-negatively-charged molecules, presumably repelled by a negative zeta potential of graphene in water. Stronger binders, or considerable excess of weaker binders readily reversed physisorption, with no evidence of structural changes from chemisorption. The fundamental nature of these different electronic interactions between organic and polyaromatic carbon is considered with relevance to electronics, charge storage, sensor, medical, pharmaceutical and environmental research.
Suzuki, Makoto; Kameda, Toshimasa; Doi, Ayumi; Borisov, Sergey; Babin, Sergey
2018-03-01
The interpretation of scanning electron microscopy (SEM) images of the latest semiconductor devices is not intuitive and requires comparison with computed images based on theoretical modeling and simulations. For quantitative image prediction and geometrical reconstruction of the specimen structure, the accuracy of the physical model is essential. In this paper, we review the current models of electron-solid interaction and discuss their accuracy. We perform the comparison of the simulated results with our experiments of SEM overlay of under-layer, grain imaging of copper interconnect, and hole bottom visualization by angular selective detectors, and show that our model well reproduces the experimental results. Remaining issues for quantitative simulation are also discussed, including the accuracy of the charge dynamics, treatment of beam skirt, and explosive increase in computing time.
Arul Dhas, D.; Hubert Joe, I.; Roy, S. D. D.; Balachandran, S.
2015-01-01
A widespread exploration on the intra-molecular charge transfer interaction through an efficient π-conjugated path from a strong electron-donor group (amino) to a strong electron-acceptor group (nitro) has been carried out using FTIR, FT-Raman, UV-Vis, fluorescence and NMR spectra on insecticide compound 4-benzyloxy-2-nitroaniline. Density functional theory method is used to determine optimized molecular geometry, harmonic vibrational wavenumbers and intensities using 6-311G(d,p) basis set by means of Gaussian 09W program suit. A comprehensive investigation on the sp2 to sp3 hybridization and non-planarity property has been performed. Natural bond orbital analysis is used to study the existence of C-H⋯O, N-H⋯O and C-H⋯π proper and improper hydrogen bonds. The HOMO and LUMO analysis reveals the possibility of charge transfer within the molecule. A complete assignment of the experimental absorption peaks in the ultraviolet region has also been performed. Isotropic chemical shifts of 13C, 1H, 15N and 18O NMR and nuclear spin-spin coupling constants have been computed using the gauge-invariant atomic orbital method. The biological activity of substituent amino and nitro groups are evident from the hydrogen bonds through which the target amino acids are linked to the drug as evidenced from molecular docking.
The suppression of radiation reaction and laser field depletion in laser-electron beam interaction
Ong, J. F.; Moritaka, T.; Takabe, H.
2018-03-01
The effects of radiation reaction (RR) have been studied extensively by using the interaction of ultraintense lasers with a counter-propagating relativistic electron. At the laser intensity at the order of 1023 W/cm2, the effects of RR are significant in a few laser periods for a relativistic electron. However, a laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulated this interaction with a beam of 109 electrons by means of a Particle-In-Cell method. We observe that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is because the ponderomotive force prevents the electrons from approaching the center of the laser pulse and leads to an interaction at the weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.
International Nuclear Information System (INIS)
Garcia de Abajo, F.J.; Ponce, V.H.; Echenique, P.M.
1994-01-01
The resonant coherent interaction of an ion with an oriented crystal surface, under grazing-incidence conditions with respect to a special direction of the crystal, gives rise to electron loss to the continuum from electronic bound states of the ion. The calculations presented below predict large probabilities for electron emission due to this mechanism. The electrons are emitted with well defined energies, expressed in terms of the condition of resonance. Furthermore, the emission takes place around certain preferential directions, which are determined by both the latter condition and the symmetry of the surface lattice. Our calculations for MeV He + ions scattered at a W(001) surface along the left-angle 100 right-angle direction with glancing angle of 0--2 mrad indicate a yield of emission close to 1. Using heavier projectiles, one obtains smaller yields, but still large enough to be measurable in some cases (e.g., ∼0.9 for 53 MeV B 4+ and an angle of incidence of 1 mrad). Besides, the initial bound state is energy shifted due to the interaction with both the crystal potential and the velocity-dependent image potential. This results in a slight shift of the peaks of emission, which suggests a possible spectroscopy for analyzing the dynamical interaction of electronic bound states with solid surfaces
Dependence of Xmax and multiplicity of electron and muon on different high energy interaction models
Directory of Open Access Journals (Sweden)
G Rastegarzadeh
2010-06-01
Full Text Available Different high energy interaction models are the applied in CORSIKA code to simulate Extensive Air Showers (EAS generated by Cosmic Rays (CR. In this work the effects of QGSJET01, QGSJETII, DPMJET, SIBYLL models on Xmax and multiplicity of secondary electrons and muons at observation level are studied.
Shipe, Ron; And Others
A study examined the development and implementation of an interactive video instruction system for teaching electronics and industrial maintenance at the University of Tennessee. The specific purposes of the study were to document unusual problems that may be encountered when this new technology is implemented, suggest corrective actions, and…
Images of Complex Interactions of an Intense Ion Beam with Plasma Electrons
International Nuclear Information System (INIS)
Kaganovich, Igor D.; Startsev, Edward; Davidson, Ronald C.
2004-01-01
Ion beam propagation in a background plasma is an important scientific issue for many practical applications. The process of ion beam charge and current neutralization is complex because plasma electrons move in strong electric and magnetic fields of the beam. Computer simulation images of plasma interaction with an intense ion beam pulse are presented
Atom Core Interactive Electronic Book to Develop Self Efficacy and Critical Thinking Skills
Pradina, Luthfia Puspa; Suyatna, Agus
2018-01-01
The purpose of this research is to develop interactive atomic electronic school book (IESB) to cultivate critical thinking skills and confidence of students grade 12. The method used in this research was the ADDIE (Analyze Design Development Implementation Evaluation) development procedure which is limited to the test phase of product design…
Kinetics of two-dimensional electron plasma, interacting with fluctuating potential
International Nuclear Information System (INIS)
Boiko, I.I.; Sirenko, Y.M.
1990-01-01
In this paper, from the first principles, after the fashion of Klimontovich, the authors derive quantum kinetic equation for electron gas, inhomogeneous in z-direction and homogeneous in XY-plane. Special attention is given to the systems with quasi-two-dimensional electron gas (2 DEG), which are widely explored now. Both interaction between the particles of 2 DEG (in general, of several sorts), and interaction with an external system (phonons, impurities, after change carries etc.) are considered. General theory is used to obtain energy and momentum balance equations and relaxation frequencies for 2 DEG in the basis of plane waves. The case of crossed electric and magnetic fields is also treated. As an illustration the problems of 2 DEG scattering on semibounded three-dimensional electron gas and on two-dimensional hole gas are considered; transverse conductivity of nondegenerate 2 DEG, scattered by impurities in ultraquantum magnetic field, is calculated
Assili, M.; Haddad, S.
2014-09-01
We derive the frequency shifts and the broadening of Γ-point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction, in graphene under uniaxial strain as a function of the electron density and the disorder amount. We show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and TO modes which contributes to the splitting of the G Raman band. The anisotropy of the electronic spectrum, induced by the strain, results in a polarization dependence of the LO and TO modes. This dependence is in agreement with the experimental results showing a periodic modulation of the Raman intensity of the split G peak. Moreover, the anomalous behavior of the frequency shift reported in undeformed graphene is found to be robust under strain.
Soft Electronics Enabled Ergonomic Human-Computer Interaction for Swallowing Training
Lee, Yongkuk; Nicholls, Benjamin; Sup Lee, Dong; Chen, Yanfei; Chun, Youngjae; Siang Ang, Chee; Yeo, Woon-Hong
2017-04-01
We introduce a skin-friendly electronic system that enables human-computer interaction (HCI) for swallowing training in dysphagia rehabilitation. For an ergonomic HCI, we utilize a soft, highly compliant (“skin-like”) electrode, which addresses critical issues of an existing rigid and planar electrode combined with a problematic conductive electrolyte and adhesive pad. The skin-like electrode offers a highly conformal, user-comfortable interaction with the skin for long-term wearable, high-fidelity recording of swallowing electromyograms on the chin. Mechanics modeling and experimental quantification captures the ultra-elastic mechanical characteristics of an open mesh microstructured sensor, conjugated with an elastomeric membrane. Systematic in vivo studies investigate the functionality of the soft electronics for HCI-enabled swallowing training, which includes the application of a biofeedback system to detect swallowing behavior. The collection of results demonstrates clinical feasibility of the ergonomic electronics in HCI-driven rehabilitation for patients with swallowing disorders.
Energetic electron precipitation in weak to moderate corotating interaction region-driven storms
Ødegaard, Linn-Kristine Glesnes; Tyssøy, Hilde Nesse; Søraas, Finn; Stadsnes, Johan; Sandanger, Marit Irene
2017-03-01
High-energy electron precipitation from the radiation belts can penetrate deep into the mesosphere and increase the production rate of NOx and HOx, which in turn will reduce ozone in catalytic processes. The mechanisms for acceleration and loss of electrons in the radiation belts are not fully understood, and most of the measurements of the precipitating flux into the atmosphere have been insufficient for estimating the loss cone flux. In the present study the electron flux measured by the NOAA POES Medium Energy Proton and Electron Detectors 0° and 90° detectors is combined together with theory of pitch angle diffusion by wave-particle interaction to quantify the electron flux lost below 120 km altitude. Using this method, 41 weak and moderate geomagnetic storms caused by corotating interaction regions during 2006-2010 are studied. The dependence of the energetic electron precipitation fluxes upon solar wind parameters and geomagnetic indices is investigated. Nine storms give increased precipitation of >˜750 keV electrons. Nineteen storms increase the precipitation of >˜300 keV electrons, but not the >˜750 keV population. Thirteen storms either do not change or deplete the fluxes at those energies. Storms that have an increase in the flux of electrons with energy >˜300 keV are characterized by an elevated solar wind velocity for a longer period compared to the storms that do not. Storms with increased precipitation of >˜750 keV flux are distinguished by higher-energy input from the solar wind quantified by the ɛ parameter and corresponding higher geomagnetic activity.
Energy Technology Data Exchange (ETDEWEB)
Westover, B. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093 (United States); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Chen, C. D.; Patel, P. K.; McLean, H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Beg, F. N., E-mail: fbeg@ucsd.edu [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093 (United States)
2014-03-15
Experiments on the Titan laser (∼150 J, 0.7 ps, 2 × 10{sup 20} W cm{sup −2}) at the Lawrence Livermore National Laboratory were carried out in order to study the properties of fast electrons produced by high-intensity, short pulse laser interacting with matter under conditions relevant to Fast Ignition. Bremsstrahlung x-rays produced by these fast electrons were measured by a set of compact filter-stack based x-ray detectors placed at three angles with respect to the target. The measured bremsstrahlung signal allows a characterization of the fast electron beam spectrum, conversion efficiency of laser energy into fast electron kinetic energy and angular distribution. A Monte Carlo code Integrated Tiger Series was used to model the bremsstrahlung signal and infer a laser to fast electron conversion efficiency of 30%, an electron slope temperature of about 2.2 MeV, and a mean divergence angle of 39°. Simulations were also performed with the hybrid transport code ZUMA which includes fields in the target. In this case, a conversion efficiency of laser energy to fast electron energy of 34% and a slope temperature between 1.5 MeV and 4 MeV depending on the angle between the target normal direction and the measuring spectrometer are found. The observed temperature of the bremsstrahlung spectrum, and therefore the inferred electron spectrum are found to be angle dependent.
International Nuclear Information System (INIS)
Krotz, R.; Neuwirth, W.; Pietsch, W.
1980-01-01
The electronic stopping cross sections for Li projectiles have been measured in various kinds of targets. They are analyzed here with respect to the different types of interactions between the constituents of the target: interactions between the atoms in a compound (chemical bonding), the ion-dipole interaction, if the target is an electrolytic solution, and the dipole-dipole interaction among polar molecules. The influence on the stopping cross section depends on the strength of these interactions; it varies from a few percent in the latter case up to 20% and more in a compound. These influences are the largest, if the velocity of the projectile is of the order of the average orbital velocity of the target atoms. (author)
A Study of the Vacancy-Impurity Interaction in Dilute Nickel Alloys by Core Electron Annihilation
Arbuzov, V. L.; Danilov, S. E.; Druzhkov, A. P.
1997-08-01
It is shown that the angular correlation of annihilation radiation can be used to identify vacancy-impurity complexes in dilute alloys. Annihilation of trapped positrons with core electrons bears information about the chemical environment of a vacancy defect. The method is especially effective for d-matrices doped with sp-impurities since annihilation parameters of positrons with d- and sp-shell electrons differ considerably. The potentialities of the method of core-electron annihilation of positrons are demonstrated taking electron-irradiated dilute Ni-P and Ni-Si alloys as an example. It is shown that the interaction between the vacancies, which migrate at the III stage of annealing, and P atoms in Ni-P causes a considerable change in the annihilation parameters of positrons with core electrons compared to pure Ni. In Ni-Si alloys the annihilation parameters of trapped positrons with core electrons do not differ from those in Ni. This fact is an evidence that Si atoms do not interact with vacancies in Ni.
Hearing shapes of few electrons quantum drums: A configuration–interaction study
Energy Technology Data Exchange (ETDEWEB)
Ţolea, F.; Ţolea, M., E-mail: tzolea@infim.ro
2015-02-01
The – highly remarkable – existence of non-congruent yet vibrationally isospectral shapes has been first proved theoretically and then also tested experimentally – by using electromagnetic waves in cavities, vibrating smectic films or electrons in nanostructures. In this context, we address the question whether isospectrality holds if two or more electrons interact electrostatically, using the accurate configuration–interaction method, in a discrete representation of the Bilby and Hawk shapes. Isospectral pairs offer an unique possibility to test how identical sets of single-particle energies may combine differently in the few-electrons eigenmodes, due to different wave functions spatial distributions. Our results point towards the break down of isospectrality in the presence of interactions. Thus one should be able to ”hear” the shapes of few electrons quantum drums. Interestingly however, for the analyzed two and three electrons cases, there exists an interaction strength (which can be tuned by changing the size of the shapes), for which the ground states energies of Bilby and Hawk coincide, but not the excited states as well. Wigner localization is studied and shown to occur at about the same size for both Bilby and Hawk shapes. Next, an exercise is proposed to use the two-electrons charge density of the Bilby and Hawk ground states in the phase extraction scheme as proposed by Moon et al. (2008). Results show that out-of-phase regions appear if the linear size of the shapes exceeds the Bohr radius as occupation of higher Slater determinants becomes significant.
Hearing shapes of few electrons quantum drums: A configuration–interaction study
International Nuclear Information System (INIS)
Ţolea, F.; Ţolea, M.
2015-01-01
The – highly remarkable – existence of non-congruent yet vibrationally isospectral shapes has been first proved theoretically and then also tested experimentally – by using electromagnetic waves in cavities, vibrating smectic films or electrons in nanostructures. In this context, we address the question whether isospectrality holds if two or more electrons interact electrostatically, using the accurate configuration–interaction method, in a discrete representation of the Bilby and Hawk shapes. Isospectral pairs offer an unique possibility to test how identical sets of single-particle energies may combine differently in the few-electrons eigenmodes, due to different wave functions spatial distributions. Our results point towards the break down of isospectrality in the presence of interactions. Thus one should be able to ”hear” the shapes of few electrons quantum drums. Interestingly however, for the analyzed two and three electrons cases, there exists an interaction strength (which can be tuned by changing the size of the shapes), for which the ground states energies of Bilby and Hawk coincide, but not the excited states as well. Wigner localization is studied and shown to occur at about the same size for both Bilby and Hawk shapes. Next, an exercise is proposed to use the two-electrons charge density of the Bilby and Hawk ground states in the phase extraction scheme as proposed by Moon et al. (2008). Results show that out-of-phase regions appear if the linear size of the shapes exceeds the Bohr radius as occupation of higher Slater determinants becomes significant
Energy Technology Data Exchange (ETDEWEB)
Xie, M. [Lawrence Berkeley Lab., CA (United States)
1995-12-31
I present an exact calculation of free-electron-laser (FEL) eigenmodes (fundamental as well as higher order modes) in the exponential-gain regime. These eigenmodes specify transverse profiles and exponential growth rates of the laser field, and they are self-consistent solutions of the coupled Maxwell-Vlasov equations describing the FEL interaction taking into account the effects due to energy spread, emittance and betatron oscillations of the electron beam, and diffraction and guiding of the laser field. The unperturbed electron distribution is assumed to be of Gaussian shape in four dimensional transverse phase space and in the energy variable, but uniform in longitudinal coordinate. The focusing of the electron beam is assumed to be matched to the natural wiggler focusing in both transverse planes. With these assumptions the eigenvalue problem can be reduced to a numerically manageable integral equation and solved exactly with a kernel iteration method. An approximate, but more efficient solution of the integral equation is also obtained for the fundamental mode by a variational technique, which is shown to agree well with the exact results. Furthermore, I present a handy formula, obtained from interpolating the numerical results, for a quick calculation of FEL exponential growth rate. Comparisons with simulation code TDA will also be presented. Application of these solutions to the design and multi-dimensional parameter space optimization for an X-ray free electron laser driven by SLAC linac will be demonstrated. In addition, a rigorous analysis of transverse mode degeneracy and hence the transverse coherence of the X-ray FEL will be presented based on the exact solutions of the higher order guided modes.
High Harmonic Inverse Free-Electron-Laser Interaction at 800 NM
Sears, Chris M S; Colby, Eric R; Cowan, Benjamin; Plettner, Tomas; Siemann, Robert; Spencer, James
2005-01-01
The inverse Free Electron Laser (IFEL) interaction has recently been proposed and used as a short wavelength modulator forμbunching of beams for laser acceleration experiments*,**. These experiments utilized the fundamental of the interaction between the laser field and electron bunch. In the current experiment, we explore the higher order resonances of the IFEL interaction from a 3 period, 1.8 centimeter wavelength undulator with a picosecond, 0.25 mJ/pulse laser at 800 nm. The resonances are observed by adjusting the gap of the undulator while keeping the beam energy constant. We will also discuss diagnostics for obtaining beam overlap and statistical techniques used to account for machine drifts and analyze the data.
Electrostatics of electron-hole interactions in van der Waals heterostructures
Cavalcante, L. S. R.; Chaves, A.; Van Duppen, B.; Peeters, F. M.; Reichman, D. R.
2018-03-01
The role of dielectric screening of electron-hole interaction in van der Waals heterostructures is theoretically investigated. A comparison between models available in the literature for describing these interactions is made and the limitations of these approaches are discussed. A simple numerical solution of Poisson's equation for a stack of dielectric slabs based on a transfer matrix method is developed, enabling the calculation of the electron-hole interaction potential at very low computational cost and with reasonable accuracy. Using different potential models, direct and indirect exciton binding energies in these systems are calculated within Wannier-Mott theory, and a comparison of theoretical results with recent experiments on excitons in two-dimensional materials is discussed.
Directory of Open Access Journals (Sweden)
E. E. Woodfield
2013-10-01
Full Text Available Jupiter has the most intense radiation belts of all the outer planets. It is not yet known how electrons can be accelerated to energies of 10 MeV or more. It has been suggested that cyclotron-resonant wave-particle interactions by chorus waves could accelerate electrons to a few MeV near the orbit of Io. Here we use the chorus wave intensities observed by the Galileo spacecraft to calculate the changes in electron flux as a result of pitch angle and energy diffusion. We show that, when the bandwidth of the waves and its variation with L are taken into account, pitch angle and energy diffusion due to chorus waves is a factor of 8 larger at L-shells greater than 10 than previously shown. We have used the latitudinal wave intensity profile from Galileo data to model the time evolution of the electron flux using the British Antarctic Survey Radiation Belt (BAS model. This profile confines intense chorus waves near the magnetic equator with a peak intensity at ∼5° latitude. Electron fluxes in the BAS model increase by an order of magnitude for energies around 3 MeV. Extending our results to L = 14 shows that cyclotron-resonant interactions with chorus waves are equally important for electron acceleration beyond L = 10. These results suggest that there is significant electron acceleration by cyclotron-resonant interactions at Jupiter contributing to the creation of Jupiter's radiation belts and also increasing the range of L-shells over which this mechanism should be considered.
UROX 2.0: an interactive tool for fitting atomic models into electron-microscopy reconstructions
International Nuclear Information System (INIS)
Siebert, Xavier; Navaza, Jorge
2009-01-01
UROX is software designed for the interactive fitting of atomic models into electron-microscopy reconstructions. The main features of the software are presented, along with a few examples. Electron microscopy of a macromolecular structure can lead to three-dimensional reconstructions with resolutions that are typically in the 30–10 Å range and sometimes even beyond 10 Å. Fitting atomic models of the individual components of the macromolecular structure (e.g. those obtained by X-ray crystallography or nuclear magnetic resonance) into an electron-microscopy map allows the interpretation of the latter at near-atomic resolution, providing insight into the interactions between the components. Graphical software is presented that was designed for the interactive fitting and refinement of atomic models into electron-microscopy reconstructions. Several characteristics enable it to be applied over a wide range of cases and resolutions. Firstly, calculations are performed in reciprocal space, which results in fast algorithms. This allows the entire reconstruction (or at least a sizeable portion of it) to be used by taking into account the symmetry of the reconstruction both in the calculations and in the graphical display. Secondly, atomic models can be placed graphically in the map while the correlation between the model-based electron density and the electron-microscopy reconstruction is computed and displayed in real time. The positions and orientations of the models are refined by a least-squares minimization. Thirdly, normal-mode calculations can be used to simulate conformational changes between the atomic model of an individual component and its corresponding density within a macromolecular complex determined by electron microscopy. These features are illustrated using three practical cases with different symmetries and resolutions. The software, together with examples and user instructions, is available free of charge at http://mem.ibs.fr/UROX/
International Nuclear Information System (INIS)
McCorkle, D.L.; Christophorou, L.G.
1985-01-01
A crucial step in our efforts to develop not only a coherent picture of radiation interaction with matter, but also to understand radiation effects and mechanisms, as well as the effects of chemical pollutants and toxic compounds, is to relate the often abundant knowledge on isolated molecules (low pressure gases) to that on liquids or solids. To understand the roles of the physical and chemical properties of molecules in biological reactions, we must know how these isolated-molecule properties change as molecules are embedded in gradually thicker and thicker (denser and denser) gaseous and, finally, liquid environments. The work initiated by us both at the Physics Department of The University of Tennessee and at the Oak Ridge National Laboratory addresses itself to this question. At both places, high pressure (40 to approx.8000 kPa) electron swarm experiments are currently in operation yielding information as to the effects of the density and nature of the environment on fundamental electron-molecule interaction processes at densities intermediate to those corresponding to low pressure gases and liquids, and the gradual transition from isolated molecule to condensed phase behavior
The effect of quantum correction on plasma electron heating in ultraviolet laser interaction
Energy Technology Data Exchange (ETDEWEB)
Zare, S.; Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir; Anvari, A. [Department of Physics, Sharif University of Technology, P.O. Box 11365-9567, Tehran (Iran, Islamic Republic of); Yazdani, E. [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Hora, H. [Department of Theoretical Physics, University of New South Wales, Sydney 2052 (Australia)
2015-04-14
The interaction of the sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in the collision frequency, the electron heating and the ion block generation in plasma are studied. It is found that due to the quantum correction, the electron heating increases considerably and the electron temperature uniformly reaches up to the maximum value of 4.91 × 10{sup 7 }K. Considering the quantum correction, the electron temperature at the laser initial coupling stage is improved more than 66.55% of the amount achieved in the classical model. As a consequence, by the modified collision frequency, the ion block is accelerated quicker with higher maximum velocity in comparison with the one by the classical collision frequency. This study proves the necessity of considering a quantum mechanical correction in the collision frequency at high plasma temperatures.
New Type of Halogen Bond: Multivalent Halogen Interacting with π- and σ-Electrons
Directory of Open Access Journals (Sweden)
Sławomir J. Grabowski
2017-12-01
Full Text Available MP2/aug-cc-pVTZ calculations were performed for complexes of BrF3 and BrF5 acting as Lewis acids through the bromine centre, with species playing a role of Lewis base: dihydrogen, acetylene, ethylene, and benzene. The molecular hydrogen donates electrons by its σ-bond, while in remaining moieties—in complexes of hydrocarbons; such an electron transfer follows from π-electrons. The complexes are linked by a kind of the halogen bond that is analyzed for the first time in this study, i.e., it is the link between the multivalent halogen and π or σ-electrons. The nature of such a halogen bond is discussed, as well as various dependencies and correlations are presented. Different approaches are applied here, the Quantum Theory of Atoms in Molecules, Natural Bond Orbital method, the decomposition of the energy of interaction, the analysis of electrostatic potentials, etc.
Thermal coupling in low fields between the nuclear and electronic spins in Tm2+ doped CaF2
International Nuclear Information System (INIS)
Urbina, Cristian.
1977-01-01
It is shown that in a CaF 2 crystal doped with divalent thulium ions there is in low fields, a thermal coupling between the electron magnetic moments of Tm 2+ and the nuclear moments of 19 F. When these ones have been lowered down to temperature through dynamical high-field polarization and adiabatic demagnetization in succession the resulting polarisation of the formed ones can overstep their original polarization in high field. A trial is given to explain this Zeeman electronic energy cooling through nuclear Zeeman energy with invoking a thermal coupling between both systems through the spin-spin electronic interaction but no theoretical model is developed in view of a quantitative explanation of the dynamics of such a process. The magnetic resonance spectrum of Tm 2 + in low field is also investigated: an important shift and narrowing of the electron resonance line in low field are obtained when 19 F nuclei are very cold. This special spectral characters are explained as due to magnetic interactions between electronic impurities and the neighbouring 19 F nuclei and a theoretical model is developed (based on the local Weiss field approximation) which explains rather well the changes in the spectral shift as a function of the 19 F nucleus temperature. A second theoretical model has also been developed in view of a quantitative explanation of both the narrowing and shift of the spectrum, but its prediction disagree with the experimental results. It is shown that in low fieldsx it is possible to get rid of paramagnetic impurities after they have been reused as reducing agents for 19 F nucleus entropy populating at about 80%, a non magnetic metastable state with these impurities [fr
Quantum ballistic transport by interacting two-electron states in quasi-one-dimensional channels
Energy Technology Data Exchange (ETDEWEB)
Huang, Danhong [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117 (United States); Center for High Technology Materials, University of New Mexico, 1313 Goddard St SE, Albuquerque, New Mexico 87106 (United States); Gumbs, Godfrey [Center for High Technology Materials, University of New Mexico, 1313 Goddard St SE, Albuquerque, New Mexico 87106 (United States); Abranyos, Yonatan [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States); Pepper, Michael; Kumar, Sanjeev [Department of Electronic and Electrical Engineering, University College London, London, WC1E 7JE (United Kingdom); London Centre for Nanotechnology, 17-19 Gordon Street, London, WC1H 0AH (United Kingdom)
2015-11-15
For quantum ballistic transport of electrons through a short conduction channel, the role of Coulomb interaction may significantly modify the energy levels of two-electron states at low temperatures as the channel becomes wide. In this regime, the Coulomb effect on the two-electron states is calculated and found to lead to four split energy levels, including two anticrossing-level and two crossing-level states. Moreover, due to the interplay of anticrossing and crossing effects, our calculations reveal that the ground two-electron state will switch from one anticrossing state (strong confinement) to a crossing state (intermediate confinement) as the channel width gradually increases and then back to the original anticrossing state (weak confinement) as the channel width becomes larger than a threshold value. This switching behavior leaves a footprint in the ballistic conductance as well as in the diffusion thermoelectric power of electrons. Such a switching is related to the triple spin degeneracy as well as to the Coulomb repulsion in the central region of the channel, which separates two electrons away and pushes them to different channel edges. The conductance reoccurrence region expands from the weak to the intermediate confinement regime with increasing electron density.
Energy Technology Data Exchange (ETDEWEB)
Ramakrishnan, Raghunathan, E-mail: r.ramakrishnan@unibas.ch [Institute of Physical Chemistry, National Center for Computational Design and Discovery of Novel Materials (MARVEL), Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland); Nest, Mathias [Theoretische Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany)
2015-01-13
Highlights: • We model electron dynamics across cyano alkanethiolates attached to gold cluster. • We present electron transfer time scales from TD-DFT and TD-CI based simulations. • Both DFT and CI methods qualitatively predict the trend in time scales. • TD-CI predicts the experimental relative time scale very accurately. - Abstract: We employ wavepacket simulations based on many-body time-dependent configuration interaction (TD-CI), and single active electron theories, to predict the ultrafast molecule/metal electron transfer time scales, in cyano alkanethiolates bonded to model gold clusters. The initial states represent two excited states where a valence electron is promoted to one of the two virtual π{sup ∗} molecular orbitals localized on the cyanide fragment. The ratio of the two time scales indicate the efficiency of one charge transfer channel over the other. In both our one-and many-electron simulations, this ratio agree qualitatively with each other as well as with the previously reported experimental time scales (Blobner et al., 2012), measured for a macroscopic metal surface. We study the effect of cluster size and the description of electron correlation on the charge transfer process.
Electron Fluid Description of Wave-Particle Interactions in Strong Buneman Turbulence
Che, Haihong
2013-10-01
To understand the nature of anomalous resistivity in magnetic reconnection, we investigate turbulence-induced momentum transport and energy dissipation associated with electron heating in Buneman instability. Using 3D particle-in-cell simulations, we find that the macroscopic effects generated by wave-particle interactions can be described by a set of electron fluid equations. These equations show that the energy dissipation and momentum transports in Buneman instability are locally quasi-static but globally non-static and irreversible. Turbulence drag dissipates both the bulk energy of electron streams and the associated magnetic energy. The decrease of magnetic field maintains an inductive electric field that re-accelerates electrons. The net loss of streaming energy is converted into electron heat and increases the electron Boltzmann entropy. The growth of self-sustained Buneman waves satisfies a Bernoulli-like equation which relates the turbulence-induced convective momentum transport and thermal momentum transport. Electron trapping and de-trapping drives local momentum transports, while phase mixing converts convective momentum into thermal momentum.These two local momentum transports sustain the Buneman waves and act as the micro-macro link in the anomalous heating process. This research is supported by the NASA Postdoctoral Program at NASA/GSFC administered by Oak Ridge Associated Universities through a contract with NASA.
Ferri, Nicola; Ambrosetti, Alberto; Tkatchenko, Alexandre
2017-07-01
Electronic charge rearrangements at interfaces between organic molecules and solid surfaces play a key role in a wide range of applications in catalysis, light-emitting diodes, single-molecule junctions, molecular sensors and switches, and photovoltaics. It is common to utilize electrostatics and Pauli pushback to control the interface electronic properties, while the ubiquitous van der Waals (vdW) interactions are often considered to have a negligible direct contribution (beyond the obvious structural relaxation). Here, we apply a fully self-consistent Tkatchenko-Scheffler vdW density functional to demonstrate that the weak vdW interactions can induce sizable charge rearrangements at hybrid metal/organic systems (HMOS). The complex vdW correlation potential smears out the interfacial electronic density, thereby reducing the charge transfer in HMOS, changes the interface work functions by up to 0.2 eV, and increases the interface dipole moment by up to 0.3 Debye. Our results suggest that vdW interactions should be considered as an additional control parameter in the design of hybrid interfaces with the desired electronic properties.
International Nuclear Information System (INIS)
Rechatin, C.
2009-09-01
In any particle accelerator, the injector plays a crucial role since it determines most of the characteristics of the accelerated beam. This is also true for laser-plasma accelerators, that are based on the interaction of an ultra short, ultra intense laser with an underdense plasma. However, due to the compactness of these accelerators, injection is a real challenge: to obtain a good beam quality, injected electron beams have to be ultra short and precisely synchronized with the laser. In this manuscript, the relevance of an optical injector, that relies on a second laser pulse, is experimentally demonstrated. With this injector, mono energetic electron beams have been produced in a stable manner. Moreover, this injector gives control over the electron beam parameters. Using the parameters of the second laser pulse, it has been proven that the energy, the charge and the energy spread of the accelerated beam can be simply tuned. Those additional controls make it possible to study in great details the physical phenomena at play during the acceleration. Beam loading effects, due to the interaction of the accelerated bunch with the plasma, have been identified and studied. With optimized injector parameters, the narrowest electron beams measured to date in the laser plasma interaction have been obtained, with a relative energy spread of 1%. (author)
A study of the interactions of high energy electron-neutrinos
International Nuclear Information System (INIS)
Nieuwenhuis, C.H.M.
1986-01-01
This thesis describes an analysis of electron-neutrino and anti-neutrino interactions with nuclei. The data were collected with the calorimeter of the Amsterdam-CERN-Hamburg-Moscow-Rome (CHARM) group in a beam dump exposure to 400 GeV/c protons from the CERN SPS in 1982. The predictions of the Standard Model for the quantities measured in this experiment are given. The results of the analysis of events without a primary muon in the final state are given in the form of an experimental y-distribution. The measured quantities are compared with the predictions of the theory and the measurements of other experiments. Presented are the cross-section ratio of neutral current and charged current electron-neutrino induced events, the prompt CC ν(anti ν) e interaction rate, the prompt (ν e +anti ν e )/(ν μ +anti ν μ ) flux ratio, the energy dependence of the prompt electron-neutrino flux and a measurement of the DantiD cross-section times semileptonic branching ratio based on prompt electron-neutrino interactions. (Auth.)
Directory of Open Access Journals (Sweden)
Yuichi Otsuka
2016-03-01
Full Text Available The metal-insulator transition has been a subject of intense research since Mott first proposed that the metallic behavior of interacting electrons could turn to an insulating one as electron correlations increase. Here, we consider electrons with massless Dirac-like dispersion in two spatial dimensions, described by the Hubbard models on two geometrically different lattices, and perform numerically exact calculations on unprecedentedly large systems that, combined with a careful finite-size scaling analysis, allow us to explore the quantum critical behavior in the vicinity of the interaction-driven metal-insulator transition. Thereby, we find that the transition is continuous, and we determine the quantum criticality for the corresponding universality class, which is described in the continuous limit by the Gross-Neveu model, a model extensively studied in quantum field theory. Furthermore, we discuss a fluctuation-driven scenario for the metal-insulator transition in the interacting Dirac electrons: The metal-insulator transition is triggered only by the vanishing of the quasiparticle weight, not by the Dirac Fermi velocity, which instead remains finite near the transition. This important feature cannot be captured by a simple mean-field or Gutzwiller-type approximate picture but is rather consistent with the low-energy behavior of the Gross-Neveu model.
Pishtshev, A.; Kristoffel, N.
2017-05-01
We outline our novel results relating to the physics of the electron-TO-phonon (el-TO-ph) interaction in a polar crystal. We explained why the el-TO-ph interaction becomes effectively strong in a ferroelectric, and showed how the electron density redistribution establishes favorable conditions for soft-behavior of the long-wavelength branch of the active TO vibration. In the context of the vibronic theory it has been demonstrated that at the macroscopic level the interaction of electrons with the polar zone-centre TO phonons can be associated with the internal long-range dipole forces. Also we elucidated a methodological issue of how local field effects are incorporated within the vibronic theory. These result provided not only substantial support for the vibronic mechanism of ferroelectricity but also presented direct evidence of equivalence between vibronic and the other lattice dynamics models. The corresponding comparison allowed us to introduce the original parametrization for constants of the vibronic interaction in terms of key material constants. The applicability of the suggested formula has been tested for a wide class of polar materials.
Theoretical modeling of the electronic structure and exchange interactions in Cu(II)Pc
Wu, Wei; Fisher, A. J.; Harrison, N. M.; Wang, Hai; Wu, Zhenlin; Gardener, Jules; Heutz, Sandrine; Jones, Tim; Aeppli, Gabriel
2012-12-01
We calculate the electronic structure and exchange interactions in a copper(II)phthalocyanine (Cu(II)Pc) crystal as a one-dimensional molecular chain using hybrid exchange density functional theory (DFT). In addition, the intermolecular exchange interactions are also calculated in a molecular dimer using Green's function perturbation theory (GFPT) to illustrate the underlying physics. We find that the exchange interactions depend strongly on the stacking angle, but weakly on the sliding angle (defined in the text). The hybrid DFT calculations also provide an insight into the electronic structure of the Cu(II)Pc molecular chain and demonstrate that on-site electron correlations have a significant effect on the nature of the ground state, the band gap and magnetic excitations. The exchange interactions predicted by our DFT calculations and GFPT calculations agree qualitatively with the recent experimental results on newly found η-Cu(II)Pc and the previous results for the α- and β-phases. This work provides a reliable theoretical basis for the further application of Cu(II)Pc to molecular spintronics and organic-based quantum information processing.
Electronic structure and exchange interactions in GdB{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Baranovskiy, A., E-mail: andriy.baranovskiy@gmail.com; Grechnev, A.
2015-02-01
The electronic structure of the antiferromagnetic Shastry–Sutherland compound GdB{sub 4} has been analyzed with density functional theory and the all-electron full-potential linearized augmented-plane wave (FP-LAPW) code. Different magnetic configurations, including the realistic dimer one, have been considered. The exchange interactions were found to be J{sub 1}/k{sub B}=−12K and J{sub 2}/k{sub B}=−2–0.8K, where, J{sub 1} and J{sub 2} are the diagonal exchange interaction and the exchange interaction along the edges of a square, respectively. - Highlights: • Electronic structure of AFM Shastry–Sutherland compound GB{sub 4} is calculated. • The mechanism of exchange parameters evaluation within Heisenberg model is proposed. • Calculated exchange parameters are found to be in agreement with experimental data. • Higher-order exchange interactions are important for dimer structure stabilizing.
Interaction of an electron with coherent dipole radiation: Role of convergence and anti-dephasing
Robinson, A. P. L.; Arefiev, A. V.
2018-05-01
The impact of longitudinal electric fields that are present in intense focusing and defocusing electromagnetic pulses on electron acceleration is investigated. These fields are typically much weaker than the transverse fields, but it is shown that they can have a profound effect on electron energy gain. It is shown that the longitudinal electric field of a defocusing pulse is directed backward along the trajectory of an accelerated electron, which leads to a continuous net energy gain. At the same time, the effect of the transverse oscillating electric field in a defocusing pulse is to reduce the electron energy over multiple oscillations. In contrast to a well-known interaction with a plane wave, the electron is able to retain a substantial amount of energy following its interaction with a defocusing pulse. The roles of the transverse and longitudinal electric fields are reversed in a focusing pulse, which leads to a reduction in the energy retention. The present analysis underscores the importance of relatively weak oscillating electric fields in focusing and defocusing pulses.
International Nuclear Information System (INIS)
Dey, G. K.
2011-01-01
Transmission Electron Microscopy (TEM), because of its ability to image atomic arrangements directly and its ability to give spectroscopic information at similar resolution has emerged as a very powerful tool for understanding the structure of materials at atomic level. TEM has been particularly useful in resolving the interface structures in materials. This form of microscopy is very suitable for resolving the structure and defects in ultrafine microstructures such as those of the nanocrystalline phases. After a brief description of the different characterization abilities of the aberration corrected transmission electron microscope, this presentation describes the results of TEM investigations on nanocrystalline microstructures generated by laser materials interaction and due to interaction of electrons and ions with materials. Excimer laser has become an attractive choice for new and precision application for ablation and deposition in recent times. In this work, a KrF excimer laser having 30 ns pulse width and 600 mJ energy at source has been used to deposit zirconia on Zr-base alloy in order to explore the ability of the thin oxide film to act as a diffusion barrier to hydrogen ingress into the alloy. It has been found that the variation in pressure by an order of three has resulted in maximum influence on the roughness of the laser deposited oxide film that has not been possible to achieve by other parameters within the range of the instrument. Present study has also indicated an interrelation among the roughness, adherence and the film-thickness, where the last one is indicated by the XPS study. Transmission electron microscopy was carried out to study the size, size distribution and defects in the deposited film. Nanocrystalline phases generated by interaction of electron and ion irradiation of Zr based alloys; Ni based alloys and Fe based alloys have been examined in detail by conventional and high resolution transmission electron microscopy. Results of
Numerical study on the interaction between a modulated electron beam and a plasma
International Nuclear Information System (INIS)
Fukumasa, Osamu; Itatani, Ryohei.
1981-09-01
Interaction of a modulated electron beam with a plasma is calculated for unbounded and bounded electron beam-plasma systems, using the method of partial simulation. In the case of the unbounded system, deformation of the beam distribution function is occurred in relation to suppression of one wave by the other wave. While, in the case of the bounded system, occurrence of deformation depends on whether feedback effects of reflected beams are present or not. The findings are qualitatively in agreement with our experimental results [19]. (author)
International Nuclear Information System (INIS)
Lazaros, Avrilios
2000-01-01
The interaction of ECRH with the m/n=2/1 tearing mode, which was observed in toroidal plasmas, is attributed to the superthermal electrons which are produced on the EC resonance by the ECRH. Superthermal electrons diffusing across the q=2 surface, exchange power with the m/n=2/1 MHD mode which is either suppressed or enhanced. When the EC resonance is outside the rational surface, the mode is always suppressed. When the EC resonance is inside the rational surface, modes with large amplitude are enhanced while modes with small amplitude are suppressed. (author)
DEVELOPMENT OF SHORT UNDULATORS FOR ELECTRON-BEAM-RADIATION INTERACTION STUDIES
Energy Technology Data Exchange (ETDEWEB)
Piot, P. [NICADD, DeKalb; Andorf, M. B. [NICADD, DeKalb; Fagerberg, G. [Northern Illinois U.; Figora, M. [Northern Illinois U.; Sturtz, A. [Northern Illinois U.
2016-10-19
Interaction of an electron beam with external field or its own radiation has widespread applications ranging from coherent-radiation generation, phase space cooling or formation of temporally-structured beams. An efficient coupling mechanism between an electron beam and radiation field relies on the use of a magnetic undulator. In this contribution we detail our plans to build short (11-period) undulators with 7-cm period refurbishing parts of the aladdin U3 undulator [1]. Possible use of these undulators at available test facilities to support experiments relevant to cooling techniques and radiation sources are outlined.
Calculation of helium-like ion dipole susceptibility with account for electron interaction
International Nuclear Information System (INIS)
Pal'chikov, V.G.; Tkachev, A.N.
1989-01-01
Numerical estimations of electron interaction effects are carried out for helium-like ions inserted in a homogeneous electric field. Statistical dipole polarizations and hyperpolarizations are calculated for the main state taking into account corrections of the first order to approximation of noninteracting electrons. Summation according to the full spectrum of intermediate states is carried out by the method of Coulomb-Green functions (CGF), that permitted to use analytical methods to calculate matrix elements of correlation diagrams. When calculating polarizations, relativistic corrections ∼(αZ) 2 , where α - the constant of a fine structure, Z-nucleus charge, are taken into account
Chirped Auger electron emission due to field-assisted post-collision interaction
Directory of Open Access Journals (Sweden)
Bonitz M.
2013-03-01
Full Text Available We have investigated the Auger decay in the temporal domain by applying a terahertz streaking light field. Xenon and krypton atoms were studied by implementing the free-electron laser in Hamburg (FLASH as well as a source of high-order harmonic radiation combined with terahertz pulses from an optical rectification source. The observed linewidth asymmetries in the streaked spectra suggest a chirped Auger electron emission which is understood in terms of field-assisted post-collision interaction. The experimentally obtained results agree well with model calculations.
Electron, ion and atomic beams interaction with solid high-molecular dielectrics
Energy Technology Data Exchange (ETDEWEB)
Milyavskij, V V; Skvortsov, V A [Russian Academy of Sciences, Moscow (Russian Federation). High Energy Density Research Center
1997-12-31
A mathematical model was constructed and numerical investigation performed of the interaction between intense electron, ion and atomic beams and solid high-molecular dielectrics under various boundary conditions. The model is based on equations of the mechanics of continuum, electrodynamics and kinetics, describing the accumulation and relaxation of space charge and shock-wave processes, as well as the evolution of electric field in the sample. A semi-empirical procedure is proposed for the calculation of energy deposition by electron beam in a target in the presence of a non-uniform electric field. (author). 4 figs., 2 refs.
Higher-order resonant electronic recombination as a manifestation of configuration interaction
International Nuclear Information System (INIS)
Beilmann, C; Amaro, P; Tashenov, S; Bekker, H; Harman, Z; Crespo López-Urrutia, J R
2013-01-01
Theoretical and experimental investigations of higher-order electron–ion recombination resonances including inter-shell excitations are presented for L-shell ions of Kr with the aim of examining details of atomic structure calculations. The particular importance of electron–electron interaction and configuration mixing effects for these recombination processes enables their use for detailed tests of electron correlation effects. A test of the required level of considered mixing configurations is presented and further experiments involving higher-order recombination channels are motivated. (paper)
Extreme field limits in the interaction of laser light with ultrarelativistic electrons
Energy Technology Data Exchange (ETDEWEB)
Bulanov, S. V.; Esirkepov, T. Zh.; Hayashi, Y.; Kando, M.; Kiriyama, H.; Koga, J.; Kondo, K.; Kotaki, H.; Pirozhkov, A.; Bulanov, S. S.; Zhidkov, A.; Chen, P.; Neely, D.; Kato, Y.; Narozhny, N. B.; Korn, G. [Kansai Photon Science Institute, JAEA, Kizugawa, Kyoto 619-0215 (Japan); University of California, Berkeley, CA 94720 (United States); Osaka University, Osaka 565-0871 (Japan); National Taiwan University, Taipei 10617, Taiwan (China); Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom); Graduate School for the Creation of New Photonics Industries, Hamamatsu, Shizuoka 431-1202 (Japan); Moscow Engineering Physics Institute (State University), Moscow 115409 (Russian Federation); Max-Planck-Institut fuer Quantenoptik, Garching 85748 (Germany) and ELI Beamline Facility, Institute of Physics, CAS, Prague 18221 (Czech Republic)
2012-07-11
The critical electric field of quantum electrodynamics is so strong that it produces electron-positron pairs from vacuum, converting the energy of light into matter. This field has become feasible through the construction of extremely high power lasers or/and with the sophisticated use of nonlinear processes in relativistic plasmas. A feasibility of the experiments on the collision of laser light and high intensity electromagnetic pulses, generated by relativistic flying mirrors, with relativistic electrons for the studying of extreme field limits in the nonlinear interaction of electromagnetic waves is discussed.
Beam-beam interaction in high energy linear electron-positron colliders
International Nuclear Information System (INIS)
Ritter, S.
1985-04-01
The interaction of high energy electron and positron beams in a linear collider has been investigated using a macroparticle Monte Carlo method based on a Cloud-In-Cells plasma simulation scheme. Density evolutions, luminosities, energy and angular distributions for electrons (positrons) and synchrotron photons are calculated. Beside beams with a symmetric transverse profile also flat beams are considered. A reasonably good agreement to alternative computer calculations as well as to an analytical approximation for the energy spectrum of synchrotron photons has been obtained. (author)
Sun, Qi-C.; Ding, Yuchen; Goodman, Samuel M.; H. Funke, Hans; Nagpal, Prashant
2014-10-01
Copper metal can provide an important alternative for the development of efficient, low-cost and low-loss plasmonic nanoparticles, and selective nanocatalysts. However, poor chemical stability and lack of insight into photophysics and plasmon decay mechanisms has impeded study. Here, we use smooth conformal ALD coating on copper nanoparticles to prevent surface oxidation, and study dephasing time for localized surface plasmons on different sized copper nanoparticles. Using dephasing time as a figure of merit, we elucidate the role of electron-electron, electron-phonon, impurity, surface and grain boundary scattering on the decay of localized surface plasmon waves. Using our quantitative analysis and different temperature dependent measurements, we show that electron-phonon interactions dominate over other scattering mechanisms in dephasing plasmon waves. While interband transitions in copper metal contributes substantially to plasmon losses, tuning surface plasmon modes to infrared frequencies leads to a five-fold enhancement in the quality factor. These findings demonstrate that conformal ALD coatings can improve the chemical stability for copper nanoparticles, even at high temperatures (>300 °C) in ambient atmosphere, and nanoscaled copper is a good alternative material for many potential applications in nanophotonics, plasmonics, catalysis and nanoscale electronics.Copper metal can provide an important alternative for the development of efficient, low-cost and low-loss plasmonic nanoparticles, and selective nanocatalysts. However, poor chemical stability and lack of insight into photophysics and plasmon decay mechanisms has impeded study. Here, we use smooth conformal ALD coating on copper nanoparticles to prevent surface oxidation, and study dephasing time for localized surface plasmons on different sized copper nanoparticles. Using dephasing time as a figure of merit, we elucidate the role of electron-electron, electron-phonon, impurity, surface and grain
2010 Electron Donor-Acceptor Interactions Gordon Research Conference, August 8 - 13, 2010.
Energy Technology Data Exchange (ETDEWEB)
Gerald Meyer
2010-08-18
The Gordon Research Conference on Electron Donor Acceptor Interactions (GRC EDAI) presents and advances the current frontiers in experimental and theoretical studies of Electron Transfer Processes and Energy Conversion. The fundamental concepts underpinning the field of electron transfer and charge transport phenomena are understood, but fascinating experimental discoveries and novel applications based on charge transfer processes are expanding the discipline. Simultaneously, global challenges for development of viable and economical alternative energy resources, on which many researchers in the field focus their efforts, are now the subject of daily news headlines. Enduring themes of this conference relate to photosynthesis, both natural and artificial, and solar energy conversion. More recent developments include molecular electronics, optical switches, and nanoscale charge transport structures of both natural (biological) and man-made origin. The GRC EDAI is one of the major international meetings advancing this field, and is one of the few scientific meetings where fundamental research in solar energy conversion has a leading voice. The program includes sessions on coupled electron transfers, molecular solar energy conversion, biological and biomimetic systems, spin effects, ultrafast reactions and technical frontiers as well as electron transport in single molecules and devices. In addition to disseminating the latest advances in the field of electron transfer processes, the conference is an excellent forum for scientists from different disciplines to meet and initiate new directions; for scientists from different countries to make contacts; for young scientists to network and establish personal contacts with other young scientists and with established scientists who, otherwise, might not have the time to meet young people. The EDAI GRC also features an interactive atmosphere with lively poster sessions, a few of which are selected for oral presentations.
Neutron production in the interaction of electrons with a dispersing lamella
International Nuclear Information System (INIS)
Soto B, T. G.; Baltazar R, A.; Medina C, D.; Vega C, H. R.
2017-10-01
When a Linac for radiotherapy operates with acceleration voltages greater than 8 MV, neutrons are produced as secondary radiation. They deposit an undesirable and not negligible dose in the patient. Depending on the type of tumor, its location in the body and the characteristics of the patient, cancer treatment with a Linac is done with photon or electron beams, which produce neutrons through reactions (γ, n) and e, e n) respectively. Because the effective section of the reaction (n, γ) is 137 times greater than the reaction (e, e n), most studies have focused on photo neutrons. When a Linac operates with electron beams, the beam that leaves the magnetic baffle is incised in the dispersion foil in order to cause quasi-elastic interactions and expand the spatial distribution of the electrons; in their interaction with the lamella the electrons produce photons and these in turn produce neutrons. Due to the radiobiological efficiency of neutrons and the ways in which they interact with matter, is important to determine the neutrons production in Linacs operating in electron mode. The objective of this work is to determine the characteristics of photons and neutrons that occur when a beam of mono-energetic electrons of 2 mm in diameter (pencil beam) is made to impinge on a tungsten lamella of 1 cm in diameter and 0.5 mm thick located in the center of a 10 cm thick tungsten shell, used to represent the accelerator head. The study was carried out using the Monte Carlo method with the MCNP6 code for electron beams of 12 and 18 MeV. The spectra of photons and neutrons were estimated in 6 point detectors, four were placed in different points equidistant from the center of the lamella and the other two were located at 50 cm and 1 m from the electron beam, simulating the totally closed head. In this work it was found that when a Linac operates with an electron beam of 12 or 18 MeV there is neutron production mainly in the head and in the direction of the beam. (Author)
He, Lin; Liu, Fei-Fei; Zhao, Mengyao; Qi, Zhen; Sun, Xuefei; Afzal, Muhammad Zaheer; Sun, Xiaomin; Li, Yanhui; Hao, Jingcheng; Wang, Shuguang
2018-04-01
Understanding the interactions between graphene nanomaterials (GNMs) and antibiotics in aqueous solution is critical to both the engineering applications of GNMs and the assessment of their potential impact on the fate and transport of antibiotics in the aquatic environment. In this study, adsorption of one common antibiotic, tetracycline, by graphene oxide (GO) and reduced graphene oxide (RGO) was examined with multi-walled carbon nanotubes (MWCNTs) and graphite as comparison. The results showed that the tetracycline adsorption capacity by the four selected carbonaceous materials on the unit mass basis followed an order of GO>RGO>MWCNTs>graphite. Upon normalization by surface area, graphite, RGO and MWCNTs had almost the same high tetracycline adsorption affinity while GO exhibited the lowest. We proposed π-electron-property dependent interaction mechanisms to explain the observed different adsorption behaviors. Density functional theory (DFT) calculations suggested that the oxygen-containing functional groups on GO surface reduced its π-electron-donating ability, and thus decreased the π-based interactions between tetracycline and GO surface. Comparison of adsorption efficiency at different pH indicated that electrostatic interaction also played an important role in tetracycline-GO interactions. Site energy analysis confirmed a highly heterogeneous distribution of the binding sites and strong tetracycline binding affinity of GO surface. Copyright © 2017. Published by Elsevier B.V.
Electron and pion interactions with nuclei. Progress report and research plans
International Nuclear Information System (INIS)
McCarthy, J.S.
1982-08-01
A series of electron scattering experiments is proposed for a quantitative investigation of the structure and dynamics of nuclei. The information developed from the electromagnetic interaction will be used as complement to a series of experiments at LAMPF in which a systematic investigation of the reaction dynamics of pion-nucleus interactions is carried out. Pion induced reactions can supply information on inelastic channels of the nucleon-nucleon interaction which are not as readily available to an electromagnetic probe. Pion absorption experiments designed to measure the off-shell behavior are complemented with a program on pion elastic and inelastic scattering to pursue the on-shell aspect of the π + N interaction. The single (SCE) and double charge exchange (DCE) reactions are unique aspects of π interactions in nuclei. The complementarity of information from different reactions is emphasized in our studies of (e,e'), (p,p'), (π,p) and (p,d) reactions at large momentum transfers (Q greater than or equal to 0.5 GeV/c). Along with the search for the reaction dynamics, the question of new nuclear structure is pursued. We now plan to start a series of experiments that will detect hadrons in the final state along with the scattered electrons. The present success of quantum chromodynamics (QCD) gives increased impetus to pursue experiments that can result in a synthesis of nuclear structure within the framework of the elementary quark; carrying the charge and weak currents within hadrons
International Nuclear Information System (INIS)
Key, M.H.; Campbell, E.M.; Cowan, T.E.; Hatchett, S.P.; Henry, E.A.; Koch, J.A.; Landgon, A.B.; Lasinski, B.F.; Lee, R.W.; MacKinnon, A.; Offenberger, A.; Pennington, D.M.; Perry, M.D.; Sangster, T.C.; Yasuike, K.; Snavely, R.; Roth, M.; Phillips, T.W.; Stoyer, M.A.; Wilks, S.C.; Singh, M.S.
1999-01-01
The interaction of laser radiation with solid targets at 1 petawatt power and intensity up to 3x10 20 Wcm -2 has been studied with emphasis on relativistic electrons and high energy ions. Secondary effects including Bremsstrahlung radiation, nuclear interactions and heating have been characterized. A collimated beam of protons with up to 55 MeV energy is emitted normal to the rear surface of thin targets and its characteristics and origin are discussed. The significance of the data for radiography, fast ignition and proton beam applications is summarized
International Nuclear Information System (INIS)
Kato, Susumu; Takahashi, Eiichi; Miura, Eisuke; Owadano, Yoshiro; Nakamura, Tatsufumi; Kato, Tomokazu
2002-01-01
The scaling of hot electron temperature and the spectrum of electron energy by intense laser plasma interactions are reexamined from a viewpoint of the difference in laser wavelength. Laser plasma interaction such as parametric instabilities is usually determined by the Iλ2 scaling, where I and λ is the laser intensity and wavelength, respectively. However, the hot electron temperature is proportional to (ncr/ne0)1/2 [(1 + a 0 2 ) 1/2 - 1] rather than [(1 + a 0 2 ) 1/2 - 1] at the interaction with overdense plasmas, where ne0 is a electron density of overdense plasmas and a0 is a normalized laser intensity
Energy Technology Data Exchange (ETDEWEB)
Limpens, Rens [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Neale, Nathan R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Fujii, Minoru [Kobe University; Gregorkiewicz, Tom [University of Amsterdam
2018-03-05
Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron-hole (e-h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P-B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction of the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e-h pairs. This is understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).
Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability
Directory of Open Access Journals (Sweden)
C. Krafft
Full Text Available Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field, the fan instability can excite VLF waves (whistlers and lower hybrid waves with characteristics close to those observed in space experiments.
Key words. Space plasma physics (waves and instabilities – Radio Science (waves in plasma – Solar physics, astrophysics and astronomy (radio emissions
Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability
Directory of Open Access Journals (Sweden)
C. Krafft
2003-07-01
Full Text Available Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field, the fan instability can excite VLF waves (whistlers and lower hybrid waves with characteristics close to those observed in space experiments.Key words. Space plasma physics (waves and instabilities – Radio Science (waves in plasma – Solar physics, astrophysics and astronomy (radio emissions
International Nuclear Information System (INIS)
Cooper, B.R.
1997-01-01
The issue addressed in the research was how to understand what controls the competition between two types of phase transition (ordering) which may be present in a hybridizing correlated-electron system containing two transition-shell atomic species; and how the variation of behavior observed can be used to understand the mechanisms giving the observed ordered state. This is significant for understanding mechanisms of high-temperature superconductivity and other states of highly correlated electron systems. Thus the research pertains to magnetic effects as related to interactions giving high temperature superconductivity; where the working hypothesis is that the essential feature governing the magnetic and superconducting behavior of copper-oxide-type systems is a cooperative valence fluctuation mechanism involving the copper ions, as mediated through hybridization effects dominated by the oxygen p electrons. (Substitution of praseodymium at the rare earth sites in the 1·2·3 material provides an interesting illustration of this mechanism since experimentally such substitution strongly suppresses and destroys the superconductivity; and, at 100% Pr, gives Pr f-electron magnetic ordering at a temperature above 16K). The research was theoretical and computational and involved use of techniques aimed at correlated-electron systems that can be described within the confines of model hamiltonians such as the Anderson lattice hamiltonian. Specific techniques used included slave boson methodology used to treat modification of electronic structure and the Mori projection operator (memory function) method used to treat magnetic response (dynamic susceptibility)
Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam
Energy Technology Data Exchange (ETDEWEB)
Othman, Mohamed A. K.; Veysi, Mehdi; Capolino, Filippo [Department of Electrical Engineering and Computer Science, University of California, Irvine, California 92697 (United States); Figotin, Alexander [Department of Mathematics, University of California, Irvine, California 92697 (United States)
2016-03-15
We propose a new amplification regime based on a synchronous operation of four degenerate electromagnetic (EM) modes in a slow-wave structure and the electron beam, referred to as super synchronization. These four EM modes arise in a Fabry-Pérot cavity when degenerate band edge (DBE) condition is satisfied. The modes interact constructively with the electron beam resulting in superior amplification. In particular, much larger gains are achieved for smaller beam currents compared to conventional structures based on synchronization with only a single EM mode. We demonstrate giant gain scaling with respect to the length of the slow-wave structure compared to conventional Pierce type single mode traveling wave tube amplifiers. We construct a coupled transmission line model for a loaded waveguide slow-wave structure exhibiting a DBE, and investigate the phenomenon of giant gain via super synchronization using the Pierce model generalized to multimode interaction.
Strong electron-phonon interaction in the high-Tc superconductors: Evidence from the infrared
International Nuclear Information System (INIS)
Timusk, T.; Porter, C.D.; Tanner, D.B.
1991-01-01
We show that low-frequency structure in the infrared reflectance of the high-temperature superconductor YBa 2 Cu 3 O 7 results from the electron-phonon interaction. Characteristic antiresonant line shapes are seen in the phonon region of the spectrum and the frequency-dependent scattering rate of the mid-infrared electronic continuum has peaks at 150 cm -1 (19 meV) and at 360 cm -1 (45 meV) in good agreement with phonon density-of-states peaks in neutron time-of-flight spectra that develop in superconducting samples. The interaction between the phonons and the charge carriers can be understood in terms of a charged-phonon model
Energy Technology Data Exchange (ETDEWEB)
Lewera, Adam; Miecznikowski, Krzysztof [Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland); Hunger, Ralf [Institute of Materials Science, Darmstadt University of Technology, Darmstadt (Germany); Kolary-Zurowska, Aneta [Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland); Wieckowski, Andrzej [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Kulesza, Pawel J., E-mail: pkulesza@chem.uw.edu.p [Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland)
2010-11-01
Se/Ru nanoparticles - a potent non-platinum catalyst towards oxygen reduction reaction - were modified by hydrated WO{sub 3} and investigated using the rotating disk/ring electrode methods and by synchrotron X-ray photoelectron spectroscopy. The modification resulted in an enhanced catalytic activity towards oxygen reduction reaction (ORR). Our data indicate that the oxygen reduction current starts ca. 70 mV more positive and formation of undesirable hydrogen peroxide has significantly decreased following the modification of Se/Ru with WO{sub 3}. X-ray photoelectron spectroscopy reveals that WO{sub 3} interacts electronically with Se/Ru as the W 4f and Se 3d line-shapes change. We therefore conclude that the electronic interactions between Se/Ru and WO{sub 3} are primarily responsible for the increase in activity and selectivity of the WO{sub 3}-modified Se/Ru towards ORR.
International Nuclear Information System (INIS)
Lewera, Adam; Miecznikowski, Krzysztof; Hunger, Ralf; Kolary-Zurowska, Aneta; Wieckowski, Andrzej; Kulesza, Pawel J.
2010-01-01
Se/Ru nanoparticles - a potent non-platinum catalyst towards oxygen reduction reaction - were modified by hydrated WO 3 and investigated using the rotating disk/ring electrode methods and by synchrotron X-ray photoelectron spectroscopy. The modification resulted in an enhanced catalytic activity towards oxygen reduction reaction (ORR). Our data indicate that the oxygen reduction current starts ca. 70 mV more positive and formation of undesirable hydrogen peroxide has significantly decreased following the modification of Se/Ru with WO 3 . X-ray photoelectron spectroscopy reveals that WO 3 interacts electronically with Se/Ru as the W 4f and Se 3d line-shapes change. We therefore conclude that the electronic interactions between Se/Ru and WO 3 are primarily responsible for the increase in activity and selectivity of the WO 3 -modified Se/Ru towards ORR.
International Nuclear Information System (INIS)
Santos, Elizabeth; Schmickler, Wolfgang
2008-01-01
A unified model for electrochemical electron transfer reactions which explicitly accounts for the electronic structure of the electrode recently proposed by us is applied to the hydrogen oxidation reaction at different metal electrocatalysts. We focus on the changes produced in the transition state (saddle point) as a consequence of the interactions with d-bands. We discuss different empirical correlations between properties of the metal and catalytic activity proposed in the past. We show which role is played by the band structure of the different metals and its interaction with the molecule for decreasing the activation barrier. Finally, we demonstrate why some metals are better electrocatalysts for the hydrogen electro-oxidation reaction than others
Directory of Open Access Journals (Sweden)
Jun He
2012-03-01
Full Text Available By means of the nonequilibrium Green's functions and the density functional theory, we have investigated the electronic transport properties of C60 based electronic device with different intermolecular interactions. It is found that the electronic transport properties vary with the types of the interaction between two C60 molecules. A fast electrical switching behavior based on negative differential resistance has been found when two molecules are coupled by the weak π − π interaction. Compared to the solid bonding, the weak interaction is found to induce resonant tunneling, which is responsible for the fast response to the applied electric field and hence the velocity of switching.
Quantum radiation reaction in head-on laser-electron beam interaction
International Nuclear Information System (INIS)
Vranic, Marija; Grismayer, Thomas; Fonseca, Ricardo A; Silva, Luis O
2016-01-01
In this paper, we investigate the evolution of the energy spread and the divergence of electron beams while they interact with different laser pulses at intensities where quantum effects and radiation reaction are of relevance. The interaction is modelled with a quantum electrodynamic (QED)-PIC code and the results are compared with those obtained using a standard PIC code with a classical radiation reaction module. In addition, an analytical model is presented that estimates the value of the final electron energy spread after the interaction with the laser has finished. While classical radiation reaction is a continuous process, in QED, radiation emission is stochastic. The two pictures reconcile in the limit when the emitted photons energy is small compared to the energy of the emitting electrons. The energy spread of the electron distribution function always tends to decrease with classical radiation reaction, whereas the stochastic QED emission can also enlarge it. These two tendencies compete in the QED-dominated regime. Our analysis, supported by the QED module, reveals an upper limit to the maximal attainable energy spread due to stochasticity that depends on laser intensity and the electron beam average energy. Beyond this limit, the energy spread decreases. These findings are verified for different laser pulse lengths ranging from short ∼30 fs pulses presently available to the long ∼150 fs pulses expected in the near-future laser facilities, and compared with a theoretical model. Our results also show that near future experiments will be able to probe this transition and to demonstrate the competition between enhanced QED induced energy spread and energy spectrum narrowing from classical radiation reaction. (paper)
Exact suppression of depolarisation by beam-beam interaction in an electron ring
International Nuclear Information System (INIS)
Buon, J.
1983-03-01
It is shown that depolarisation due to beam-beam interaction can be exactly suppressed in an electron storage ring. The necessary ''spin matching'' conditions to be fulfilled are derived for a planar ring. They depend on the ring optics, assumed linear, but not on the features of the beam-beam force, like intensity and non-linearity. Extension to a ring equipped with 90 0 spin rotators is straightorward
Renormalization theory of beam-beam interaction in electron-positron colliders
International Nuclear Information System (INIS)
Chin, Y.H.
1989-07-01
This note is devoted to explaining the essence of the renormalization theory of beam-beam interaction for carrying out analytical calculations of equilibrium particle distributions in electron-positron colliding beam storage rings. Some new numerical examples are presented such as for betatron tune dependence of the rms beam size. The theory shows reasonably good agreements with the results of computer simulations. 5 refs., 6 figs
Three-wave interaction during electron cyclotron resonance heating and current drive
DEFF Research Database (Denmark)
Nielsen, Stefan Kragh; Jacobsen, Asger Schou; Hansen, Søren Kjer
2016-01-01
Non-linear wave-wave interactions in fusion plasmas, such as the parametric decay instability (PDI) of gyrotron radiation, can potentially hamper the use of microwave diagnostics. Here we report on anomalous scattering in the ASDEX Upgrade tokamak during electron cyclotron resonance heating...... experiments. The observations can be linked to parametric decay of the gyrotron radiation at the second harmonic upper hybrid resonance layer....
Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction
Energy Technology Data Exchange (ETDEWEB)
Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H. [Department of Physics and Astronomy, UCLA, Los Angeles California, 90095 (United States)
2012-12-21
A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.
Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction
International Nuclear Information System (INIS)
Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H.
2012-01-01
A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.
Directory of Open Access Journals (Sweden)
Emma Emanuilova Yandybaeva
2015-03-01
Full Text Available The methods of information subjects and objects interaction rules formalization in the electronic trading platform system has been developed. They are based on mathematical model of mandatory role-based access control. As a result of the work we have defined set of user roles and constructed roles hierarchy. For the roles hierarchy restrictions have been imposed to ensure the safety of the information system.
Photon and electron interaction databases and their use in medical applications
International Nuclear Information System (INIS)
Cullen, D.E.
1994-05-01
This paper discusses the All Particle-Method photon and electron interaction, and atomic relaxation data bases, that were initially developed for use in medical applications. Currently these data bases are being used in both medical and industrial applications. The All Particle Method data bases are designed to allow modelling of individual collisions in as much detail as possible. Elastic scattering can be modelled as single, as opposed to multiple, scattering events. Ionization can be modelled at the atomic subshell level, to define which subshell was ionized, spectrum of the initially emitted electron, as well as the spectra of electron and photons emitted as the atom relaxes back to neutrality. These data bases are currently being used in applications involving rather small spatial regions, where detailed calculations of individual events are required. While initially designed for use in medical applications, these data bases are now being used in a variety of industrial applications, e.g., transport in microelectronics
International Nuclear Information System (INIS)
Thompson, K.; Martinez, T.J.
1999-01-01
We present a new approach to first-principles molecular dynamics that combines a general and flexible interpolation method with ab initio evaluation of the potential energy surface. This hybrid approach extends significantly the domain of applicability of ab initio molecular dynamics. Use of interpolation significantly reduces the computational effort associated with the dynamics over most of the time scale of interest, while regions where potential energy surfaces are difficult to interpolate, for example near conical intersections, are treated by direct solution of the electronic Schroedinger equation during the dynamics. We demonstrate the concept through application to the nonadiabatic dynamics of collisional electronic quenching of Li(2p). Full configuration interaction is used to describe the wave functions of the ground and excited electronic states. The hybrid approach agrees well with full ab initio multiple spawning dynamics, while being more than an order of magnitude faster. copyright 1999 American Institute of Physics
Dynamics of electron bunches at the laser–plasma interaction in the bubble regime
Energy Technology Data Exchange (ETDEWEB)
Maslov, V.I., E-mail: vmaslov@kipt.kharkov.ua; Svystun, O.M., E-mail: svistun_elena@mail.ru; Onishchenko, I.N.; Tkachenko, V.I.
2016-09-01
The multi-bunches self-injection, observed in laser–plasma accelerators in the bubble regime, affects the energy gain of electrons accelerated by laser wakefield. However, understanding of dynamics of the electron bunches formed at laser–plasma interaction may be challenging. We present here the results of fully relativistic electromagnetic particle-in-cell (PIC) simulation of laser wakefield acceleration driven by a short laser pulse in an underdense plasma. The trapping and acceleration of three witness electron bunches by the bubble-like structures were observed. It has been shown that with time the first two witness bunches turn into drivers and contribute to acceleration of the last witness bunch.
Zeroth order regular approximation approach to electric dipole moment interactions of the electron
Gaul, Konstantin; Berger, Robert
2017-07-01
A quasi-relativistic two-component approach for an efficient calculation of P ,T -odd interactions caused by a permanent electric dipole moment of the electron (eEDM) is presented. The approach uses a (two-component) complex generalized Hartree-Fock and a complex generalized Kohn-Sham scheme within the zeroth order regular approximation. In applications to select heavy-elemental polar diatomic molecular radicals, which are promising candidates for an eEDM experiment, the method is compared to relativistic four-component electron-correlation calculations and confirms values for the effective electric field acting on the unpaired electron for RaF, BaF, YbF, and HgF. The calculations show that purely relativistic effects, involving only the lower component of the Dirac bi-spinor, are well described by treating only the upper component explicitly.
Influence of effective electron interaction on critical current of Josephson weak links
International Nuclear Information System (INIS)
Kupriyanov, M.Yu.; Likharev, K.K.; Lukichev, V.F.
1981-01-01
On the basis of microscopic theory of superconductivity, the dc Josphson effect in weak links of the type of variable thickness bridges or high ohmic interlayer sandwiches is studied. The Isub(C)Rsub(N) product is calculatied as a function of temperature T and weak link length L for various amplitudes and both signs of effective electron-electron interaction constant lambda. If the weak link material is superconducting with critical temperature Tsub(C) > 0 (lambda > 0), the maximum value of Isub(C)Rsub(N) product (under condition of the singlevalued Isub(S)(phi) relationship) can be achieved at L approx. <= 3xisup(*) when Tsub(C) approx. <= Tsub(CS)/2, and at L=(4 / 6)xisup(*) when Tsub(C) = Tsub(CS). Electron repulsion inside the weak link (lambda < 0) results in some reduction of the Isub(C)Rsub(N) product in comparison with the case of 'really normal' weak link material (lambda = 0). (orig.)
Investigation of processes of interaction relativistic electrons with the solutions of organic dyes
International Nuclear Information System (INIS)
Buki, A.Yu.; Gokov, S.P.; Kazarinov, Yu.G.; Kalenik, S.A.; Kasilov, V.I.; Kochetov, S.S.; Makhnenko, P.L.; Mel'nitskiy, I.V.; Tverdohvalov, A.V.; Tsyatsko, V.V.; Shopen, O.A.
2014-01-01
Investigation of the processes of interaction of ionizing radiation with complex organic objects can solve a number of fundamental and applied problems in radiation physics, chemistry and biology. In this work we investigated the dose dependence (dose range 1...5MRad) optical density relative concentrations of water, alcohol and glycerine solution following organic dyes: methylene blue - C 16 H 18 N 3 SCl and methyl orange - C 14 H 14 N 3 O 3 SNa, irradiated with an electron beam with an energy of 16MeV. In the analysis of absorption spectra, it was found that water solutions of dyes have less resistance to radiation as compared with the alcohol and glycerol. Also, all solutions of methyl orange less radiation resistant than the methylene blue solution. Analysis of the spectra showed that these relationships are close to linear in the range of doses. To understand the physical and chemical processes occurring in the interaction of relativistic electrons with the studied organic objects were performed the computer simulations of the energy spectra of ions formed due to breaking the chemical bonds of molecules of dye solutions using the program SRIM-2010. The analysis showed that radiation - stimulated chemical processes play a major role in the destruction of the source of organic dye molecules. The remaining processes (interaction of electrons and nuclei, the cascade processes) accounts for about 10% of all molecular breaks.
Electron acceleration by femtosecond laser interaction with micro-structured plasmas
Goers, Andy James
Laser-driven accelerators are a promising and compact alternative to RF accelerator technology for generating relativistic electron bunches for medical, scientific, and security applications. This dissertation presents three experiments using structured plasmas designed to advance the state of the art in laser-based electron accelerators, with the goal of reducing the energy of the drive laser pulse and enabling higher repetition rate operation with current laser technology. First, electron acceleration by intense femtosecond laser pulses in He-like nitrogen plasma waveguides is demonstrated. Second, significant progress toward a proof of concept realization of quasi-phasematched direct acceleration (QPM-DLA) is presented. Finally, a laser wakefield accelerator at very high plasma density is studied, enabling relativistic electron beam generation with ˜10 mJ pulse energies. Major results from these experiments include: • Acceleration of electrons up to 120 MeV from an ionization injected wakefield accelerator driven in a 1.5 mm long He-like nitrogen plasma waveguide • Guiding of an intense, quasi-radially polarized femtosecond laser pulse in a 1 cm plasma waveguide. This pulse provides a strong drive field for the QPM-DLA concept. • Wakefield acceleration of electrons up to ˜10 MeV with sub-terawatt, ˜10 mJ pulses interacting with a thin (˜200 mum), high density (>1020 cm-3) plasma. • Observation of an intense, coherent, broadband wave breaking radiation flash from a high plasma density laser wakefield accelerator. The flash radiates > 1% of the drive laser pulse energy in a bandwidth consistent with half-cycle (˜1 fs) emission from violent unidirectional acceleration of electron bunches from rest. These results open the way to high repetition rate (>˜kHz) laser-driven generation of relativistic electron beams with existing laser technology.
Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction
Scisciò, M.; Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Papaphilippou, Y.; Antici, P.
2016-03-01
In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequency (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.
An experimental study of electron transfer and emission during particle-surface interactions
International Nuclear Information System (INIS)
McGrath, C.T.
2000-09-01
A new coincidence technique has been developed and used to study the secondary electron emission that arises during the interaction of ions with surfaces. This coincidence technique allows the secondary electron emission statistics due to the impact of singly, doubly and multiply charged ions on surfaces to be measured in coincidence with reflected particles, in specific charge states and with specific post-collision trajectories. This system has been used to study the impact of 8 keV H + ions on polycrystalline copper and aluminium targets. Under these conditions the potential emission contribution is negligible and the electron emission is almost entirely due to kinetic emission processes. The sub-surface contribution to the observed electron emission has been isolated using two newly developed models. These models provide valuable information about the depth and amount of surface penetration and on the probability for subsequent electron transport to the surface. The impact of 2 - 100 keV Xe q+ (q = 1 - 10) ions on polycrystalline copper has also been studied using this system. From the subsequent data the potential and kinetic contributions to secondary electron emission have been separated using a previously established model for potential emission. The resulting kinetic emission yield increases with increasing ion impact energy, consistent with current concepts on quasimolecular ionisation. For ions impacting at large incident angles evidence for sub-surface emission has also been observed. The degree of penetration increases with ion impact energy, consistent with current concepts on this effect. The formation of H - ions from incident H + ions has also been studied by measuring the secondary electron emission statistics in coincidence with reflected particles in specific final charge states. This preliminary data is consistent with a two-step process of Auger neutralisation followed by resonant electron capture to the affinity level. However this mechanism
Fermi-edge singularity in one-dimensional electron systems with long-range Coulomb interactions
International Nuclear Information System (INIS)
Otani, H.; Ogawa, T.
1996-01-01
Effects of long-range Coulomb interactions on the Fermi-edge singularity in optical spectra are investigated theoretically for one-dimensional spin-1/2 fermion systems with the use of the Tomonaga-Luttinger bosonization technique. Low-energy excitation spectrum near the Fermi level shows that dispersion of the charge-density fluctuation remains gapless but is nonlinear when the electron-electron (e-e) Coulomb interaction is of the x -1 type (i.e., an infinite force range). Temporal behavior of the current-current correlation function is calculated analytically for arbitrary force ranges, λ e and λ h , of the e-e and the electron-hole (e-h) Coulomb interactions. (i) When both the e-e and the e-h interactions have large but finite force ranges (λ e h max[λ e ,λ h ]/v F . Corresponding optical spectrum near the Fermi edge (within an energy range of ℎv F /max[λ e ,λ h ]) exhibits the power-law divergence or the power-law convergence, which is an ordinary Fermi-edge singularity. (ii) When either the e-e or the e-h interaction is of the x -1 type (i.e., λ e →∞ and/or λ h →∞), an exponent of the correlation function is dependent on time to lead the faster decay than that of any power laws. Then the optical spectra show no power law dependence and always converge (become zero) at the Fermi edge, which is in striking contrast to the ordinary power-law singularity
Krüger, Dennis; Brinkmann, Ralf Peter
2017-11-01
This publication reports analytical and numerical results concerning the interaction of gyrating electrons with a plasma boundary sheath, with focus on partially magnetized technological plasmas. It is assumed that the electron Debye length {λ }{{D}} is much smaller than the electron gyroradius {r}{{L}}, and {r}{{L}} in turn much smaller than the mean free path λ and the gradient length L of the fields. Focusing on the scale of the gyroradius, the sheath is assumed as infinitesimally thin ({λ }{{D}}\\to 0), collisions are neglected (λ \\to ∞ ), the magnetic field is taken as homogeneous, and electric fields (=potential gradients) in the bulk are neglected (L\\to ∞ ). The interaction of an electron with the electric field of the plasma boundary sheath is represented by a specular reflection {v}\\to {v}-2{v}\\cdot {{e}}z {{e}}z of the velocity {v} at the plane z = 0 of a naturally oriented Cartesian coordinate system (x,y,z). The electron trajectory is then given as sequences of helical sections, with the kinetic energy ɛ and the canonical momenta p x and p y conserved, but not the position of the axis (base point {{R}}0), the slope (pitch angle χ), and the phase (gyrophase φ). A ‘virtual interaction’ which directly maps the incoming electrons to the outgoing ones is introduced and studied in dependence of the angle γ between the field and the sheath normal {{e}}z. The corresponding scattering operator is constructed, mathematically characterized, and given as an infinite matrix. An equivalent boundary condition for a transformed kinetic model is derived.
Energy Technology Data Exchange (ETDEWEB)
Kandemir, B S; Keskin, M [Department of Physics, Faculty of Sciences, Ankara University, 06100 Tandogan, Ankara (Turkey)
2008-08-13
In this paper, exact analytical expressions for the entire phonon spectra in single-walled carbon nanotubes with zigzag geometry are presented by using a new approach, originally developed by Kandemir and Altanhan. This approach is based on the concept of construction of a classical lattice Hamiltonian of single-walled carbon nanotubes, wherein the nearest and next nearest neighbor and bond bending interactions are all included, then its quantization and finally diagonalization of the resulting second quantized Hamiltonian. Furthermore, within this context, explicit analytical expressions for the relevant electron-phonon interaction coefficients are also investigated for single-walled carbon nanotubes having this geometry, by the phonon modulation of the hopping interaction.
International Nuclear Information System (INIS)
Kandemir, B S; Keskin, M
2008-01-01
In this paper, exact analytical expressions for the entire phonon spectra in single-walled carbon nanotubes with zigzag geometry are presented by using a new approach, originally developed by Kandemir and Altanhan. This approach is based on the concept of construction of a classical lattice Hamiltonian of single-walled carbon nanotubes, wherein the nearest and next nearest neighbor and bond bending interactions are all included, then its quantization and finally diagonalization of the resulting second quantized Hamiltonian. Furthermore, within this context, explicit analytical expressions for the relevant electron-phonon interaction coefficients are also investigated for single-walled carbon nanotubes having this geometry, by the phonon modulation of the hopping interaction
Rhodes, Penny; Small, Neil; Rowley, Emma; Langdon, Mark; Ariss, Steven; Wright, John
2008-09-01
Two routine consultations in primary care diabetes clinics are compared using extracts from video recordings of interactions between nurses and patients. The consultations were chosen to present different styles of interaction, in which the nurse's gaze was either primarily toward the computer screen or directed more toward the patient. Using conversation analysis, the ways in which nurses shift both gaze and body orientation between the computer screen and patient to influence the style, pace, content, and structure of the consultation were investigated. By examining the effects of different levels of engagement between the electronic medical record and the embodied patient in the consultation room, we argue for the need to consider the contingent nature of the interface of technology and the person in the consultation. Policy initiatives designed to deliver what is considered best-evidenced practice are modified in the micro context of the interactions of the consultation.
Bayne, Michael G; Scher, Jeremy A; Ellis, Benjamin H; Chakraborty, Arindam
2018-05-21
Electron-hole or quasiparticle representation plays a central role in describing electronic excitations in many-electron systems. For charge-neutral excitation, the electron-hole interaction kernel is the quantity of interest for calculating important excitation properties such as optical gap, optical spectra, electron-hole recombination and electron-hole binding energies. The electron-hole interaction kernel can be formally derived from the density-density correlation function using both Green's function and TDDFT formalism. The accurate determination of the electron-hole interaction kernel remains a significant challenge for precise calculations of optical properties in the GW+BSE formalism. From the TDDFT perspective, the electron-hole interaction kernel has been viewed as a path to systematic development of frequency-dependent exchange-correlation functionals. Traditional approaches, such as MBPT formalism, use unoccupied states (which are defined with respect to Fermi vacuum) to construct the electron-hole interaction kernel. However, the inclusion of unoccupied states has long been recognized as the leading computational bottleneck that limits the application of this approach for larger finite systems. In this work, an alternative derivation that avoids using unoccupied states to construct the electron-hole interaction kernel is presented. The central idea of this approach is to use explicitly correlated geminal functions for treating electron-electron correlation for both ground and excited state wave functions. Using this ansatz, it is derived using both diagrammatic and algebraic techniques that the electron-hole interaction kernel can be expressed only in terms of linked closed-loop diagrams. It is proved that the cancellation of unlinked diagrams is a consequence of linked-cluster theorem in real-space representation. The electron-hole interaction kernel derived in this work was used to calculate excitation energies in many-electron systems and results
Strong field QED in lepton colliders and electron/laser interactions
Hartin, Anthony
2018-05-01
The studies of strong field particle physics processes in electron/laser interactions and lepton collider interaction points (IPs) are reviewed. These processes are defined by the high intensity of the electromagnetic fields involved and the need to take them into account as fully as possible. Thus, the main theoretical framework considered is the Furry interaction picture within intense field quantum field theory. In this framework, the influence of a background electromagnetic field in the Lagrangian is calculated nonperturbatively, involving exact solutions for quantized charged particles in the background field. These “dressed” particles go on to interact perturbatively with other particles, enabling the background field to play both macroscopic and microscopic roles. Macroscopically, the background field starts to polarize the vacuum, in effect rendering it a dispersive medium. Particles encountering this dispersive vacuum obtain a lifetime, either radiating or decaying into pair particles at a rate dependent on the intensity of the background field. In fact, the intensity of the background field enters into the coupling constant of the strong field quantum electrodynamic Lagrangian, influencing all particle processes. A number of new phenomena occur. Particles gain an intensity-dependent rest mass shift that accounts for their presence in the dispersive vacuum. Multi-photon events involving more than one external field photon occur at each vertex. Higher order processes which exchange a virtual strong field particle resonate via the lifetimes of the unstable strong field states. Two main arenas of strong field physics are reviewed; those occurring in relativistic electron interactions with intense laser beams, and those occurring in the beam-beam physics at the interaction point of colliders. This review outlines the theory, describes its significant novel phenomenology and details the experimental schema required to detect strong field effects and the
Semi-local invariance in Ising models with multi-spin interaction
International Nuclear Information System (INIS)
Lipowski, A.
1996-08-01
We examine implications of semi-local invariance in Ising models with multispin interaction. In ergodic models all spin-spin correlation functions vanish and the local symmetry is the same as in locally gauge-invariant models. The d = 3 model with four-spin interaction is nonergodic at low temperature but the magnetic symmetry remains unbroken. The d = 3 model with eight-spin interaction is ergodic but undergoes the phase transition and most likely its low-temperature phase is characterized by a nonlocal order parameter. (author). 7 refs, 1 fig
Relativistic electron beam interaction and $K_{\\alpha}$-generation in solid targets
Fill, E; Eder, D; Eidmann, K; Saemann, A
1999-01-01
When fs laser pulses interact with solid surfaces at intensities I lambda /sup 2/ >10/sup 18/ W/cm/sup 2/ mu m/sup 2/, collimated relativistic electron beams are generated. These electrons can be used for producing intense X-radiation (bremsstrahlung or K/sub alpha /) for pumping an innershell X-ray laser. The basic concept of such a laser involves the propagation of the electron beam in a material which converts electron energy into appropriate pump photons. Using the ATLAS titanium-sapphire laser at Max-Planck-Institut fur Quantenoptik, we investigate the generation of hot electrons and of characteristic radiation in copper. The laser (200 mJ/130 fs) is focused by means of an off-axis parabola to a diameter of about 10 mu m. By varying the position of the focus, we measure the copper K/sub alpha /-yield as a function of intensity in a range from 10/sup 15/ to 2 x 10/sup 18/ W/cm/sup 2/ while keeping the laser pulse energy constant. Surprisingly, the highest emission is obtained at an intensity of about 10/s...
Refinement of Monte Carlo simulations of electron-specimen interaction in low-voltage SEM
International Nuclear Information System (INIS)
Kieft, Erik; Bosch, Eric
2008-01-01
A Monte Carlo tool is presented for the simulation of secondary electron (SE) emission in a scanning electron microscope (SEM). The tool is based on the Geant4 platform of CERN. The modularity of this platform makes it comparatively easy to add and test individual physical models. Our aim has been to develop a flexible and generally applicable tool, while at the same time including a good description of low-energy (<50 eV) interactions of electrons with matter. To this end we have combined Mott cross-sections with phonon-scattering based cross-sections for the elastic scattering of electrons, and we have adopted a dielectric function theory approach for inelastic scattering and generation of SEs. A detailed model of the electromagnetic fields from an actual SEM column has been included in the tool for ray tracing of secondary and backscattered electrons. Our models have been validated against experimental results through comparison of the simulation results with experimental yields, SE spectra and SEM images. It is demonstrated that the resulting simulation package is capable of quantitatively predicting experimental SEM images and is an important tool in building a deeper understanding of SEM imaging.
Interaction between Solid Nitrogen and 1-3-keV Electrons
DEFF Research Database (Denmark)
Schou, Jørgen; Sørensen, H.
1978-01-01
V. At 3 keV, the SEE coefficient is 12 times that for solid deuterium. This is attributed partly to the larger production rate for low-energy electrons in nitrogen and partly to the larger escape probability for these electrons. Moreover, measurements were made of the electron-reflection coefficient, both......Experimental studies were made of the interaction between solid nitrogen and beams of 1-2-keV electrons. The projected range for the electrons was measured by means of the mirror-substrate method (gold substrate), giving the result 9.02×1016 E1.75 molecules/cm2 with the energy given in ke...... for solid nitrogen and for the carbon substrate. For nitrogen, it varied from 0.17 el/el at 1 keV to 0.13 el/el at 3 keV, and for carbon it varied from 0.13 to 0.12. The observations are discussed and comparisons made with other theoretical and experimental results. The agreement ranges from good to fair...
Neutrons production during the interaction of monoenergetic electrons with a thin tungsten target
International Nuclear Information System (INIS)
Soto B, T. G.; Medina C, D.; Baltazar R, A.; Vega C, H. R.
2016-10-01
When a linear accelerator for radiotherapy operates with acceleration voltages higher than 8 MV, neutrons are produced, as secondary radiation which deposits an undesirable and undesirable dose in the patient. Depending on the type of tumor, its location in the body and the characteristics of the patient, the cancer treatment with a Linac is performed with photon or electron beams, which produce neutrons through reactions (γ, n) and (e, e n) respectively. Because the effective section for the neutrons production by reactions (γ, n) is approximately two orders of magnitude larger than the effective section of the reactions (e, e n), studies on the effects of this secondary radiation have focused on photo neutrons. en a Linac operates with electron beams, the beam coming out of the magnetic deflector is impinged on the dispersion lamella in order to cause quasi-elastic interactions and to expand the spatial distribution of the electrons; the objective of this work is to determine the characteristics of the photons and neutrons that occur when a mono-energetic electron beam of 2 mm in diameter (pencil beam) is made to impinge on a tungsten lamella of 1 cm in diameter and 0.5 mm of thickness. The study was done using Monte Carlo methods with code MCNP6 for electron beams of 8, 10, 12, 15 and 18 MeV. The spectra of photons and neutrons were estimated in 4 point detectors placed at different equidistant points from the center of the lamella. (Author)
Solar Wind 0.1-1 keV Electrons in the Corotating Interaction Regions
Wang, L.; Tao, J.; Li, G.; Wimmer-Schweingruber, R. F.; Jian, L. K.; He, J.; Tu, C.; Tian, H.; Bale, S. D.
2017-12-01
Here we present a statistical study of the 0.1-1 keV suprathermal electrons in the undisturbed and compressed slow/fast solar wind, for the 71 corotating interaction regions (CIRs) with good measurements from the WIND 3DP and MFI instruments from 1995 to 1997. For each of these CIRs, we separate the strahl and halo electrons based on their different behaviors in pitch angle distributions in the undisturbed and compressed solar wind. We fit both the strahl and halo energy spectra to a kappa function with an index κ index and effective temperature Teff, and calculate the pitch-angle width at half-maximum (PAHM) of the strahl population. We also integrate the electron measurements between 0.1 and 1.0 keV to obtain the number density n and average energy Eavg for the strahl and halo populations. We find that for both the strahl and halo populations within and around these CIRs, the fitted κ index strongly correlates with Teff, similar to the quiet-time solar wind (Tao et al., ApJ, 2016). The number density of both the strahl and halo shows a strong positive correlation with the electron core temperature. The strahl number density ns is correlated with the magnitude of interplanetary magnetic field, and the strahl PAHM width is anti-correlated with the solar wind speed. These results suggest that the origin of strahl electrons from the solar corona is likely related to the electron core temperature and magnetic field strength, while the production of halo electrons in the interplanetary medium could depend on the solar wind velocity.
International Nuclear Information System (INIS)
Krishtopenko, S. S.
2015-01-01
The effect of the electron-electron interaction on the spin-resonance frequency in two-dimensional electron systems with Dresselhaus spin-orbit coupling is investigated. The oscillatory dependence of many-body corrections on the magnetic field is demonstrated. It is shown that the consideration of many-body interaction leads to a decrease or an increase in the spin-resonance frequency, depending on the sign of the g factor. It is found that the term cubic in quasimomentum in Dresselhaus spin-orbit coupling partially decreases exchange corrections to the spin resonance energy in a two-dimensional system
Energy Technology Data Exchange (ETDEWEB)
Krishtopenko, S. S., E-mail: sergey.krishtopenko@mail.ru [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)
2015-02-15
The effect of the electron-electron interaction on the spin-resonance frequency in two-dimensional electron systems with Dresselhaus spin-orbit coupling is investigated. The oscillatory dependence of many-body corrections on the magnetic field is demonstrated. It is shown that the consideration of many-body interaction leads to a decrease or an increase in the spin-resonance frequency, depending on the sign of the g factor. It is found that the term cubic in quasimomentum in Dresselhaus spin-orbit coupling partially decreases exchange corrections to the spin resonance energy in a two-dimensional system.
International Nuclear Information System (INIS)
Galasso, V.; Kovac, B.; Modelli, A.
2007-01-01
The equilibrium structures of artemisinin and a selection of its derivatives (potent antimalarial drugs) have been studied with the density functional theory ansatz B3LYP. Of the five rings of the artemisinin framework, it is only the pyranose ring B that exhibits a marked conformational flexibility, especially on addition of a pendant side chain at C-10. For the derivatives, the β isomer with the axial substituent group is found to be energetically more stable than the α isomer with the equatorial group. The assignment of the vibrational fundamentals has been supported by calculations on related model molecules and a normal coordinate analysis. This allows for a reliable characterization of the normal modes, mainly involving the peroxide linkage, in the claimed fingerprint region of 1,2,4-trioxanes. The electronic structures have also been studied by measuring and calculating significant features of the NMR, photoelectron and electron transmission spectra. In particular, a representative set of NMR chemical shifts and nuclear spin-spin coupling constants, obtained with DFT formalisms, compares favourably with experiment and fits expectation in terms of stereoelectronic effects of the vicinal oxygen lone pairs. Based on ab initio outer valence Green's function calculations, a consistent interpretation of the uppermost bands in the photoelectron spectra of artemisinin and derivatives has been advanced. The top ionization energies reflect a complex interaction of the various oxygen lone pair orbitals. Electron transmission spectroscopy is applied for the first time to compounds containing the peroxide bond and elucidates the empty level electronic structure of artemisinin and derivatives in the 0-6 eV energy range, with the support of MO calculations and comparison with the spectra of reference molecules. Electron attachment to the lowest-lying empty σ* MO, mainly localized on the O-O bridge, occurs at an energy (1.7 eV) exceptionally low for compounds not
Kalpana, Panneer Selvam; Jayakumar, Kalyanasundaram
2017-11-01
We study the effect of magnetic field on the Coulomb interaction between the two electrons confined inside a CdTe/Cd1-xMnxTe Quantum Well (QW), Quantum Well Wire (QWW) and Quantum Dot (QD) for the composition of Mn2+ ion, x = 0.3. The two particle Schrodinger equation has been solved using variational technique in the effective mass approximation. The results show that the applied magnetic field tremendously alters the Coulomb interaction of the electrons and their binding to the donor impurity by shrinking the spatial extension of the two particle wavefunction and leads to tunnelling through the barrier. The qualitative phenomenon involved in such variation of electron - electron interaction with the magnetic field has also been explained through the 3D - plot of the probability density function.
Digital video analysis of health professionals' interactions with an electronic whiteboard
DEFF Research Database (Denmark)
Rasmussen, Rasmus; Kushniruk, Andre
2013-01-01
As hospital departments continue to introduce electronic whiteboards in real clinical settings a range of human factor issues have emerged and it has become clear that there is a need for improved methods for designing and testing these systems. In this study, we employed a longitudinal and natur......As hospital departments continue to introduce electronic whiteboards in real clinical settings a range of human factor issues have emerged and it has become clear that there is a need for improved methods for designing and testing these systems. In this study, we employed a longitudinal...... and naturalistic method in the usability evaluation of an electronic whiteboard system. The goal of the evaluation was to explore the extent to which usability issues experienced by users change as they gain more experience with the system. In addition, the paper explores the use of a new approach to collection...... and analysis of continuous digital video recordings of naturalistic "live" user interactions. The method developed and employed in the study included recording the users' interactions with system during actual use using screen-capturing software and analyzing these recordings for usability issues...
International Nuclear Information System (INIS)
Lovric, D.; Gumhalter, B.
1988-01-01
The relevance of van der Waals interactions in the scattering of neutral atoms from adsorbates has been recently confirmed by highly sensitive molecular-beam techniques. The theoretical descriptions of the collision dynamics which followed the experimental studies have necessitated very careful qualitative and quantitative examinations and evaluations of the properties of atom-adsorbate van der Waals interactions for specific systems. In this work we present a microscopic calculation of the strengths and reference-plane positions for van der Waals potentials relevant for scattering of He atoms from CO adsorbed on various metallic substrates. In order to take into account the specificities of the polarization properties of real metals (noble and transition metals) and of chemisorbed CO, we first calculate the spectra of the electronic excitations characteristic of the respective electronic subsystems by using various data sources available and combine them with the existing theoretical models. The reliability of the calculated spectra is then verified in each particular case by universal sum rules which may be established for the electronic excitations of surfaces and adsorbates. The substrate and adsorbate polarization properties which derive from these calculations serve as input data for the evaluation of the strengths and reference-plane positions of van der Waals potentials whose computed values are tabulated for a number of real chemisorption systems. The implications of the obtained results are discussed in regard to the atom-adsorbate scattering cross sections pertinent to molecular-beam scattering experiments
International Nuclear Information System (INIS)
Alizadeh, E.; Sanche, L.
2014-01-01
A novel technique has been developed to investigate low energy electron (LEE)-DNA interactions in the presence of small biomolecules (e.g., N 2 , O 2 , H 2 O) found near DNA in the cell nucleus, in order to simulate cellular conditions. In this technique, LEEs are emitted from a metallic surface exposed by soft X-rays and interact with DNA thin films at standard ambient temperature and pressure (SATP). Whereas atmospheric N 2 had little effect on the yields of LEE-induced single and double strand breaks, both O 2 and H 2 O considerably modified and increased such damage. The highest yields were obtained when DNA is embedded in a combined O 2 and H 2 O atmosphere. In this case, the amount of additional double strand breaks was supper-additive. The effect of modifying the chemical and physical stability of DNA by platinum-based chemotherapeutic agents (Pt-drugs) including cisplatin, carboplatin and oxaliplatin was also investigated with this technique. The results obtained provide information on the role played by subexcitation-energy electrons and dissociative electron attachment in the radiosensitization of DNA by Pt-drugs, which is an important step to unravel the mechanisms of radiosensitization of these agents in chemo-radiation cancer therapy. (authors)
Alizadeh, Elahe; Sanche, Léon
2014-04-01
A novel technique has been developed to investigate low energy electron (LEE)-DNA interactions in the presence of small biomolecules (e.g., N2, O2, H2O) found near DNA in the cell nucleus, in order to simulate cellular conditions. In this technique, LEEs are emitted from a metallic surface exposed by soft X-rays and interact with DNA thin films at standard ambient temperature and pressure (SATP). Whereas atmospheric N2 had little effect on the yields of LEE-induced single and double strand breaks, both O2 and H2O considerably modified and increased such damage. The highest yields were obtained when DNA is embedded in a combined O2 and H2O atmosphere. In this case, the amount of additional double strand breaks was supper-additive. The effect of modifying the chemical and physical stability of DNA by platinum-based chemotherapeutic agents (Pt-drugs) including cisplatin, carboplatin and oxaliplatin was also investigated with this technique. The results obtained provide information on the role played by subexcitation-energy electrons and dissociative electron attachment in the radiosensitization of DNA by Pt-drugs, which is an important step to unravel the mechanisms of radiosensitisation of these agents in chemoradiation cancer therapy.
Interaction of non-equilibrium phonons with electron-hole plasmas in germanium
International Nuclear Information System (INIS)
Kirch, S.J.
1985-01-01
This thesis presents results of experiments on the interaction of phonons and photo-excited electron-hole plasmas in Ge at low temperature. The first two studies involved the low-temperature fluid phase known as the electron-hole liquid (EHL). The third study involved a wider range of temperatures and includes the higher temperature electron-hole plasma (EHP). In the first experiment, superconducting tunnel junctions are used to produce quasi-monochromatic phonons, which propagate through the EHL. The magnitude of the absorption of these non-equilibrium phonons gives a direct measure of the coupling constant, the deformation potential. In the second experiment, the nonequilibrium phonons are generated by laser excitation of a metal film. An unusual sample geometry allows examination of the EHL-phonon interaction near the EHL excitation surface. This coupling is examined for both cw and pulsed EHL excitation. In the third experiment, the phonons are byproducts of the photo-excited carrier thermalization. The spatial, spectral and temporal dependence of the recombination luminescence is examined. A phonon wind force is observed to dominate the transport properties of the EHL and the EHP. These carriers are never observed to move faster than the phonon velocity even during the laser pulse
Wang, Hao
2010-09-27
We present first-principles electronic structure calculations for the zigzag spin-chain compound In2VO5 using the generalized gradient approximation both with and without inclusion of an on-site Coulomb interaction. It has been proposed that In2VO5 is characterized by itinerant V 3d electrons at high temperature and localized electrons at low temperature. Consequently, it is to be expected that electronic correlations play an important role for the magnetic transition from ferromagnetic to antiferromagnetic exchange around 120 K. In this context, we study the electronic and magnetic properties of a set of possible spin configurations. Our calculations show that inclusion of an on-site Coulomb interaction in fact changes the ground state from ferromagnetic to antiferromagnetic. © 2010 IOP Publishing Ltd.
Shantappa, A.; Hanagodimath, S. M.
2014-01-01
Effective atomic numbers, electron densities of some vitamins (Retinol, Riboflavin, Niacin, Biotin, Folic acid, Cobalamin, Phylloquinone and Flavonoids) composed of C, H, O, N, Co, P and S have been calculated for total and partial photon interactions by the direct method for energy range 1 keV-100 GeV by using WinXCOM and kinetic energy released in matter (Kerma) relative to air is calculated in energy range of 1 keV-20 MeV. Change in effective atomic number and electron density with energy is calculated for all photon interactions. Variation of photon mass attenuation coefficients with energy are shown graphically only for total photon interaction. It is observed that change in mass attenuation coefficient with composition of different chemicals is very large below 100 keV and moderate between 100 keV and 10 MeV and negligible above 10 MeV. Behaviour of vitamins is almost indistinguishable except biotin and cobalamin because of large range of atomic numbers from 1(H) to 16 (S) and 1(H) to 27(Co) respectively. K a value shows a peak due to the photoelectric effect around K-absorption edge of high- Z constituent of compound for biotin and cobalamin.
Electron gas interacting in a metal, submitted to a strong magnetic field
International Nuclear Information System (INIS)
Alcaraz, Francisco Castilho
1977-01-01
Using the propagator's technique in the grand ensemble developed by Montroll and Ward we investigate the magnetic properties of an interacting electron gas in a strong magnetic field. The free propagator properly constructed shows that the spin paramagnetism does not have a term with strong temperature dependence, contrary to the result of Isihara. Considering the electron density to be constant, the dHVA oscillations in the magnetic susceptibility and sound velocity, considering the effects of first exchange interactions, show only one phase in agreement with experimental result, while Ichimura and Isihara obtained two phases differing by π/2. The effects of first order exchange interactions in the dHVA oscillations of the magnetic susceptibility and sound velocity give rise to an exponential factor in the amplitudes of oscillator (Dingle factor), being the Dingle temperature linearly dependent of the Fermi velocity. The calculations of the ring diagram contribution to the grand partition function, show that the approximation used by Isihara for this calculations is not good and the dHVA oscillations of the contributions from the ring diagrams for the grand partition function have a phase differing by π/2 from that obtained by Isihara. (author)
Simulation of the interaction of positively charged beams and electron clouds
International Nuclear Information System (INIS)
Markovik, Aleksandar
2013-01-01
The incoherent (head-tail) effect on the bunch due to the interaction with electron clouds (e-clouds) leads to a blow up of the transverse beam size in storage rings operating with positively charged beams. Even more the e-cloud effects are considered to be the main limiting factor for high current, high-brightness or high-luminosity operation of future machines. Therefore the simulation of e-cloud phenomena is a highly active field of research. The main focus in this work was set to a development of a tool for simulation of the interaction of relativistic bunches with non-relativistic parasitic charged particles. The result is the Particle-In-Cell Program MOEVE PIC Tracking which can track a 3D bunch under the influence of its own and external electromagnetic fields but first and foremost it simulates the interaction of relativistic positively charged bunches and initially static electrons. In MOEVE PIC Tracking the conducting beam pipe can be modeled with an arbitrary elliptical cross-section to achieve more accurate space charge field computations for both the bunch and the e-cloud. The simulation of the interaction between positron bunches and electron clouds in this work gave a detailed insight of the behavior of both particle species during and after the interaction. Further and ultimate goal of this work was a fast estimation of the beam stability under the influence of e-clouds in the storage ring. The standard approach to simulate the stability of a single bunch is to track the bunch particles through the linear optics of the machine by multiplying the 6D vector of each particle with the transformation matrices describing the lattice. Thereby the action of the e-cloud on the bunch is approximated by a pre-computed wake kick which is applied on one or more points in the lattice. Following the idea of K.Ohmi the wake kick was pre-computed as a two variable function of the bunch part exiting the e-cloud and the subsequent parts of a bunch which receive a
Theory of electron-phonon-dislon interacting system—toward a quantized theory of dislocations
Li, Mingda; Tsurimaki, Yoichiro; Meng, Qingping; Andrejevic, Nina; Zhu, Yimei; Mahan, Gerald D.; Chen, Gang
2018-02-01
We provide a comprehensive theoretical framework to study how crystal dislocations influence the functional properties of materials, based on the idea of a quantized dislocation, namely a ‘dislon’. In contrast to previous work on dislons which focused on exotic phenomenology, here we focus on their theoretical structure and computational power. We first provide a pedagogical introduction that explains the necessity and benefits of taking the dislon approach and why the dislon Hamiltonian takes its current form. Then, we study the electron-dislocation and phonon-dislocation scattering problems using the dislon formalism. Both the effective electron and phonon theories are derived, from which the role of dislocations on electronic and phononic transport properties is computed. Compared with traditional dislocation scattering studies, which are intrinsically single-particle, low-order perturbation and classical quenched defect in nature, the dislon theory not only allows easy incorporation of quantum many-body effects such as electron correlation, electron-phonon interaction, and higher-order scattering events, but also allows proper consideration of the dislocation’s long-range strain field and dynamic aspects on equal footing for arbitrary types of straight-line dislocations. This means that instead of developing individual models for specific dislocation scattering problems, the dislon theory allows for the calculation of electronic structure and electrical transport, thermal transport, optical and superconducting properties, etc, under one unified theory. Furthermore, the dislon theory has another advantage over empirical models in that it requires no fitting parameters. The dislon theory could serve as a major computational tool to understand the role of dislocations on multiple materials’ functional properties at an unprecedented level of clarity, and may have wide applications in dislocated energy materials.
Energy Technology Data Exchange (ETDEWEB)
Lü, Jing-Tao, E-mail: jtlu@hust.edu.cn [School of Physics, Huazhong University of Science and Technology, 430074 Wuhan (China); Zhou, Hangbo [Department of Physics and Center for Computational Science and Engineering, National University of Singapore, 117551 Singapore (Singapore); NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 117456 Singapore (Singapore); Jiang, Jin-Wu [Shanghai Institute of Applied Mathematics and Mechanics, Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai University, 200072 Shanghai (China); Wang, Jian-Sheng [Department of Physics and Center for Computational Science and Engineering, National University of Singapore, 117551 Singapore (Singapore)
2015-05-15
The topic of this review is the effects of electron-phonon interaction (EPI) on the transport properties of molecular nano-conductors. A nano-conductor connects to two electron leads and two phonon leads, possibly at different temperatures or chemical potentials. The EPI appears only in the nano-conductor. We focus on its effects on charge and energy transport. We introduce three approaches. For weak EPI, we use the nonequilibrium Green’s function method to treat it perturbatively. We derive the expressions for the charge and heat currents. For weak system-lead couplings, we use the quantum master equation approach. In both cases, we use a simple single level model to study the effects of EPI on the system’s thermoelectric transport properties. It is also interesting to look at the effect of currents on the dynamics of the phonon system. For this, we derive a semi-classical generalized Langevin equation to describe the nano-conductor’s atomic dynamics, taking the nonequilibrium electron system, as well as the rest of the atomic degrees of freedom as effective baths. We show simple applications of this approach to the problem of energy transfer between electrons and phonons.
Effect of interwall interaction on the electronic structure of double-walled carbon nanotubes
International Nuclear Information System (INIS)
Soto, M; Boyer, T A; Biradar, S; Ge, L; Vajtai, R; Ajayan, P M; Barrera, E V; Elías-Zúñiga, A
2015-01-01
Through this study, the results of density functional theory calculations within the local density approximation of the electronic structure of zigzag–zigzag double-walled carbon nanotubes (DWCNTs), with chiral indices (n, 0)@(m, 0) for n = 7–15, and m = 15–26, has been presented and the effects of interwall interaction and orbital hybridization on the electronic structure of these systems has been discussed. It was observed that the electronic band gap of the aforementioned DWCNTs depends on the interwall distance only for metallic–semiconductor configurations and on the intrinsic properties of the constituent tubes in all other combinations. It was also observed that the calculated band gap for most of the metallic–metallic DWCNTs was smaller than semiconductor–metallic, metallic–semiconductor, and semiconductor–semiconductor configurations. Metallic–semiconductor DWCNTs were found to be desirable for band gap tuning applications because of their dependence on interwall distance, opening up the possibility of using such systems in electronic device applications, such as transistors. Other applications include the use of DWCNTs in macroscopic carbon nanotube conducting wires, for which metallic–metallic and semiconducting–metallic zigzag–zigzag DWCNTs were found to be the most desirable configurations due to their small band gaps. (paper)
Fast ions and hot electrons in the laser--plasma interaction
International Nuclear Information System (INIS)
Gitomer, S.J.; Jones, R.D.; Begay, F.; Ehler, A.W.; Kephart, J.F.; Kristal, R.
1986-01-01
Data on the emission of energetic ions produced in laser--matter interactions have been analyzed for a wide variety of laser wavelengths, energies, and pulse lengths. Strong correlation has been found between the bulk energy per AMU for fast ions measured by charge cups and the x-ray-determined hot electron temperature. Five theoretical models have been used to explain this correlation. The models include (1) a steady-state spherically symmetric fluid model with classical electron heat conduction, (2) a steady-state spherically symmetric fluid model with flux limited electron heat conduction, (3) a simple analytic model of an isothermal rarefaction followed by a free expansion, (4) the lasneX hydrodynamics code [Comments Plasma Phys. Controlled Fusion 2, 85 (1975)], calculations employing a spherical expansion and simple initial conditions, and (5) the lasneX code with its full array of absorption, transport, and emission physics. The results obtained with these models are in good agreement with the experiments and indicate that the detailed shape of the correlation curve between mean fast ion energy and hot electron temperature is due to target surface impurities at the higher temperatures (higher laser intensities) and to the expansion of bulk target material at the lower temperatures (lower laser intensities)
Influencing the electronic interaction in diferrocenyl-1-phenyl-1H-pyrroles.
Hildebrandt, Alexander; Lang, Heinrich
2011-11-28
Functionalised diferrocenyl-1-phenyl-1H-pyrroles were synthesised using Negishi C,C cross-coupling reactions. The influence of different substituents at the phenyl moiety on the electronic interaction was studied using electrochemistry (cyclic and square-wave voltammetry) and spectro-electrochemistry (in situ UV/Vis-NIR spectroscopy). The ferrocenyl moieties gave rise to two sequential, reversible redox processes in each of the diferrocenyl-1-phenyl-1H-pyrroles. The observed ΔE(1/2) values (ΔE(1/2) = difference between first and second oxidation) range between 420 and 480 mV. A linear relationship between the Hammett constants σ of the substituents and the separation of the redox potentials exists. The NIR measurements confirm electronic communication between the iron centers as intervalence charge transfer (IVCT) absorptions were observed in the corresponding mixed-valent monocationic species. All compounds were classified as class II systems according to Robin and Day (M. B. Robin and P. Day, Adv. Inorg. Chem., 1967, 10, 247-423). The oscillator strength of the charge transfer transition highly depends on the electron donating or electron withdrawing character of the phenyl substituents. This enables direct tuning of the intermetallic communication by simple modification of the molecule's functional group. Hence, this series of molecules may be regarded as model compounds for single molecule transistors.
International Nuclear Information System (INIS)
Lü, Jing-Tao; Zhou, Hangbo; Jiang, Jin-Wu; Wang, Jian-Sheng
2015-01-01
The topic of this review is the effects of electron-phonon interaction (EPI) on the transport properties of molecular nano-conductors. A nano-conductor connects to two electron leads and two phonon leads, possibly at different temperatures or chemical potentials. The EPI appears only in the nano-conductor. We focus on its effects on charge and energy transport. We introduce three approaches. For weak EPI, we use the nonequilibrium Green’s function method to treat it perturbatively. We derive the expressions for the charge and heat currents. For weak system-lead couplings, we use the quantum master equation approach. In both cases, we use a simple single level model to study the effects of EPI on the system’s thermoelectric transport properties. It is also interesting to look at the effect of currents on the dynamics of the phonon system. For this, we derive a semi-classical generalized Langevin equation to describe the nano-conductor’s atomic dynamics, taking the nonequilibrium electron system, as well as the rest of the atomic degrees of freedom as effective baths. We show simple applications of this approach to the problem of energy transfer between electrons and phonons
Electron-muon correlation as a new probe of strongly interacting quark-gluon plasma
International Nuclear Information System (INIS)
Akamatsu, Yukinao; Hatsuda, Tetsuo; Hirano, Tetsufumi
2009-01-01
As a new and clean probe to the strongly interacting quark-gluon plasma (sQGP), we propose an azimuthal correlation of an electron and a muon that originate from the semileptonic decay of charm and bottom quarks. By solving the Langevin equation for the heavy quarks under the hydrodynamic evolution of the hot plasma, we show that substantial quenching of the away-side peak in the electron-muon correlation can be seen if the sQGP drag force acting on heavy quarks is large enough as suggested from the gauge/gravity correspondence. The effect could be detected in high-energy heavy ion collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider.
International Nuclear Information System (INIS)
Angyan, Janos G.; Gerber, Iann C.; Savin, Andreas; Toulouse, Julien
2005-01-01
Long-range exchange and correlation effects, responsible for the failure of currently used approximate density functionals in describing van der Waals forces, are taken into account explicitly after a separation of the electron-electron interaction in the Hamiltonian into short- and long-range components. We propose a 'range-separated hybrid' functional based on a local density approximation for the short-range exchange-correlation energy, combined with a long-range exact exchange energy. Long-range correlation effects are added by a second-order perturbational treatment. The resulting scheme is general and is particularly well adapted to describe van der Waals complexes, such as rare gas dimers
Directory of Open Access Journals (Sweden)
Mykola A. Meleshko
2014-02-01
Full Text Available The article discusses the content of the «flash-book» construct, defining its properties and possible components. There are presented some examples of components programming steps of “authoring flash – book”, considered the possibility of using such an electronic document to optimize the learning process at the Technical University in the performance of laboratory training on general physics. The technique of its using to provide individualized approach to learning and the use of various experimental base from classical to digital equipment laboratories is proposed. It was carried out the analysis of ways to improve such interactive electronic document for the development of information technology competence of engineering students.
Harris, J. R.; Miller, R. B.
2018-02-01
The generation and evolution of modulated particle beams and their interactions with resonant radiofrequency (RF) structures are of fundamental interest for both particle accelerator and vacuum electronic systems. When the constraint of propagation in a vacuum is removed, the evolution of such beams can be greatly affected by interactions with matter including scattering, absorption, generation of atmospheric plasma, and the production of multiple generations of secondary particles. Here, we study the propagation of 21 MeV and 25 MeV electron beams produced in S-band and L-band linear accelerators, and their interaction with resonant RF structures, under a number of combinations of geometry, including transmission through both air and metal. Both resonant and nonresonant interactions were observed, with the resonant interactions indicating that the RF modulation on the electron beam is at least partially preserved as the beam propagates through air and metal. When significant thicknesses of metal are placed upstream of a resonant structure, preventing any primary beam electrons from reaching the structure, RF signals could still be induced in the structures. This indicated that the RF modulation present on the electron beam was also impressed onto the x-rays generated when the primary electrons were stopped in the metal, and that this RF modulation was also present on the secondary electrons generated when the x-rays struck the resonant structures. The nature of these interactions and their sensitivities to changes in system configurations will be discussed.
Harle, Christopher A; Golembiewski, Elizabeth H; Rahmanian, Kiarash P; Krieger, Janice L; Hagmajer, Dorothy; Mainous, Arch G; Moseley, Ray E
2017-12-19
The purpose of this study was to assess patient perceptions of using an interactive electronic consent (e-consent) application when deciding whether or not to grant broad consent for research use of their identifiable electronic health record (EHR) information. For this qualitative study, we conducted a series of 42 think-aloud interviews with 32 adults. Interview transcripts were coded and analyzed using a modified grounded theory approach. We identified themes related to patient preferences, reservations, and mixed attitudes toward consenting electronically; low- and high-information-seeking behavior; and an emphasis on reassuring information, such as data protections and prohibitions against sharing data with pharmaceutical companies. Participants expressed interest in the types of information contained in their EHRs, safeguards protecting EHR data, and specifics on studies that might use their EHR data. This study supports the potential value of interactive e-consent applications that allow patients to customize their consent experience. This study also highlights that some people have concerns about e-consent platforms and desire more detailed information about administrative processes and safeguards that protect EHR data used in research. This study contributes new insights on how e-consent applications could be designed to ensure that patients' information needs are met when seeking consent for research use of health record information. Also, this study offers a potential electronic approach to meeting the new Common Rule requirement that consent documents contain a "concise and focused" presentation of key information followed by more details. © The Author(s) 2017. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com
Preliminary results of a broad beam RF ion source with electron plasma interaction. Vol. 2
Energy Technology Data Exchange (ETDEWEB)
Abdelaziz, M E; Zakhary, S G; Ghanem, A A; Abdel-Ghaffar, A M [Ion Sources and Accelerators Department, Nuclear Research Center, Atomic Energy Authority, Cairo, (Egypt)
1996-03-01
A new design of a broad beam RF ion source is made to be capable to deliver wide and uniform beam with currents reaching (100 {mu} A up to 30 mA) at extraction voltages (200 V up to 2 kV). Its plasma intensifying system is made with the addition of electrons from an immersed filament in the discharge and axial magnetic field (70 up to 300 G). A uniform beam distribution is made with a planner graphite cathode which has a number of holes arranged to produce perveance matching with the normal Gaussian distribution of the beam density. These holes are arranged in a consequent orbits with equal distance between the adjacent holes in each orbit. These holes increase in diameter with increasing the orbit radius. This allows increasing the extracted ion currents at the source outer edges and decreases its value at the source inner region; producing wide and uniform beam which is suitable for material modifications. The beam profiles are traced with electromechanical scanner and X-Y recorder. The perveance matching is found to produce a beam uniformity of =66% of its width which reaches =6 cm. The variation of the output currents are with the variation of extraction voltages, magnetic field, discharge pressure and electron injection into the plasma. The extracted current increases with the increase of the discharge pressure, RF power and magnetic field intensity. The influence of electron plasma interaction is found to have a great effect on increasing the ion currents to about four times its value without electron interaction, however, this increase is limited due to presence of breakdown at V{sub ex} > 2 kV. The simple design of this source, its cleanness due to the use of pyrex discharge bottle, easy operation and maintenance adds other features to this broad beam type ion source which makes it suitable for metallurgical applications in broad beam accelerators. 6 figs.
Holguín-Gallego, Fernando José; Chávez-Calvillo, Rodrigo; García-Revilla, Marco; Francisco, Evelio; Pendás, Ángel Martín; Rocha-Rinza, Tomás
2016-07-15
The electronic energy partition established by the Interacting Quantum Atoms (IQA) approach is an important method of wavefunction analyses which has yielded valuable insights about different phenomena in physical chemistry. Most of the IQA applications have relied upon approximations, which do not include either dynamical correlation (DC) such as Hartree-Fock (HF) or external DC like CASSCF theory. Recently, DC was included in the IQA method by means of HF/Coupled-Cluster (CC) transition densities (Chávez-Calvillo et al., Comput. Theory Chem. 2015, 1053, 90). Despite the potential utility of this approach, it has a few drawbacks, for example, it is not consistent with the calculation of CC properties different from the total electronic energy. To improve this situation, we have implemented the IQA energy partition based on CC Lagrangian one- and two-electron orbital density matrices. The development presented in this article is tested and illustrated with the H2 , LiH, H2 O, H2 S, N2 , and CO molecules for which the IQA results obtained under the consideration of (i) the CC Lagrangian, (ii) HF/CC transition densities, and (iii) HF are critically analyzed and compared. Additionally, the effect of the DC in the different components of the electronic energy in the formation of the T-shaped (H2 )2 van der Waals cluster and the bimolecular nucleophilic substitution between F(-) and CH3 F is examined. We anticipate that the approach put forward in this article will provide new understandings on subjects in physical chemistry wherein DC plays a crucial role like molecular interactions along with chemical bonding and reactivity. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
Anto Sulaksono
2011-11-01
Full Text Available The differential cross-section of neutrino interaction with dense and warm electron gasses has been calculated by takinginto account the neutrino electromagnetic form factors. The significant effect of electromagnetic properties of neutrinocan be found if the neutrino dipole moment, μ ν , is ≥ 5.10-9 μB and neutrino charge radius, Rv, is ≥ 5.10-6 MeV-1. Theimportance of the retarded correction, detailed balance and Pauli blocking factors is shown and analyzed. Many-bodyeffects on the target matter which are included via random phase approximation (RPA correlation as well as photoneffective mass are also investigated.
Optical transitions and electronic interactions in self-assembled cobalt-fullerene mixture films
Czech Academy of Sciences Publication Activity Database
Lavrentiev, Vasyl; Chvostová, Dagmar; Lavrentieva, Inna; Vacík, Jiří; Daskal, Y.; Barchuk, M.; Rafaja, D.; Dejneka, Alexandr
2017-01-01
Roč. 50, č. 48 (2017), č. článku 485305. ISSN 0022-3727 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk LM2015088; GA MŠk LM2015056 Institutional support: RVO:68378271 ; RVO:61389005 Keywords : fullerene * cobalt * electronic interaction * optical absorption * mixture film Subject RIV: BM - Solid Matter Physics ; Magnetism; BO - Biophysics (FZU-D) OBOR OECD: Condensed matter physics (including formerly solid state physics , supercond.); Biophysics (FZU-D) Impact factor: 2.588, year: 2016
Interactive Numerical and Symbolic Analysis: A New Paradigm for Teaching Electronics
Directory of Open Access Journals (Sweden)
Jean-Claude Thomassian
2008-09-01
Full Text Available Analog Insydes, Mathematica’s symbolic circuit analysis toolbox, uses modern algorithms of expression simplification depending on comparisons with a numerical reference solution of the circuit under investigation. Some insight is offered on how the complexity of an expression barrier is overcome followed by two classical examples, a BJT emitter follower and a MOSFET common-gate amplifier stage to illustrate the proposed method at work. A concluding section discusses that time spent teaching introductory electronics by computer-aided circuit analysis, interactive numerical and symbolic, is a worthwhile investment.
[Experiment studies of electron-positron interactions at the Stanford Linear Accelerator Center
International Nuclear Information System (INIS)
Hertzbach, S.S.; Kofler, R.R.
1993-01-01
The High Energy Physics group at the University of Massachusetts has continued its' program of experimental studies of electron-positron interactions at the Stanford Linear Accelerator Center (SLAC). The group activities have included: analysis of data taken between 1982 and 1990 with the TPC detector at the PEP facility, continuing data collection and data analysis using the SLC/SLD facility, planning for the newly approved B-factory at SLAC, and participation in design studies for future high energy linear colliders. This report will briefly summarize these activities
Powerful effective one-electron Hamiltonian for describing many-atom interacting systems
International Nuclear Information System (INIS)
Lugo, J.O.; Vergara, L.I.; Bolcatto, P.G.; Goldberg, E.C.
2002-01-01
In this paper, we present an alternative way to build the effective one-electron picture of a many-atom interacting system. By simplifying the many-body general problem we present two different options for the bond-pair model Hamiltonian. We have found that the successive approximations in order to achieve the effective description have a dramatic influence on the result. Thus, only the model that introduces the correct renormalization in the diagonal term due to the overlap is able to reproduce, even in a quantitative fashion, the main properties of simple homonuclear diatomic molecules. The success of the model resides in the accurate definitions (free of parametrization) of the Hamiltonian terms, which, therefore, could be used to describe more complex interacting systems such as polyatomic molecules, adsorbed species, or atoms scattered by a surface
Energy Technology Data Exchange (ETDEWEB)
Nascimento, Daniel R.; DePrince, A. Eugene, E-mail: deprince@chem.fsu.edu [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390 (United States)
2015-12-07
We present a combined cavity quantum electrodynamics/ab initio electronic structure approach for simulating plasmon-molecule interactions in the time domain. The simple Jaynes-Cummings-type model Hamiltonian typically utilized in such simulations is replaced with one in which the molecular component of the coupled system is treated in a fully ab initio way, resulting in a computationally efficient description of general plasmon-molecule interactions. Mutual polarization effects are easily incorporated within a standard ground-state Hartree-Fock computation, and time-dependent simulations carry the same formal computational scaling as real-time time-dependent Hartree-Fock theory. As a proof of principle, we apply this generalized method to the emergence of a Fano-like resonance in coupled molecule-plasmon systems; this feature is quite sensitive to the nanoparticle-molecule separation and the orientation of the molecule relative to the polarization of the external electric field.
Tahir, M.; Sabeeh, K.; Schwingenschlö gl, Udo; Shaukat, A.
2013-01-01
Since the discovery of graphene, a lot of interest has been attracted by the zeroth Landau level, which has no analog in the conventional two dimensional electron gas. Recently, lifting of the spin and valley degeneracies has been confirmed experimentally by capacitance measurements, while in transport experiments, this is difficult due to the scattering in the device. In this context, we model interaction effects on the quantum capacitance of graphene in the presence of a perpendicular magnetic field, finding good agreement with experiments. We demonstrate that the valley degeneracy is lifted by the substrate and by Kekule distortion, whereas the spin degeneracy is lifted by Zeeman interaction. The two cases can be distinguished by capacitance measurements.
Tahir, M.
2013-12-10
Since the discovery of graphene, a lot of interest has been attracted by the zeroth Landau level, which has no analog in the conventional two dimensional electron gas. Recently, lifting of the spin and valley degeneracies has been confirmed experimentally by capacitance measurements, while in transport experiments, this is difficult due to the scattering in the device. In this context, we model interaction effects on the quantum capacitance of graphene in the presence of a perpendicular magnetic field, finding good agreement with experiments. We demonstrate that the valley degeneracy is lifted by the substrate and by Kekule distortion, whereas the spin degeneracy is lifted by Zeeman interaction. The two cases can be distinguished by capacitance measurements.
Ioffe, A
2002-01-01
A new experimental approach in the determination of the neutron-electron interaction amplitude is proposed. The main idea of this approach is to use a perfect-crystal neutron interferometer as both a sample and a device for the measurement of the extra phase shift caused by the neutron interaction with atoms of Si. Indeed, such a sample (an interferometer blade) has a well-known atomic density and is a priori perfectly aligned with respect to the crystal lattice of the interferometer crystal. This results in the minimization of systematic errors caused by sample alignment and increases the overall experimental accuracy. Some theoretic estimations and details of an experimental setup are discussed. (orig.)
Magnetism of singlet - singlet ions interacting with an electron gas: application to PrAl2
International Nuclear Information System (INIS)
Palermo, L.
1986-01-01
Various magnetic quantities are investigated for a system consisting of singlet-singlet ions interacting with an electron gas. In obtaining the magnetic state equations, the molecular field approximation is used. At T=0, an onset magnetic order condition in function of crystal field and exchange parameters and eletronic density of states at Fermi level is derived. A parametric study of the model is performed numerically. Main results are shown on diagrams. From the experimental data existent in the literature for magnetisation, susceptibility and magnetic specific heat of the PrAl 2 , a fitting with the model predictions is obtained using the following parameters: exchange interaction: 611meV; crystal field parameters: 2,5 meV; band with: 10 eV (of a rectangular density of states with 0,8 el/atom). (author) [pt
Millaku, Agron; Drobne, Damjana; Torkar, Matjaz; Novak, Sara; Remškar, Maja; Pipan-Tkalec, Živa
2013-09-15
We provide data obtained by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) on the interaction of ingested tungsten nanofibers with epithelial cells of the digestive tubes of a test organism Porcellio scaber. Conventional toxicity endpoints including feeding behaviour, weight loss and mortality were also measured in each investigated animal. No toxicity was detected in any of exposed animals after 14 days of feeding on tungsten nanofiber dosed food, but when nanofibers enter the digestive system they can react with epithelial cells of the digestive tubes, becoming physically inserted into the cells. In this way, nanofibers can injure the epithelial cells of digestive gland tubes when they are ingested with food. Our SEM data suggest that peristaltic forces may have an important role, not predicted by in vitro experiments, in the interactions of nanomaterials with digestive intestinal cells. Copyright © 2013 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Tahir, M.; Sabeeh, K.; Shaukat, A.; Schwingenschlögl, U.
2013-01-01
Since the discovery of graphene, a lot of interest has been attracted by the zeroth Landau level, which has no analog in the conventional two dimensional electron gas. Recently, lifting of the spin and valley degeneracies has been confirmed experimentally by capacitance measurements, while in transport experiments, this is difficult due to the scattering in the device. In this context, we model interaction effects on the quantum capacitance of graphene in the presence of a perpendicular magnetic field, finding good agreement with experiments. We demonstrate that the valley degeneracy is lifted by the substrate and by Kekule distortion, whereas the spin degeneracy is lifted by Zeeman interaction. The two cases can be distinguished by capacitance measurements
Molecular modeling of interactions in electronic nose sensors for environmental monitoring
Shevade, A. V.; Ryan, M. A.; Homer, M. L.; Manfreda, A. M.; Yen, S. -P. S.; Zhou, H.; Manatt, K.
2002-01-01
We report a study aimed at understanding analyte interactions with sensors made from polymer-carbon black composite films. The sensors are used in an Electronic Nose (ENose) which is used for monitoring the breathing air quality in human habitats. The model mimics the experimental conditions of the composite film deposition and formation and was developed using molecular modeling and simulation tools. The Dreiding 2.21 Force Field was used for the polymer and analyte molecules while graphite parameters were assigned to the carbon black atoms. The polymer considered for this work is methyl vinyl ether / maleic acid copolymer. The target analytes include both inorganic (NH3) and organic (methanol) types of compound. Results indicate different composite-analyte interaction behavior.
Energy Technology Data Exchange (ETDEWEB)
Millaku, Agron, E-mail: agron.mi@hotmail.com [Limnos-Company for Applied Ecology Ltd, Podlimbarskega 31, 1000 Ljubljana (Slovenia); Drobne, Damjana [University of Ljubljana, Biotechnical Faculty, Department of Biology, Večna pot 111, 1000 Ljubljana (Slovenia); Centre of Excellence, Advanced Materials and Technologies for the Future (CO NAMASTE), Jamova cesta 39, 1000 Ljubljana (Slovenia); Centre of Excellence, Nanoscience and Nanotechnology (Nanocentre), Jamova cesta 39, 1000 Ljubljana (Slovenia); Torkar, Matjaz [Institute of Metals and Technology IMT, Lepi pot 11, 1000 Ljubljana (Slovenia); Jožef Stefan Institute, Condensed Matter Physics Department, Jamova cesta 39, 1000 Ljubljana (Slovenia); Novak, Sara [University of Ljubljana, Biotechnical Faculty, Department of Biology, Večna pot 111, 1000 Ljubljana (Slovenia); Remškar, Maja [Jožef Stefan Institute, Condensed Matter Physics Department, Jamova cesta 39, 1000 Ljubljana (Slovenia); Pipan-Tkalec, Živa [University of Ljubljana, Biotechnical Faculty, Department of Biology, Večna pot 111, 1000 Ljubljana (Slovenia)
2013-09-15
Graphical abstract: Scanning electron microscopy is particularly well suited to the observation of nanofibre/cell interaction in the endothelial cells lining the hepatopancreas. (a) Tungsten oxide nanofibres, (b) test organism Porcellio scaber and schematic appearance of digestive tubes, (c) digestive tube (hepatopancreas) prepared for SEM investigation, (d) digestive gland cells (C) with nanofibres (NF) embedded in the cell membrane and (e) nanofibres inserted deeply in the cells and damaged nanofibres due to peristalsis. -- Highlights: • Tungsten oxide nanofibres react physically with digestive gland epithelial cells in Porcellio scaber. • Physical peristaltic forces of lead to insertion of nanofibres into the cells. • No toxic responses as measured by conventional toxicity biomarkers were detected. • Physical interactions were observed in a majority of the investigated animals. -- Abstract: We provide data obtained by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) on the interaction of ingested tungsten nanofibers with epithelial cells of the digestive tubes of a test organism Porcellio scaber. Conventional toxicity endpoints including feeding behaviour, weight loss and mortality were also measured in each investigated animal. No toxicity was detected in any of exposed animals after 14 days of feeding on tungsten nanofiber dosed food, but when nanofibers enter the digestive system they can react with epithelial cells of the digestive tubes, becoming physically inserted into the cells. In this way, nanofibers can injure the epithelial cells of digestive gland tubes when they are ingested with food. Our SEM data suggest that peristaltic forces may have an important role, not predicted by in vitro experiments, in the interactions of nanomaterials with digestive intestinal cells.
International Nuclear Information System (INIS)
Millaku, Agron; Drobne, Damjana; Torkar, Matjaz; Novak, Sara; Remškar, Maja; Pipan-Tkalec, Živa
2013-01-01
Graphical abstract: Scanning electron microscopy is particularly well suited to the observation of nanofibre/cell interaction in the endothelial cells lining the hepatopancreas. (a) Tungsten oxide nanofibres, (b) test organism Porcellio scaber and schematic appearance of digestive tubes, (c) digestive tube (hepatopancreas) prepared for SEM investigation, (d) digestive gland cells (C) with nanofibres (NF) embedded in the cell membrane and (e) nanofibres inserted deeply in the cells and damaged nanofibres due to peristalsis. -- Highlights: • Tungsten oxide nanofibres react physically with digestive gland epithelial cells in Porcellio scaber. • Physical peristaltic forces of lead to insertion of nanofibres into the cells. • No toxic responses as measured by conventional toxicity biomarkers were detected. • Physical interactions were observed in a majority of the investigated animals. -- Abstract: We provide data obtained by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) on the interaction of ingested tungsten nanofibers with epithelial cells of the digestive tubes of a test organism Porcellio scaber. Conventional toxicity endpoints including feeding behaviour, weight loss and mortality were also measured in each investigated animal. No toxicity was detected in any of exposed animals after 14 days of feeding on tungsten nanofiber dosed food, but when nanofibers enter the digestive system they can react with epithelial cells of the digestive tubes, becoming physically inserted into the cells. In this way, nanofibers can injure the epithelial cells of digestive gland tubes when they are ingested with food. Our SEM data suggest that peristaltic forces may have an important role, not predicted by in vitro experiments, in the interactions of nanomaterials with digestive intestinal cells
Interactions between low energy electrons and DNA: a perspective from first-principles simulations
Kohanoff, Jorge; McAllister, Maeve; Tribello, Gareth A.; Gu, Bin
2017-09-01
DNA damage caused by irradiation has been studied for many decades. Such studies allow us to better assess the dangers posed by radiation, and to increase the efficiency of the radiotherapies that are used to combat cancer. A full description of the irradiation process involves multiple size and time scales. It starts with the interaction of radiation—either photons or swift ions—and the biological medium, which causes electronic excitation and ionisation. The two main products of ionising radiation are thus electrons and radicals. Both of these species can cause damage to biological molecules, in particular DNA. In the long run, this molecular level damage can prevent cells from replicating and can hence lead to cell death. For a long time it was assumed that the main actors in the damage process were the radicals. However, experiments in a seminal paper by the group of Leon Sanche in 2000 showed that low-energy electrons (LEE), such as those generated when ionising biological targets, can also cause bond breaks in biomolecules, and strand breaks in plasmid DNA in particular (Boudaiffa et al 2000 Science 287 1658-60). These results prompted a significant amount of experimental and theoretical work aimed at elucidating the role played by LEE in DNA damage. In this Topical Review we provide a general overview of the problem. We discuss experimental findings and theoretical results hand in hand with the aim of describing the physics and chemistry that occurs during the process of radiation damage, from the initial stages of electronic excitation, through the inelastic propagation of electrons in the medium, the interaction of electrons with DNA, and the chemical end-point effects on DNA. A very important aspect of this discussion is the consideration of a realistic, physiological environment. The role played by the aqueous solution and the amino acids from the histones in chromatin must be considered. Moreover, thermal fluctuations must be incorporated when
Directory of Open Access Journals (Sweden)
Ning Cao
2017-08-01
Full Text Available In this paper, classified theoretical models, consisting of contact with and placement of microsphere and picking operations, are simplified and established to depict the interactive behaviors of external and internal forces in pushing manipulations, respectively. Sliding and/or rolling cases, resulting in the acceleration of micromanipulations, are discussed in detail. Effective contact detection is achieved by combining alterations of light-shadow and relative movement displacement between the tip-sphere. Picking operations are investigated by typical interactive positions and different end tilt angles. Placements are realized by adjusting the proper end tilt angles. These were separately conducted to explore the interactive operations of nonconductive glass microspheres in a scanning electron microscope. The experimental results demonstrate that the proposed contact detection method can efficiently protect the end-tip from damage, regardless of operator skills in initial positioning operations. E-beam irradiation onto different interactive positions with end tilt angles can be utilized to pick up microspheres without bending the end-tip. In addition, the results of releasing deviations away from the pre-setting point were utilized to verify the effectiveness of the placement tilt angles.
International Nuclear Information System (INIS)
Namsrai, Kh.; Nyamtseren, N.
1994-09-01
A model of the extended electron is constructed by using definition of the d-operation. Gauge invariance of the nonlocal theory is proved. We use the Efimov approach to describe the nonlocal interaction of quantized fields. (author). 4 refs