Cerium Isotopes Research Articles

Sequential separation of cerium (Ce) and neodymium (Nd) in geological samples for high-precision analysis of stable Ce isotopes, and stable and radiogenic Nd isotopes by MC-ICP-MS

Stable isotopes of cerium (Ce) and neodymium (Nd), two rare earth elements (REEs), have emerged recently as useful tracers for a range of geological and environmental processes, such as redox changes in environments or continental weathering.

Quantum entanglement of SO(6)-U(5) transitional nuclei in the interacting boson model-2 (IBM-2)

The quantum shape phase transition between the spherical and deformed γ-unstable (U(5)−O(6)) even-even nuclei within the frameworks of Interacting Boson Model-1 and 2 (IBM-1,2) for low-lying states, using the “entanglement entropy” (S) has been studied. In both frameworks, the theoretical results showed that there exist minimum and maximum entanglement values between s bosons in the U(5) and O(6) limits, respectively. In order to confirmation of the theoretical results, we have calculated and analyzed the entanglement entropy of s−d bosons and proton (π) - neutron (ν) bosons in Cerium (C58122−136e) isotopes. The results indicate that the entanglement entropy correctly describes the transition from U(5) to O(6), for ground state (01+), but it cannot accurately determine the transitional nucleus.

Stable cerium isotopes as a tracer of oxidation reactions

Stable cerium isotopes as a tracer of oxidation reactions

Stable cerium isotope analysis of geological materials by MC-ICP-MS

We report stable cerium (Ce) isotopic compositions of terrestrial rocks and investigate Ce isotopic fractionation during column chemistry in this study. Cerium was separated from matrix elements by a single-stage extraction technique using Eichrom DGA resin. Ce isotope ratios were measured using a Thermo Scientific Neptune Plus MC-ICP-MS employing a sample–standard combined with a Sm-doping method. The data accuracy and precision of Ce isotope analyses were rigorously examined by two different laboratories. The δ142Ce values of mono-elemental Ce standards (JMC304 and CDUT-Ce) relative to NIST SRM 3110 solution were − 0.005 ± 0.042‰ (2SD, N = 9) and 0.118 ± 0.033‰ (2SD, N = 6), respectively. The δ142Ce of the manganese nodule (NOD-P-1) measured in two laboratories were 0.177 ± 0.035‰ (2SD, N = 7) and 0.172 ± 0.034‰ (2SD, N = 8), respectively; NOD-A-1 were 0.116 ± 0.028‰ (2SD, N = 8) and 0.104 ± 0.028‰ (2SD, N = 9), respectively. The offset between these two manganese nodules could be possibly related with their unique diagenetic environments. The δ142Ce of two USGS standards diabase W-2a was −0.036 ± 0.046‰ (2SD, N = 3), basalt BHVO-2 was −0.019 ± 0.036‰ (2SD, N = 4). Ce isotopic compositions of three Chinese reference standards granite gneiss GBW07121, diabase GBW07123, and stream sediment GBW07301a were 0.039 ± 0.033‰ (2SD, N = 5), 0.068 ± 0.027‰ (2SD, N = 5) and 0.046 ± 0.015‰ (2SD, N = 3), respectively. The reported data will be helpful for quality assurance and inter-laboratory comparison for high-precision Ce isotopic studies.Full recovery is important to achieve high precision and high accuracy data for metal isotopes. To understand Ce isotope behavior during column separation, an experiment with different Ce cuts was conducted. The δ142Ce of JMC304 and NIST SRM 3110 in five different Ce subcuts varied from 0.047 ± 0.020‰ (2SD, N = 3; 0–25% cut) to −0.029 ± 0.047‰ (2SD, N = 5; 45–100% cut), and 0.058 ± 0.047‰ (2SD, N = 4; 0–11% cut) to −0.022 ± 0.033‰ (2SD, N = 4; 32–100% cut), respectively. δ142Ce of these subcuts showed small ranges, but isotopic fractionation of Ce did occur during column chemistry and light isotopes are preferentially retained in the DGA resin.

The cerium isotope fingerprints of redox fluctuation in bauxites

We measured the Ce concentration, oxidation state, and isotope composition of bauxites developed on the Columbia River Basalts (CRBs) to evaluate the impacts of redox and non-redox processes on the Ce isotopic variability on Earth's surface. Bauxites recovered from drill cores show upward increasing Ce concentration (5.4–88.7 μg/g) and overall depletion of Ce (mass transfer coefficient, τCe,Nb: -0.96 to -0.52, i.e., net depletion of 52-96% relative to their parent CRBs). There is a wide range of the Ce anomaly (Ce/Ce⁎) from 0.4 to 6.3 and 0.6 to 1.4 in the Cowlitz and Columbia bauxites, respectively. The most positive Ce anomalies appear at the shallow regolith (2-5 m depth). Cerium primarily presents in its trivalent form in deposited exogenous materials (wind-blown dust from an old, weathered region of the continent) and primary CRBs. There is a downward increase in the fraction of Ce (IV) in the regolith. Bauxite δ142Ce ranges from -0.161±0.034 to -0.018±0.043‰ and -0.277±0.034 to -0.046±0.034‰ in the Cowlitz and Columbia profiles, respectively. The Ce isotope record reflects the redox cycle of Ce and Mn and is masked by dust accretion on the top. The enrichment of Ce (IV) occurs in the transition zone (the bottom of the shallow regolith) with minor Ce isotope shifts from the CRBs (δ142Ce from -0.080±0.034 to -0.04±0.034‰) likely caused by minor isotopic fractionation linked to O2-driven CeO2 precipitation. There are negative Ce isotope shifts from the basaltic parents and the enrichment of oxidized Ce and Mn in the deep regolith (5-9 m depth), where large isotopic fractionation probably induced by Ce oxidative adsorption on MnO2 plays a vital role. The vertical difference between Ce/Ce⁎ and δ142Ce may be attributed to the climatic oxidation-reduction cycle of Mn and Ce, leaving discrete CeO2 grains in the shallow regolith while transferring isotopically light Ce associated to oxidized Mn deposits down to the deep regolith. We conclude that a combination of Ce species isotopes and anomalies potentially records terrestrial redox status and fluctuation.

Macroscopic and microscopic description of phase transition in cerium isotopes

The spherical-to-deformed phase transition in cerium isotopes recently suggested to occur between $^{146}\mathrm{Ce}$ and $^{148}\mathrm{Ce}$ has been examined in the framework of the macroscopic algebraic collective model and two microscopic approaches, namely Skyrme-Hartree-Fock $+$ Bardeen-Cooper-Schrieffer (BCS) calculations and the symmetry conserving configuration mixing method with Gogny energy density functionals applied also to the neighboring nuclei along the cerium isotopic chain. Possible spectral signatures of the phase transition are discussed in more details. The microscopic calculations predict octupole softness manifested by rather flat potential energy curves as a function of the octupole deformation parameter ${\ensuremath{\beta}}_{3}$ for $^{146}\mathrm{Ce}$ and $^{148}\mathrm{Ce}$ and shape coexistence characterized by axially symmetric ${0}^{+}$ states, triaxial ${2}^{+}$ bands, and octupole deformation for the lowest ${1}^{\ensuremath{-}}$ states.

Investigation of β-decay properties of neutron-rich Cerium isotopes

Reliable and precise knowledge of the β-decay properties of neutron-rich nuclei is important for a better understanding of the r-process. We report the computation of β-decay properties of neutron-rich Cerium isotopes calculated within the proton-neutron quasiparticle random phase approximation (pn-QRPA) approach. A total of 34 isotopes of Ce in the mass range 120 ≤ A ≤ 157 were considered in our calculation. Pairing gaps are recognized amongst the key parameters in the pn-QRPA model to compute Gamow-Teller (GT) transitions. We employed two different values of the pairing gaps obtained from two different empirical formulae in our computation. The GT strength distributions changed considerably with a change in the pairing gap values. This in turn resulted in contrasting centroid and total strength values of the GT distributions and led to differences in calculated half-lives using the two schemes. The traditional pairing gaps resulted in significant fragmentation of GT strength. However, the pairing gaps, calculated employing the formula based on separation energies of neutron and proton, led to computed half-lives in better agreement with the measured data.

Theoretical Calculation of the IBM1 Parameters and Band Crossing in Even Cerium Isotopes

An extended microscopic version of the interacting-boson model is developed. The properties of yrast-band states in even cerium isotopes up to the spin–parity of $$I^{\pi}=18^{+}$$ are calculated on the basis of this model. These spin values include those at which band crossing occurs. The model parameters are calculated on the basis of employing an average spherical potential and residual multipole forces. An extension of the model is accomplished via taking into account high-spin quasiparticle pairs, whereby a satisfactory description of energies and $$B(E\text{2})$$ values was obtained without introducing effective charges. The present investigation is a continuation of a similar analysis of the properties of low-lying collective states in even xenon and barium isotopes.

Measurement and covariance analysis of 140Ce(n,2n)139Ce and 142Ce(n,2n)141Ce reactions with the neutron energy of 13.5 MeV

The (n,2n) reaction cross sections of cerium isotopes have been experimentally measured at the neutron energy of 13.50 ± 0.15 MeV by using the method of activation and off-line γ-ray spectroscopy. The neutron energy was obtained from the D-T reaction using the Purnima Neutron Generator at BARC. The natCe sample was irradiated along with the gold and indium monitor foils. The cross sections of 140Ce(n,2n)139Ce and 142Ce(n,2n)141Ce reactions were measured by using both the gold and indium as a monitor and then collapsed to get the best values of reactions cross sections. The uncertainties in the measured cross sections of 140Ce(n,2n)139Ce and 142Ce(n,2n)141Ce reactions were determined using covariance analysis by considering uncertainties in various attributes. The measured values from the present work were compared with the literature data based on EXFOR compilation, evaluated data from different libraries and theoretically calculated values from TALYS-1.95 and EMPIRE-3.2.

Description of Stabilization of Octupole Deformation in Alternating-Parity Bands of Heavy Nuclei

The angular-momentum dependences are analyzed for parity splitting and electric dipole transitions in alternating-parity bands of heavy nuclei. It is shown that these dependences can be treated universally by employing a single parameter taken to be a critical angular momentum that characterizes the phase transition from octupole vibrations to a stable octupole deformation. Analytic expressions for parity splitting and the electric dipole transitional moment are obtained on the basis of a simple model. The results are compared with experimental data for various barium, cerium, and neodymium isotopes.

High-precision cerium isotope analysis by thermal ionization mass spectrometry using the Ce+ technique

A new method is presented for high-precision measurement of cerium isotope ratios in geological samples by TIMS with the Ce+ technique.

New Constraints on the Origin of the EM‐1 Component Revealed by the Measurement of the La‐Ce Isotope Systematics in Gough Island Lavas

AbstractHot spot lavas show a large diversity of isotope compositions resulting from the recycling of surface material into the convective mantle. Amongst the mantle end‐members, EM‐1 (enriched mantle) is widely debated and scenarios involving either old pelagic sediments subducted into the deep mantle or subcontinental lithospheric material incorporated at shallow depths are commonly evoked. We selected 12 lavas from Gough Island (south Atlantic Ocean) for the measurement of 138La‐138Ce, 147Sm‐143Nd, and 176Lu‐177Hf isotope systems. Results show limited ranges for ε143Nd, ε138Ce, and ε176Hf values, and Ce/Ce* do not correlate with measured isotope ratios. Cerium isotope compositions allow us to exclude the contribution of old sedimentary material carrying a negative, elemental cerium anomaly in the mantle source. Pelagic sediments are indeed characterized by strongly negative, elemental cerium anomalies and also high La/Ce ratios. Modeling a primitive mantle source contaminated by 0.4% to 2.2% of different 2.5 Ga‐old pelagic components is able to reproduce the lowest Ce/Ce* values. However, the cerium isotope measurements show ε138Ce values between −0.39 and 0.15, too low to give support to the incorporation of recycled pelagic sediments in the mantle source of the lavas. Our results suggest that the incorporation of subcontinental lithospheric material at shallow depths during the plume ascent is a more suitable model to explain the formation of the EM‐1 component. Hafnium and Nd isotopes also support this scenario. Subcontinental lithosphere sampled via kimberlites and lamproites has isotopic compositions that plot generally below the mantle array, a signature that is also seen in Gough lavas.

Cross sections of (n,x) reactions on cerium isotopes induced by D-T neutrons

Neutron induced reaction cross sections of Cerium isotopes (136Ce, 138Ce, 140Ce, 142Ce) were investigated for the (n, 2n), (n, α), (n, p) and (n, γ) reactions in the neutron energy around 14 MeV. Experimental cross sections have been obtained for 136Ce(n, 2n)135m+gCe, 138Ce(n, 2n)137mCe, 140Ce(n, 2n)139m+gCe, 142Ce(n, 2n)141gCe, 140Ce(n, p)140gLa, 142Ce(n, p)142gLa, 140Ce(n, α)137mBa, 142Ce(n, α)139Ba and 142Ce(n, γ)143Ce reactions. The measured values were compared with the literature data as well as the evaluated nuclear data from ENDF/B-VII.1, CENDL-3.1, JENDL-4.0 and the calculated results by Talys-1.8 code.

Evolution of Nuclear Shapes and Structure in Tellurium, Xenon, Barium and Cerium Isotopes

Evolution of Nuclear Shapes and Structure in Tellurium, Xenon, Barium and Cerium Isotopes

Examination of analytical conditions of cerium (Ce) isotope and stable isotope ratio of Ce in geochemical standards

Examination of analytical conditions of cerium (Ce) isotope and stable isotope ratio of Ce in geochemical standards

Shell Closure N = 82 nuclei interpretation by the Cranked Nilsson-Strutinsky Model : 136-138Ce

A theoretical studying of nuclei in the shell closure region (N =82), in particular cerium isotopes 136-138Ce, has been made in the frame of macroscopic-microscopic, Cranked Nilsson Strutinsky (CNS)model. Many nuclear properties have been calculated and discussed: the single particle energy, the total energy, the liquid drop energy, the moments of inertia, the deformation parameters, the nuclei shape, and potential energy surfaces (PES) have been presented. High spin rotational bands of these isotopes have been studied and interpreted based on fixed configurations in the frame of CNS code. A good agreement is found with the observed results for these nuclei in the recent works.

Measurement of isomeric yield ratios for the heavy cerium isotopes in the (γ,n) reactions

Measurement of isomeric yield ratios for the heavy cerium isotopes in the (γ,n) reactions

New limits on $2 \varepsilon$ 2 ɛ , $\varepsilon \beta^{+}$ ɛ β + and $2 \beta^{+}$ 2 β + decay of 136Ce and 138Ce with deeply purified cerium sample

A search for double electron capture ($2\varepsilon$), electron capture with positron emission ($\varepsilon\beta^+$), and double positron emission $2\beta^+$) in $^{136}$Ce and $^{138}$Ce was realized with a 465 cm$^3$ ultra-low background HP Ge $\gamma$ spectrometer over 2299 h at the Gran Sasso underground laboratory. A 627 g sample of cerium oxide deeply purified by liquid-liquid extraction method was used as a source of $\gamma$ quanta expected in double $\beta$ decay of the cerium isotopes. New improved half-life limits were set on different modes and channels of double $\beta$ decay of $^{136}$Ce and $^{138}$Ce at the level of $T_{1/2}>10^{17}-10^{18}$ yr.

Neutron-induced activation cross-sections on natural cerium up to 20 MeV

Cross sections of (n,2n), (n,p), and (n,α) reactions on cerium isotopes have been measured in the neutron energy range of 13.5–14.8 MeV using the activation technique and a coaxial HPGe γ-ray detector. Samples were activated along with Nb and Al monitor foils to determine the incident neutron flux. Data are reported for the following reactions: 136Ce(n,2n)135m+gCe, 140Ce(n,2n)139mCe, 140Ce(n,2n)139gCe, 140Ce(n,2n)139m+gCe, 142Ce(n,2n)141Ce, 140Ce(n,p)140La, 142Ce(n,p)142La and 140Ce(n,α)137mBa. The cross sections were also estimated with the TALYS-1.6 nuclear model code at neutron energies varying from the reaction threshold to 20 MeV. Results are also discussed and compared with corresponding values found in the literature.

Search for double beta decay of 136Ce and 138Ce with HPGe gamma detector

Search for double $\beta$ decay of $^{136}$Ce and $^{138}$Ce was realized with 732 g of deeply purified cerium oxide sample measured over 1900 h with the help of an ultra-low background HPGe $\gamma$ detector with a volume of 465 cm$^3$ at the STELLA facility of the Gran Sasso National Laboratories of the INFN (Italy). New improved half-life limits on double beta processes in the cerium isotopes were set at the level of $\lim T_{1/2}\sim 10^{17}-10^{18}$~yr; many of them are even two orders of magnitude larger than the best previous results.