ELFT HÍRADÓ

[Nagy Denes Lajos <nagy AT rmki.kfki.hu>]

                            M E G H Í V Ó

a KFKI RMKI és a KFKI CMRC nukleáris anyagkutatási szemináriumának
következõ elõadására

                           Dr. Olaf Leupold
           European Synchrotron Radiation Facility, Grenoble

        Nuclear Resonance Scattering of Synchrotron Radiation:
            Recent Results and Developments from the ESRF

Az elõadás helye: 1121 Budapest, Konkoly-Thege M. út 29-33.
                  KFKI RMKI 3. épület tanácsterem

Az elõadás idõpontja: 2002. június 16., hétfõ, 14:00.

Az elõadáson minden érdeklõdõt szeretettel látunk.

                                                Nagy Dénes Lajos

Az elõadás kivonata:
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Since its observation in 1985 nuclear resonant scattering (NRS)
of synchrotron radiation has become an excellent spectroscopic tool
with its two main branches: nuclear forward scattering (NFS)
and nuclear inelastic scattering (NIS). The former probes hyperfine
interactions and slow dynamics, the latter enables one to study
dynamical effects (phonons) in solids.

NFS as a time differential method has proven to be complementary to
Mossbauer spectroscopy, an energy differential method. In NFS the
time behaviour of the reemitted photons following the nuclear
excitation by the synchrotron radiation pulse coherently exhibits
characteristic modulations, bearing information on the splitting
of nuclear levels by the hyperfine fields. Due to the polarization
of the synchrotron radiation this quantum beat structure gives more
information on the direction of the hyperfine fields than can be obtained
by classical Mossbauer spectroscopy.

In NIS the dynamics of solids is probed in the meV regime, the
resonant nuclei in the sample act as fixed energy analyzers, the
incoming radiation is tuned around resonance by means of high resolution
monochromators. The annihilation or creation of phonons is observed in
the resulting energy spectrum by recording only the delayed reemitted
photons after the nuclear resonant excitation.

We will first give a short introduction to the NRS method and then
focus on technical aspects like high energy resolution monochromators
and focusing optics for synchrotron radiation.

Then we will give examples on experiments which can especially benefit
from the outstanding properties of the synchrotron radiation, i.e. the
small beam size and divergence. These are experiments under high pressure
and in grazing incidence geometry.

We will finish with examples of NIS on various Mossbauer isotopes also
under extreme conditions like high pressure or low temperatures.