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  • 2000-2004  (7)
  • 1985-1989
  • 1975-1979
  • 2001  (7)
  • PACS. 32.80.Pj Optical cooling of atoms; trapping – 34.50.Rk Laser-modified scattering and reactions  (3)
  • PACS. 03.75.Be Atom and neutron optics – 42.25.Fx Diffraction and scattering  (2)
  • PACS. 64.70.Pf Glass transitions – 05.70.Ln Nonequilibrium and irreversible thermodynamics  (2)
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  • 2000-2004  (7)
  • 1985-1989
  • 1975-1979
Year
  • 2001  (7)
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Validity of the zero-thermodynamic law in off-equilibrium coupled harmonic oscillators (2001)
    Springer
    The European physical journal 20 (2001), S. 105-122 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 64.70.Pf Glass transitions – 05.70.Ln Nonequilibrium and irreversible thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In order to describe the thermodynamics of the glassy systems it has been recently introduced an extra parameter, the effective temperature which generalizes the fluctuation-dissipation theorem (FDT) to off-equilibrium systems and supposedly describes thermal fluctuations around the aging state. Using this concept we investigate the applicability of a zeroth thermodynamic law for non-equilibrium systems. In particular we study two coupled systems of harmonic oscillators with Monte Carlo dynamics. We analyze in detail two types of dynamics: 1) sequential dynamics where the coupling between the subsystems comes only from the Hamiltonian and 2) parallel dynamics where there is a further coupling between the subsystems arising from the dynamics. We show that the coupling described in the first case is not enough to make asymptotically the effective temperatures of the two interacting subsystems equalize, the reason being the too small thermal conductivity between them in the aging state. This explains why different interacting degrees of freedom in structural glasses may stay at different effective temperatures without never mutually thermalizing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313919
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Heat transfer and Fourier's law in off-equilibrium systems (2001)
    Springer
    The European physical journal 21 (2001), S. 115-120 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 64.70.Pf Glass transitions – 05.70.Ln Nonequilibrium and irreversible thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the most suitable procedure to measure the effective temperature in off-equilibrium systems. We analyze the stationary current established between an off-equilibrium system and a thermometer and the necessary conditions for that current to vanish. We find that the thermometer must have a short characteristic time-scale compared to the typical decorrelation time of the glassy system to correctly measure the effective temperature. This general conclusion is confirmed analyzing an ensemble of harmonic oscillators with Monte Carlo dynamics as an illustrative example of a solvable model of a glass. We also find that the current defined allows to extend Fourier's law to the off-equilibrium regime by consistently defining effective transport coefficients. Our results for the oscillator model explain why thermal conductivities between thermalized and frozen degrees of freedom in structural glasses are extremely small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01315082
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Atom diffraction from magnetic gratings in the thin phase-grating approximation (2001)
    Springer
    The European physical journal 14 (2001), S. 289-297 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 03.75.Be Atom and neutron optics – 42.25.Fx Diffraction and scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The problem of atom diffraction from a reflecting magnetic diffraction grating is solved in the thin phase-grating approximation. The general problem for scalar diffraction is modelled using a semi-classical method in which the grating potential is separated into a reflecting term and a diffracting term. The trajectory of the atom in the reflecting potential is solved classically and the atom wave function in the diffracting potential found by integrating the phase change along the classical trajectory. The diffraction orders are obtained after Fourier transforming the result. This can be done independently of the grating potential resulting in a general formula for the diffraction efficiencies. The general result is applied to the problem of atom diffraction from a magnetic grating. Several approximations are required to reduce the problem to a form amenable to analytic solution. The results are compared with an accurate numerical method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170195
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Inversion analysis of K 2 coupled electronic states with the Fourier grid method (2001)
    Springer
    The European physical journal 17 (2001), S. 319-328 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Pj Optical cooling of atoms; trapping – 34.50.Rk Laser-modified scattering and reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present a new determination of the potential curves and interactions of the coupled electronic states A 1 Σ + u and b 3 Π u of the potassium dimer, based on new laser spectroscopy measurements within a molecular beam, combined with data available in the literature. We used a new global deperturbation approach, involving the Fourier Grid Hamiltonian method for energy level calculation. A standard deviation of 1.2 is obtained corresponding to a variance of 7.5×10 -3 cm-1, representing a significant improvement compared to the standard deviation of 4 yielded by the traditional local deperturbation approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170006
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Modelling the diffraction of laser-cooled atoms from magnetic gratings (2001)
    Springer
    The European physical journal 14 (2001), S. 111-118 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 03.75.Be Atom and neutron optics – 42.25.Fx Diffraction and scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The diffraction of laser-cooled atoms from a spatially-periodic potential is modelled using rigorous coupled-wave analysis. This numerical technique, normally applied to light-diffraction, is adapted for use with atomic de Broglie waves incident on a reflecting diffraction grating. The technique approximates the potential by a large number of constant layers and successively solves the complex eigenvalue problem in each layer, propagating the solution up to the surface of the grating. The method enables the diffraction efficiencies to be calculated for any periodic potential. The results from the numerical model are compared with the thin phase-grating approximation formulae for evanescent light-wave diffraction gratings and idealised magnetic diffraction gratings. The model is applied to the problem of diffracting Rb atoms from a grating made from an array of permanent magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170242
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Cold rubidium molecule formation through photoassociation: A spectroscopic study of the 0 g - long-range state of 87 Rb 2 (2001)
    Springer
    The European physical journal 15 (2001), S. 189-198 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Pj Optical cooling of atoms; trapping – 34.50.Rk Laser-modified scattering and reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report the detailed analysis of translationally cold rubidium molecule formation through photoassociation. Cold molecules are formed after spontaneous decay of photoexcited molecules from a laser cooled atomic sample, and are detected by selective mass spectroscopy after two-photon ionization into Rb 2 + ions. A spectroscopic study of the 0 g - (5 S + 5 P 3/2 ) pure long-range state of 87Rb2 is performed by detecting the ion yield as a function of the photoassociation laser frequency; the spectral data are theoretically analyzed within the semiclassical RKR approach. Molecular ionization is resonantly enhanced through either the 2 3 Π g or the 2 3 Σ + g intermediate molecular states. Some vibrational levels of the latter electronic state are observed and assigned here for the first time. Finally, cold molecules formation rates are calculated and compared to the experimentally measured ones, and the vibrational distribution of the formed molecules in the a 3 Σ + u ground triplet state is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170165
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Penning collisions of laser-cooled metastable helium atoms (2001)
    Springer
    The European physical journal 14 (2001), S. 15-22 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Pj Optical cooling of atoms; trapping – 34.50.Rk Laser-modified scattering and reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient β on the excited state ( 23 P 2) and metastable state ( 23 S 1) populations is also investigated. From these results we infer a rather uniform rate constant K sp = (1±0.4)×10-7 cm3/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170228
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    Paper (German National Licenses)
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