Hyperfine spectrum of NaF

The molecular beam electric resonance technique has been used to conduct a high precision examination of the hyperfine spectrum of ²³Na¹⁹F. Coupling constants for the nuclear electric quadrupole interactions, the spin-rotation interactions, the tensor and scalar spin-spin interactions, and their dependence on vibrational and rotational state have been determined.     

Hyperfine interaction measurements inMnSi-alloys

PAC-experiments were performed on¹¹¹Cd in Mn_1−xSi_x (x=8.8at%) alloys. The high-field site (h) due to the local moments existing at site II positions is almost unaffected by the Si-impurities. For the second field site (1), supposed to be due to SDW, the ordering temperature is shifted to 77(2)K, although the field value is very similar to the pure α-Mn value. This observation supports our earlier interpretation of the magnetism in pure α-Mn.     

Hyperfine interactions in chromium

Conclusion Our experiments suggest that Tantalum in Chromium is non magnetic and does not clamp the S.D.W. The various transitions of chromium have been observed. On the other hand rhodium seems to couple with the S.D.W. but the interaction, if any, between rhodium and the S.D.W. does not strongly modify the shape of the S.D.W. TDPAC experiments are therefore a useful tool to investigate the magnetic properties of impurities dissolved in a chromium matrix. This is extremely interesting because the formation of a localized moment in an itinerant antiferromagnet as well as their interaction with the S.D.W.'s have never been studied. It is also interesting to note that S.D.W.'s could couple magnetic impurities at very large distances and then could give rise to a special type of spin glass.     

Hyperfine spectrum of RbI

The molecular beam electric resonance technique has been used to conduct a high precision examination of the hyperfine spectrum of RbI. Coupling constants for the nuclear electric quadrupole interactions, the spin-rotation interactions, the tensor and scalar spin-spin interactions, and their dependence on vibrational and rotational state have been determined.     

Hyperfine interaction in charge-ordered manganites

Nonempirical calculations of the unpaired-spin density and NMR frequencies for charge-ordered compounds La_0.333Ca_0.667MnO₃ and La_0.5Ca_0.5MnO₃ are carried out. The effect of the local-structure parameters on the resonance frequencies is shown to be dominant.     

Hyperfine field in Li-Zn-Ti ferrites

The paper reports the⁵⁷Fe Mössbauer effect investigations on the solid solutions of Li_0.5Zn_xTi_xFe_2.5–2xO₄ (x=0 to 0. 6) at 300K. The samples with x0.4 exhibit well defined Zeeman pattern consisting of two sextets corresponding to Fe³⁺ ions at tetrahedral and octahedral sites. The composition with x=0.5 shows a strong ferrimagnetic relaxation whereas the composition with x=0.6 exhibits paramagnetic behaviour. The internal magnetic field at⁵⁷Fe nuclei decreases with increasing x at both the sublattices. This variation is explained in terms of cation distribution and super-exchange interactions. The s-electron density has been observed to be independent of substitution level.     

Hyperfine interactions in cubic perovskites

ABO₃ perovskites display several physical properties determined by the characteristics of A and B cations. These compounds have cubic structure at high temperature. Lower symmetry cells that are distorted cubes are found at low temperature. Defects modify the properties of these compounds. Under standard conditions oxygen vacancies are produced. Cation substitution also alters the characteristics of perovskites. These materials have been studied by Perturbed Angular Correlation (PAC) spectroscopy and other hyperfine techniques. In this way abundant information is available to determine charge distributions close to probes. In the cubic phase perturbations were detected that are produced by the interaction of probes with defects. To show up these effects we analyze the quadrupole interaction at ¹⁸¹Ta in several compounds: ABO₃ with A=Ca, Sr and Ba, BaTi_1−x Hf _x O₃ and PbZr_1−x Ti _x O₃ for 0⩽x⩽1. Three different quadrupole interactions were found and are interpreted in terms of distinct probe-oxygen vacancy configurations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Gravitational Correction to Hyperfine Structure

The effective Hamiltonian of a fermion with spin-spin coupling to another fermion is derived from the non-relativistic approximation of the generally covariant Dirac equation in a weak gravitational field. This makes hyperfine structure of s-state of atomic hydrogen to be triplet other than the doublet in fiat spacetime. The difference is large enough to be measured for the atomic hydrogen on the earth and the sun.     

Hyperfine interactions in isolated ions

Conclusion It has been demonstrated that the effect of a tilted multifoil array on an ensemble of nuclei approaches a regular precession in a field of magnitude pH in the direction of the tilt axis. The magnitude of the precession can, under certain circumstances, be considerably larger than in a transient field, the only other method available today for measurements in the picosecond range. The technology of multifoil arrays has not been fully mastered to date, the immediate objective being the construction of arrays which keep their shape and spacings for many hours in a particle beam.     

Hyperfine spectroscopy in diffraction geometry

Hyperfine Interactions - With the advent of third generation synchrotron radiation sources nuclear Bragg diffraction became a powerful technique for the determination of hyperfine parameters and...     

Hyperfine interaction using grazing beams

The interaction of fast ions with solid surfaces at grazing incidence yields a large anisotropy in the spatial distribution of the orbital angular momenta of atoms and ions. This anisotropy is partially transferred via hyperfine interaction to the nuclear spin system so that high-resolution atomic spectroscopy and the polarization of nuclear spins are feasible.     

Hyperfine structure of lithium-like scandium

The hyperfine structure of the ground state of the lithium-like scandium ion (Z = 21) is considered. The effects of electron-electron interaction are taken into account in the first order in 1/Z using the quantum electrodynamic perturbation theory and in higher orders using the method of configuration interaction in the Dirac-Fock-Sturm basis. One-loop radiative corrections are calculated in all orders in αZ with an effective local screening potential. The corrections for the finite nuclear size and the distribution of the magnetic moment over the nucleus have been refined.     

Hyperfine fields in erbium metal

The hyperfine Splitting of the 80.6-keVγ transition in Er¹⁶⁶ has been measured in erbium metal between 4.2 °K and 40 °K using the Mössbauer effect. There is evidence for a unique magnetic field and electric fieldgradient at all nuclei in erbium metal. The magnetic field decreases from (7.55±0.20)·10⁶ Oe at 4.2 °K to (6.10±0.40)·10⁶ Oe at 40 °K. Extrapolation to 0 °K yieldsH (0 °K)=(7.60±0.20)·10⁶ Oe. The quadrupole interaction energy for the 80.6-keV state iseQ V _Z′Z′/4=(0.95±0.20)·10^?6 eV at 4.2 °K. These results are discussed and compared with other measurements.     

Hyperfine fields in acid ferric phosphate

Mössbauer spectra of acid ferric phosphate show that the iron ion site has a nearly cubic symmetry. Below 30 K the substance is magnetically ordered and undergoes a phase transition at about 11 K. At 4.2 K ferrimagnetic order with canted spins was found, and a 13% contribution of antiferromagnetically ordered spins.On leave from the University of Mainz, Germany.Prof. P. Gütlich's interest in this work, experimental assistance by H.-J. Guttman, and financial support by the Bundesministerium für Forschung und Technologie are gratefully acknowledged.