Hyperfine Interactions

We present the results of an experiment performed at PSI to investigate muon catalyzed fusion in pure deuterium gas of 5% density (LHD) at temperatures ranging from 28 K to 350 K. Using a new high pressure ionization chamber the reactions dd→ n+ 3 He and ...

Conversion electron-gamma PAC measurements of the 49–37 keV cascade in 80Br through the intermediate 2− state with T 1/2=7.4 ns were performed with a system of two magnetic lens spectrometers and two BaF2 scintillation detectors. The parent 80mBr activity with a halflife of 4.4 hrs was implanted into Ni, Zn and graphite at the ISOLDE separator at CERN. The observed

A systematic study has been made of the initial corrosion products which form on mild steel capons exposed near the coastal region of Oman and at some industrial areas. The phases and compositions of the products formed at different periods of exposure were examined by using Mössbauer spectroscopy (295 and 78 K) and X-ray diffraction (XRD) techniques. The results show that lepidocorcite and maghemite are early corrosion products and goethite starts to form after 2 months of metal exposure to the atmosphere. Akaganeite is an early corrosion product but it forms in marine environments only, which reflects the role of chlorine effect in the atmosphere. The 12 months coupons showed the presence of goethite, lepidocorcite and maghemite, but no akaganeite being seen in the products of one of the studied areas.

The present paper represents the simplest proof that the general relativity principle does not come to the particular relativity principle in case of inertial motion in an empty space. It admits an existence of phenomena, where a violation of the particular relativity principle occurs within the scope of the general relativity principle. Under modern development of experimental techniques, a search of such hypothetical phenomena can be made only by means of the Mössbauer effect. A scheme of possible experiment has been proposed.

The generalized Heusler compounds Mn2CoZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) with the Hg2CuTi structure are of large interest due to their half-metallic ferrimagnetism. The complex magnetic interactions between the constituents are studied by first principles calculations of the Heisenberg exchange coupling parameters, and Curie temperatures are calculated from those. Due to the direct Mn-Mn exchange interaction in Mn2CoZ, the Curie temperature decreases, while the total moment increases when changing Z from one group to another. The exchange interactions are dominated by a strong direct exchange between Co and its nearest neighbor Mn on the B site, which is nearly constant. The coupling between the nearest-neighbor Mn atoms scales with the magnetic moment of the Mn atom on the C site. Calculations with different lattice parameters suggest a negative pressure dependence of the Curie temperature, which follows from decreasing magnetic moments. Curie temperatures of more than 800 K are predicted for Mn2CoAl (890 K), Mn2CoGa (886 K), and Mn2CoIn (845 K).

Nuclear resonant scattering of synchrotron radiation was applied to investigate the spin‐crossover complex Fe(tpa)(NCS)2 (tpa=tris(2‐pyridylmethyl)amine). The nuclear forward scattering experiments are compared with conventional Mössbauer experiments, and the nuclear inelastic scattering experiments are compared with the results from a theoretical normal mode analysis based on molecular orbital calculations.

The ferrites Mg0.9Mn0.1Crx Fe2−x O4 ( $0 \leqslant {\text{x}} \leqslant 0.9$ ) were prepared using the conventional double sintering method. The XRD showed that the samples maintain a single spinel cubic phase. The Mössbauer measurements were carried out at room and liquid nitrogen temperatures. From the area ratios of the A and B sites, it was found that the Fe cation population of the A and B sites decreases in proportion to Cr concentration. The contact hyperfine fields at the A and B sites were found to decrease with increasing Cr contents. This was found to be in approximate agreement with the results of magnetization measurement. The distributions of Mg and Mn cations versus Cr concentration were also determined using the Mössbauer and magnetization results. The Curie temperatures were determined and found to agree with the reported values. As the Cr contents increases the relative magnetization, was found to increase at low temperatures and decreases at higher temperatures.

Hyperfine interaction techniques like Mossbauer spectroscopy are very sensitive tools to study the local probe interactions in dilute magnetic semiconductors. We report here a Mossbauer study on the concentration dependence in Fe0.008Ge1 − x Tex for x = 0, 0.008, 0.016, 0.03 and 0.05. At room temperature magnetic interactions were observed for all concentrations of Te and the population of magnetic site was found to increase gradually with the Te concentration. A constant magnetic hyperfine field of 136 KOe was found. A quadrupole doublet due to the FeTe2 compound phase was also seen.

A large number of ceramic sherds from Chavin, Peru, as well as recent clay samples from the same region have been studied by Mössbauer spectroscopy. The changes of the Mössbauer spectra of the clay were studied as a function of firing temperature and atmosphere. From a comparison of these data with those form the sherds one can make estimates of the precolumbian firing conditions.

Iron limited growth of microbes results in derepression of siderophore receptor and transport-systems which can be utilized for controlled and specific siderophore mediated57Fe incorporation, yielding a suitable resonance nuclide concentration inside the cell. We have employed in vivo Mssbauer spectroscopy to analyze57Fe siderophore uptake and to monitor time-dependent processes of microbial iron metabolism inE. coli. The cell spectra display the

Magnetic Hyperfine and Nuclear Quadrupole Interactions (HPI and NQI) are now important tools for characterization of systems of interest in materials research and industry. Boron-Trifluoride is an inorganic compound that is very important in this respect as a catalyst in chemical physics research and industry, forming complexes in the process with compounds like ammonia, water and methyl alcohol. The present paper deals with the BP3-NH3 complex and methyl derivatives BP3NHx(CH3)3-x for which we have studied the electronic structures, binding energies, and 19F* (I=5/2) nuclear quadrupole interactions using the first-principles Hartree-Fock-Roothaan procedure combined with electron correlation effects. Our results for the 19F* nuclear quadrupole coupling constant (e 2qQ/h) in units of MHz compare well with experiment. Trends in the binding energies and NQI parameters between the complexes are discussed.

The green chlorite, occurring as monomineralic mass in the Sukinda (India) area has been investigated by57Fe Mössbauer spectroscopy together with IR, XRD and XRF analyses. The Mössbauer spectra (at RT and 100 K), split into four symmetric doublets, show hyperfine parameters suggesting Fe2+ atcis and brucite sites and Fe3+ attrans andcis sites. The results show that susceptibility to oxidation (Fe2+→Fe3+) is highest in thetrans site, moderate in thecis site, and least in the brucite site.

57Fe Mössbauer spectroscopic measurements have been carried out on (Fe0.93Ni0.07)2P in the temperature range 85 405 K. Obtained values of hyperfine field at the two metallic sites are slightly smaller than in Fe2P. But the reduction is much less than as reported in Cr or Mn or Co substituted analogues of Fe2P.

The concept of the heterodyne/stroboscopic detection of nuclear resonance scattering of synchrotron radiation is extended to the grazing incidence geometry. Model calculations for an antiferromagnetic [57Fe/Cr]20 multilayer are shown and discussed. Principles and methodological aspects of stroboscopic synchrotron Mossbauer reflectometry are briefly reviewed.

The phases and compositions of the corrosion products of a mild steel (A-36) and two weathering steels (A-588 and COR 420) formed after 3 months exposure to the tropical marine atmosphere of Panama were examined using FTIR and Mössbauer spectroscopy. The results show that amorphous or crystallized iron oxyhydroxides goethite α-FeOOH and lepidocrocite γ-FeOOH are early corrosion products. Maghemite γ-Fe2O3 and magnetite Fe3O4 have also been identified and found to be prominent components for steels exposed to the most aggressive conditions. The formation of akaganeite β-FeOOH was observed when chlorides were occluded within the rust. FTIR showed the presence of hematite α-Fe2O3 in one sample.

The electronic structure of the heme unit of deoxyhemoglobin including the proximal imidazole has been studied using the first-principles Hartree-Fock procedure. Our results for the 57mFe isomer shift and asymmetry parameter are in very good agreement with the values obtained from Mössbauer spectroscopy measurements. The 57mFe nuclear quadrupole coupling constant is smaller than the experimental result and possible ways to improve the agreement in the future are discussed. Improved analysis of the Mössbauer data, removing some approximations made for deriving the magnetic hyperfine tensor for the 57mFe nucleus, is suggested to allow quantitative comparison with our results in the future.

The spin structure of the (37,35) energy level of antiprotonic helium-4 in permanent homogenous external magnetic field has been calculated in first order of perturbation theory. For weak magnetic fields the effect is observed as an additional broadening of the spectral lines. For magnetic fields of the order of kG and higher, the magnetic and hyperfine interactions become comparable to each other, and the hyperfine spectrum is rearranged.

The properties of nanocrystalline Ni0.5Zn0.5Fe2O4 synthesized by an auto-combustion method have been investigated by magnetic measurements and Mössbauer spectroscopy. The as-synthesized single phase nanosized ferrite powder is annealed at different temperatures in the range 673–1,273 K to obtain nanoparticles of different sizes. The powders are characterized by powder X-ray diffraction, vibrating sample magnetometer, transmission electron microscopy and Mössbauer spectroscopy. The as-synthesized powder with average particle size of ~9 nm is superparamagnetic. Magnetic transition temperature increases up to 665 K for the nanosized powder as compared to the transition temperature of 548 K for the bulk ferrite. This has been confirmed as due to the abnormal cation distribution, as evidenced from room temperature Mössbauer spectroscopic studies.

Rapid stress annealing induced changes in structural and magnetic properties in Fe74.5Cu1Nb3Si15.5B6 are reported. Obtained results suggest changes in spin texture with preferred orientation along ribbon axis. Fraction of A site in the DO3 lattice occupied by Si atoms, increases, with increase of applied stress during annealing. Volume fraction of the nanograins up to 60% (exhibiting quite similar mean grain diameter ∼9 nm) is observed. Lattice parameter values suggest that Si content in the nanocrystalline phase is between 14% and 19% and increase of lattice parameter suggests the elongation of the unit cell. Studied stress annealed samples exhibit soft magnetic behavior (coercive field ranging between 4 and 8 Am − 1). Stress annealing reduces permeability whereas anisotropy field increases almost linearly exhibiting the induction of uniaxial and perpendicular to the ribbon axis anisotropy. Obtained stress-induced-anisotropy constant values range between 50 and 2,140 Jm − 3.