Magnetic hyperfine anomaly in muonic193Ir

The nuclear decay of the 5/2⁺ 139 keV state to the 3/2⁺ ground state was observed in muonic¹⁹³Ir. The hyperfine splitting of the 3/2⁺ state and 5/2⁺ state was determined to be 640±100 eV and 1280±160 eV, respectively. The ground state splitting is about twice that of a point nucleus, an anomaly never observed this large. This is mainly due to the different radial distribution of spin and orbital magnetization of a d_3/2 proton configuration for which these contributions nearly cancel to zero in the magnetic moment. But calculations including configuration mixing and coupling to a vibrating or a deformed core show deviations. The groundstate anomaly is in line with that observed by the Mössbauer technique.     

Magnetic hyperfine structure of muonic and electronic atoms

The magnetic hyperfine structure of atoms is studied. A new compact expression is introduced for the magnetic hyperfine anomaly. A theoretical foundation is given for an empirical formula discovered by Moskowitz and Lombardi. The effects of core polarization and mesonic exchange currents are discussed. There are two kinds of core polarization, Δl = 0 and Δl = 2. The latter is shown to be important to explain certain isotope shifts, though it is smaller than the former Δl = 0 effect.     

Magnetic hyperfine interaction of Br in Ni

The magnetic hyperfine splitting frequency of ⁸²BrNi in an external magnetic field of 0.2 T has been measured by NMR-ON method at 8 mK. The centre of resonance frequency was determined to be 18.7(2) MHz. With the known g-factor of g(⁸²Br)= 0.3254(1), the hyperfine field of ⁸²BrNi was deduced as B_hf(⁸²BrNi)= 7.34(8) T. The measured value is compared with the calculated value based on band structure using bonding states. This revised version was published online in August 2006 with corrections to the Cover Date.     

Breit interaction determination of muonic hyperfine anomalies: Large but not giant

Muon-nuclear-hyperfine anomalies are determined from Breit interaction calculations based on unrestricted Dirac-Fock solutions which explicitly include all electrons and the negative muon. We obtain anomalies of a few (3) percent, which are much larger than corresponding Bohr-Weisskopf electron-nuclear anomalies, but are much smaller than the giant, ≈(36 ± 5)%, anomaly reported by Yamazaki et al. for μ^-Pd⁺ vs. Rh. We suggest the possibility that interstitial μ^-Pd⁺ was observed and that the small anomaly for substitutional μ^-Pd⁺ may also be seen at higher temperatures.     

Theory of hyperfine anomalies in muonic atoms

Negative muon spin precession experiments by Yamazaki et al. have found giant hyperfine anomalies in muonic atoms ranging from a few percent up to 36%. In order to understand their results, we present Breit interaction calculations based on atomic self-consistent unrestricted Dirac-Fock solutions which explicitly include all electrons and the negative muon. The Breit interaction results (including the relativistic correction for the bound muong-factor), vary from near zero for ^–O/N to –5% for ^–Pd/Rh; this latter is much larger than the calculated muonic or nuclear Bohr-Weisskopf anomalies and much smaller than the 36% measured value. For ^}Ni/Co we find a calculated range of results (depending on assumed electronic configurations) of –2.3 to –2.7% in excellent agreement with recent measurements of the Yamazaki group. This excellent agreement in ^}Ni/Co provides strong support for the earlier suggestions that the discrepancy in the case of ^–Pd/Rh is due to experimental factors.This work was supported by the U.S. National Science Foundation (DMR Grant No. 82-16543) and the U.S. Department of Energy.     

Magnetic field focusing of hyperfine interaction in hydrogen

We find a new correction to hyperfine splitting in the ground state of hydrogen atom in magnetic field. The physical basis for this effect is the reduction of the size of the electron orbit in magnetic field. As a result, the value of the wavefunction at the origin increases which can be called magnetic focusing. Another magnetic-field-induced effect is the appearance of field dependent tensor forces.     

Magnetic hyperfine interaction of 59Fe in nickel

Nuclear magnetic resonance on oriented nuclei (NMR-ON) on ⁵⁹Fe isotope in Ni was performed. The magnetic hyperfine splitting frequency of was determined to be ν(B ₀?=?0)?=?48.32 (2) MHz. Using the known magnetic moment the magnetic hyperfine field was deduced as B _HF?=???28.32 (5) T. The effective nuclear spin-lattice relaxation time was also measured. The measured value is compared with experimental values of 3d-impurity in nickel host.     

Induced pseudoscalar interaction in weak nucleon current and muon capture in hyperfine states of muonic deuterium

Muon capture rate in muonic deuterium can be calculated with less ambiguities in nuclear wave functions, since we know the bound and scattering states of the two nucleons with higher accuracy theoretically. It is, however, dependent on the pion-nucleon-delta coupling constant through the exchange current effect. This dependence is considerably reduced for the ratio of the capture rates from two hyperfine states of muonic deuterium. This ratio is, therefore, useful to study the strength of the induced pseudoscalar term. Several other physical quantities in light nuclei are also introduced here for the same purpose.     

Magnetic hyperfine interaction after77Br implantation into iron

Radioactive⁷⁷Br ions were implanted at 60 keV and 270 keV into polycrystalline iron foils. The magnetic hyperfine interaction of the daughter nucleus⁷⁷Se in the 250 keV isomeric level was investigated using the perturbed angular correlation technique and fast BaF₂ detectors. The Larmor frequency at room temperature was determined as ω_L=1272(2) MHz, leading to a substitutional hyperfine field ofB _hf(SeFe)=62(6) T. The substitutional fraction rises from 21% at room temperature to about 100% at 790 K annealing temperature. No other well-defined magnetic or electric hyperfine component attributable to impurity-defect complexes was identified. The diffusion of Br atoms in the surface region during the annealing process was studied via Rutherford backscattering with 1.0 MeV α-particles.     

Electro-weak interaction in muonic atoms

The parity non-conserving effective neutral current interaction between charged leptons and nucleons is studied in its implications for atomic physics. Present results on heavy electronic atoms are discussed within the standard electroweak theory and beyond. The new features provided by muonic atoms open the way to the nuclear-spin-dependent parity non-conserving effects. Different observables proposed to study these effects in muonic atoms are reviewed.     

The Sachs moment and finite size effects in muonic hyperfine structure

In calculations of finite size effect in muonic hyperfine structure, the meson exchange part of nuclear magnetism has so far not been taken explicitly into account. We investigate this effect for the Sachs moment and show that the reduction factor is approximately the same as for the orbital part. Consequences for theoretical values of the h.f.s. constant A₁ are discussed for the special nucleus ²⁰⁹Bi.     

The temperature dependence of the hyperfine interaction of the transition metal osmium in a gadolinium host matrix

Integral perturbed angular correlations of the 931-155keVγγ-cascade of¹⁸⁸Os in Gd have been measured. With this technique the combined magnetic and electric hyperfine interaction of the 155 keV level of¹⁸⁸Os as an impurity in a Gd host has been studied as a function of temperature. The result for the electric field gradient of Os in Gd at 300 K is: $$\left| {V_{zz} \left( {Os:\underline {Gd} } \right)} \right| = \left( {12.8_{ - 1.9}^{ + 3.1} } \right) \cdot 10^{17} {V \mathord{\left/ {\vphantom {V {cm^2 }}} \right. \kern-\nulldelimiterspace} {cm^2 }}.$$ For the magnetic hyperfine field at 4.2 K the value $$H_{hf} \left( {Os:\underline {Gd} } \right) = - 134\left( {26} \right)kG$$ was obtained. Sign and magnitude of the magnetic hyperfine field suggest the existence of a localized moment of about ?0.4 µ _B at the site of Os in Gd. With increasing temperature the magnetic hyperfine field decreases much stronger than the magnetization of the host. Possible explanations for this anomalous temperature dependence are discussed.     

Magnetic hyperfine interaction of swift43 K ions recoiling in helium and xenon

The 738 keV 7/2^– isomeric state in⁴³K (=292 ± 5 ns,g=1.266 ± 0.015) was produced in the reaction⁴He(⁴⁰Ar,p) using the 185 MeV pulsed⁴⁰Ar beam of VICKSI and a 2–7 bar helium target cell. The suitability of this isomeric state for hyperfine studies during recoil in gases and after implantation into solids was investigated via the TDPAD technique. The hyperfine deorientation of highly stripped⁴³K ions in He and Xe was investigated and interpreted with the AbragamPound model. When adding up to 15% Xe to the He target gas, a near-exponential loss of alignment with the Xe partial pressure was observed. This effect can be explained by K-hole production in⁴³K in the Xe-K collision for which a cross section of=5 · 10^–18 cm² was estimated.     

Shell model analysis of the magnetic hyperfine splitting in muonic thallium

The magnetic hyperfine splitting of the ground and first excited state in muonic²⁰³Tl and²⁰⁵Tl is calculated on the basis of the shell model with configuration mixing. Fair agreement with the recently measured ground state splitting is found.     

Magnetic hyperfine interaction near Fe(100) surfaces in ultrahigh vacuum

The DCEMS technique in UHV has been used to measure for the first time the temperature dependence (31 to 295 K) of the magnetic hyperfine field B_HF averaged over several atomic layers near the surface of α-⁵⁷Fe(100) thin films covered by residual gas adatoms. The measured B_HF(T) curve closely follows that of bulk α-Fe. The surface magnetic moment of a residual gas coated Fe(100) surface in UHV appears to be not significantly modified as compared to the bulk.     

The hyperfine field of silver and of indium in cobalt

The hyperfine field of Ag and In in cobalt has been determined using the nuclear orientation technique, as 349(20) and 158(20) kG respectively. For In in cobalt we also determined the sign to be negative. A comparison with different theoretical models is given.     

Anomalous interaction of muons and muonic atoms

Restrictions for the constants of possible anomalous interactions of muons with nucleons which follow from available muonic-atom data are obtained. The possible contribution of anomalous interactions to (a) difference between radii of nuclei obtained from the data on muonic atoms and from electron scattering, (b) fine and (c) hyperfine splitting of muonic-atom levels, is discussed.