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The European Physical Journal D

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Electron-electron bremsstrahlung for bound target electrons

Wed, 08/27/2008 - 15:49

Abstract  For the process of electron-electron (e-e) bremsstrahlung the momentum and energy distributions of the recoiling electrons are calculated in the laboratory frame. In order to get the differential cross section and the photon spectrum for target electrons which are bound to an atom, these formulae are multiplied by the incoherent scattering function and numerically integrated over the recoil energy. The effect of atomic binding is most pronounced at low energies of the incident electrons and for target atoms of high atomic numbers. The results are compared to those of previous calculations.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00156-5
  • Authors
    • E. Hauga, Universität Tübingen Institut für Astronomie und Astrophysik Auf der Morgenstelle 10 72076 Tübingen Germany

Ionisation and fragmentation of tetraphenyl iron (III) porphyrin chloride induced by slow multiply charged ion impact

Wed, 08/27/2008 - 15:49

Abstract  Ionisation and ion-induced fragmentation of tetraphenyl iron (III) porphyrin chloride (FeTPPCl) molecules have been studied after slow collisions (ν ∼ 0.2 a.u.) with multiply charged ions (O3+, Ar8+). Intact molecules and large fragments are observed in charge states up to q = 4. For q = 1, the intact molecule is the most abundant species, in particular, when projectiles in higher charge states are used. When the internal energy of the singly charged ion is increased by the energy transfer during the collision, the singly charged system de-excites by the emission of a neutral Cl-atom, a free electron or possibly a negative Cl anion. The processes are observed as direct as well as delayed processes on a μs-time scale. For q = 2 to 4 the loss of the Cl-atom and some phenyl groups becomes more likely due to the lower stability and the larger energy transfer. The charge state distribution of atomic fragments is found to be very different, in particular, when C q+ and Cl q+ ions are compared. In the first case mainly singly charged ions are detected, whereas in the second case ions in charge states up to q = 6 are observed with high intensities. These phenomena are discussed in terms of the intramolecular charge mobility.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00153-8
  • Authors
    • V. Bernigaud, CEA/CNRS/ENSICAEN/UCBN Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP) BP 5133, boulevard Henri Becquerel 14070 Caen Cedex 05 France
    • B. Manil, CEA/CNRS/ENSICAEN/UCBN Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP) BP 5133, boulevard Henri Becquerel 14070 Caen Cedex 05 France
    • L. Maunoury, CEA/CNRS/ENSICAEN/UCBN Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP) BP 5133, boulevard Henri Becquerel 14070 Caen Cedex 05 France
    • J. Rangama, CEA/CNRS/ENSICAEN/UCBN Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP) BP 5133, boulevard Henri Becquerel 14070 Caen Cedex 05 France
    • B. A. Huber, CEA/CNRS/ENSICAEN/UCBN Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP) BP 5133, boulevard Henri Becquerel 14070 Caen Cedex 05 France

Exact results on decoherence and entanglement in a system of N driven atoms and a dissipative cavity mode

Wed, 08/27/2008 - 15:49

Abstract  We solve the dynamics of an open quantum system where N strongly driven two-level atoms are equally coupled on resonance to a dissipative cavity mode. Analytical results are derived on decoherence, entanglement, purity, atomic correlations and cavity field mean photon number. We predict decoherencefree subspaces for the whole system and the N-qubit subsystem, the monitoring of quantum coherence and purity decay by atomic populations measurements, the conditional generation of atomic multi-partite entangled states and of cavity cat-like states. We show that the dynamics of atoms prepared in states invariant under permutation of any two components remains restricted within the subspace spanned by the completely symmetric Dicke states. We discuss examples and applications in the cases N = 3, 4.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00160-9
  • Authors
    • M. Bina, Università di Milano Dipartimento di Fisica via Celoria 16 20133 Milano Italy
    • F. Casagrande, Università di Milano Dipartimento di Fisica via Celoria 16 20133 Milano Italy
    • A. Lulli, Università di Milano Dipartimento di Fisica via Celoria 16 20133 Milano Italy

Collision induced dissociation of deuterium enriched protonated 2′-deoxyguanosine

Wed, 08/27/2008 - 15:49

Abstract  Collision induced dissociation in mass spectrometry of protonated nucleosides typically yields as charged fragment the protonated nucleobase augmented by one hydrogen transferred from the 2′-deoxyribose, [bH2]. The origin of the hydrogen transfer for the protonated 2′-deoxyguanosine has been investigated by collision induced dissociation of deuterium enriched molecules. [1′-2H]2′-deoxyguanosine, [2′,2″′-2H2]2′-deoxyguanosine, and [5′,5′′-2H2]2′-deoxyguanosine have been studied and deuterium/hydrogen back exchange has been used following complete or partial exchange of the 2′-deoxyguanosine in solution. Based on the fragmentation of the deuterated molecular ions, the hydrogen transferred from the 2′-deoxyribose to the guanine is found to originate from the O5′ atom on the 2′-deoxyribose. A fragmentation mechanism involving a hydrogen shift from the 2′ position to the oxygen atom O5′ and supported by the kinetic isotope effect on the survival yield curves is proposed. The influence of the 2′-deoxyguanosine conformation on the hydrogen transfer and the fragmentation mechanism is discussed.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00149-4
  • Authors
    • J. -F. Greisch, University of Liège Department of Chemistry, B6c 6700 Liège Belgium
    • B. Leyh, University of Liège Department of Chemistry, B6c 6700 Liège Belgium
    • E. De Pauw, University of Liège Department of Chemistry, B6c 6700 Liège Belgium

Scattering effect of atoms through a Bose-Einstein condensate in an optical Lattice with a single defect

Wed, 08/27/2008 - 15:49

Abstract  We study the transport of atoms across a localized Bose-Einstein condensate in an onedimensional optical lattice with a single defect. Our analytical and numerical results show that the defect as well as the nonlinear parameter can control the transmission of the atoms beam and the position of total reflection caused by Fano resonance. These interesting features may be a very useful basis for devising tunable atom filters or a button.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00155-6
  • Authors
    • C. X. Zhang, Zhejiang Ocean University Physical Department Zhoushan 316000 P.R. China
    • B. Zhou, The University of Hong Kong Department of Physics, and Center for Theoretical and Computational Physics Pokfulam Road Hong Kong P.R. China
    • Y. H. Nie, Shanxi University Institute of Theoretical Physics and Department of Physics Taiyuan Shanxi 030006 P.R. China
    • J. Q. Liang, Shanxi University Institute of Theoretical Physics and Department of Physics Taiyuan Shanxi 030006 P.R. China
    • J. Liu, Institute of Applied Physics and Computational Mathematics P.O. Box 8009 (28) 100088 Beijing P.R. China

Excitation-autoionization cross sections and rate coefficients for Ga-like ions

Wed, 08/27/2008 - 15:49

Abstract  Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct and indirect ionization of ions belonging to the GaI isoelectronic sequence (ground 3d 104s 24p) have been performed. The cross sections are presented in the energy range near the threshold for the five ions Kr5+, Mo11+, Xe23+, Pr28+ and Dy35+. The rate coefficients are given for ions from Kr5+ to U61+ in the GaI sequence at seven electron temperatures (kT e = 0.1E I , 0.3E I , 0.5E I , 0.7E I ,E I , 2E I and 10E I , where E I is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the framework of the distorted wave (DW) approximation for the 4s-nl, 3d-nl and 3p-nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along the GaI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 10 is predicted for instance for La26+ (Z = 57) at electron temperature of coronal equilibrium maximum abundance.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00159-2
  • Authors
    • P. Mandelbaum, Ramat Beth Hakerem Jerusalem College of Engineering 91035 Jerusalem Israel
    • J. L. Schwob, The Hebrew University Racah Institute of Physics 91904 Jerusalem Israel

Calculation of radiative transition probabilities and radiative recombination rate coefficients for H2, OH, H 2+ and OH+ molecules

Wed, 08/27/2008 - 15:49

Abstract  A method is presented to calculate the radiative transition probabilities and the radiative recombination rate coefficients between electronic molecular states. Total transition probabilities are determined from vibrational transition probabilities without considering the detailed rotational structure of the molecular electronic states. Radiative recombination rate coefficients are obtained from the computation of vibrational photo-ionisation cross sections. Concerning spontaneous emission, Lyman (B → X) and Werner (C → X) band systems of H2 and Meinel (A → X), (B → A) and (B → X) band systems of OH are investigated. For radiative recombination, transitions between H2+ (X) and H2(X), and between OH+(X, a, A, b, and c) and OH(X) are considered. Transition probabilities and recombination rate coefficients are calculated as a function of temperature in the range 1500–15 000 K.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00157-4
  • Authors
    • R. Riahi, Université de Tunis el Manar Laboratoire de Spectroscopie Atomique, Moléculaire et Applications (LSAMA), Faculté des Sciences de Tunis 1060 Tunis Tunisia
    • P. Teulet, Université Paul Sabatier Toulouse 3 Laboratoire Plasma et Conversion d’Energie (LAPLACE), UMR UPS-INP-CNRS 5213 118 route de Narbonne 31062 Toulouse Cedex 09 France
    • Y. Cressault, Université Paul Sabatier Toulouse 3 Laboratoire Plasma et Conversion d’Energie (LAPLACE), UMR UPS-INP-CNRS 5213 118 route de Narbonne 31062 Toulouse Cedex 09 France
    • A. Gleizes, Université Paul Sabatier Toulouse 3 Laboratoire Plasma et Conversion d’Energie (LAPLACE), UMR UPS-INP-CNRS 5213 118 route de Narbonne 31062 Toulouse Cedex 09 France
    • Z. Ben Lakhdar, Université de Tunis el Manar Laboratoire de Spectroscopie Atomique, Moléculaire et Applications (LSAMA), Faculté des Sciences de Tunis 1060 Tunis Tunisia

Electronic states of neutral and ionized tetrahydrofuran studied by VUV spectroscopy and ab initio calculations

Wed, 08/27/2008 - 15:49

Abstract  The electronic spectroscopy of isolated tetrahydrofuran (THF) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 5.8–10.6 eV with absolute cross-section measurements derived. In addition, an electron energy loss spectrum was recorded at 100 eV and 10° over the 5–11.4 eV range. The He(I) photoelectron spectrum was also collected to quantify ionisation energies in the 9–16.1 eV spectral region. These experiments are supported by the first high-level ab initio calculations performed on the excited states of the neutral molecule and on the ground state of the positive ion. The excellent agreement between the theoretical results and the measurements allows us to solve several discrepancies concerning the electronic state spectroscopy of THF. The present work reconsiders the question of the lowest energy conformers of the molecule and its population distribution at room temperature.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00154-7
  • Authors
    • A. Giuliani, Synchrotron Soleil DISCO beamline L’Orme des Merisiers, Saint-Aubin 91192 Gif-sur-Yvette France
    • P. Limão-Vieira, Universidade Nova de Lisboa Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física 2829-516 Caparica Portugal
    • D. Duflot, Université des Sciences et Technologies de Lille Laboratoire de Physique des Lasers, Atomes et Molécules (PhLAM), UMR CNRS 8523, Centre d’Études et de Recherches Lasers et Applications (CERLA, FR CNRS 2416) 59655 Villeneuve d’Ascq Cedex France
    • A. R. Milosavljevic, Institute of Physics Laboratory for atomic collision processes Pregrevica 118 11080 Belgrade Serbia
    • B. P. Marinkovic, Institute of Physics Laboratory for atomic collision processes Pregrevica 118 11080 Belgrade Serbia
    • S. V. Hoffmann, University of Aarhus Institute for Storage Ring Facilities Ny Munkegade 8000 Aarhus C Denmark
    • N. Mason, The Open University Centre of Molecular and Optical Sciences, Department of Physics and Astronomy Walton Hall, Milton Keynes MK7 6AA UK
    • J. Delwiche, Université de Liège, Institut de Chimie-Bât. B6c Laboratoire de Spectroscopie d’Électrons Diffusés 4000 Liège 1 Liege Belgium
    • M. -J. Hubin-Franskin, Université de Liège, Institut de Chimie-Bât. B6c Laboratoire de Spectroscopie d’Électrons Diffusés 4000 Liège 1 Liege Belgium

Effect of electron inertia on large amplitude solitary waves in presence of kinematic viscosity in dusty plasma

Wed, 08/27/2008 - 15:49

Abstract  Nonlinear dust acoustic solitary waves in a dusty plasma are studied for nonzero kinematic viscosity. Sagdeev’s potential can be obtain upto any order in ϕ. The existence of soliton solution is determined by pseudopotential approach. It is seen that the electron inertia has a significant effect on the existence of solitary waves in presence of kinematic viscosity.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00158-3
  • Authors
    • B. Sen, Visva-Bharati University Department of Mathematics P.O. Santiniketan 731235 West Bengal Birbhum India
    • B. Das, Visva-Bharati University Department of Mathematics P.O. Santiniketan 731235 West Bengal Birbhum India
    • P. Chatterjee, Visva-Bharati University Department of Mathematics P.O. Santiniketan 731235 West Bengal Birbhum India

Optical characterization and manipulation of alkali metal nanoparticles in porous silica

Sun, 08/24/2008 - 16:42

Abstract  Rubidium and cesium metal nanoparticles were grown in nanoporous silica samples placed in alkali vapor cells. Their size and shape were investigated by measuring the sample optical transmittance. Spectral changes due to photodesorption processes activated by weak light were also analyzed. Alkali atoms photoejected from the silica walls diffuse through and out of the nanopores, modifying both the nanoparticle distribution in the silica matrix and the atomic vapor pressure in the cell volume. The number of rubidium and cesium atoms burst out of the samples was measured as a function of photon energy and fluence. The optical absorption measurements together with the analysis of the photodesorption yield give a complete picture of the processes triggered by light inside the nanopores. We show that atomic photodesorption, upon proper choice of light frequency and intensity, induces either growth or evaporation of nanosized alkali metal clusters. Cluster size and shape are determined by the host-guest interaction.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00164-5
  • Authors
    • A. Burchianti, University of Siena CNISM and Physics Department 53100 Siena Italy
    • A. Bogi, University of Siena CNISM and Physics Department 53100 Siena Italy
    • C. Marinelli, University of Siena CNISM and Physics Department 53100 Siena Italy
    • C. Maibohm, University of Siena CNISM and Physics Department 53100 Siena Italy
    • E. Mariotti, University of Siena CNISM and Physics Department 53100 Siena Italy
    • S. Sanguinetti, University of Pisa Physics Department 56127 Pisa Italy
    • L. Moi, University of Siena CNISM and Physics Department 53100 Siena Italy

Fractal model of the atom and some properties of the matter through an extended model of scale relativity

Sun, 08/17/2008 - 16:13

Abstract  The scale relativity model was extended for the motions on fractal curves of fractal dimension D F and third order terms in the equation of motion of a complex speed field. It results that, in a fractal fluid, the convection, dissipation and dispersion are compensating at any scale (differentiable or non-differentiable), whereas a generalized Schrödinger type equation is obtained for an irrotational movement of the fractal fluid. For D F = 2 and the dissipative approximation of the motions, the fractal model of atom is build: the real part of the complex speed field describes the electron motion on stationary orbits according to a quantification condition, while the imaginary part of the complex speed field gives the electron energy quantification. For D F = 3 and the dispersive approximation of motions, some properties of the matter are explained: at the differentiable scale the flowing regimes (non-quasi-autonomous and quasi-autonomous) of the fractal fluids are separated by the experimental “0.7 structure”, while for the non-differentiable scale the fractal potential acts as an energy accumulator and controls through coherence the transport phenomena. Moreover, the compatibility between the differentiable and non-differentiable scales implies a Cantor space-time, and consequently a fractal at any scale. Thus, some properties of the matter (the anomaly of nano-fluids thermal conductivity, the superconductivity etc.) can be explained by this model.

  • Content Type Journal Article
  • DOI 10.1140/epjd/e2008-00161-8
  • Authors
    • M. Agop, University of Athens Department of Physics 15771 Athens Greece
    • P. E. Nica, University of Athens Department of Physics 15771 Athens Greece
    • P. D. Ioannou, University of Athens Department of Physics 15771 Athens Greece
    • A. Antici, Technical Gh. Asachi University Department of Physics 700050 Iasi Romania
    • V. P. Paun, Faculty of Applied Sciences, Politehnica University of Bucharest Department of Physics I 313 Splaiul Independentei street 060042 Bucharest Romania