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Fluorination of pure C60 and a C60/C70 mixture has been studied under different experimental conditions: reaction time, temperature, fluorine pressure. The products obtained have been characterized by IR and NMR spectroscopy, X-ray diffraction, and mass spectrometry analysis by positive and negative ions.

X-ray diffraction and thermodynamic measurements show that crystalline fullerene C70 obtained from toluene solutions is a C70, toluene 1:1 solvate. Its structure is orthorhombic with space group Pbca (a = 21.075 A, b = 32.990 A, c = 10.844 A). The evolution of this solvate towards the face-centred cubic and hexagonal phases of pure C70 is described and a hierarchy of relative stabilities of these latter phase is tentatively proposed.

Recent studies carried out on an organic superconductor, s-(BEDT-TTF) 2 I 3 , have shown the important role played by the 13 C isotope on the T c transition, when substitution is made on the central CC bond of the molecule. Simultaneously, Raman studies determined the frequency shifts observed in the CC stretching vibrations in the substituted samples and consequently, put in evidence the role of the intramolecular Ag vibrations. We have extended these studies to compounds of the new carbon family, the fullerenes, in which 82% of the carbon atoms were substituted with 13 C in C 60 . The superconducting transition measured on the same sample doped with potassium is lowered by 1.5 to 2K as compared to the standard material doped in similar conditions. In the Raman spectrum, the main Ag band measured at 1467 cm −1 in 12 C 60 is shifted to 1420 cm −1 in enriched 13 C 60 . Taking into account the ratio between the molecular weight of the enriched 13 C 60 and of the standard material, one predicts a theoretical value for this mode at 1418 cm −1 in the enriched sample. A preliminary analysis of the Raman spectrum will be presented.

We report the temperature and pressure dependence of 13 C nuclear spin-lattice relaxation time T 1 on K 3 C 60 in the normal state. Within the BCS electron-phonon pairing mechanism, we estimate the coupling strength and the relevant phonon mode involved to account for superconductivity.

In order to test the isotope effect in the superconducting doped fullerenes, we made the K 3 C 60 compound in which the C 60 molecules are enriched in 13 C. The 13 C concentration in C 60 powder, as determined by mass spectrometry, was found to be 82%. A standard sample K 3 12 C 60 was prepared in the same conditions. The superconducting transition was measured on both samples by an ac susceptibility technique. The onset transition temperature observed at T c = 19.6±0.1K for the standard sample is lowered by 1.8K in the 13 C compound which leads to α ≈ 1.45±0.3 in the usual BCS formula T c ∼ M − α . From 13 C NMR measurements of the relaxation time T 1 on these two compounds, the isotopic shift leads to α ≈ 1.1±0.3 in a magnetic field of 9.4T, which remains strongly higher than the theoretical value α = 0.5.

A network of optical parametric oscillators has been harnessed to find solutions to a complex problem in statistical physics that is difficult to solve using numerical computing algorithms.

We report the pressure and temperature dependences of 13C nuclear spin-lattice relaxation time T1 in the normal state of K3C60. From the 1/T1T temperature and pressure profiles, a Fermi-liquid theory is used to investigate the variation of the density of states and the amplitude of electron-electron interaction. Finally the results obtained are shown to support a pairing mechanism for superconductivity that would involve high-frequency modes.

We have measured the electrical resistivity as a function of temperature up to pressures of 25 GPa of pure fullerenes C60, C70 and the compound C60I4. For the three materials the best fit in our temperature range corresponds to a three-dimensional variable-range hopping conductivity, signature of an important disorder. A dramatic decrease of the resistivity, by two orders of magnitude per GPa, is observed at low pressures. However, no metallic state is attained as all the samples present a phase transformation in the high-pressure range, probably originated by the crossover from sp2 to sp3 hybridization of the carbon orbitals at high pressures.

International audience; We study the photon correlation properties of broadband parametric down-converted light. The measurement of the photon correlation is carried out thanks to a modified Hanbury Brown-Twiss interferometer based on two photon absorption in GaAs detector. Since this method is not affected by the phase matching conditions of the detecting apparatus (so called “final state post-selection”), the detection bandwidth can be extremely large. This is illustrated by studying, with the same apparatus, the degree of second order coherence of parametric light in both degenerate and non-degenerate cases. We show that our experiment is able to determine the coherent as well as the incoherent contributions to the degree of second order coherence of parametric light with a time resolution in the fs range scale.

In this chapter we shall describe the principle of the operation of lasers, their common features and the properties of the light they emit. Our aim is not to provide an exhaustive catalogue of the types of laser available at the time of writing. Such an account would, in any case, soon be obsolete. Rather, we shall use concrete examples of existing systems to illustrate important features or general principles. We do not want either to give an extensive theoretical description of a laser's properties and of its dynamics. We restrict ourselves here to a rather simplified approach to its main features and refer the reader to more specialized handbooks for further information (see the further reading section at the end of the main chapter). The physical principles accounting for laser operation can appear quite straightforward. This impression stems from the fact that the essential concepts are now well understood, whilst the detail and some incorrect notions are passed over in silence. It is interesting to note, however, how painstaking our progress in understanding lasers has been. It is usually considered that the prehistory of the laser commenced in 1917 when Einstein introduced the notion of stimulated emission . In fact, Einstein was led to the conclusion that such a phenomenon must occur from considerations of the thermodynamic equilibrium of the radiation field and a sample of atoms at a finite temperature T .

Covering a number of important subjects in quantum optics, this textbook is an excellent introduction for advanced undergraduate and beginning graduate students, familiarizing readers with the basic concepts and formalism as well as the most recent advances. The first part of the textbook covers the semi-classical approach where matter is quantized, but light is not. It describes significant phenomena in quantum optics, including the principles of lasers. The second part is devoted to the full quantum description of light and its interaction with matter, covering topics such as spontaneous emission, and classical and non-classical states of light. An overview of photon entanglement and applications to quantum information is also given. In the third part, non-linear optics and laser cooling of atoms are presented, where using both approaches allows for a comprehensive description. Each chapter describes basic concepts in detail, and more specific concepts and phenomena are presented in 'complements'.

The C[sub 60] fullerene was used as the carbon source to carry out the catalyzed synthesis of diamond, at 6.7 GPa and temperatures between 1200 and 1850[degrees]C; the catalysts used were Ni, Co, and a Co alloy. Under these conditions, the graphite used as the carbon source gave a diamond yield of about 90%; the yield with C[sub 60] depended on the catalyst. With Co, about the same quantity of diamond was obtained from C[sub 60] as from graphite, whereas almost no diamond was synthesized when pure C[sub 60] was used as the carbon source with Ni and the Co alloy as catalysts. The diamond yield recovered to a high level with these two catalysts when a small quantity (about 10%) of graphite was added to the C[sub 60] fullerene. This effect of the addition of graphite to a non-graphite carbon in the synthesis of diamond is different from that observed with amorphous carbons. In all these experiments under high pressure and high temperature with Ni, Co, or Co alloy, the C[sub 60] fullerene was destroyed and transformed into diamond, graphite, or poorly crystallized carbon. 27 refs., 2 figs., 1 tab.