The quadrupole interaction of57Fe in Ti

The quadrupole interaction of⁵⁷Fe in titanium was studied by Mössbauer spectroscopy and by the time-differential perturted angular correlation technique, using an implanted and diffused source of⁵⁷Co in titanium. From the latter measurements a quadrupole interaction frequencyv _Q = 2.22 ± 0.42 MHz was derived. The modulation amplitude of the delayed coincidence spectrum combined with the Mössbauer spectra indicate a high degree of substitutionality of the cobalt in the titanium.     

Double resonance NMR-on study on oriented188Ir in iron

The quadrupole splitting of oriented¹⁸⁸Ir in iron was studied at 8.6 mK using a double resonance NMR-ON method. With r.f. power applied at the strongest resonance frequency, a second frequency was used to simultaneously investigate the second resonance component, where the splitting is caused by an electric quadrupole interaction. The electric hyperfine splitting frequency ν_Q=e ² qQ/h was measured to be 3.37(11) MHz. With the known electric field gradient of −0.283(6)×10¹⁷ V/cm² at Ir in iron, the spectroscopic quadrupole moment of¹⁸⁸Ir was deduced to be 0.492(26)b. The present results show that the double resonance method is a powerful tool in establishing the quadrupole splitting, if it leads to well-resolved NMR-ON resonance components.     

Nuclear magnetic resonance on oriented192Ir in Fe and Ni

The hyperfine interaction of¹⁹²Ir nuclei as dilute impurities in Fe and Ni has been investigated with NMR on oriented nuclei. With the use of highly dilute and pure alloys the line widths could be reduced so far that the quadrupole splitting of¹⁹²IrFe and¹⁹²IrNi could be resolved. Taking hyperfine anomalies into account the ground state nuclear moments of¹⁹²Ir are deduced as |μ|=1.924(10)μ _N andQ=2.36(ll) b. The hyperfine field of IrNi was investigated as a function of the Ir concentrationc between 0.01 at % and 5 at %. The dependence ofH _HF onc was found to be significantly smaller than that reported from Mössbauer effect measurements. Forc=0.01 at %H _HF=?454.7(2.3)kG is deduced. The resonance shift with an external magnetic field has been studied precisely, yieldingK=0.012(23) andK=0.026(12) for the Knight-shift of¹⁹²Ir in Fe and Ni, respectively.     

TDPAC characterization of tin oxides using181Ta

In connection with a general study of the evolution of tin-oxygen thin films, we report here on the hyperfine interactions of¹⁸¹Ta substitutionally replacting tin in the isolated phases SnO and SnO₂. For this purpose, pure SnO pressed powder and a thin SnO₂ film were implanted with¹⁸¹Hf. In both cases, unique quadrupole frequencies were found after thermal annealing treatments. The results indicate that the following hyperfine parameters: υ _Q = 740.6(2.1) MHz, η=0.07(2) and υ _Q = 971.5(1.9) MHz, η=0.72(1) characterize¹⁸¹Ta in SnO and SnO₂, respectively.     

Hyperfine structure and nuclear moments of99Ru and101Ru

The atomic-beam magnetic-resonance method in combination with the triple resonance technique has been used to determine the nuclear magnetic dipole moments of⁹⁹Ru and¹⁰¹Ru. The moments are deduced fromrf transition measurements in the⁵F₅ and⁵F₄ states at magnetic fields between 770 and 2400 Oe. In order to reduce the part of the uncertainty of the moments which arises from the uncertainty of the hyperfine structure constants more precise values of the constants than those available up to now were determined from low field measurements. After making corrections for hyperfine and Zeeman interactions with neighbouring atomic states we obtain the following values for the magnetic dipole moments:μ ₉₉=?0.6381 (51)μ _N andμ ₁₀₁=?0.7152 (60)μ _N (uncorrected for diamagnetic shielding). The results of the present work combined with the results of an earlier hyperfine structure investigation in the⁵F multiplet are analysed with respect to the effective-operator formalism. From this analysis we obtain the following values for the electric quadrupole moments:Q ₉₉=0.076 (7) b andQ ₁₀₁=0.44 (4) b (uncorrected for Sternheimer shielding or antishielding).     

The magnetic hyperfine field at Cu in Fe,Co and Ni and the magnetic moment of the 41 keV, 2+ state of62Cu

The magnetic hyperfine interaction of Cu in Fe, Co and Ni was studied by means of the γ-γ perturbed angular correlation method using⁶²Zn(⁶²Cu) as a probe. With the publishedg-factor (g=+0.661(12)) of the 41 keV, 2⁺ state hyperfine fields ofB _HF=16.95(51) T,B _HF=13.15(41) T andB _HF=4.05(30) T atT=0 K for Cu in Fe, Co and Ni are derived, respectively. The systematic discrepancy of these values with several independent measurements of these hyperfine fields is removed by deriving a new value ofg=0.55(5) for the 41 keV, 2⁺ state of⁶²Cu.     

Goldanskii-karyagin effect at mössbauerE2-transitions

Investigations of anisotropic Debye-Waller factors have been carried out mainly using the M1-transitions of⁵⁷Fe and¹¹⁹Sn. For this case the theory of the Goldanskii Karyagin effect is well established. Mössbauer studies of electric quadrupole interactions in hafnium and tungsten compounds made it necessary to extend the theory to the more complex case of E2-transitions. As the investigated compounds show a strong axial anisotropy of the electric field gradient, a similar behaviour has to be expected in principle for the tensor of the mean-square displacements, which determines the Debye-Waller factor immediately. A fitting procedure taking into account an axial asymmetric Debye Waller factor is worked out and applied to measurements performed with several complex hafnium and tungsten fluorine compounds. With NaWO₂F₃ the quadrupole interactions of¹⁸²W,¹⁸³W, and¹⁸⁴W have been measured yieldingQ ^5/2+(¹⁸³W)/Q ²+(¹⁸²W)=0-86(6) andQ ²+(¹⁸⁴W)/Q ²+(¹⁸²W)=0.955 (3).     

The DFT–DVM theoretical study of the differences of quadrupole splitting and the iron electronic structure for the rough heme models for α- and β-subunits in deoxyhemoglobin and for deoxymyoglobin

Quantum chemical calculations of the iron electron structure and ⁵⁷Fe quadrupole splitting were made by density functional theory and Xα discrete variation method for the rough heme models for α- and β-subunits in deoxyhemoglobin and for deoxymyoglobin accounting stereochemical differences of the active sites in native proteins. The calculations revealed differences of quadrupole splitting temperature dependences for three models indicating sensitivity of quadrupole splitting and Fe(II) electronic structure to small variations of iron stereochemistry.     

Pressure evolution of the EFG and magnetic hyperfine field in the layered antiferromagnet FeI2

When FeI₂ is subjected to pressures of up to 20 GPa, a change of approximately 20% occurs in the unit cell volume.⁵⁷Fe Mössbauer spectroscopy (MS) in a diamondanvil cell has been used to monitor the pressure evolution of the hyperfine interaction parameters of this layered antiferromagnetic insulator. The pressure dependence of the quadrupole splittingQS at 296 K exhibits a maximum at 12 GPa and the saturation magnetic hyperfine fieldH ₀ increases from 7.4 T at ambient pressure to 12 T at 18 GPa. A qualitative analysis identifies the pressure evolution ofQS with changes in the trigonal component of the crystal field splitting. The pressure variation ofH ₀ is attributed to an increase in the average value of the 3d charge density distribution.     

The influence of the local surrounding on the hyperfine interactions in Zr(Fe1−x Ni x )2 compounds

Mössbauer spectroscopy and the TDPAC method have been used to study Zr(Fe_1–x Ni _x )₂ compounds forx0.30. The hyperfine magnetic field at the Fe sites and the quadrupole splitting as functions of nickel concentration were analysed by use of⁵⁷Fe Mössbauer spectroscopy. Values of the internal magnetic field on¹⁸¹Ta nuclei have been found by means of the TDPAC method.     

An ab initio study of the hyperfine structure in the X2 Π electronic state of HCCS–calculation of vibronically averaged components of the anizotropic hyperfine tensor

The results of ab initio calculations of the vibronically averaged components of the anisotropic magnetic hyperfine tensor in the low-lying vibronic species of the X²Π electronic state of the HCCS radical are reported. The electronically averaged hyperfine coupling constants for hydrogen, deuterium, ¹³C and ³³S are obtained as functions of two bending vibrational modes by the density functional theory method. The vibronic wave functions are calculated with the help of a variational approach which takes into account the Renner–Teller effect and spin-orbit coupling. The results of ab initio calculations are compared to the corresponding experimental findings.     

LMR quadrupole interaction measurement on69mGe and71mGe in Zn

A new experimental set-up to perform in-beam LMR (Level Mixing Resonance) measurements is briefly outlined. The first results are reported here. The quadrupole interaction of^69mGeZn is measured and in good agreement with earlier measurements:v _Q=80.6(4) MHz; for^71mGeZn, the valuev _Q=33.1(30)MHz is found. In addition, the relaxation behaviour and radiation damage of Ge recoil implanted in Zn is studied.     

Theoretical investigation of Q A −· -ligand interactions in bacterial reaction centers ofRhodobacter sphaeroides

Density functional theory was used to calculate magnetic resonance parameters for the primary stable electron acceptor anion radical (Q _A ^?· ) in its binding site in the bacterial reaction center (bRC) ofRhodobacter sphaeroides. The models used for the calculations of the Q _A ^?· binding pocket included all short-range interactions of the ubiquinone with the protein surroundings in a gradual manner and thus allowed a decomposition and detailed analysis of the different specific interactions. Comparison of the obtained hyperfine and quadrupole couplings with experimental data demonstrates the feasibility and reliability of calculations on such complex biologically relevant systems. With these results, the interpretation of previously published 3-pulse electron spin echo envelope modulation data could be extended and an assignment of the observed double quantum peak to a specific amino acid is proposed. The computations provide evidence for a slightly altered binding site geometry for the Q_A ground state as investigated by X-ray crystallography with respect to the Q _A ^t-· anion radical state as accessible via EPR spectroscopy. This new geometry leads to improved fits of the W-band correlated-coupled radical pair spectra of Q _A ^?· -P ₈₆₅ ^+· compared to orientation data from the crystal structure. Finally, a correlation of the¹⁴N quadrupole parameters of His219 with the hydrogen bond geometry and a comparison with previous systematic studies on the influence of hydrogen bond geometry on quadrupole coupling parameters (J. Fritscher: Phys. Chem. Chem. Phys. 6, 4950–4956, 2004) is presented.     

135Ba and137Ba Fourier transform NMR and NQR studies

¹³⁵Ba and¹³⁷Ba Fourier transform nuclear magnetic resonance and nuclear quadrupole resonance investigations are reported in liquids resp. solids. From these measurements ratios of g₁-factors, hyperfine structure anomalies, magnetic moments, atomic shielding constants and the ratio of the quadrupole moments are evaluated using also data from literature.     

Mössbauer studies of57Fe doped single crystals of GdBa2Cu3O7-δ

⁵⁷Fe Mössbauer effect measurements have been performed on single crystals of⁵⁷Fe doped GdBa₂Cu₃O_7- at various c-axis orientations and temperatures. The analysis of the data yields information on the sign and direction of V_zz, the direction of B_hf with respect to V_zz and the anisotropy of the f-factor for the individual observed three quadrupole doublets. From these data we conclude that the quadrupole doublet with E_Q 1.9 mm/s is due to Fe on a regular Cu(1)-site (4-fold oxygen coordination) with distorted local symmetry (V_zz isnot parallel to the c-axis), while the other quadrupole doublets have higher oxygen coordinations (higher Lamb-Mössbauer-factor).     

Isotope shift and hyperfine structure measurements at the242f Am fission isomer

Istope shift and hyperfine structure measurements have been performed for the^242fAm fission isomer with target production rates of only a few per second. The method is based on resonance ionization spectroscopy (RIS) in a buffer gas cell with radioactive decay detection of the ionization process (RADRIS). A relative isotope shift ratioX _exp=IS^242f,241/ IS^243,241=41.7±0.9 has been measured for the 500.02 nm transition corresponding to a nuclear parameter ^242f,241=5.4±0.3 fm². The analysis of the quadrupole moment based on the deformed Fermi-model of the nuclear charge distribution including second order corrections results inQ ₂₀=38.2 ±1.4( _–0.8 ^+0.4 )_model eb. The measurement of the hyperfine structure splitting of the transition at 466.28 nm yields a negativeg-factor and a nuclear spin ofI=2 orI=3.Work supported by the Bundesministerium für Bildung und Forschung under contract 06 MZ 5661.     

TDPAC measurements in textured hcp samples

Time differential perturbed angular correlation measurements done on the 482 keV level of¹⁸¹Ta probe nuclei in well annealed reference foil samples ofα-ZrHf,α-TiHf andα-Hf indicate that all probe nuclei are defect free, substitutional and experience quadrupole frequencies characteristic of these matrices. But mostly the ratio of the intensities of the harmonic components of the quadrupole frequency is never in 3:2:1, which is understood to be due to the selective orientation of microcrystallites brought out by the pre thermo-mechanical treatments on the sample. This paper illustrates as to how texturing in general could cause ambiguities in the measurements of the hyperfine interaction parameters of probe nuclei particularly in hcp foil samples with or without the association of any defects and the ways to delineate the effect of texturing.     

Hyperfine and Zeeman studies of low-lying atomic levels of181Ta and the nuclear electric quadrupole moment

The hyperfine structure of the atomic levels 5d ³ 6s ^{2 4} F _{7/2, 9/2} and⁴ P _1/2 in¹⁸¹Ta has been studied by atomic-beam magnetic-resonance. Using intermediate coupling wave functions derived for the configurations (5d+6s)⁵ the hyperfine structure data of six low-lying metastable states have been analyzed with respect to the effective operator formalism. The effective radial parameters for the magnetic dipole and electric quadrupole interactions are determined from these measurements and compared with relativistic calculations. The value obtained for the spectroscopic quadrupole moment of the¹⁸¹Ta nuclear ground state is Q_hfs=3.44(17) barn (uncorrected for configuration interaction effects).     

Feasibility of arsenic and antimony NMR spectroscopy in solids: An investigation of some group 15 compounds

The feasibility of obtaining ⁷⁵As and ^121/123Sb NMR spectra for solids at high and moderate magnetic field strengths is explored. Arsenic-75 nuclear quadrupolar coupling constants and chemical shifts have been measured for arsenobetaine bromide and tetraphenylarsonium bromide. Similarly, ^121/123Sb NMR parameters have been measured for tetraphenylstibonium bromide and potassium hexahydroxoantimonate. The predicted pseudo-tetrahedral symmetry at arsenic and the known trigonal bipyramidal symmetry at antimony in their respective tetraphenyl-bromide “salts” are reflected in the measured ⁷⁵As and ¹²¹Sb nuclear quadrupole coupling constants, C_Q(⁷⁵As)=7.8 MHz and C_Q(¹²¹Sb)=159 MHz, respectively. Results of density functional theory quantum chemistry calculations for isolated molecules using ADF and first-principles calculations using CASTEP, a gauge-including projector augmented wave method to deal with the periodic nature of solids, are compared with experiment. Although the experiments can be time consuming, measurements of ⁷⁵As and ¹²¹Sb NMR spectra (at 154 and 215 MHz, respectively, i.e., at B₀=21.14 T) with linewidths in excess of 1 MHz are feasible using uniform broadband excitation shaped pulse techniques (e.g., WURST and WURST-QCPMG).     

First Principles Determination of Hyperfine Parameters on fcc-Fe8X (X = C, N) Arrangements

In order to investigate some of the fundamental physical properties of the fcc-FeX (X = C, N) austenite solid solutions, we compare the hyperfine parameters obtained by Mössbauer ⁵⁷Fe spectrometry and those obtained by the full-potential linear augmented-plane wave (FLAPW) method. We have focused the study on isomer shifts and quadrupole splittings at Fe sites obtained by FLAPW assuming an Fe₈X structure to sketch the austenite. In the present work, we will discuss this point and compare the results of the calculations with experimental data.