Eu Isotopes Research Articles

A Chromatographic Approach for High-Precision Eu Isotope Analysis.

Eu isotopes are promising tracers across various scientific domains such as planetary, earth, and marine science, yet their high-precision analysis has been challenging due to the similar geochemical properties of rare earth elements (REEs). In this study, a novel two-column chromatographic approach was developed utilizing AG50W-X12 and TODGA resins to separate Eu effectively from matrix and interfering elements like Ba, Nd, Sm, and Gd, while ensuring high Eu yields (99.4 ± 0.4%, n = 19) and low blanks (<20 pg). The robustness of this method is evidenced by various rock types and different Eu loading masses. The efficient purification of Eu facilitated the establishment of a high-precision calibration technique with standard-sample bracketing (SSB) and internal normalization (Nd). When a Nu Plasma 1700 multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) instrument was employed, repeated purification and analysis of various Geological Reference Materials (GRMs) confirmed that the long-term external precision of δ153/151Eu is better than 0.04‰ (2 standard deviation (2SD)), which represents a 2-5-fold increase in precision compared to previously reported methods. Additionally, the high-precision Eu isotopic compositions of five GRMs, including basalts, andesite, syenite, and marine sediment, were measured. The high-precision Eu isotope techniques presented herein open up new avenues for Eu isotope geochemistry.

Optimization of separation and MC-ICP-MS methods for determining Eu isotopic ratios in Si- and Ba-rich fractionated igneous rocks and other natural materials

Eu isotope ratio can be precisely measured by MC-ICP-MS using a Sm isotope pair as spike for normalization. The standard chemical reagent NIST3117a exhibits almost no Eu isotope fractionation regardless of the kind of Sm isotope pairs used in normalization. However, Eu isotope fractionation can appear even in high purity Eu chemical reagents due to Gd and Ba impurities, interference with Sm isotope pair or use of different sample introduction methods. The Eu isotope fractionation in highly fractionated igneous rocks or feldspar minerals can arise from Gd and Ba impurities left by incomplete chemical separation. This study describes a modified, optimal method for accurately and precisely determining the degree of Eu isotope fractionation in highly fractionated Si-rich igneous rocks and Ba-rich feldspar. Ba oxide effects on Sm, Eu and Gd isotopes were monitored by MC-ICP-MS using different wet and dry plasma conditions for sample introduction. The Gd impurities exerts more influence than Ba impurities on Eu isotope ratios. The highly fractionated igneous rocks and feldspar materials showed consistent enrichment in the lighter Eu isotope (151Eu) which becomes a negative Eu isotopic value relative to NIST3117a. Results showed that highly purified Eu solutions from reagents containing no detectable Gd and Ba gave consistent Eu isotopic values regardless of Sm isotope pair (e.g., 147Sm149Sm, 147Sm152Sm, 147Sm154Sm, 149Sm154Sm, 150Sm154Sm) used in normalization. In order to obtain the best estimates of Eu isotope fractionation in different kinds of geological materials (including Si- and Ba-rich materials), Ba and Gd matrix must be completely removed and the Eu isotopic values calculated using four or more Sm spike isotope pairs.

Direct accurate Eu anomaly analysis in very high Ba/Eu silicate samples by triple-quadrupole ICP-MS in MS/MS mass shift mode

The concentration of Eu relative to neighbouring rare earth elements (REE) is an important tool in petrology and geobiology. In most sample matrices, precise and accurate middle REE concentration data can be obtained by direct ICP-MS analysis with careful correction of interferences (chiefly, BaO+ on Eu+ and NdO+ on Gd+). However, geologically interesting samples, including sediments from mid-ocean-ridge and other hydrothermal settings, certain limestones, Precambrian cherts, and some alkali-feldspars have such high Ba/Eu ratios that signals on both Eu isotopes are dominated by BaO. This necessitates high resolution mass spectrometry, highly accurate oxide-correction in these matrices, or requires the separation of the REE from the Ba-rich matrix prior to ICP-MS analysis. Here we report experiments with a triple-quadrupole ICP-MS where Eu was analysed as the mass shifted EuO+ after reaction with N2O or O2 for analysis of Palaeoarchaean cherts. Results were compared to conventional REE analysis with a generic oxide correction as well as individual sample oxide correction. It was found that the triple-quadrupole ICP-MS method with N2O reaction and the conventional ICP-MS analysis with individual sample oxide correction yielded indistinguishable middle REE data for samples with Ba/Eu of up to 125,000. The other two methods overestimated the Eu concentration in samples with Ba/Eu > 10,000, leading to spuriously high positive Eu anomalies, which could be misinterpreted as dominant high-temperature hydrothermal venting into the ancient ocean, for which there is currently no convincing evidence. The triple-quadrupole ICP-MS method with N2O reaction offers a fast, low-blank and high-sensitivity solution to REE analysis of high Ba/Eu geological matrices. Based on the insight from these experiments, we propose criteria with which legacy Eu anomaly data can be assessed for accuracy and inclusion into deep time secular trend studies.

Light- and Chemical-Doping-Induced Magnetic Behavior of Eu Molecular Systems.

Variable temperature electron paramagnetic resonance (VT-EPR) was used to investigate the role of the environment and oxidation states of several coordinated Eu compounds. We find that while Eu(III) chelating complexes are diamagnetic, simple chemical reduction results in the formation of paramagnetic species. In agreement with the distorted D3h symmetry of Eu molecular complexes investigated in this study, the EPR spectrum of reduced complexes showed axially symmetric signals (g⊥ = 2.001 and g∥ = 1.994) that were successfully simulated with two Eu isotopes with nuclear spin 5/2 (151Eu and 153Eu with 48% and 52% natural abundance, respectively) and nuclear g-factors 151Eu/153Eu = 2.27. Illumination of water-soluble complex Eu(dipic)3 at 4 K led to the ligand-to-metal charge transfer (LMCT) that resulted in the formation of Eu(II) in a rhombic environment (gx = 2.006, gy = 1.995, gz = 1.988). The existence of LMCT affects the luminescence of Eu(dipic)3, and pre-reduction of the complex to Eu(II)(dipic)3 reversibly reduces red luminescence with the appearance of a weak CT blue luminescence. Furthermore, encapsulation of a large portion of the dipic ligand with Cucurbit[7]uril, a pumpkin-shaped macrocycle, inhibited ligand-to-metal charge transfer, preventing the formation of Eu(II) upon illumination.

Geochemical implication of Eu isotopic ratio in anorthosite: new evidence of Eu isotope fractionation during feldspar crystallization

Geochemical implication of Eu isotopic ratio in anorthosite: new evidence of Eu isotope fractionation during feldspar crystallization

Enhanced Schiff and magnetic quadrupole moments in deformed nuclei and their connection to the search for axion dark matter

Deformed nuclei possess enhanced moments violating time reversal invariance ($T$) and parity ($P$). Collective magnetic quadrupole moments (MQM) appear in nuclei with a quadrupole deformation (which have ordinary $T$,$P$-conserving collective electric quadrupole moments). Nuclei with an octupole deformation have a collective electric octupole moment, electric dipole moment (EDM), Schiff moment and MQM in the intrinsic frame which rotates with the nucleus. In a state with definite angular momentum in the laboratory frame, these moments are forbidden by $T$ and $P$ conservation, meaning their expectation values vanish due to nuclear rotation. However, nuclei with an octupole deformation have doublets of close opposite parity rotational states with the same spin, which are mixed by $T$,$P$-violating nuclear forces. This mixing polarises the orientation of the nuclear axis along the nuclear spin, and all moments existing in the intrinsic frame appear in the laboratory frame (provided the nuclear spin $I$ is sufficiently large to allow such a moment). Such a mechanism produces enhanced $T$,$P$-violating nuclear moments. This enhancement also takes place in nuclei with a soft octupole vibration mode. In this paper we present updated estimates for the enhanced Schiff moment in isotopes of Eu, Sm, Gd, Dy, Er, Fr, Rn, Ac, Ra, Th, Pa, U, Np and Pu in terms of the CP-violating $\pi$-meson--nucleon interaction constants $\bar{g}_{0},\bar{g}_{1}$ and $\bar{g}_{2}$, the QCD parameter $\bar{\theta}$ and the quark chromo-EDMs. The implications of the enhanced $T$,$P$-violating moments to the search for axion dark matter in solid state experiments are also discussed, with potential alternative candidate compounds in which we may expect enhanced effects suggested.

Measuring the β-decay Properties of Neutron-rich Exotic Pm, Sm, Eu, and Gd Isotopes to Constrain the Nucleosynthesis Yields in the Rare-earth Region

The β-delayed neutron-emission probabilities of 28 exotic neutron-rich isotopes of Pm, Sm, Eu, and Gd were measured for the first time at RIKEN Nishina Center using the Advanced Implantation Detector Array (AIDA) and the BRIKEN neutron detector array. The existing β-decay half-life (T 1/2) database was significantly increased toward more neutron-rich isotopes, and uncertainties for previously measured values were decreased. The new data not only constrain the theoretical predictions of half-lives and β-delayed neutron-emission probabilities, but also allow for probing the mechanisms of formation of the high-mass wing of the rare-earth peak located at A ≈ 160 in the r-process abundance distribution through astrophysical reaction network calculations. An uncertainty quantification of the calculated abundance patterns with the new data shows a reduction of the uncertainty in the rare-earth peak region. The newly introduced variance-based sensitivity analysis method offers valuable insight into the influence of important nuclear physics inputs on the calculated abundance patterns. The analysis has identified the half-lives of 168Sm and of several gadolinium isotopes as some of the key variables among the current experimental data to understand the remaining abundance uncertainty at A = 167–172.

Gd matrix effects on Eu isotope fractionation using MC-ICP-MS: Optimizing europium isotope ratio measurements in geological rock samples

Europium (Eu) has only two isotopes (151Eu and 153Eu). As sequential rare earth elements, Eu and Gd do not easily separate from each other during column chromatography, making it difficult to measure accurate and precise Eu isotope ratio during mass spectral analysis. Eu isotope ratios can be determined by MC-ICP-MS using internal Sm or Gd spikes to correct for mass discrimination. In this report, we discuss and propose optimal conditions for precise and accurate Eu isotope ratio measurements in geological materials (igneous rock samples) using MC-ICP-MS. The NIST3117a ultrapure chemical reagent showed almost no Eu isotope fractionation regardless of the kind of isotope pair used in normalization. A pure Eu fraction with almost no Gd matrix extracted from rock samples also showed nearly the same degree of Eu isotope fractionation regardless of the isotope pair used in normalization. In the case of Eu fraction extracted from highly fractionated granite and high silica volcanic rocks, when 154Gd interference relative to the internal 154Sm standard exceeded ca. 0.1% (due to incomplete Eu separation), this Gd matrix effect created artifactual variation in Eu isotope ratios during MC-ICP-MS analysis. In order to obtain the best estimates of Eu isotope fractionation in geological samples, especially high silica rocks, our analytical methods require complete Eu separation without Gd matrix during sample preparation.

Image Reconstruction Based on Total Variation Minimization for Radioactive Wastes Tomographic Gamma Scanning From Sparse Projections

Tomographic Gamma Scanning (TGS) is one of the most important non-destructive analyzed techniques for radioactive waste drums. By reconstructing the radioactivity distribution image, it can accurately realize the qualitative, quantitative, and positioning analysis of the radionuclides in the drum. However, the time consuming of the scanning is long and the reconstructed image is rough, which limits its good application in the practical assay of the waste drum. In this work, the total variational minimization (TVM) method was applied to improve the iterative process of the conventional algorithms of maximum likelihood expectation maximization (MLEM) and algebraic reconstruction technique (ART), then the MLEM-TVM and ART-TVM reconstruction methods were developed. The transmitted experiments were carried out where four kinds of materials were arranged in a segment whose densities ranging from 1.04 g/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> to 2.02 g/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">152</sup> Eu isotope was set up as a transmission source. Compared with the traditional algorithms MLEM and ART, the MLEM-TVM and the ART-TVM algorithms have a better performance on the accuracy and the signal-to-noise ratio, and the MLEM-TVM algorithm achieves the best results, which means the quality of the reconstructed image is improved. The accuracy and effectiveness of the TVM method used in the TGS image reconstruction are verified in the work, and moreover, it can save the scanning time and enhance the TGS image resolution through sparse projection sampling.

Measurement of k0 values for europium, lutetium and iridium at FRM\xa0II with a very well thermalized neutron spectrum

The k0 values of 6 non-1/v nuclides (152Eu, 152mEu, 154Eu, 177Lu, 192Ir and 194Ir) were determined using the extended Høgdahl formalism at the research reactor FRM II with very high f values. Standards were irradiated in 4 channels at different local temperatures between 40 °C and 55 °C measured using temperature sensitive irreversible labels. A good agreement with the recommended values was found for 152Eu, 154Eu and 177Lu using the original g(Tn) factors by Gryntakis, however, the k0 values for 152mEu in this work were 7% higher. New k0 values were also determined using the g(Tn) factors by Van Sluijs. Differences up to 6% were found for Eu isotopes compared with the recommended values. The recommended k0 values for 192Ir and 194Ir could be confirmed using g = 1. The theoretical k0 values for 177Lu were calculated using new nuclear data. They are up to 6% less than the recommended values. The present k0 values determined in this work showed a similar trend. The influence of different g(Tn) factors on the determination of the k0 values was investigated.

Theoretical calculation by Talys code in combination with Geant4 simulation for consideration of [formula omitted] reactions of Eu isotopes in the giant dipole resonance region

In this work, the differential cross-sections of 151Eu(γ,n)150Eu and 153Eu(γ,n)152Eu photonuclear reactions in the giant dipole resonance region (GDR) were considered by theoretical models available in Talys 1.8 code. Isomeric ratios of these two reactions induced by bremsstrahlung with end-point energies in (GDR) region were then simulated using the calculated cross-section in combination with Monte-Carlo simulation using Geant4 toolkit based code which was implemented to simulate bremsstrahlung and photonuclear reaction. Moreover, a simple model was added into Geant4 for populating multi-isomeric states. The theoretical results were compared with the experimental data from the existing literature to examine the validity of the theoretical modes.

Hyperfine Anomaly in Eu Isotopes and the Universiability of the Moskowitz–Lombardi Formula

A method for determining the hyperfine anomaly, without using the nuclear magnetic moments, is used on a series of unstable isotopes of Eu. The large number of experimental data in Eu makes it possible to extract the hyperfine anomaly for a number of unstable isotopes. Calculations of the Bohr–Weisskopf effect and hence the hyperfine anomaly are performed using the particle-rotor formalism. The result from the calculations and experiments is compared with other theoretical calculations and the empirical Moskowitz–Lombardi formula. The results show that the Moskowitz–Lombardi formula is not universal.

Optimization of HPGe detector response using fast and reliable method

Safeguards system with high effectiveness and efficiency must comprise a set of measurements with capabilities satisfactory for the verification of nuclear materials. In this paper, we present key parameter measurements of detector modeling in a commercial n-type low energy germanium detector of a planar crystal with a relative efficiency of nearly 15 %. The detector optimization will hold a significant function in measuring nuclear materials for safeguards application. Standard nuclear materials with diverse enrichment (depleted and low enriched) of uranium and point-like sources (137Cs, 60Co) and mixed radioactive source for Eu isotopes (152Eu, 154Eu, and 155Eu) were benefited to explore the energy resolution and detector efficiency. The energy resolution is measured over a wide range of rise time and flattop. In addition to the experimental work, the Monte Carlo simulation code is used for modeling the setup configuration to obtain the absolute efficiency at different energies. A fast and reliable method was applied in detector efficiency measurements. The data are discussed and interpreted.

Determination of rare earth elements in environmental samples with high concentrations of barium by quadrupole inductively coupled plasma mass spectrometry

This paper proposes a new method of sample preparation for the determination of rare earth elements (REE) by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) in challenging environmental samples with high Ba concentrations. The method consists in adding 10% (v/v) sulfuric acid to the wet sample digest, obtained after acid decomposition in an open system, in order to precipitate and separate BaSO4. The removal of BaO interference in Eu isotopes was efficient for Ba concentrations in solution higher than 0.1 mg L−1. The methodology was applied to asphalt pavement and the crushed stone used to produce it. Accuracy was assessed using two certified materials, NIST 688 Standard Reference Material of basalt rock and Geological Survey G2 granite, resulting in acceptable recoveries. Additionally, all samples were decomposed by fusion, and the concentrations of major elements and Eu were determined by inductively coupled plasma optical emission spectrometry (ICP OES). Eu results were in agreement with the proposed methodology, and limits of detection for REE varied from 0.003 mg L−1 (Lu) to 0.010 mg L−1 (Gd). The NASC normalized profiles of REE in the crushed stone showed a positive Eu anomaly, that was not observed in the asphalt sample. As well, the latter was enriched in heavy REE (Tb-Lu), suggesting a loss of carbonatite minerals, consequently to the weathering of the pavement.

Determination of Eu isotopic ratio by multi-collector inductively coupled plasma mass spectrometry using a Sm internal standard

This contribution describes methods for measuring Eu isotopic ratios in geological materials using multi-collector inductively coupled plasma mass spectrometer. These methods require an initial external correction of mass discrimination effects (between the two Eu isotopes) using a Sm isotopic spike (150Sm/154Sm = 0.3244) added to samples. Eu was then estimated according to an exponential law. We measured Eu isotope ratios (151Eu/153Eu) for six high-purity commercial Eu reagents using the NIST 3117a standard as a reference (δ151/153Eu = 0.0‰). The Eu reagents showed minor fractionation effects ranging from 0.029 ± 0.007‰ (1σ, n = 22) to 0.061 ± 0.006‰ (1σ, n = 13). We then investigated Eu isotope fractionation during cation exchange chromatography, which efficiently separates the Eu fraction (>99.99% purity). A known amount of rare earth element (REE) standard solution was eluted from columns using 2-hydroxyisobutyric acid. Fourteen sequentially collected Eu fractions gave δ151/153Eu values ranging from −1.80‰ for early eluting fractions to 2.56‰ for late eluting fractions. A numerically integrated value for the 14 fractions resembled that measured for the total eluted solution. These results indicate that different reagents give different Eu isotopic values. Fractionation may occur during reagent production or it may be inherited from geological source materials. We also measured Eu isotopic variation among five different geochemical reference rocks (BCR2, BHVO2, BIR1a, GSP2, JG1a). The reference standards also gave slightly different 151/153Eu isotope ratios. These results suggest Eu isotopic fractionation during rock-forming processes.

Nuclear quantum shape-phase transitions in odd-mass systems

Microscopic signatures of nuclear ground-state shape phase transitions in odd-mass Eu isotopes are explored starting from excitation spectra and collective wave functions obtained by diagonalization of a core-quasiparticle coupling Hamiltonian based on energy density functionals. As functions of the physical control parameter -- the number of nucleons -- theoretical low-energy spectra, two-neutron separation energies, charge isotope shifts, spectroscopic quadrupole moments, and $E2$ reduced transition matrix elements accurately reproduce available data, and exhibit more pronounced discontinuities at neutron number $N=90$, compared to the adjacent even-even Sm and Gd isotopes. The enhancement of the first-order quantum phase transition in odd-mass systems can be attributed to a shape polarization effect of the unpaired proton which, at the critical neutron number, starts predominantly coupling to Gd core nuclei that are characterized by larger quadrupole deformation and weaker proton pairing correlations compared to the corresponding Sm isotopes.

A systematic study of band structure and electromagnetic properties of neutron rich odd mass Eu isotopes in the projected shell model framework

The positive and negative parity rotational band structure of the neutron rich odd mass Eu isotopes with neutron numbers ranging from 90 to 96 are investigated up to the high angular momentum. In the theoretical analysis of energy spectra, transition energies and electromagnetic transition probabilities we employ the projected shell model. The calculations successfully describe the formation of the ground and excited band structures from the single particle and multi quasiparticle configurations. Calculated excitation energy spectra, transition energies, exact quantum mechanically calculated B(E2) and B(M1) transition probabilities are compared with experimental data wherever available and a reasonably good agreement is obtained with the observed data. The change in deformation in the ground state band with the increase in angular momentum and the increase in neutron number has also been established.

Beyond-mean-field boson-fermion model for odd-mass nuclei

A novel method for calculating spectroscopic properties of medium-mass and heavy atomic nuclei with an odd number of nucleons is introduced, based on the framework of nuclear energy density functional theory and the particle-core coupling scheme. The deformation energy surface of the even-even core, as well as the spherical single-particle energies and occupation probabilities of the odd particle(s), are obtained in a self-consistent mean-field calculation determined by the choice of the energy density functional and pairing interaction. This method uniquely determines the parameters of the Hamiltonian of the boson core, and only the strength of the particle-core coupling is specifically adjusted to selected data for a particular nucleus. The approach is illustrated in a systematic study of low-energy excitation spectra and transition rates of axially deformed odd-mass Eu isotopes.

Bohr Hamiltonian with different mass parameters applied to band structures of Eu isotopes built on Nilsson orbitals

The band structure of the proton-odd nuclei 153,155Eu, built on Nilsson orbitals, is investigated within the framework of a recently developed extended Bohr Hamiltonian model. The relative distance between spherical orbitals is taken into account by considering single-particle energies as a parameter which changes with increasing neutron number. Energy levels of each band and B(E2) values inside the ground-state band are calculated and compared with the available experimental data. Thus, more comprehensive information on the structure of deformed nuclei can be obtained by studying the rotation–vibration spectra of odd nuclei built on Nilsson single-particle orbitals.

Investigation of radionuclides in the Yenisey River floodplain systems: Relation of the topsoil radionuclide contamination to landscape features

Landscape–radiometric survey and soil sampling performed in the islands of Beriozovy and Balchug (20km downstream the Krasnoyarsk Mining and Chemical Combine), and in the Mikhin Island (180km downstream) showed that the distribution of technogenic radionuclides depends upon the history of contamination and landscape features of the floodplain. Contamination densities of 137Cs appeared to be significantly higher than could be expected from global fallout (1.75–2.5kBq/m2): in 2000 the maximum value for 137Cs in the Beriozovy Island equaled 663kBq/m2, in the Balchug site — 577kBq/m2 and in the Mikhin Island — 518kBq/m2). 137Cs contamination density was practically independent of the remoteness from the KMCC that proved its considerable migration in the water-soluble or fine particulate forms. Vertical distributions of man-made nuclides in soil cores depended upon the different half-life of the studied radionuclides, the soil profile relative altitude, its structure and texture. The two main burial depths of 137Cs activity depended upon the intensity of sedimentation and varied from 5cm to 20–25cm. In 2000 maximum contamination by 60Co and 152,154Eu isotopes was associated with the top layer and decreased exponentially with depth.Obtained data is believed to be important for ecological monitoring of the flood plains subjected to radionuclide contamination.