Year-2017 nuclear quadrupole moments

A ‘year-2017’ set of nuclear quadrupole moments, Q, is presented. Compared to the previous, ‘year-2008’ set, a major revision of the value, or an improvement of the accuracy is reported for ²₁H, ^{37, 39}₁₈Ar, ^{39, 40, 41}₁₉K, ⁶⁷₃₀Zn, ₄₈Cd, ₄₉In, ₅₀Sn (Mössbauer state), ₅₁Sb, ₈₇Fr and ₉₀Th. Slight improvements or valuable reconfirmations exist for ₄Be, ₆C, ₁₆S, ₁₇Cl, ₃₃As, ₃₅Br, ₅₃I, ₅₄Xe, ₅₆Ba, ₅₇La and ₇₂Hf.     

Nuclear moment of the 23.8 keV state and hyperfine anomaly in119Sn

Using the Mössbauer effect of the 23.8 keV transition in¹¹⁹Sn, the nuclear magnetic dipole moment of the 23.8 keV 3/2⁺ state is measured to be 0.632(3)μ _n . From a comparison with previously published results a hyperfine anomaly of ?8.8(5)% is obtained.     

Comment on “mössbauer studies of the 6.2 keVγ-rays of 181 Ta in Ta-dichalcogenides”

The reported discrepancy between TDPAC and Mössbauer measurements of the electric field gradient at Ta in 2H-TaS₂ is shown to be an artifact. Combining both results a new value for the 482 keV state quadrupole moment of ¹⁸¹Ta is derived: Q(5/2) = (+)2.36(5) b.     

Magnetic moment measurement in125Te by IPAC

The magnetic moment of the 35.5 keV (3/2⁺) excited state in¹²⁵Te was measured in an external magnetic field. The value obtained μ=0.57 ± 0.07μ _N agrees with Mössbauer determinations and Kisslinger-Sorensen calculations.     

Chemical states of57Fe-atoms after ec-decay of57Co-labelled Co(BrO3)2·6H2O studied by coincidence Mössbauer spectroscopy

Two kinds of time differential Mössbauer spectra of⁵⁷Co-labelled Co(BrO₃)₂·6H₂O were measured at room temperature by delayed coincidence technique, i.e., one was the delayed coincidence between 122 keV γ ray and 14.4 keV γ ray (γ, γ-ray coincidence), and another was the coincidence between 6.3 keV KX ray and 14.4 keV γ ray (X, γ-ray coincidence). The time dependence of chemical states of⁵⁷Fe-species were observed on γ, γ-ray and X, γ-ray coincidence Mössbauer spectra. The relative area intensities of⁵⁷Fe(II) observed on the X, γ-ray coincidence spectra were larger than those on the γ, γ-ray coincidence spectra on every time windows.     

Emission Mössbauer spectroscopic studies of57Fe atoms produced in57Co-labelled trinuclear cobalt-iron halogenoacetate complexes

Mixed-valence states of⁵⁷Fe atoms produced after EC-decay of⁵⁷Co in a series of trinuclear cobalt-iron halogenoacetate complexes, [Co^IIFe ₂ ^III O(CH_3?nX_nCO₂)₆(H₂O)₃] (0≤n≤3, X=Cl, Br, and I), were studied by comparing the results obtained by emission Mössbauer spectroscopy with those observed in absorption Mössbauer spectra of analogous trinuclear iron complexes, [Fe^IIFe ₂ ^III O(CH_3?nX_nCO₂)₆(H₂O)₃]. Some of the emission Mössbauer spectra show a temperature-dependent mixed-valence state as found in the absorption Mössbauer spectra. Others show a somewhat different temperature dependence compared with the absorption Mössbauer spectra. The results were interpreted in terms of after-effects of the EC-decay.     

Mössbauer effect and magnetic moment of the 75.9 keV level in Yb171

The Mössbauer effect of the second excited state of theK=1/2 rotational band in Yb¹⁷¹ at 75.9 keV withI=5/2 was studied to determine its magnetic moment μ=(1.01±0.01)nm. This value agrees well with the one predicted by the previously determined magnetic parameters of theK=1/2 rotational band, confirming the adiabatic separation of intrinsic and rotational wave functions.     

Lamb–Mössbauer factor of electronically excited molecular states measured by time‐differential Mössbauer emission spectroscopy

The Lamb-Mössbauer Factor (LMF) of molecular crystals is expected to depend on the electronic molecular states by their different intramolecular vibrational frequencies. Revisiting Mössbauer spectra obtained by time differential Mössbauer emission spectroscopy of the low spin compound [⁵⁷Co/Mn(bipy)₃](PF₆)₂ (bipy= 2,2'-bipyridine) a ratio of 1.25 for the LMFs of the low spin ground state and of an excited high spin state decaying in the Mössbauer time window could be evaluated. The difference found is in line with the change of LMF observed for spin crossover compounds where the excited high spin state is populated by the so‐called LIESST effect. The initial population of the high spin state is close to 100%.     

Relation of contact densities with Mössbauer isomer shifts for 35.46 keV M1 transition of125Te

The internal conversion electron and Mössbauer isomer shifts associated with the 35.46 keV M1 transition of¹²⁵Te were observed for different metal samples into which radioactive¹²⁵I as probe atoms were introduced by means of ion-implantation. From the correlation between the Mössbauer isomer shifts and intensity ratios of O shell to N_I shell conversion electrons, a relation between 5s-electron contact densityp _5s(0) in a.u. and isomer shift δ in mm/s was deduced to bep _5s(0)=106+30.3 δ±4.3[(δ?0.30)²+0.069]^1/2, where δ was measured relative to ZnTe in mm/s. The change of the nuclear charge radius in the 35.46 keV M1 transition of¹²⁵Te was found to be ΔR/R=(0.85±0.12)×10^?4 (corresponding to Δ<r ²>=(3.7±0.5)×10^?3 fm²) when a theoretical 4s-electron contact density of 928 a.u. was used.     

Magnetic insulator glasses

An outline is given of the use of Mössbauer spectroscopy as a probe of the amorphous structure and magnetic coordination in magnetic insulator glasses. Using the⁵⁷Fe Mössbauer resonance as an example in the context of amorphous ferric oxides and fluorides, the manner in which both paramagnetic and hyperfine-field-split spectra can be analyzed is presented. Emphasis is given to the information contained in Mössbauer lineshapes and linewidths in addition to the more obvious line-position data. A number of general findings are set out for ferric speromagnetics with particular references to Mössbauer studies of amorphous Fe₂O₃, Y₃Fe₅O₁₂ (YIG), FeF₃ and NaFeF₄.     

155Gd Mössbauer investigation of the magnetic order and spin-reorientation in Gd3Ag4Sn4

In a recent study of the magnetic order in Gd₃Ag₄Sn₄ by neutron powder diffraction and ¹¹⁹Sn Mössbauer Spectroscopy we showed that both the Gd(2d) and Gd(4e) sublattices order antiferromagnetically at 28.8(2) K. We also demonstrated that the ‘magnetic event’ around 8 K is in fact a ‘plane to axis’ spin-reorientation of the Gd magnetic structure. Here, we extend our study with ¹⁵⁵Gd Mössbauer Spectroscopy. The initial magnetic ordering at 30(2) K is clear for both sites and substantial changes in the hyperfine fields are observed at 8 K when the magnetic structure reorients.     

Microscopic calculations of matter and charge distributions of exotic nuclei within the Dynamic Correlation Model

We have studied nano-sized Au catalysts supported on Mg(OH)₂ and TiO₂ using ¹⁹⁷Au Mössbauer spectroscopy. ¹⁹⁷Au Mössbauer spectra observed for Au/Mg(OH)₂ catalysts can be decomposed into one singlet with zero isomer shift and several doublets. One of the doublets shows an isomer shift that is typical for Au^I, and other doublets are due to Au^III. The relative area of the Au^I component shows the maximum value for a specimen calcined at 523 K, which also shows the highest catalytic activity.     

Spin-transition in nearly cubic site in [FeII(L)3][PF6]2

The spin-transition (¹A₁?⁵T₂) behaviour of a new mononuclear iron(II) compound [Fe^II(L)₃][PF₆]₂[L = 2-[3-(2′-pyridyl)pyrazole-1-ylmethyl]pyridine] has been investigated by ⁵⁷Fe Mössbauer spectroscopy. Analysis of the Mössbauer spectra revealed low value of the quadrupole splitting of the high-spin state which reflects iron(II) to be in nearly cubic lattice site. Mössbauer spectra under light show the light-induced excited spin state trapping effect and the observed quadrupole splitting of the metastable high-spin state is found little sensitive to the high-spin fraction value. DFT calculations are in progress to document the almost cubic nature of the ligand-field acting on the iron atom.     

151Eu-Mössbauer investigation in some new ternary Eu2M3Si5 systems (M=Ni,Pd, Cu,Rh)

The series Eu₂M₃Si₅ (M=Ni, Cu, Pd, Rh) have been synthesised for the first time. The Ni, Cu, Pd systems form in U₂Co₃Si₅ type structure.¹⁵¹Eu Mössbauer spectroscopy shows that Eu is in valence fluctuating (VF) state in Ni system, while in Cu and Pd systems it is in stable divalent state. These observations are further confirmed by magnetic susceptibility studies. The material Eu₂Rh₃Si₅ shows two lines in the Mössbauer resonance, one of which shows VF behaviour.     

151Eu and57Fe Mössbauer effect studies of magnetic interactions in europium transition element oxides solution

The solid state solutions of europium transition element oxides Eu (Fe0.8M0.2)O₃ (M=Sc,Cr,Mn,Co) are synthesized. The X-ray diffraction of the compound shows that all the compounds possess the perovskite structures. Both the¹⁵¹Eu Mössbauer spectra and the⁵⁷Fe Mössbauer spectra are measured. The hyperfine magnetic field and non-axisymmetric electric field gradient are observed in the¹⁵¹Eu Mössbauer spectrum. The⁵⁷Fe Mössbauer spectrum shows that there are four components of hyperfine fields corresponding to four kinds of different neighbours of the Fe ion.     

Phase composition at surface of Fe-3%Si alloy

The structure, phase and chemical compositions of surface layers in different depths of Fe-3%Si alloy were investigated. According to the X-ray Photoelectron Spectroscopy (XPS) spectrum (penetration depth of up to ∼ 1nm) of the as-prepared sample, a layer of SiO₂ was present on the top. After the subsequent Ar⁺ sputtering (removing the SiO₂ layer), a segregation of Si atoms and two other phases were observed. The phases were described as the cubic c-FeSi and Fe₃Si. The emission⁵⁷Fe M?ssbauer spectra confirmed a presence of these phases. The α-Fe and solid solution of α-Fe + 1wt.%Si were recognized in the Conversion Electron M?ssbauer spectra (penetration depth ∼ 300nm) while the M?ssbauer spectra taken in scattering geometry with detection of 14.4 keV gamma radiation (scanning depth of ∼ 30 μm) indicate Fe-3wt.%Si solid solution as a main phase. Presented at International Colloquium “M?ssbauer Spectroscopy in Materials Science”, Všemina, Czech Republic, June 1–4, 2004. This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic (Contract No. IAA1041404).     

Low spin Fe(IV) arising from electron transfer in a mixed-valence compound: A Mössbauer study

Co(en)₃Fe(CN)₆ a mixed-valence compound, where ‘en’ corresponds to ethylene diamine, exhibits a heteronuclear charge transfer between iron and cobalt ions; both the ions being in oxidation state III. An ⁵⁷Fe Mössbauer investigation confirms the creation of the rare species Fe(IV) as a result of charge transfer.     

Nuclear resonance fluorescence from the 58keV level in159Tb

The half-life of the 58keV level of¹⁵⁹Tb was determined by classical resonance absorption using the centrifuge technique and by Mössbauer spectroscopy measuring the natural line width and found to beτ _1/2=(58±10)ps. Mössbauer spectra for Tb and Tb₂O₃ absorbers and for Dy₂O₃ and GdFe₂ sources were investigated for temperatures between 9 and 385 K. Results for hyperfine interactions and Debye Waller factors are given. The Debye Waller factors are compared with predictions obtained from other experimental results.     

Paramagnetic relaxation of Nd3+ in glasses from Mössbauer spectra

Glasses containing Nd₂O₃ were studied by¹⁴⁵Nd(72.5 keV) Mössbauer spectroscopy. The spectra depend strongly on the concentration of Nd³⁺ and on temperature.     

Determination of the quadrupole splitting of the first excited state of 119Sn in β-tin by the e- -γ TDPAC technique

It is shown that for the determination of the quadrupole splitting (ω₀ = 28.5 ± 1.0 MHz) of the first excited 23.8 keV state of ¹¹⁹Sn in β-tin the e^- -γ time-differential perturbed angular correlation technique is superior to the Mössbauer method.