The present synchrotron sources with brilliant x-ray beams, due to high photon fluxes, small source sizes and high collimation, have revolutionized x-ray physics.Enormous progress has been initiated in all established x-ray methods, with the aim of the development of new types of spectroscopy. This is particularly true for the spectroscopy of the dynamics in condensed matter. Meanwhile, there are two powerful x-ray methods with very high-energy resolution available for the study of low energetic excitations like phonons.This review summarizes the developments of these methods focusing on these instrumental developments of the spectrometers using either crystal optics in close-to-backscattering geometry or nuclear resonant techniques.Applications to measurements of phonon dispersion curves and of phonon density of states in ordered and disordered solids and in liquids are presented. It is shown how x-ray results are stimulating improvements in the theoretical approaches to the dynamics. New insights into the dynamics of liquids are discussed.The sensitivities of the spectroscopies allow the study of vibrational behaviour in very small amounts of material even in nanometre-sized thin films or particles. We can already analyse the phonon spectrum of a monolayered nuclear resonant isotope. Prospects of the techniques are also demonstrated.

We present high resolution inelastic x-ray scattering measurements of the coherent dynamic structure factor S͑Q, v͒ of liquid lithium at momentum transfers 0.36 # Q # 5 Å 21 . The determined S͑Q, v͒ agrees much better with molecular dynamic simulations using the neutral pseudo-atom potential rather than the empty core potential. We observe a positive dispersion in the sound velocity confirming that in liquid lithium the longitudinal dynamics reaches a solid-like response at high frequencies.[S0031-9007 (97)02529-5] PACS numbers: 61.25.Mv, 61.10.Eq, 61.20.Ne Recently, Canales et al. [1] calculated the dynamic structure factor of liquid lithium by means of molecular dynamic (MD) simulations using two different pair potentials: the empty core potential derived by Ashcroft [2]and an ab initio calculation for a pair potential deduced from the neutral pseudoatom method (NPA potential) [3]. Although the shapes of these two potentials are quite different, most of the calculated structural and thermodynamic properties are very similar [1]. Significant differences are observed in the calculations of the coherent part of the dynamic structure factor.Inelastic neutron experiments on the dynamic structure factor of liquid 7 Li were performed by de Jong et al. [4]. However, these measurements yielded no decision which of the two pair potential approaches is the more favorable. The reason is that an essential part of the coherent structure factor-the Brillouin modes-could not be observed at small momentum transfers Q. Because of the momentum-energy relation for a classical particle there exists a maximum energy transfer v at a momentum transfer Q, which is determined by the flight velocity of the incident neutron. In the neutron experiment mentioned above the Brillouin excitations were not detectable for Q , 1.2 Å 21 . Moreover, the high fraction of incoherent scattering at small Q and the uncertainties in the incoherent cross section of 7 Li makes it difficult to extract the coherent part from the experimental data.In contrast, these limitations do not appear in an inelastic x-ray scattering experiment with sufficient high energy resolution. At energy transfers of about a few meV the observed intensity originates dominantly from coherent scattering. The energy-momentum relation of the photon allows an almost unlimited energy transfer at any accessible momentum transfer [5,6].Previous experiments on liquid lithium were performed at the synchrotron laboratory HASYLAB in Hamburg [7,8]. The experiments reported here were carried out during the commissioning phase of the inelastic x-ray scattering beamline (ID16) at the European Synchrotron Facility (ESRF) in Grenoble. The x-ray radiation, coming from an undulator, was monochromized by a combination of a cryogenically cooled heat load monochromator and a silicon backscattering monochromator [Si(7,7,7) with E 13.8 keV]. The analyzer, a two dimensional focusing array of silicon crystals, is positioned at a 2.5 m distance from the sample in backscattering geometry. Details of the back...

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We have investigated the magnetic spin structure of a soft-magnetic film that is exchange-coupled to a hard-magnetic layer to form an exchange-spring layer system. The depth dependence of the magnetization direction was determined by nuclear resonant scattering of synchrotron radiation from ultrathin 57Fe probe layers. In an external field a magnetic spiral structure forms that can be described within a one-dimensional micromagnetical model. The experimental method allows one to image vertical spin structures in stratified media with unprecedented accuracy.

We use synchrotron radiation and time resolved x-ray detection to measure structural relaxations of glycerol [C 3 H 5 (OH) 3 ] having time scales of 30 to 200 ns at 1.5 Å 21 momentum transfer. Foils containing 57 Fe (14.4 keV nuclear resonance, 141 ns lifetime) are placed before and after the nonresonant sample, and a small difference ͑ϳ70 MHz͒ is established in their nuclear response frequencies. Quasielastic scattering from the sample perturbs the 70 MHz quantum beat pattern of the nuclear scattering. A simple model relates the perturbation to the dynamic structure factor of the sample. [S0031-9007(97)