Introduction

The High Resolution and Resonance Scattering Group's activity comprises many more scientific topics and applications than can be reported here in sufficient detail. This year we are going to focus on two fields: Surface Science/Nano-structures and Earth Science. These are good examples that demonstrate the continual advances necessary to address the problems most relevant today. In addition, to the improvements of the quality and flux of the synchrotron radiation beam, we also witness better beamline optics and more sophisticated sample environments. Higher photon flux and a smaller X-ray beam allow high pressure and surface investigations with energy resolution down to the neV range and time resolution down to the ns regime. All these developments and investigations need the full dedication of the beamline staff and the expertise brought by our external users and collaborators.

The group is involved in two European projects: firstly VOLPE, which is nearing the end of a successful final year, and secondly DYNASYNC, which had only just started in 2004. In the framework of "Volume photoemission from solids" (VOLPE), the well-established surface sensitive technique of photoemission in the soft X-ray regime has been expanded to the hard X-ray regime being now bulk sensitive. First results on vanadium oxide have been achieved with an overall energy resolution of 70 meV at 6 keV [1]. With this resolution we are now looking forward to fully exploiting this new experimental environment. In the project on Dynamics in Nano-scale Materials Studied with Synchrotron Radiation (DYNASYNC) we apply nuclear resonance techniques in order to explore - under the same conditions and preferably in parallel - magnetic/ electronic properties and slow (diffusional and rotational motions) and fast (phonons) dynamics in systems such as iron on tungsten, metal/oxide systems, and multilayers. Arriving too late to be reported on in these Highlights, the first measurements of the phonon density of states of monolayers, islands and bulk iron on tungsten have been conducted showing a tremendous difference in their phonon spectra and by this in their dynamical behaviour. Furthermore, magnetic properties could be followed during the growth process.

The emerging techniques of inelastic X-ray (IXS) and nuclear inelastic scattering (NIS) have again shown that their full potential has not yet been explored. First studies demonstrated that IXS has the capability to map not only dispersion curves but also to determine directly the density of phonon states. The very first experiments are reported on the model systems diamond and MgO [2]. In case of molecular systems, i.e. those with well-resolved optical/localised modes, NIS proved capable of separating the vibrational density of states of each phase in heterogeneous systems and also the (thermo-)dynamical quantities derived from it [3].

Finally, the study of glasses and disordered systems has continued. The following two examples on Basic Dynamics of Glasses demonstrate that the techniques have contributed to the fundamental understanding of these systems. Matic et al. compare the low energy dynamics of polymorphic ethanol in the glassy, rotationally disordered and crystalline phases and conclude on a common origin of the vibrational behaviour. The contribution by Chumakov et al. exposes the collective nature of the Boson peak in several systems and discusses a universal exponential "trans-Boson" behaviour in glasses.

R. Rüffer

 

References
[1] P. Torelli et al., Rev. Sci. Instr. 76, 23909 (2005).
[2] A. Bossak et al., submitted to PRL (2005).
[3] A.I. Chumakov et al., PRL 92, 243001 (2004).