On the search for the possible microscopic origin of free electric charges to stabilize the ferroelectric order in PVDF, chemical decomposition into various radicals like H, H2, HF, CH3 by the polarizing electric field was reported [1]. We investigated possible chemical changes caused by these radicals within the electrodes of metallic iron by CEMS. The sensitivity of this method is less than a monolayer of reacted material. No chemical changes could be found unless the poling electrical field had exceeded the threshold of electrical breakthrough, when an iron 2+ high spin compound was detected at the negatively charged electrode. A chemical decomposition of the polymer by electric fields used to polarize the material could not be confirmed.

A new type of an ultra-narrow frequency transmission filter for ψ-rays is presented. The principle of its operation is based on the Mössbauer-sideband-spectroscopy [1–3]: A resonant absorber onto a thin piezo-electric polymer foil vibrates piston like at an ultrasonic frequency ω. At certain definite amplitudes the zero-order-sideband, i.e. the transition energy ω0, is fully transmitted without any resonant absorption, whereas simultanously sidebands displaced by energies ±hhΩ from ω0 are resonantly absorbed. Using several absorbers of this type in series having different frequencies a broadband filter for ψ-rays with a well defined transmission-profile can be designed. Symmetrically, on both sides of the central transmission window there exist resonant absorption bands. The energy width of these different bands is only limited by the possible ultrasonic frequencies and can be adjusted from 10−o to 10−5 eV. First experimental results using such an assembly of absorbers are presented. The limit of the efficiency of the filter, caused by non-resonant scattering is discussed.

A new method is presented for the determination of the vibrational amplitude of electrically driven piezoelectric polymer films. Both the absolute value of the amplitude and its orientation relative to the surface can be measured with precision. The application of this method to polymer films showed rather surprising deviations of the dynamic pizoelectric constants from the high static values.

The high TC superconductor Ba2EuCu307±δ with measured Tc=94±2 K was investigated by Mössbauer spectroscopy. It is shown that the material at low temperatures has either a very high Debye temperature θD > 800 K, or it is crystallographically not single phased with one component (87%) with θD = 378±30 K and the other (13%) with θD = 136±13 K.

Conversion Electron Mössbauer Sideband Spectroscopy is presented as a new and the most accurate method to study the dynamics of piezoelectric polymer materials at high frequencies. With raising amplitude of driven vibrations, complete oscillating behaviour of the Mössbauer sideband-intensities is found. The amplitudes of vibrations can be measured with an accuracy of 0.005 Å. Variations of the piezoelectric constant with temperature and frequency can be determined to better than 1%. Beside piezoelectricity the thermally induced dynamic behaviour of polymer surfaces can also be studied by CEMS.

A new model is presented which explains well the dramatic decrease of the Mössbauer line intensities with raising temperatures for freely dispersed iron microscrystals. In contrast to other theories which consider mainly vibration to be responsible we discuss here the decrease in terms of large amplitude diffusive rotational or translational jumps of the particles. Such diffusive jumps lead — in agreement with the observation — to a strong reduction of the Mössbauer-intensity without broadening the line width in a noticeable way. The typical potential well for a diffusing particle in an equilibrium position is derived quantitatively to be 13 meV. The model might be important also for a new understanding of the dynamics of catalytic clusters either in contact with each other or with larger solid surfaces.

The temperature dependence of the Mößbauer line intensities for iron particles coated with iron oxide is found to be the same for both the iron and the iron oxide subspectra. For the first time, this result gives direct experimental evidence that the dramatic decrease of the line intensities with raising temperaures /1,2/ is not due to changes in the phonon spectrum, but to motions of the particles instead. These motions are not influenced by external magnetic fields up to 10 T. The result is discussed in terms of different possibilities for the movement of the particles. Further more it is shown, that the geometric arrangement is different for the particles contributing to the Mößbauer effect at high, from those contributing at low temperatures.

The preparation, at low temperatures by the Rüdorff method, of quaternary cointercalates containing Eu-, NH3- and H-guest particles is described. The stoichiometry of the blue phase is wide. Longer reaction times increase the Eu and H contents. The Mössbauer spectra show a mixture of Eu2+ and Eu3+ at room temperature. The intensity of the Eu2+ line decreases in the higher stage compounds. Irreversible reorganisation in the guest layers is observed.

Mössbauer effect investigations on the cubic intermetallic compound YbBe13 in the temperature range between 0.065 K and 81 K are reported. Above the magnetic ordering temperatureTNeel=1.27 K the results cannot be explained by a Γ7 groundstate of Yb3+. There is evidence for the Yb ion being in a mixed valent state and the degree of hybridisasation being dependent on the magnetic ordering. Below the magnetic ordering temperature a Γ7 groundstate of a 3+ Yb ion is found.

A simple additional device is shown to introduce specimen without contact to air into the Siemens electron microscope EM-101. The construction, the function and handlinf of the modified specimen airlock is described. The device is used to study oxidable crystals by electron microscopy and diffraction, and might also be promising for ultracytochemical and molecular biological problems.

Iron microcrystal ranging in size from 70 to 450 Å have been investigated by the Mössbauer effect. There is, compared to the bulk value, a small enhancement of the magnetic field at the site of the nucleus of about 1% which can be interpreted as due to the demagnetisation field of the microcrystals and their geometric arrangement. The observed drastic size and temperature dependent lowering of the Debye Waller factor cannot be explained by a change of the Debye temperature of the microcrystals. Two different models are proposed to explain the effect.