Search results for: S. Rols

Items from 1 to 20 out of 25 results

article

Dynamics of the phase-change material GeTe across the structural phase transition

T. Chatterji, S. Rols, U. D. Wdowik

Frontiers of Physics > 2019 > 14 > 2 > 1-7

Results of inelastic neutron scattering experiments and ab initio molecular dynamics simulations for GeTe–the parent compound of phase-change materials are reported. The inelastic neutron spectra of GeTe powder samples have been determined in the temperature range extending from 300 to 700 K. The phonon peaks undergo thermal shifts resulting from anharmonic effects being weaker for acoustic than optic...

chapter

Spectroscopies on Carbon Nanotubes

J.-L. Sauvajol, E. Anglaret, S. Rols, O. Stephan

Lecture Notes in Physics > Understanding Carbon Nanotubes > 277-334

In a spectroscopy experiment, radiation is used as a probe of the properties of a system. A typical experiment of spectroscopy is schematized in Fig. 5.1. The source (probe) can be X-rays, laser light (visible and infrared radiations), neutrons, electrons, … . A monochromatic radiation is obtained by using a relevant monochromator device. As long as the response of the material to the radiation...

article

Crystal field manifestation in inelastic neutron scattering, magnetic susceptibility and specific heat of the antiferromagnetic CeCoAl4

T. Toliński, K. Synoradzki, A. Hoser, S. Rols

Journal of Magnetism and Magnetic Materials > 2013 > 345 > C > 243-248

Inelastic and quasielastic excitations in the neutron scattering on the compounds CeCo1−xCuxAl4 (x=0, 0.05, 0.1) have been studied above and below the antiferromagnetic ordering temperature. The quasielastic contribution disappears below the Néel temperature, TN=13.5K, and its linewidth Γ/2 is below TN, therefore these results suggest that Kondo screening is not relevant in these Ce compounds. Based...

article

Inelastic neutron scattering an ab-initio calculation of negative thermal expansion in Ag2O

M.K. Gupta, R. Mittal, S. Rols, S.L. Chaplot

Physica B: Physics of Condensed Matter > 2012 > 407 > 12 > 2146-2149

The compound Ag ₂ O undergoes large and isotropic negative thermal expansion over 0–500K. We report temperature dependent inelastic neutron scattering measurements and ab-initio calculations of the phonon spectrum. The temperature dependence of the experimental phonon spectrum shows strong anharmonic nature of phonon modes of energy around 2.4meV. The ab-initio calculations reveal that the...

article

From Heavy Fermion and Spin-Glass Behavior to Magnetic Order in CeT_4M Compounds

T. Toliński, A. Kowalczyk, M. Falkowski, K. Synoradzki, more

Acta Physica Polonica A > 2012 > 121 > 5-6 > 1014-1018

We report on the transitions between the ferromagnetic order, spin-glass behavior, heavy fermion and fluctuating valence state in a series of isostructural compounds CeT_4M (T = Ni, Cu; M = Al, Ga, Mn). The dilution of Ce or the T and M elements allowed us to follow the physical properties evolution employing the measurements of the heat capacity, dc magnetic susceptibility, frequency dependent ac...

article

Nanometric confinement: Toward new physical properties and technological developments

J.-M. Zanotti, K. Lagrené, N. Malikova, P. Judeinstein, more

The European Physical Journal Special Topics > 2012 > 213 > 1 > 129-148

In numerous real life situations, molecular systems are not found in bulk but instead trapped in limited volumes of nanometric size: this is nanometric confinement. The complex interplay of the confinement topology, dimensionality (3D to 1D) and surface/volume ratio significantly affects the physical properties of the confined material. After decades of intense fundamental research, we are now entering...

article

Unravelling low lying phonons and vibrations of carbon nanostructures: The contribution of inelastic and quasi-elastic neutron scattering

S. Rols, C. Bousige, J. Cambedouzou, P. Launois, more

The European Physical Journal Special Topics > 2012 > 213 > 1 > 77-102

We illustrate the contribution of inelastic neutron scattering to the understanding of the vibrations and lattice excitations of fullerenes and carbon nanotubes, through some significant experimental results. Particular emphasis is placed on the study of intra and inter-molecular modes of fullerene C₆₀, as well as on the order/disorder transition characteristic of these molecules. In addition, a significant...

article

Neutron diffraction study of p-phenylene oligomer molecules adsorbed onto graphite

E.J. Kintzel, K.W. Herwig, S. Rols

Thin Solid Films > 2010 > 518 > 14 > 3786-3791

Neutron scattering experiments have been carried out on low-coverage films of the aromatic p-phenylene oligomer molecules (p-nP, C _6n H _10+4(n ₋ ₂₎ , where n indicates the number of phenyl units per molecule) physisorbed onto the surface of graphite. The molecular arrangement within these films has been determined as a function of temperature, number of molecular layers, and...

article

Crystal field states in CeCu4Al

T. Toliński, A. Hoser, S. Rols, A. Kowalczyk, more

Solid State Communications > 2009 > 149 > 47-48 > 2240-2243

Heavy fermion CeCu ₄ Al compound has been studied by inelastic neutron diffraction (INS), heat capacity and magnetic susceptibility measurements. A single Crystal Electric Field (CEF) peak has been detected in the INS spectra, which may be explained by a quasi-quartet state suggested by the analysis of the Schottky anomaly contributing to the magnetic part of the specific heat. The Kondo interactions...

article

Lattice Dynamics of Oligo(phenylenethienylene)s: A Far-Infrared and Inelastic Neutron Scattering Study

P. Hermet, S. Lois-Sierra, J.-L. Bantignies, S. Rols, more

The Journal of Physical Chemistry B > 2009 > 113 > 13 > 4197 - 4202

article

New Insight into the Vibrational Behavior of Nickel Hydroxide and Oxyhydroxide Using Inelastic Neutron Scattering, Far/Mid-Infrared and Raman Spectroscopies

J.L. Bantignies, S. Deabate, A. Righi, S. Rols, more

The Journal of Physical Chemistry C > 2008 > 112 > 6 > 2193 - 2201

article

Size-Dependent Phase Transition of Diamond to Graphite at High Pressures

V.A. Davydov, A.V. Rakhmanina, S. Rols, V. Agafonov, more

The Journal of Physical Chemistry C > 2007 > 111 > 35 > 12918 - 12925

article

Melting mechanism of monolayers adsorbed in cylindrical pores: An influence of the pore wall roughness

B. Kuchta, L. Firlej, R. Denoyel, P. Boulet, more

Applied Surface Science > 2007 > 253 > 13 > 5601-5605

We have analyzed the mechanism of melting of layers adsorbed in cylindrical pores of porous materials. The goal was to understand the melting mechanism of simple fluids adsorbed in pores with heterogeneous wall surface. The studied system was a monolayer of methane molecules adsorbed in MCM-41 pore of diameter d=4nm. Both experimental (neutron scattering) and simulation (Monte Carlo) results proved...

article

Diffraction of oriented nano-peapods

R. Almairac, J. Cambedouzou, S. Rols, J.-L. Sauvajol

The European Physical Journal B > 2006 > 49 > 2 > 147-155

. This paper presents an investigation of the structural properties of oriented A@SWNT peapods, where A represents any molecular species organized on a 1D cristalline chain inside the single wall nanotubes (SWNT). This study is based on the use of diffraction methods applied to the case of oriented A@SWNT samples. Two preferential orientations of tubes are considered, 1D (fiber) and 2D (pellet) both...

article

Dynamical disorder and reorientation of the CH ₃ groups in N-methylacetamide

S. Rols, H.N. Bordallo, K.W. Herwig, M. Barthès

Physica B: Physics of Condensed Matter > 2004 > 350 > 1-3 Supplement > E587-E589

By selective deuteration the influence of the environment on the geometry of the motion of each hydrogen group in N-methylacetamide (NMA, CH ₃ NHCOCH ₃ ) was probed using quasi-elastic neutron scattering. From 100K to ambient very good agreement was obtained over the entire Q-range (0.35-2.35A), by fitting the data to a uniaxial rotational model of the methyl groups around the C ...

article

On the diffraction pattern of C $\mathsf{_{60}}$ peapods

J. Cambedouzou, V. Pichot, S. Rols, P. Launois, more

The European Physical Journal B > 2004 > 42 > 1 > 31-45

. We present detailed calculations of the diffraction pattern of a powder of bundles of C₆₀ peapods. The influence of all pertinent structural parameters of the bundles on the diffraction diagram is discussed, which should lead to a better interpretation of X-ray and neutron diffraction diagrams. We illustrate our formalism for X-ray scattering experiments performed on peapod samples synthesized from...

article

Neutron diffraction and numerical modelling investigation of methane adsorption on bundles of carbon nanotubes

M.R. Johnson, S. Rols, P. Wass, M. Muris, more

Chemical Physics > 2003 > 293 > 2 > 217-230

Neutron diffraction measurements on a powder sample of bundles of single-walled carbon nanotubes are used to gain insight into adsorption sites for methane molecules. In parallel, numerical methods, based on empirical force-fields, are employed to calculate the adsorption of methane in bundles of nanotubes and neutron diffraction patterns based on these structures. Adsorption sites in grooves on the...

article

Phonons in single wall carbon nanotube bundles

J.-L. Sauvajol, E. Anglaret, S. Rols, L. Alvarez

Carbon > 2002 > 40 > 10 > 1697-1714

We review recent and original results on the vibrational properties of single wall carbon nanotubes (SWNT). We especially focus on calculations and experiments performed on nanotube bundles. So far, the main technique for probing the dynamics has been Raman spectroscopy. Here, we discuss: (i) the relation between frequency of the A ₁ _g radial breathing mode and nanotube diameter, (ii)...

article

Excitation energy dependence of the Raman spectrum of single-walled carbon nanotubes

L. Alvarez, A. Righi, S. Rols, E. Anglaret, more

Chemical Physics Letters > 2000 > 320 > 5-6 > 441-447

We investigate the excitation energy dependence of Raman modes in the 600-1200 cm ^- ¹ range. The main features are first, two lines around 860 and 1060 cm ^- ¹ independent of the energy and second, energy-dependent couples of lines, each of them composed of one first-order mode and one substractive combination band. In each couple, the frequency of the lines is found to follow...

article

Diameter distribution of single wall carbon nanotubes in nanobundles

S. Rols, A. Righi, L. Alvarez, E. Anglaret, more

The European Physical Journal B > 2000 > 18 > 2 > 201-205

Abstract: The frequency of the Raman active A1g radial breathing mode has been widely used as a tool to estimate the distribution of diameters of single wall carbon nanotubes (SWNT). However, the relation between frequency and diameter is not straightforward and results are model-dependent. Because most of the experiments are performed on bundles and not on isolated tubes, the model should especially...

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Keywords

NEUTRON DIFFRACTION (3)
INELASTIC NEUTRON SCATTERING (2)
NEUTRON SCATTERING (2)
71.20.LP (1)
71.27.+A (1)
75.30.CR (1)
75.30.MB (1)
75.50.LK (1)
78.70.NX (1)
A. CARBON NANOTUBES (1)
AB INITIO MOLECULAR DYNAMICS (1)
ADSORPTION (1)
ALPHA-HELICAL PROTEINS (1)
ANTIFERROMAGNET (1)
C. RAMAN SPECTROSCOPY (1)
CARBON NANOTUBES (1)
COMPUTING (1)
CRYSTAL FIELD (1)
D. HEAT CAPACITY (1)
D. HEAVY FERMIONS (1)
D. KONDO EFFECTS (1)
D. PHONONS (1)
E. NEUTRON SCATTERING (1)
GRAPHITE (1)
HEAT CAPACITY (1)
MAGNETIC SUSCEPTIBILITY (1)
MELTING (1)
MONOLAYERS (1)
MONTE CARLO (1)
NANO-PORES (1)
NEUTRON INELASTIC SCATTERING (1)
OPTOELECTRONIC DEVICES (1)
P-PHENYLENE OLIGOMERS (1)
PACS. 61.12.BT THEORIES OF DIFFRACTION AND SCATTERING - 61.10.DP THEORIES OF DIFFRACTION AND SCATTERING - 61.46.+W CLUSTERS, NANOPARTICLES, AND NANOCRYSTALLINE MATERIALS (1)
PHASE-CHANGE MATERIALS (1)
PHONONS IN CRYSTAL LATTICE (1)
POLYPEPTIDES (1)
RAMAN SCATTERING (1)
SIMPLEST MODEL SYSTEM (1)
SINGLE WALL CARBON NANOTUBES (1)
THERMAL PROPERTIES OF CRYSTALLINE SOLIDS (1)
[PHYSICAL ASTRONOMY CLASSIFICATION SCHEME] 28.20.CZ (1)
[PHYSICAL ASTRONOMY CLASSIFICATION SCHEME] 61.43.BN (1)
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Synthetic Metals (2)
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Frontiers of Physics (1)
Journal of Magnetism and Magnetic Materials (1)
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INFONA - science communication portal

Search results for: S. Rols

Dynamics of the phase-change material GeTe across the structural phase transition

Spectroscopies on Carbon Nanotubes

Crystal field manifestation in inelastic neutron scattering, magnetic susceptibility and specific heat of the antiferromagnetic CeCoAl4

Inelastic neutron scattering an ab-initio calculation of negative thermal expansion in Ag2O

From Heavy Fermion and Spin-Glass Behavior to Magnetic Order in CeT_4M Compounds

Nanometric confinement: Toward new physical properties and technological developments

Unravelling low lying phonons and vibrations of carbon nanostructures: The contribution of inelastic and quasi-elastic neutron scattering

Neutron diffraction study of p-phenylene oligomer molecules adsorbed onto graphite

Crystal field states in CeCu4Al

Lattice Dynamics of Oligo(phenylenethienylene)s: A Far-Infrared and Inelastic Neutron Scattering Study

New Insight into the Vibrational Behavior of Nickel Hydroxide and Oxyhydroxide Using Inelastic Neutron Scattering, Far/Mid-Infrared and Raman Spectroscopies

Size-Dependent Phase Transition of Diamond to Graphite at High Pressures

Melting mechanism of monolayers adsorbed in cylindrical pores: An influence of the pore wall roughness

Diffraction of oriented nano-peapods

Dynamical disorder and reorientation of the CH ₃ groups in N-methylacetamide

On the diffraction pattern of C $\mathsf{_{60}}$ peapods

Neutron diffraction and numerical modelling investigation of methane adsorption on bundles of carbon nanotubes

Phonons in single wall carbon nanotube bundles

Excitation energy dependence of the Raman spectrum of single-walled carbon nanotubes

Diameter distribution of single wall carbon nanotubes in nanobundles

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