[en] The hyperfine interaction (HFI) of ¹¹¹Cd in different indium-halides was studied by perturbed angular correlation (PAC). The ¹¹¹Cd ion arises from a ¹¹¹In by electron capture decay (EC) and joined Auger cascade. Coulomb fragmentation of the indium-halide molecule produces the free excited ¹¹¹Cd ion. The nucleus decays via a γ-γ-cascade which is perturbed by the HFI. Collisions of the ¹¹¹Cd ion with indium-halide molecules can strongly change the perturbation. The perturbation was measured by the attenuation coefficient G₂₂(∞) and G₂₂(t). The molecular densities varied between 10¹⁴ and 10²⁰ cm^-3. The present article shows the temperature dependence of the indium(III)-halides and a fit for an empirical basic approach. The investigation of the InBr shows the independence of the attenuation coefficient from the temperature by indium(I)-halides in contrast to the dependence of the indium(III)-halides

[en] The time dependence of the recoil velocity of a ¹⁴⁰Ce nucleus in a La and a LaF₃ lattice after β emission is studied via the Doppler shift of the 1.596 MeV γ transition in ¹⁴⁰Ce. Evidence is obtained that the nucleus does not leave the lattice site even at a recoil energy of about 20 eV but carries out a damped oscillation. The quantitative comparison of the recoil velocity with the predictions of lattice theory leads to partial agreement. (orig.)

[en] Up-to-date α-decay data of the double-even, N=84 isotones are presented, including the presently remeasured values for ¹⁴⁶Sm. For this nuclide a half-life, T_1/2=1.031(45)x10⁸ y, and α-ray energy, E_α=2455(4) keV were measured. The significance of these data for the subshell closure at Z=64 observed in α-decay is discussed. (orig.)

[en] With the time-integral perturbed angular correlation (TIPAC) method the pressure dependence of the perturbation of the 121.1 - 279.5 keV γ-γ cascade in ⁷⁵As has been investigated using gaseous H₂⁷⁵Se sources in different buffer environments. The obtained attenuation coefficients in the range of 0.55 to 1.0 were fitted with a theoretical stochastic model. In the region of low density, where the correlation time is large compared to the lifetime of the intermediate level of the nucleus, charge transfer collision cross sections have been evaluated between 8.1x10^-16 cm² for He, 1.3x10^-14 cm² for Xe and 1.8x10^-14 cm² for the molecular H₂ buffer gas. For increasing densities of the buffer gases the correlation time became small compared to the intermediate lifetime. The main effect in this region is the depolarization, and cross sections were found between 5.2x10^-15 cm² for He, 8.7x10^-14 cm² for Xe and 1.2x10^-13 cm² for the H₂ buffer gas. (Auth.)

[en] Using gaseous sources of I₂ and HI containing the radioactive isotopes ¹²⁴I and ¹²⁶I effective cross sections for nuclear resonance scattering from the first 2⁺ states of ¹²⁴Te and ¹²⁶Te were measured. Information is obtained about the charging of the nonradioactive molecular partner after EC decay, the interaction of highly charged ions with neutral molecules, and the slowing down of atoms in a Xe buffer gas. Indications of an iodine complex being stable in the gaseous phase are found. (orig.)

[en] Published in summary form only

No abstract available

[en] Some 10¹² radioactive ¹¹¹In-tracer atoms are routinely implanted at 400 keV into different samples to perform perturbed angular correlation (PAC) measurements. The experimental details and the tricks used during the preparation and implantation are summarized. As an alternative to ion-implantation, a method to deposit submonolayer ¹¹¹In-tracer films into metallic multilayers is described. The different applications and benefits of both techniques are compared. (orig.)

[en] Perturbed angular correlation (PAC) experiments with implanted ¹¹¹In tracers have recently been used to investigate magnetic phase transitions in metal oxides. Here we report on PAC measurements for ¹¹¹Cd in polycrystalline Fe₃O₄ in the neighborhood of the Verwey phase transition (T_V∼ 120 K). Perturbed angular correlation spectra were taken for implanted ¹¹¹In probes at temperatures between 9 and 850 K. The two observed Larmor frequencies are attributed to the two possible cation sites in the cubic inverse spinel lattice. For T > 120 K, the temperature dependence of both Larmor frequencies follows a Curie-Weiss power law ω_L(T)/ ω_L(0)=(1-T/T_N)^β, with the parameters T_N=848(2) K and β= 0.392(2). At the Verwey temperature we find a rapid change of both Larmor frequencies, with ω_L1 increasing from 178(2) MHz at 120 K to 191(4) MHz at 100 K, and ω_L2 decreasing from 173(4) MHz to 151(5) MHz. The Verwey transition also affects the widths of the frequency distributions, which more or less double below T_V. This possibly indicates the presence of several components with Larmor frequencies similar to those found in the previous Moessbauer data, or for electronic after-effects correlated with the semiconductivity of magnetite below T_V

[en] The slowing down of ⁷⁵As recoil atoms with energies approx. <=10 eV in He, Ne and H₂ was investigated by measuring Doppler-widened line profiles of the 265 keV gamma line emitted by the recoil nuclei. The line profiles contain information on the stopping powers of gases for heavy ion with initial velocities ν approx. <= 3 x 10⁵ cm s^-1. They are analyzed in terms of the continuous slowing down theory developed by Falcone et al. The profiles observed with He and Ne are well described by assuming the stopping power to be based on Lenz-Jensen elastic interaction between recoil and moderator atoms. The profiles observed with H₂ do not agree with predictions based on that interaction. The stopping power of H₂ for the ⁷⁵As recoil atoms is found to be larger than that of He. (orig.)