R. Rüffer

Nuclear Bragg Diffraction of Synchrotron Radiation at the 8.41 keV Resonance of Thulium

For the first time nuclear Bragg diffraction of synchrotron radiation at the 8.41 keV resonance of 169Tm was observed. Time differential measurements were performed with the pure nuclear (424) reflection of a thulium iron garnet single crystal. The dynamical theory of Mossbauer optics is applied to evaluate the time spectra. The measurements reveal information about the hyperfine fields which has not been accessible before by conventional Mossbauer spectroscopy with polycrystalline samples.

A high resolution spectrometer using nuclear Bragg diffraction

A high resolution spectrometer for synchrotron radiation using nuclear Bragg diffraction has been constructed at a DORIS beamline (DESY, Hamburg). This spectrometer provides a γ-ray beam for hyperfine spectroscopy and for other application which need high resolution in energy and/or time.

Nuclear Bragg diffraction using synchrotron radiation A new method for hyperfine spectroscopy

Abstract Nuclear Bragg diffraction with synchrotron radiation as source will become a powerful new X-ray source in the A region. The brilliance of conventional Mossbauer sources is already exceeded; giving hyperfine spectroscopy a further impulse. As examples applications to yttrium iron garnet (YIG) and iron borate will be discussed.

A γ-ray detector with good time resolution and high signal-to-noise ratio

Abstract A coincidence detector for an energy range between 8 and 50 keV with a good time resolution and a high signal-to-noise ratio was developed for time-differential experiments using nuclear Bragg diffraction with synchrotron radiation as a source.

Recent theoretical and experimental development of Mössbauer effect with synchrotron radiation

The elements of a dedicated beam line are introduced. Computer simulations of the nuclear monochromator response to an incident broad band of radiation show the special features of the new source-speed up, dynamical beats, quantum beats and polarization mixing. Experiments with YIG and FeBO3 confirm the theoritical picture. It is shown that time differential measurements have the potential of greatly improving the accuracy of future experiments. New fields of investigations will be broadband spectroscopy in the μeV range and γ-optics.

Nuclear Resonant Filtering of Synchrotron Radiation by Grazing-Incidence Antireflection Films

Coherent nuclear diffraction of synchrotron radiation has been observed from grazing-incidence antireflection films (GIAR films) containing 57Fe. These films, which consisted of polycrystalline 57FeCrNi on a Pd backing, reduced the electronic reflectivity to 710-4. Nuclear reflection of the resonant photons led to a counting rate of ≈ 0.05 Hz of delayed quanta. The measurements show that nuclear resonant filtering of synchrotron radiation by GIAR films is possible.

Nuclear Bragg diffraction using synchrotron radiation — A new method for hyperfine spectroscopy

Nuclear Bragg diffraction with synchrotron radiation as source will become a powerful new X-ray source in the Å-region. This source exceeds by now the brilliance of conventional Mössbauer sources giving hyperfine spectroscopy further momentum. As examples applications to yttrium iron garnel (YIG) and iron horate will be discussed.

Quantum beat dilation due to magnetisation breakdown

The temperature dependence of the magnetisation of a nearly perfect single crystal57FeBO3 was studied in between room temperature and Néel temperature by measuring the time dependence of the nuclear response to a flashlike excitation by pulsed synchrotron radiation

Dependence of nuclear diffraction on the azimuthal angle: (002)- and (0010)-reflections of YIG

Nuclear diffraction of synchrotron radiation has been investigated using YIG single crystals in different scattering geometries. Time resolved quantum beat spectra of pure nuclear (002) and (0010) Bragg reflections were observed in a set-up where the hyperfine interaction was kept constant, while the azimuthal angle in the (001) surface between the [100] axis and the scattering plane (kin,kout) was varied. The time spectra were analyzed by means of the dynamical theory for coherent nuclear scattering. The results revealed the high sensitivity of this experimental technique on the complete set of hyperfine interaction parameters and on the specific geometrical conditions for nuclear diffraction of polarized γ-rays.

Shaping of Nuclear Bragg Reflected SR-Pulses by Broad Resonance Absorbers

Time and energy spectra have been studied of Mossbauer filter systems consisting of a pure nuclear reflection 3FeBO57(333) in connection with a broad resonance absorber. The energy spectra show how much of each line of the multiplet has been absorbed. The corresponding time spectra show the modified quantum beats to be expected from this, and also display risetime effects revealing the absorbers action. Part of the motivation is to produce simpler wave packets suitable for subsequent analysis of 57Fe-containing materials.