References of "Rüffer, R"
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See detailNuclear forward scattering of synchrotron radiation by Ru 99
Bessas, D.; Merkel, D. G.; Chumakov, A. I. et al

in Physical Review Letters (2014), 113(14),

We measured nuclear forward scattering spectra utilizing the Ru99 transition, 89.571(3) keV, with a notably mixed E2/M1 multipolarity. The extension of the standard evaluation routines to include mixed ... [more ▼]

We measured nuclear forward scattering spectra utilizing the Ru99 transition, 89.571(3) keV, with a notably mixed E2/M1 multipolarity. The extension of the standard evaluation routines to include mixed multipolarity allows us to extract electric and magnetic hyperfine interactions from Ru99-containing compounds. This paves the way for several other high-energy Mössbauer transitions, E∼90keV. The high energy of such transitions allows for operando nuclear forward scattering studies in real devices. © 2014 American Physical Society. [less ▲]

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See detailRole of disorder in the thermodynamics and atomic dynamics of glasses
Chumakov, A. I.; Monaco, G.; Fontana, A. et al

in Physical Review Letters (2014), 112(2),

We measured the density of vibrational states (DOS) and the specific heat of various glassy and crystalline polymorphs of SiO2. The typical (ambient) glass shows a well-known excess of specific heat ... [more ▼]

We measured the density of vibrational states (DOS) and the specific heat of various glassy and crystalline polymorphs of SiO2. The typical (ambient) glass shows a well-known excess of specific heat relative to the typical crystal (α-quartz). This, however, holds when comparing a lower-density glass to a higher-density crystal. For glassy and crystalline polymorphs with matched densities, the DOS of the glass appears as the smoothed counterpart of the DOS of the corresponding crystal; it reveals the same number of the excess states relative to the Debye model, the same number of all states in the low-energy region, and it provides the same specific heat. This shows that glasses have higher specific heat than crystals not due to disorder, but because the typical glass has lower density than the typical crystal. © 2014 American Physical Society. [less ▲]

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See detailNuclear forward and inelastic spectroscopy on 125Te and Sb2 125Te3 2
Wille, H.-C.; Hermann, Raphaël ULg; Sergueev, I. et al

in Europhysics Letters [=EPL] (2010)

We report on the observation of nuclear forward and nuclear inelastic scattering of synchrotron radiation by Te-125 and the application of both spectroscopic methods to tellurium compounds by using a high ... [more ▼]

We report on the observation of nuclear forward and nuclear inelastic scattering of synchrotron radiation by Te-125 and the application of both spectroscopic methods to tellurium compounds by using a high-resolution backscattering sapphire monochromator in combination with fast detection electronics. The lifetime of the nuclear resonance and the energy of the transition were determined to be 2.131(12) ns and 35493.12(30) eV, respectively. As applications, the nuclear inelastic spectrum in Sb2Te3 and the nuclear forward scattering by Te metal were measured. These measurements open the field of nuclear resonance spectroscopy on tellurium compounds such as thermoelectric and superconducting materials. [less ▲]

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See detailNeutron and nuclear inelastic scattering study of the Einstein oscillators in Ba-, Sr-, and Eu-filled germanium clathrates
Hermann, Raphaël ULg; Schweika, W.; Leupold, O. et al

in Physical Review b (2005), 72(17),

Inelastic neutron scattering measurements on Ba8Ga16Ge30 and Sr8Ga16Ge30 indicate the presence of soft local modes with Einstein oscillator energies of 4.9 +/- 0.1 and 4.4 +/- 0.1 meV, modes which are ... [more ▼]

Inelastic neutron scattering measurements on Ba8Ga16Ge30 and Sr8Ga16Ge30 indicate the presence of soft local modes with Einstein oscillator energies of 4.9 +/- 0.1 and 4.4 +/- 0.1 meV, modes which are associated with the lowest "rattling" mode of the Ba(B) and Sr(B) guests, respectively. Nuclear inelastic scattering measurements on Eu8Ga16Ge30 yield Einstein oscillator energies of between 3.0 +/- 0.3 and 7.5 +/- 1.2 meV for the different modes of the Eu guests. Further, the resonant character of the measurements on Eu8Ga16Ge30 reveals, without question, that neither of the Eu guests exhibit any vibrational modes above 9 meV. [less ▲]

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See detailStrongly decoupled europium and iron vibrational modes in filled skutterudites
Long, G. J.; Hermann, Raphaël ULg; Grandjean, Fernande ULg et al

in Physical Review b (2005), 71(14),

The europium partial vibrational density of states (DOS) in EuFe4Sb12 and the iron partial vibrational DOS in both EuFe4Sb12 and (CeFe4Sb12)-Fe-57 have been obtained by nuclear inelastic scattering. The ... [more ▼]

The europium partial vibrational density of states (DOS) in EuFe4Sb12 and the iron partial vibrational DOS in both EuFe4Sb12 and (CeFe4Sb12)-Fe-57 have been obtained by nuclear inelastic scattering. The results reveal the strong independence of the iron and rare-earth vibrational modes. The cage filling europium only participates significantly to the low-energy local vibrational modes. The force constants have been obtained from the measured probability of nuclear absorption. The energies of the peaks in the europium and iron DOS are in excellent agreement with the calculated DOS in LaFe4Sb12. The results indicate that nuclear inelastic scattering is the technique of choice for the study of the localized vibrational modes in thermoelectric "phonon glass" materials. [less ▲]

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