Isotopes Of Nd Research Articles

Fusion studies in O16+Nd142,150 reactions at energies near the Coulomb barrier

Background: Enhancement in fusion cross sections over one-dimensional barrier penetration model (1D-BPM) predictions has been observed at sub-barrier energies owing to the coupling of various internal degrees of freedom to the relative motion. On the other hand, hindrance in fusion is noticed at energies well above the barrier in a few cases.Purpose: The purpose is to probe the dynamics of heavy ion fusion at energies below and well above the Coulomb barrier.Methods: Fusion excitation functions for the $^{16}\mathrm{O}+^{142,150}\mathrm{Nd}$ reactions are measured using the Heavy Ion Reaction Analyzer (HIRA) at IUAC, New Delhi. Measurements have been performed in the range $12%$ below to $50%$ above the Coulomb barrier for both systems. The measured fusion cross sections are compared with coupled channels calculations using ccfull code. The cross sections are also compared with reactions using $^{16}\mathrm{O}$ beams with other isotopes of Nd to explore the systematic behavior of fusion.Results: Compared with 1D-BPM predictions, fusion enhancement is observed in both $^{16}\mathrm{O}+^{142}\mathrm{Nd}$ and $^{16}\mathrm{O}+^{150}\mathrm{Nd}$ reactions at below-barrier energies, with the latter reaction showing a higher enhancement. Coupled channels calculations incorporating the collective excitations of the target nuclei reproduce the fusion cross sections in both reactions. The collective excitations of the projectile nucleus do not seem to contribute to the observed fusion enhancement. Calculations using Aky\"uz-Winther potential parameters fail to reproduce the fusion cross sections at energies well above the barrier.Conclusions: Fusion enhancement is observed in both reactions studied. Degree of enhancement of sub-barrier fusion cross section is larger for the reaction using $^{150}\mathrm{Nd}$ target. Fusion hindrance is observed in both reactions at very high energies. The hindrance seems to increase with increasing beam energy. Larger value of diffuseness parameter compared with the value consistent with elastic-scattering measurements is required to reproduce the fusion excitation function at energies well above the barrier. This could be a strong indication of dynamical effects in fusion at very high energies.

Precision Mass Measurements of Neutron-Rich Neodymium and Samarium Isotopes and Their Role in Understanding Rare-Earth Peak Formation.

The Canadian Penning Trap mass spectrometer at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility was used to measure the masses of eight neutron-rich isotopes of Nd and Sm. These measurements are the first to push into the region of nuclear masses relevant to the formation of the rare-earth abundance peak at A∼165 by the rapid neutron-capture process. We compare our results with theoretical predictions obtained from "reverse engineering" the mass surface that best reproduces the observed solar abundances in this region through a Markov chain MonteCarlo technique. Our measured masses are consistent with the reverse-engineering predictions for a neutron star merger wind scenario.

The TRANSURANUS burn-up model for thorium fuels under LWR conditions

The Transuranus Burn-up (TUBRNP) model for (Th,Pu) O2 and (Th,U) O2 fuels is described and validated. To this end, the depletion equations of the nuclides 232Th, 233U and 234U were included as well as the breeding of 235U through a neutron capture in 234U. The Monte Carlo code Serpent was utilized to derive the one-group effective cross sections and the radial power-shape functions that account for the resonance absorption in the epithermal range of neutron energies in 232Th and 240Pu. Finally, TUBRNP is completed by extending the fission yields of 233U for the most representative isotopes of Nd, Xe, Kr and Cs. The validation of TUBRNP for (Th,Pu) O2 type fuels was carried out in two steps. A comparison of the normalised radial distributed concentrations of Th, U, Pu, Nd, Xe and Cs between TUBRNP, Serpent and Electron probe microanalysis (EPMA) data points measured on a sample from a rodlet irradiated at Kernkraftwerk Obrigheim (KWO) allows checking the correctness in the derivation of the radial functions. In a second step, a comparison of the radially averaged values of the same elements between TUBRNP, Serpent, EPMA and benchmark codes under same conditions indicates the agreement in the computation of the one-group cross sections. For (Th,U) O2 fuels isotopic compositions measured in a rod segment from the Light Water Breeder Reactor (LWBR) Shippingport irradiation programme were employed to validate the calculation of the 1-group cross sections in TUBRNP for this type of fuel.

Magma mixing origin for the Aolunhua porphyry related to Mo–Cu mineralization, eastern Central Asian Orogenic Belt

Many Cu–Mo–Au deposits are considered to be related to adakitic porphyries formed in non-arc settings, e.g., in collisional orogenic zones and intra-plate environments, but their genesis is still under discussion. The Aolunhua porphyry complex and its related Mo–Cu deposit from the eastern Central Asian Orogenic Belt (CAOB) provide important insights into this issue. The porphyries are characterized by high Sr (496–705ppm) and Sr/Y and La/Yb ratios similar to those of typical adakitic rocks, and low ISr ratios (0.7049–0.7052) and positive εNd(t) (+0.5 to +1.4) and εHf(t) (+3.5 to +9.8) values. These features, along with the occurrence of mafic microgranular enclaves (MMEs), compositional and textural disequilibrium of plagioclase phenocrysts and relatively high Mg# values (45–52), indicate that they were derived from mixing of felsic magma from partial melting of a juvenile arc-type lower crust and mafic magma from a lithospheric mantle previously metasomatized by subduction zone fluids/melts. High Sr/Y and La/Yb ratios are indicative of contribution from enriched mantle-derived materials (with high LILEs; e.g., Sr, La), which were strengthened by subsequent fractionation of ferromagnesian phases such as pyroxene and hornblende. MMEs hosted by the ore-bearing porphyry have zircon U–Pb ages of ca. 132Ma, similar to those of the host rocks. The enclaves have elevated Mg# (56–63), LILEs (e.g., Sr=660–891ppm), LREE (LaN=68–150, (La/Sm)N=3.0–4.0, (La/Yb)N=12.0–19.6) and ratios of radiogenic isotopes of Nd- and Hf (εNd=+0.7 to +1.6; εHf=+3.3 to +10.9), suggesting that their parental magmas were derived from the metasomatized mantle source. The Mo–Cu mineralization was probably related to the high water content, high oxygen and sulfur fugacity of hybrid magma. Formation of the adakitic porphyries and related Mo–Cu deposits of the eastern CAOB could be related to the Early Cretaceous lithospheric extension, caused by the subduction of the Paleo-Pacific plate and its induced reactivation of juvenile arc-type lower crust.

Coupling between chip based isotachophoresis and multi-collector inductively coupled plasma mass spectrometry for separation and measurement of lanthanides

This paper presents the conception and fabrication of a microsystem for lanthanides separation and its coupling with a multicollector inductively coupled plasma mass spectrometer for isotope ratio measurements. The lanthanides separation is based on the isotachophoresis technique and the microsystem conception has been adapted in order to fit with glove box limitations in view of future spent nuclear fuels analysis. The micro-device was tested by using a mixture of standard solutions of natural elements and the separation of 13 lanthanides was successfully performed. The micro-device was then coupled to a multicollector inductively coupled plasma mass spectrometer for the on-line measurements of Nd and Sm isotope ratios. The isotopes of Nd and Sm were acquired online in multicollection mode after separation of the two elements with an injection amount of 5 ng. Results obtained on the Nd and Sm isotope ratio measurements on transient signals are presented and discussed.

Geochemical proxies of ocean circulation and weathering inputs: Radiogenic isotopes of Nd, Pb, Sr, Hf, and Os

Marine records of the radiogenic isotope composition of the elements neodymium (Nd), lead (Pb), hafnium (Hf), strontium (Sr), and osmium (Os) allow the reconstruction of past continental weathering inputs on different time scales as a function of their respective oceanic residence times. Sr and Os have oceanic residence times significantly longer than the global mixing time of the ocean and are efficiently mixed on a global scale. Their isotope composition changes on long time scales as a function of plate tectonics and major orogenies, which allows their use as precise stratigraphic tools for the entire Phanerozoic. In contrast, Hf, Pb, and in particular Nd, have residence times on the order of or shorter than the global mixing time of the ocean, which results in distinct isotopic signatures of water masses and allows the reconstruction of past water mass mixing and weathering inputs on both long and short time scales. Here applications of these isotopes systems with a focus on the shorter residence time tracers are reviewed (without claiming to be comprehensive) and problems and potential solutions are discussed.

Fractionation and mixing in a thermal ionization mass spectrometer source: Implications and limitations for high-precision Nd isotope analyses

We present a large dataset of normal Nd standard analyses to evaluate the adequacy of commonly used “laws” to correct for the mass dependent isotope fractionation introduced in a thermal ionization mass spectrometer (TIMS) source, and to assess if the assumption of homogenous sample evaporation and ionization from one sample domain on the filament can be considered valid when obtaining high precision (better than 5 ppm, 2 σ) 142Nd/ 144Nd ratios for studies in geo- and cosmochemistry. The exponential law is fully adequate to correct for the mass fractionation at the current level of obtainable precision and surprisingly performs better than the Rayleigh law. Our modelling shows that the observed correlations in the isotope ratios that remain after data have been corrected using the exponential law are a consequence of correlated uncertainties in counting statistics. These correlations are therefore not from residuals resulting from inadequate correction. Application of the exponential law, however, assumes evaporation from a single homogenous domain on the filament—a condition which was impossible to maintain even under optimal sample loading and heating conditions. While a majority of samples showed an increase in heavy/light isotope ratio with time (normal fractionation), many samples showed the reverse trend (reverse fractionation) indicating evaporation and mixing from variably depleted domains on the filament. Our modelling suggests that up to 50% of the calculated external reproducibility (=standard deviation of the population, σ p of n independent measurements) can be explained by the ion emission from multiple domains of somewhat different isotopic composition on the filament. The fractionation behaviour of a sample is not necessarily a good indicator of the extent of domain mixing as mixing effects in data collected during reverse fractionation are similar to those of data collected during normal fractionation before and after periods of reverse fractionation. Domain mixing effects in 142Nd/ 144Nd isotope ratios can be assessed by examining variations in stable 148Nd/ 144Nd and 150Nd/ 144Nd ratios. The 148Nd and 150Nd data from recent reports of 142Nd deficits in terrestrial samples suggest that the 142Nd anomalies are likely produced from domain mixing during analysis rather than from the decay of short-lived 146Sm during the early history of the earth. It is imperative to measure all the isotopes of Nd to the utmost possible precision and to examine domain mixing effects by normalizing the data using multiple isotope pairs.

Separation of similar elements and isotopes separation in non-stationary conditions

The new separation extraction method was created based on oscillatory extraction/stripping process in two extractors coupled by bulk liquid membrane (LM). The experimental set-up to investigate the kinetics of non-stationary processes was built in Saint Petersburg State Institute of Technology at Rare Earth Department. To induce the oscillatory extraction–stripping process the cyclic Belousov–Zhabotinsky (BZ) reaction or cyclic electrochemical oxidation–reduction was used. The experimental evidences of cerium and neodymium isotopes separation were obtained. The separation of 142Ce and 140Ce isotopes between aqueous phases of two extractors coupled by bulk LM in the experiments with cyclic chemical oxidation/reduction with enrichment factor about 2.5% was observed. In the same conditions the separation of the Nd isotopes (heavy isotopes of Nd: 144Nd, 145Nd, 146Nd, 148Nd and 150Nd from the light isotope: 143Nd) in the same experiment with enrichment factor about 0.7–1.4% was observed.

Oscillatory extraction — new method of similar elements and isotopes separation

The new separation extraction method was created based on oscillatory extraction/stripping process in two extractors coupled by bulk liquid membrane (LM). The experimental setup to investigate the kinetics of non-stationary processes was built in Saint Petersburg State Institute of Technology in the Rare Earth Department. To induce the oscillatory extraction-stripping process the cyclic Belousov-Zhabotinsky (BZ) reaction or cyclic electrochemical oxidation-reduction was used. The possibility to use oscillatory extraction approach to separate similar elements by using the differences in their kinetic properties is demonstrated. The experimental evidences of uranium, cerium and neodymium isotopes separation were obtained. The separation of 142Ce and 140Ce isotopes between aqueous phases of two extractors coupled by bulk LM in the experiments with cyclic chemical oxidation/reduction with enrichment factor about 2.5% was observed. Under the same conditions the separation of the Nd isotopes (heavy isotopes of Nd − 144Nd, 145Nd, 146Nd, 148Nd, and 150Nd from the light isotope — 143Nd) in the same experiment with enrichment factor about 0.7–1.4% was observed.

Changes of the Nuclear Charge Distribution of Nd from OpticalIsotope Shifts

The isotope shifts and hyperfine structures of seven optical transitions forall seven stable isotopes of Nd II were measured by using collinearfast-ion-beam laser spectroscopy. The nuclear parameter λ wasobtained from the measured optical isotope shifts for all seven stableisotopes with improved accuracy. The λ values were analysed byusing the Fermi distribution for the nuclear charge density. The values ofδ⟨r2⟩, δ⟨r4⟩ and δ⟨r6⟩ were determined.

Examining the overlooked implications of natural reactors

On April 7,1972, scientists at the French Atomic Energy Establishment at Pierrelatte discovered a 0.4% anomaly in the uranium isotopic ratio of a sample of natural uranium. In a masterful example of analytical detective work, the French scientists traced the anomaly to a particular area of a uranium mine located at Oklo in the Republic of Gabon. In that area they found uranium that was deficient in U‐235 and was accompanied by fission‐produced isotopes of Nd and Sm. On September 25, 1972, the French Atomic Energy Commission announced their conclusion that self‐sustaining nuclear chain reactions had occurred on Earth about 2000 million years ago [Neuilly et al., 1972]. Later, other natural nuclear fission reactors were discovered in the region [Gauthier‐Lafaye et al., 1996].

Tagging In-Stack Suspended Particles from a Coal-fired Power Plant with an Enriched Isotopic Tracer

A device was constructed for tagging coal fly-ash particles with enriched isotopes of Nd for use in atmospheric tracer experiments by thermally degrading vapor of the 2,2,6,6-tetramethyl 3,5-heptanedione chelate of the metal in the presence of fly-ash laden flue gas. Microanalysis measurements of individual fly-ash particles verify the surface residence of the tracer material and show that particle surfaces are devoid of individual Nd particles. The prototype device was used to release 148Nd- and 145Nd-tagged fly-ash particles for an urban-scale field test at isotope delivery rates of 25–54 mg/h.

Changes of the Nuclear Charge Distribution of Nd, Sm, Gd and Dy from Optical Isotope Shifts

Isotope shifts and hyperfine structures in 28 optical transitions for 28 stable isotopes of Nd, Sm, Gd and Dy were measured by means of the atomic-beam laser-spectroscopy. The nuclear parameter λ was obtained from the isotope shift measurement for all the stable nuclei with the improved accuracy. The λ values were analyzed by using the Fermi distribution for the nuclear charge density. As a result, the diffuseness at the nuclear surface or the hollow depth near the center of nucleus in the charge distribution depends on the neutron number. The values of δ and also δ were determined. It is shown that λ is a good probe into the systematic change of the nuclear charge distribution.

The effects of crystal field on Nd(su3+) in the laser host YVO(in4)

The behavior of Nd 3+ in the laser host yttrium orthovanadate, YVO 4, has been investigated with respect to its absorption spectra By taking into consideration intermediate coupling, a new set of crystal field parameters is obtained which gives a lower rms deviation between observed and calculated energies for 25 of the 26 levels of the 4 I term than that reported earlier using a pure Russell-Saunders basis. The computed g-factors are also in good accord with resonance results Vanous quantities including the nuclear hyperfine parameters have been calculated Nuclear properties which depend on the crystal field are predicted for both the isotopes of Nd

Coulomb-nuclear interference for the (d, d′) reaction on isotopes of Nd

Excitation functions at 140\ifmmode^\circ\else\textdegree\fi{} laboratory angle have been measured for inelastic deuteron scattering to the first ${2}^{+}$ states of $^{142,144,146,148,150}\mathrm{Nd}$. The anomalous destructive Coulomb-nuclear interference previously observed for other $N=82$ isotones also occurs for $^{142}\mathrm{Nd}$. This anomaly is seen to be a sudden change in the nature of the interference rather than a gradual change as one approaches this closed shell.NUCLEAR REACTIONS $^{142,144,146,148,150}\mathrm{Nd}(d, {d}^{\ensuremath{'}})$, $E=5\ensuremath{-}16$ MeV; measured $\ensuremath{\sigma}(E)$ at ${\ensuremath{\theta}}_{\mathrm{lab}}=140\ifmmode^\circ\else\textdegree\fi{}$. Deduced deformation parameters ${\ensuremath{\beta}}_{2}$. Enriched targets.

Recoil study of multinucleon transfer reactions: Capture of six charges by Nd targets in Ar induced reactions

Multinucleon transfer reactions induced with Ar ions and involving the capture of six charges by the target have been studied. The targets were all the separated isotopes of Nd, and the observed nuclei were 149gTb, 150Dy, 151Dy. The experimental technique involved the measurement of the cross sections, angular distributions, and recoil range at each recoil angle, of the heavy residual nuclei. After transformation of the data into the c.m. system, the angular distributions appear to be peaked backwards, close to 180°. This observation suggests that the present reactions are of the same type as the multinucleon transfer reactions studied by other authors for which the angular distribution of the light fragment was peaked forward in the c.m. system. The energy distributions in the c.m. system were used to check the feasibility of various mechanisms which could lead to the production of the observed isotopes. Each mechanism was supposed to be a two-step process: the first step was the exchange, from the projectile to the target, of a number n of nucléons, leading to an excited intermediate nucleus, and the second step the deexcitation of the intermediate nucleus by nuclear evaporation. This analysis indicates that the most probable mechanisms correspond to n close to 12 (6 protons and 6 neutrons), and to an excitation energy of about 60 MeV for the intermediate nucleus. The distribution of cross sections versus the number of nucléons gained by the target is also in accord with this reaction model.

X-Ray Isotope Shifts and Variations of Nuclear Charge Radii in Isotopes of Nd, Sm, Dy, Yb, and Pb

Isotope shifts of electronic $K\ensuremath{\alpha}$ x-ray transitions have been measured in isotopes of Nd, Sm, Dy, Yb, and Pb using a curved crystal spectrometer. The $\ensuremath{\delta}〈{r}^{2}〉$ values of the nuclear charge distribution, as derived from the data, are presented. A combination with results from optical isotope shifts yields an improved accuracy for $\ensuremath{\delta}〈{r}^{2}〉$. The optical mass shifts and the electronic coefficients can also be obtained. A comparison with muonic x-ray isotope shifts is presented for Nd and Pb. Consistancy between electronic and muonic data is noted.

Elastic deuteron scattering on the even Nd isotopes

Elastic scattering cross sections for 12 MeV deuterons on the even isotopes of Nd, 142 ≦ A ≦ 150, have been measured from 15° to 150°, using a solid state counter in connection with a magnetic spectrograph. The results have been analysed in terms of the optical model. The optical model parameters were extracted using an optical model automatic search code. A systematic behaviour of the optical model parameters, going from the spherical 142Nd to the deformed 150Nd, was found if search on four parameters, U, W, a and a′, was done.

Variations of Charge Radii of Nd FromKX-Ray Isotope Shifts

The variations of nuclear charge radii in isotopes of Nd were determined from $K$ x-ray isotope shifts. The results, $\ensuremath{\delta}〈{\mathcal{r}}^{2}〉$, in ${\mathrm{F}}^{2}$ are ${\mathrm{Nd}}^{142\ensuremath{-}144}$, 0.32\ifmmode\pm\else\textpm\fi{}0.02; ${\mathrm{Nd}}^{144\ensuremath{-}146}$, 0.26\ifmmode\pm\else\textpm\fi{}0.03; ${\mathrm{Nd}}^{146\ensuremath{-}148}$, 0.03\ifmmode\pm\else\textpm\fi{}0.04; and ${\mathrm{Nd}}^{148\ensuremath{-}150}$, 0.44\ifmmode\pm\else\textpm\fi{}0.02. The odd-even staggering parameters for ${\mathrm{Nd}}^{143}$ and ${\mathrm{Nd}}^{145}$ were determined to be $\ensuremath{\gamma}=0.60\ifmmode\pm\else\textpm\fi{}0.07$ and $\ensuremath{\gamma}=0.25\ifmmode\pm\else\textpm\fi{}0.20$, respectively.

Precise Atomic Mass Differences Involving Isotopes of Nd, Sm, Cd, and Pb

During the past year, certain of our experimental techniques have been re-evaluated and modified. In the course of these investigations, we have re-determined two atomic mass differences involving isotopes of cadmium and one involving isotopes of lead. The new values are consistent with reaction data and with our older measurements. Thirteen mass differences involving isotopes of neodymium and samarium have also been determined, several for the first time. These new results are consistent with reaction data and with other recent mass spectroscopic data, but indicate that our previously-reported mass differences in the neodymium-samarium region are systematically too large by small but real amounts. An unusually concordant situation now exists in this region of the mass table.