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9 results on '"Ruffer, Rudolf"'

1. Collective lamb shift in single-photon superradiance

Author

Rohlsberger, Ralf, Schlage, Kai, Sahoo, Balaram, Couet, Sebastien, and Ruffer, Rudolf

Subjects
Spectrum analysis -- Methods, Science and technology
Abstract

Superradiance, the cooperative spontaneous emission of photons from an ensemble of identical atoms, provides valuable insights into the many-body physics of photons and atoms. We show that an ensemble of resonant atoms embedded in the center of a planar cavity can be collectively excited by synchrotron radiation into a purely superradiant state. The collective coupling of the atoms via the radiation field leads to a substantial radiative shift of the transition energy, the collective Lamb shift. We simultaneously measured the temporal evolution of the superradiant decay and the collective Lamb shift of resonant 57Fe nuclei excited with 14.4-kilo-electron volt synchrotron radiation. Our experimental technique provides a simple method for spectroscopic analysis of the superradiant emission. doi: 10.1126/science.1187770

Published
2010
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2. In situ study of the <tex>\alpha$</tex>-Sn to <tex>\beta$</tex>-Sn phase transition in low-dimensional systems : phonon behavior and thermodynamic properties

Author

Houben, Kelly, Jochum, Johanna K, Lozano, Daniel P, Bisht, Manisha, Menendez, Enric, Merkel, Daniel G, Ruffer, Rudolf, Chumakov, Aleksandr, Roelants, Sam, Partoens, Bart, Milosevic, Milorad, Peeters, Francois M, Couet, Sebastien, Vantomme, Andre, Temst, Kristiaan, and Van Bael, Margriet J

Subjects
DYNAMICS, Technology, INSB(001), Science & Technology, PSEUDOPOTENTIALS, Physics, Materials Science, Materials Science, Multidisciplinary, FILMS, Physics, Applied, Condensed Matter::Materials Science, EQUILIBRIUM, Physics, Condensed Matter, TIN, Physical Sciences, MOSSBAUER, GROWTH, GREY, TEMPERATURE
Abstract

The densities of phonon states of thin Sn films on InSb substrates are determined during different stages of the alpha-Sn to beta-Sn phase transition using nuclear inelastic x-ray scattering. The vibrational entropy and internal energy per atom as a function of temperature are obtained by numerical integration of the phonon density of states. The free energy as a function of temperature for the nanoscale samples is compared to the free energy obtained from ab initio calculations of bulk tin in the alpha-Sn and beta-Sn phase. In thin films this phase transition is governed by the interplay between the vibrational behavior of the film (the phase transition is driven by the vibrational entropy) and the stabilizing influence of the substrate (which depends on the film thickness). This brings a deeper understanding of the role of lattice vibrations in the phase transition of nanoscale Sn.

Published
2019

3. Pressure tuning of charge ordering in iron oxide

Author

Ovsyannikov, Sergey V., Bykov, Maxim, Bykova, Elena, Glazyrin, Konstantin, Manna, Rudra Sekhar, Tsirlin, Alexander A., Cerantola, Valerio, Kupenko, Ilya, Kurnosov, Alexander V., Kantor, Innokenty, Pakhomova, Anna S., Chuvashova, Irina, Chumakov, Aleksandr I., Ruffer, Rudolf, McCammon, Catherine, Dubrovinsky, Leonid S., Ovsyannikov, Sergey V., Bykov, Maxim, Bykova, Elena, Glazyrin, Konstantin, Manna, Rudra Sekhar, Tsirlin, Alexander A., Cerantola, Valerio, Kupenko, Ilya, Kurnosov, Alexander V., Kantor, Innokenty, Pakhomova, Anna S., Chuvashova, Irina, Chumakov, Aleksandr I., Ruffer, Rudolf, McCammon, Catherine, and Dubrovinsky, Leonid S.

Abstract

A Verwey-type charge-ordering transition in magnetite at 120 K leads to the formation of linear units of three iron ions with one shared electron, called trimerons. The recently-discovered iron pentoxide (Fe4O5) comprising mixed-valent iron cations at octahedral chains, demonstrates another unusual charge-ordering transition at 150 K involving competing formation of iron trimerons and dimerons. Here, we experimentally show that applied pressure can tune the charge-ordering pattern in Fe4O5 and strongly affect the ordering temperature. We report two charge-ordered phases, the first of which may comprise both dimeron and trimeron units, whereas, the second exhibits an overall dimerization involving both the octahedral and trigonal-prismatic chains of iron in the crystal structure. We link the dramatic change in the charge-ordering pattern in the second phase to redistribution of electrons between the octahedral and prismatic iron chains, and propose that the average oxidation state of the iron cations can pre-determine a charge-ordering pattern.

Published
2018

4. Stability of iron-bearing carbonates in the deep Earth's interior

Author

Cerantola, Valerio, Bykova, Elena, Kupenko, Ilya, Merlini, Marco, Ismailova, Leyla, McCammon, Catherine, Bykov, Maxim, Chumakov, Alexandr I., Petitgirard, Sylvain, Kantor, Innokenty, Svitlyk, Volodymyr, Jacobs, Jeroen, Hanfland, Michael, Mezouar, Mohamed, Prescher, Clemens, Ruffer, Rudolf, Prakapenka, Vitali B., Dubrovinsky, Leonid, Cerantola, Valerio, Bykova, Elena, Kupenko, Ilya, Merlini, Marco, Ismailova, Leyla, McCammon, Catherine, Bykov, Maxim, Chumakov, Alexandr I., Petitgirard, Sylvain, Kantor, Innokenty, Svitlyk, Volodymyr, Jacobs, Jeroen, Hanfland, Michael, Mezouar, Mohamed, Prescher, Clemens, Ruffer, Rudolf, Prakapenka, Vitali B., and Dubrovinsky, Leonid

Abstract

The presence of carbonates in inclusions in diamonds coming from depths exceeding 670 km are obvious evidence that carbonates exist in the Earth's lower mantle. However, their range of stability, crystal structures and the thermodynamic conditions of the decarbonation processes remain poorly constrained. Here we investigate the behaviour of pure iron carbonate at pressures over 100 GPa and temperatures over 2,500 K using single-crystal X-ray diffraction and Mossbauer spectroscopy in laser-heated diamond anvil cells. On heating to temperatures of the Earth's geotherm at pressures to similar to 50 GPa FeCO3 partially dissociates to form various iron oxides. At higher pressures FeCO3 forms two new structures-tetrairon(III) orthocarbonate Fe43+C3O12, and diiron(II) diiron(III) tetracarbonate Fe22+Fe23+C4O13, both phases containing CO4 tetrahedra. Fe4C4O13 is stable at conditions along the entire geotherm to depths of at least 2,500 km, thus demonstrating that self-oxidation-reduction reactions can preserve carbonates in the Earth's lower mantle.

Published
2017

5. Magnetism under Pressure with Synchrotron Radiation

Author

D'Astuto, Matteo, Barla, Alessendro, Kernavanois, Nolwell, Rueff, Jean-Pascal, Baudelet, Francois, Ruffer, Rudolf, Paolasini, Luigi, Couzinet, Bernard, Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Université Grenoble Alpes (UGA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), Institut Laue-Langevin (ILL), ILL, Laboratoire de Chimie Physique - Matière et Rayonnement (LCPMR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Département de Recherche Fondamentale sur la Matière Condensée (DRFMC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other]
Abstract

The magnetic properties of materials depend strongly on the distance between ions and on the volume available for each magnetic ion. In this article, we introduce a bird's eye view of the various possible effects of pressure on the magnetic state and the consequences of these effects on the fundamental understanding of the magnetism in condensed matter and on the physics and chemistry of minerals in the interior of the Earth and planets. We will give basic information about the ex- perimental possibilities offered by synchrotron-radiation-based techniques in order to explore the magnetic state of matter at high pressure, their interest and feasi- bility. Finally, we will present some experimental highlights where x-ray techniques using synchrotron radiation have been successfully applied to show and explain the magnetic state of matter at high density.

Published
2006

7. Insight to Dynamics of Molecules with Nuclear Inelastic Scattering.

Author

Chumakov, Aleksandr I., Ruffer, Rudolf, Leupold, Olaf, and Sergueev, Ilia

Subjects
MOLECULAR dynamics, SYNCHROTRON radiation, ELECTROMAGNETIC wave scattering
Abstract

Discusses an application of the nuclear inelastic scattering of synchrotron radiation to molecular dynamics. Mossbauer effect; Nuclear inelastic absorption measurements; Energy spectrum of absorption of synchrotron radiation.

Published
2003

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