Ne Isotopes Research Articles

Multi-reference many-body perturbation theory for nuclei

The neon isotopic chain displays a rich phenomenology, ranging from clustering in the ground-state of the self-conjugate doubly open-shell stable $$^{20}$$ Ne isotope to the physics of the island of inversion around the neutron-rich $$^{30}$$ Ne isotope. This second (i.e. Paper II) of the present series proposes an extensive ab initio study of neon isotopes based on two complementary many-body methods, i.e. the quasi-exact in-medium no-core shell model (IM-NCSM) and the projected generator coordinate method (PGCM) that is ideally suited to capturing strong static correlations associated with shape deformation and fluctuations. Calculations employ a state-of-the-art generation of chiral effective field theory Hamiltonians and evaluate the associated systematic uncertainties. In spite of missing so-called dynamical correlations, which can be added via the multi-reference perturbation theory proposed in the first paper (i.e. Paper I) of the present series [1], the PGCM is shown to be a suitable method to tackle the low-lying spectroscopy of complex nuclei. Still, describing the physics of the island of inversion constitutes a challenge that seems to require the inclusion of dynamical correlations. This is addressed in the third paper (i.e. Paper III) of the present series [2].

Complex burial histories of Apollo 12 basaltic soil grains derived from cosmogenic noble gases: Implications for local regolith evolution and future in situ investigations

AbstractWe report the concentrations and isotope ratios of light noble gases (He, Ne, Ar) in 10 small basalt fragments derived from lunar regolith soils at the Apollo 12 landing site. We use cosmic ray exposure (CRE) and shielding condition histories to consider their geological context. We have devised a method of using cosmogenic Ne isotopes to partition the CRE history of each sample into two stages: a duration of “deep” burial (shielding of 5–500 g cm−2) and a duration of near‐surface exposure (shielding of 0 g cm−2). Three samples show evidence of measurable exposure at the lunar surface (durations of between 6 ± 2 and 7 ± 2 Myr). The remaining seven samples show evidence of a surface residence duration of less than a few hundred thousand years prior to collection. One sample records a single‐stage CRE age range of between 516 ± 36 and 1139 ± 121 Myr, within 0–5 g cm−2 of the lunar surface. This is consistent with derivation from ballistic sedimentation (i.e., local regolith reworking) during the Copernicus crater formation impact at ~800 Myr. The remaining samples show CRE age clusters around 124 ± 11 Myr and 188 ± 15 Myr. We infer that local impacts, including Surveyor crater (180–240 Ma) and Head crater (144 Ma), may have brought these samples to depths where the cosmic ray flux was intense enough to produce measurable cosmogenic Ne isotopes. More recent small impacts that formed unnamed craters may have exhumed these samples from their deep shielding conditions to the surface (i.e., ~0–5 g cm−2) prior to collection from the lunar surface during the Apollo 12 mission.

Self-consistent description of the halo nature of 31Ne with continuum and pairing correlations

Background: A relativistic structure model has previously been used to predict a halo structure for 31Ne (Zhang et al 2014 Phys. Lett. B 730 30), consistent with halo signatures from measured reaction cross sections of Ne isotopes bombarding Carbon targets. However, previous attempts to calculate those cross sections with reaction models were missing contributions from resonances and pairing correlations in their structure input. Purpose: Use a reaction model with our relativistic fully microscopic structure model input to predict these cross sections and momentum distributions and analyze for possible halo signatures. Methods: Structure input for exotic Ne isotopes were obtained via the analytical continuation of the coupling constant (ACCC) method based on the relativistic mean field (RMF) theory with Bardeen–Cooper–Schrieffer (BCS) pairing approximation, the RAB approach. Total reaction cross sections, one-neutron removal cross sections, and momentum distributions of breakup reaction products were calculated with a Glauber model using our relativistic structure input. Results: Our predictions of total reaction and one-neutron removal cross sections of 31Ne on a Carbon target were significantly enhanced compared with those of neighboring Neon isotopes, agreeing with measurements at 240 MeV/nucleon and consistent with a single neutron halo. Furthermore, our calculations of the inclusive longitudinal momentum distribution of the 30Ne and valence neutron residues from the 31Ne breakup reaction indicate a dilute density distribution in coordinate space, another halo signature. Conclusions: We give a full description of the halo nature of 31Ne that includes a self-consistent use of pairing and continuum contributions that makes predictions consistent with reaction cross section measurements. This approach can be utilized to determine the halo structure of other exotic nuclei.

Neon isotopic signature applied to detrital provenance assignment in foreland basins

Cosmogenic noble gas isotope 21Ne in terrestrial rocks has been used primarily to determine timing and rates of the Earth's surface evolution. Here we explore the ability of detrital 21Ne as a provenance tracer, considering that Ne isotopes produced in source rocks could be preserved in minerals over geological time and might be predominant in total Ne inventory of sediments sunk in basins. This ability is predicated on potential source terranes of a given stratigraphic section with distinct neon isotopic signatures. Here we analyze neon isotopes of a well-dated Miocene–Pleistocene sedimentary archives in Kuqa foreland basin of southern Tianshan. The data suggest that the neon isotopic signature, which is expressed as εNe and defined in this work as the excess 21Ne/20Ne-ratio relative to atmospheric ratio, is stratigraphically sensitive to changes in local source terranes. This result is compatible with U/Pb provenance analysis and also supported by evidences from sandstone petrography and heavy mineral analysis. Influence of other non-source related 21Ne components in sedimentary archives on sensitivity of εNe has proven to be negligible. Furthermore, the integrated stratigraphic signatures of neon isotope and U/Pb age permit the detection of differential erosion in drainage basin, by which the tectonic or climatic effects on geomorphic evolution could be deciphered.

Evidence from gas-rich ultramafic xenoliths for Superplume-derived recycled volatiles in the East African sub-continental mantle

Volatile-rich fluids are believed to play a key role in the metasomatic enrichment of the East African sub-continental lithospheric mantle (SCLM), but limited data is available on key volatile tracers such as CO2 and N2. We report new CO2 and N2 isotope and relative abundance data in exceptionally gas-rich mantle peridotite and pyroxenite xenoliths from nine localities throughout the eastern branch of the East African Rift System (EARS). Importantly for our study, the xenolith localities straddle the transition between continental and oceanic lithosphere. In addition, we report major and trace element contents together with oxygen isotopes on host crystals and bulk multiple sulfur isotope data on select pyroxene crystals from the same xenolith suite. These new data are interpreted alongside previously published He, Ne and Ar isotope and relative abundance data.Pyroxenite xenoliths formed from the infiltration and crystallization of mafic melts in the lithospheric mantle. This was followed by fluids fracturing through the pyroxenites leaving gas-rich fluid inclusions. The elemental and isotope systematics of the fluid inclusion-hosted volatile species (He, Ar, N, CO2) within the mantle xenoliths are consistent with the enrichment of the EARS SCLM by CO2-rich mantle fluids from subducted carbonate-rich material. Such CO2 enrichments (CO2/3He > 7 × 109, δ13C ~0‰) are also associated with positive δ15N values (as high as +3.4‰), reinforcing the link between the metasomatic fluids and subduction of hydrothermally altered oceanic crust. Recycled signatures are also consistent with oxygen and sulfur isotope compositions of host crystals, which are distinct from compositions typical for the depleted upper MORB-source mantle.The occurrence of recycled volatile signatures in the EARS SCLM is widespread and must therefore be associated with a large-scale mantle process currently supplying material to EARS magmas. Notably, mantle xenoliths with high 3He/4He from the Ethiopian Rift are also associated with δ15N and δ13C values similar to the composition of sediments. This suggest that recycled materials have been entrained within the deep-seated African Superplume, which supplies the EARS with both primordial and recycled volatiles.

Geochemical Characteristics of Hydrothermal Volatiles From Southeast China and Their Implications on the Tectonic Structure Controlling Heat Convection

Hot springs and igneous rocks are present widely in southeast China, influenced by the subduction of the Western Pacific and Philippine Sea Plates. This study reports on new data of chemical compositions and He–Ne–C isotopes for gas samples from representative hot springs and wells in the Guangdong and Fujian provinces to identify the origin of hydrothermal volatiles and provide insight into geothermal tectonic affinities. The primary hydrothermal volatile component from southeast China is atmospheric N2, with a volumetric percentage of 82.19%–98.29%. It indicates medium-low temperature geothermal systems where geothermal fluids suffered a shallow circulation in closed fracture systems. Low CO2 and CH4 contents and their depleted δ13C values confirmed the small number of deep-derived components in the study area. However, spatially discernible geochemical characteristics imply enhanced hydrothermal fluid convection in the adjacent area of the two provinces, including the Fengshun, Zhangzhou, Longyan, and Sanming geothermal fields. Specifically, the He–Ne isotopes from this area exhibit mantle He contribution of more than 10% and mantle heat flow accounts for more than half of the total heat flow. Moreover, according to the thermal background calculations, the highest heat flow value of 77.7 mW/m2 is indicated for the Zhangzhou geothermal area and the lowest value of 54.7 mW/m2 is indicated for the Maoming geothermal area. Given the epicenter distributions and the corresponding earthquake magnitudes, the NE-trending faults are heat-control tectonic structures and their intersections with the NW-trending faults provided expedite channels for geothermal fluids rising to the surface. Therefore, the preferred development potential of geothermal resources can be expected in the adjacent area of the two provinces where two sets of active faults crossed. This study provides critical information on understanding the geothermal distribution controlled by the tectonic structure in southeast China.

Enormous nuclear surface diffuseness of Ne and Mg isotopes in the island of inversion

Background: The density profile of exotic nuclei can be a rich source of information on the nuclear surface. In particular, the nuclear surface diffuseness is correlated with the occupation probability of nucleons in distinct nuclear orbits, especially those with low angular momenta.Purpose: The aim of this paper is to investigate the relationship between the nuclear surface diffuseness and spectroscopic information of neutron-rich Ne and Mg isotopes both at the cusp and inside the island of inversion.Method: We use the microscopic antisymmetrized molecular dynamics model to calculate the densities and other spectroscopic information related to Ne and Mg isotopes. A two-parameter Fermi density distribution is then used to define the diffuseness parameter and the matter radius. These quantities are extracted by minimizing the difference between these two densities. To relate them with observables, the two densities are given as inputs to a Glauber model calculation of nucleon-nucleus elastic scattering differential cross section, with the demand that they reproduce the first peak position and its magnitude.Results: A marked increase in the occupation of neutrons in the $pf$ orbit is noted in Ne and Mg isotopes from $N=19$ onwards. We observed that the nuclear surface diffuseness is strongly correlated with the nuclear deformation, in the island of inversion, and gradually increases with the occupation of neutrons in the $1{p}_{3/2}$ orbit. This result is also confirmed by a single-particle estimate of the valence neutron density distribution, with $^{29}\mathrm{Ne}$ as a test case. An exception is noted for $^{35--37}\mathrm{Mg}$, where the filling up of the holes in the $sd$ shell partially compensates the increase in diffuseness due to filling up of the $1{p}_{3/2}$ orbit.Conclusion: Information on nuclear density profile of neutron-rich medium mass nuclei can be reliably extracted by studying the first diffraction peak of the nucleon-nucleus elastic scattering differential cross section. The enormous surface diffuseness of Ne and Mg isotopes, in the island of inversion, could be attributed to the increasing neutron occupation of the $1{p}_{3/2}$ orbit.

Surface properties for Ne, Na, Mg, Al, and Si isotopes in the coherent density fluctuation model using the relativistic mean-field densities

We have systematically studied the surface properties, such as symmetry energy, neutron pressure, and symmetry energy curvature coefficient for Ne, Na, Mg, Al, and Si nuclei from the proton to neutron drip lines. The coherent density fluctuation model (CDFM) is used to estimate these quantities taking the relativistic mean-field densities as inputs. The Brückner energy density functional is taken for the nuclear matter binding energy and local density approximation is applied for its conversion to coordinate space. The symmetry energy again decomposed to the volume and surface components within the liquid drop model formalism to the volume and surface parts separately. Before calculating the surface properties of finite nuclei, the calculated bulk properties are compared with the experimental data, whenever available. The NL3* parameter set with the Bardeen–Cooper–Schrieffer (BCS) pairing approach in an axially deformed framework is used to take care of the pairing correlation when needed. The deformed density is converted to its spherical equivalent with a two-Gaussian fitting, which is used as an input for the calculation of weight function in the CDFM approximation. With the help of the symmetry energy, the isotopes 29F, 28Ne, 29,30Na, and 31,35,36Mg are considered to be within the island of inversion (Han et al. Phys. Lett. B, 772, 529 (2017). doi:10.1016/j.physletb.2017.07.007). Although we get large symmetry energies corresponding to a few neutron numbers for this isotopic chain as expected, an irregular trend appears for all these considered nuclei. The possible reason behind this abnormal behavior of symmetry energy for these lighter mass nuclei is also included in the discussion, which gives a direction for future analysis.

Cross-Shell Excitation in F and Ne Isotopes around N = 20

Within the framework of the configuration–interaction shell model, the present work applies three effective interactions to investigate the effects of the cross-shell excitation on F and Ne isotopes around N = 20, which are significantly proton–neutron asymmetric, and have different properties compared with the proton–neutron symmetric nuclei. It is shown that cross-shell excitation is necessary in order to reproduce separation energies, neutron drip lines, and low-energy levels of these isotopes. Furthermore, the cross-shell excitation of (0–5)ħω is suggested to be important in the description of 29F and 30Ne. However, the three interactions are insufficient in describing the bound structure of 29,31Ne, and provide inconsistent shell structures and evolutions in the target nuclei. Their cross-shell interactions are suggested to be improved.

Light noble gas records and cosmic ray exposure histories of recent ordinary chondrite falls

AbstractWe measured noble gas concentrations and isotopic ratios (He, Ne, and Ar isotopes) in six recent ordinary chondrite falls: Mangui (L6), Viñales (L6), Ozerki (L6), Tamdakht (H5), Kheneg Ljouâd (LL5/6), and Katol (L6). Among them, the three L6 chondrites Mangui, Viñales, and Ozerki fell in only a few months' interval; their apparent similar petrographic and mineralogic characteristics might indicate source crater pairing. To test this hypothesis, we have investigated those meteorites for their cosmic ray exposure (CRE) histories, using the cosmogenic noble gases 3He, 21Ne, and 38Ar. We systematically (re)calculated the CRE ages as well as the gas retention ages of these meteorites. The CRE age of the Mangui is, based on noble gases, <1 Ma, which is unusually short for an L chondrite. Indeed, the range of exposure ages for L chondrites is generally distributed between ˜1 and ˜60 Ma, with major peaks occurring around ˜5, ˜30, and ˜40 Ma. In addition, the cosmogenic 3Hecos data of two Mangui duplicates are consistent with a remarkably high loss of helium by diffusion due to heating by solar radiation. Such a short parent body‐Earth transfer time (<1 Ma) can be explained by a delivery from an Earth‐crossing object. Regarding the other L6 chondrites, Viñales has a nominal CRE age of ˜9.4 Ma, whereas the Ozerki meteorite has a nominal CRE age of ˜1.2 Ma, which is consistent with Korochantseva et al. (2019). Based on their CRE ages as well as on their gas retention ages, it appears that none of these three recent L6 chondrite falls are source crater paired, and therefore, all three originate from different meteoroids. The nominal exposure ages of Tamdakht, Kheneg Ljouâd, and Katol are ˜3.2, ˜11, and ˜30 Ma, respectively, and are consistent with identified age peaks on the exposure age histogram of H, LL, and L chondrites, respectively. The nominal CRE age of Tamdakht is consistent with previous observations for H chondrites and implies that they are dominated by small impact events occurring in several parent bodies.

He, Ne, Ar and CO2 systematics of the Rungwe Volcanic Province, Tanzania: Implications for fluid source and dynamics

Volatiles, such as carbon and noble gases, are continuously degassed from Earth's mantle and crust to Earth's surface in continental rifting systems. Here, we present He-Ne-Ar abundances and isotopes as well as major gas chemistry (CO2, He, Ar and CH4) data for (n = 13) naturally-degassing seeps in the Rungwe Volcanic Province (RVP) of the East African Rift System (EARS) in southwestern Tanzania, Africa. Helium isotopes (3He/4He) suggest that trace gases are derived from mantle sources, with moderate crustal additions, in agreement with previous studies from RVP (e.g., Pik et al., 2006; Barry et al., 2013). Samples broadly fall into two groups: 1) dominantly mantle-like, with 3He/4He ranging from 5.2–6.3RA, which can be explained by release of magmatic volatiles, and 2) those with slightly lower 3He/4He (3.0–4.1RA), representing more 4He (i.e., crustal) additions. Furthermore, we report the first Ne and Ar isotopes from RVP, which show 20Ne/22Ne from 9.67–10.0 and 40Ar/36Ar from 301.2–412.2, respectively, which are broadly air-like. We employ a solubility degassing model to show that elemental ratios (4He/40Ar*, CO2/40Ar* and CO2/3He) in the gases can be explained by variable extents of open and closed system degassing from a melt with an initial mantle-like composition. However, we note that CO2/3He observations require additional carbon assimilation, likely derived from the thick nearby cratonic crust.

New System for Measuring Cosmogenic Ne in Terrestrial and Extra-Terrestrial Rocks

Cosmogenic Ne isotopes are used for constraining the timing and rate of cosmological and Earth surface processes. We combined an automated gas extraction (laser) and purification system with a Thermo Fisher ARGUS VI mass spectrometer for high through-put, high precision Ne isotope analysis. For extra-terrestrial material with high cosmogenic Ne concentrations, we used multi-collection on Faraday detectors. Multiple measurements (n = 26) of 1.67 × 10−8 cm3 air-derived 20Ne yielded an uncertainty of 0.32%, and 21Ne/20Ne = 0.17% and 22Ne/20Ne = 0.09%. We reproduced the isotope composition of cosmogenic Ne in the Bruderheim chondrite and Imilac pallasite in a sub-ten mg sample. For lower Ne amounts that are typical of terrestrial samples, an electron multiplier detector was used in peak jumping mode. Repeated analysis of 3.2 × 10−11 cm3 STP 20Ne from air reproduced 21Ne/20Ne and 22Ne/20Ne with 1.1% and 0.58%, respectively, and 20Ne intensity with 1.7% (n = 103) over a 4-month period. Multiple (n = 8) analysis of cosmogenic Ne in CREU-1 quartz yielded 3.25 ± 0.24 × 108 atoms/g (2 s), which overlaps with the global mean value. The repeatability is comparable to the best data reported in the international experiments performed so far on samples that are 2–5× smaller. The ability to make precise Ne isotope determinations in terrestrial and extra-terrestrial samples that are significantly smaller than previously analysed suggests that the new system holds great promise for studies with limited material.

Deformation effect on nuclear density profile and radius enhancement in light- and medium-mass neutron-rich nuclei

Abstract The mass number dependence of nuclear radii is closely related to the properties of nuclear matter. It is known that most nuclei exhibit some deformation. We discuss how the nuclear density profile is modified by nuclear deformation to elucidate the enhancement mechanism of nuclear radii through a systematic investigation of neutron-rich Ne, Mg, Si, S, Ar, Ti, Cr, and Fe isotopes. Skyrme–Hartree–Fock calculations are performed in a 3D Cartesian grid to describe the nuclear deformation in a non-empirical way. The role of nuclear deformation in nuclear density profiles is explored in comparison to calculations with a spherical limit. We find correlations between nuclear deformation and the internal nuclear density. The evolution of nuclear radii appears to follow the core swelling mechanism recently proposed in spherical nuclei [W. Horiuchi and T. Inakura, Phys. Rev. C 101, 061301(R) (2020)], and the radius is further enhanced by nuclear deformation. This study demands further theoretical and experimental investigations for the internal density.

Possible shape coexistence in Ne isotopes and the impurity effect of Λ hyperon

Possible shape coexistence in Ne isotopes and the impurity effect of Λ hyperon

Melting and metasomatism in West Eifel and Siebengebirge Sub-Continental Lithospheric Mantle: Evidence from concentrations of volatiles in fluid inclusions and petrology of ultramafic xenoliths

The possibility of constraining the composition and evolution of specific portions of the Sub-Continental Lithospheric Mantle (SCLM) by means of an integrated study of petrography, mineral chemistry, and concentrations of volatiles in fluid inclusions (FI) is a novel approach that can provide clues on the recycling of volatiles within the lithosphere. This approach is even more important in active or dormant volcanic areas, where the signature of the gaseous emissions at the surface can be that of the underlying lithospheric mantle domains. In this respect, the ultramafic xenoliths brought to the surface in West Eifel (~0.5–0.01 Ma) and Siebengebirge (~30–6 Ma) volcanic fields (Germany) are ideal targets, as they provide direct information on one of the most intriguing portions of SCLM beneath the Central European Volcanic Province (CEVP). Five distinct populations from these localities were investigated using petrographic observations, mineral phase analyses and determination of He, Ne, Ar and CO2 contents in olivine-, orthopyroxene-, and clinopyroxene-hosted FI. The most refractory Siebengebirge rocks have highly forsteritic olivine, high-Mg#, low-Al pyroxene, and spinel with high Cr#, reflecting high extents (up to 30%) of melt extraction. In contrast, xenoliths from West Eifel are modally and compositionally heterogeneous, as indicated by the large forsterite range of olivine (Fo83–92), the Cr# range of spinel (0.1–0.6), and the variable Al and Ti contents of pyroxene. Equilibration temperatures vary from 870 °C to 1070 °C in Siebengebirge, and from ⁓900 °C to ⁓1190 °C in West Eifel xenoliths, at oxygen fugacity values generally between −0.5 and + 1.3 ΔlogƒO2 [FMQ]. In both areas, the FI composition was dominated by CO2, with clinopyroxene, and most of the orthopyroxene had the highest concentrations of volatiles, while olivine was gas-poor. The noble gas and CO2 distributions suggest that olivine is representative of a residual mantle that experienced one or more melt extraction episodes. The 3He/4He ratio corrected for air contamination (Rc/Ra values) varied from 6.8 Ra in harzburgitic lithotypes to 5.5 Ra in lherzolites and cumulate rocks, indicating that the original MORB-like mantle signature was progressively modified by interaction with crustal-related components and melts having 3He/4He and 4He/40Ar* values consistent with those published for magmatic gaseous emissions. The Ne and Ar isotope systematics indicated that most of the data were consistent with mixing between a recycled atmospheric component and a MORB-like mantle, which does not necessarily require the involvement of a lower mantle plume beneath this portion of the CEVP. The major element distribution in mineral phases from West Eifel and Siebengebirge, together with the systematic variations in FI composition, the positive correlation between Al enrichment in pyroxene and equilibration temperatures, and the concomitant Rc/Ra decrease with increasing temperature, suggest that the SCLM beneath Siebengebirge represented the Variscan lithosphere in CEVP prior to the massive infiltration of melts/fluids belonging to the Quaternary Eifel volcanism. In contrast, West Eifel xenoliths reflect multiple heterogeneous metasomatism/refertilisation events that took place in the regional SCLM between ~6 and ~ 0.5 Ma.

Effects of three-nucleon force on the low-lying states of <sup>28</sup>F and<sup>29</sup>Ne within <italic>ab initio</italic> calculations

One of the most interesting anomalies in nuclear physics is the island of inversion (IOI), which indicates that the magic numbers disappear. It provides a good platform to understand single-particle motion, many-body correlation, and nucleon-nucleon interaction. In neutron-rich isotopes near N =20 area, many experiments have found that the spectra, electromagnetic transitions, radii, and two-neutron separation energies of these nuclei are abnormal. This region is called the N =20 IOI, because it is characterized by neutron particle-hole excitations related to deformation from the 1s0d shell into the 1p0f shell across the N =20 shell gap. Recent experiments show that the ground states of 29Ne and 28F have negative parities, indicating that these two nuclei are within the N =20 IOI. This provides new opportunities and challenges for theoretical models in this area. With the standard shell model, the N =20 IOI has been proved by many works to have a strong cross-shell effect between 1s0d and 1p0f shells. They proposed that the tensor force and three-nucleon force should have an important influence on the microscopic description of neutron-rich nuclei in this area, especially in Ne and Mg isotopes. However, the N =20 IOI is still rarely studied in ab initio calculations. Recently, an extension of the ab initio valence-space in-medium similarity renormalization group method was presented to study the physics of neutron-rich nuclei by Miyagi et al. In the present paper, based on chiral force including nucleon-nucleon and three-nucleon force, we have performed ab initio calculations for the low-lying states of 28F and 29Ne, focusing on the relative excitation energies of the positive- and negative-parity states in these nuclei. In order to study the effect of three-nucleon force on the N =20 IOI, we use nucleon-nucleon force at N3LO with or without three-nucleon force at N2LO in our calculations. Using the open-shell many-body perturbation theory, the cross shell sd-pf realistic effective Hamiltonian, including single-particle energies and effective two-body interactions, is constructed self-consistently without introducing parameters. The constructed effective Hamiltonian is diagonalized with the shell model method. In shell model calculation, we use a truncation with up to five nucleons (including protons and neutrons) occupying the pf orbit. The low-lying states of 28F and 29Ne are calculated with NN and NN+3N interactions. The results show that three-nucleon force is important in the descriptions of low-lying states of 28F and 29Ne, especially in 29Ne while the first negative state turned to be ground state due to the three-nucleon force. Our calculations give that three-nucleon force gives large effects for the relative position between the 0d3/2 and 1p3/2 single-particle orbitals, causing the two orbitals to reverse. Furthermore, the configurations of low-lying states of 28F and 29Ne are calculated within our ab initio calculations with NN+3N interaction. The results give that the lowest positive and negative parity states in 28F and 29Ne are dominated by 2 ℏ ω and 1 ℏ ω components, respectively. We have also calculated the configurations of the ground state in neutron-rich even-even Ne isotopes, and the results indicate that the three-nucleon force could enhance the cross-shell excitations in the nuclei in the vicinity of IOI, which is essential for the exotic properties of these nuclei. Furthermore, we have also performed the phenomenological shell model calculations with SDPF-MU effective interactions, and the results are similar to our ab initio calculations including three-nucleon force.

Combined petrography, noble gas, stable isotope and fluid inclusion chemistry of carbonatites from Uganda: Implications for the origin of the carbonatite melt in continental rift setting

An integrated petrographic, fluid inclusion, noble gas, and stable isotope study was performed for the Late Oligocene, spatially associated Sukulu and Tororo carbonatite complexes in SE Uganda in order to understand their genesis and provide additional constraints on the evolution of the East African Rift System (EARS). Both carbonatite complexes comprise mainly ring-shaped calcio‑carbonatites with accessory primary magmatic phases, including olivine, phlogopite, aegirine and pyrochlore. Absent or low Na deficiency on the A-site and high F contents (0.4–1.2 apfu) reveal the magmatic origin of pyrochlore. In contrast, the corroded rims of olivine, Sr-enrichments of the rims of apatite, as well as the occurrence of Sr- and Mg-rich lamellae in calcite, coupled with the presence of barite, REE-witherite, siderite, pyrite, bastnäsite and galena as secondary phases imply a hydrothermal overprint of the primary magmatic mineral assemblage.Fluid inclusions found in the cores of clustered apatite crystals are primary, two-phase H2O + NaCl aqueous inclusions in Sukulu-, and two-, or multi-phase H2O + NaCl ± NaHCO3 ± other solid inclusions in Tororo Complex. In the gas phase of some inclusions small amounts of CO2 or CH4 have been detected by micro-Raman analysis. The estimated trapping temperature of 330–425 °C and pressure of 465–1330 bars using the accepted denudation rates calculated for the EARS as independent barometers, reveal subsolidus crystallization conditions for the intercrystalline clustered apatite aggregates. Stable C-O isotope compositions of both carbonatite complexes suggest ultimately a mantle origin for the carbonate phase.Helium, neon and argon isotope compositions, liberated by crushing of bulk rock, apatite and calcite samples, show a systematic variation between the analyzed phases. Relatively low 3He/4He ratios of apatite and pyroxene separates (<5.3 Ra) are accounted for by radiogenic production of 4He in these minerals, whereas the air-corrected values in calcite reach as high as 9.6 Ra, characteristic for plume sources. Whole-rock Ne isotope ratios provide evidence for a depleted MORB mantle (DMM) trend. Combined (21Ne/22Ne)EX (air-corrected 21Ne/22Ne ratio extrapolated to Ne-B composition Holland and Ballentine, 2006; Trieloff et al., 2000) versus 4He/3He are indicative of mixing of a plume-like and a DMM-like component in the source region of the parental carbonatite magmas, which is in contrast to some recent interpretations of recent/sub-recent magmas in the EARS. Based on new noble gas data from this study we argue that in the early phase of the magmatic activity of the EARS, a low-viscosity carbonatite magma may have intruded into the shallow crust rapidly, without any significant contamination by the sub-continental lithospheric mantle.Combined fluid inclusion data and noble gas results collectively imply that the carbonatites worldwide are carbothermal (hydrothermal) rather than purely magmatic products and that they crystallized at sub-solidus temperatures from dominantly magma-derived fluids.

Formation of Venus, Earth and Mars: Constrained by Isotopes

We discuss the current state of knowledge of terrestrial planet formation from the aspects of different planet formation models and isotopic data from 182Hf-182W, U-Pb, lithophile-siderophile elements, 48Ca/44Ca isotope samples from planetary building blocks, 36Ar/38Ar, 20Ne/22Ne, 36Ar/22Ne isotope ratios in Venus' and Earth's atmospheres, the expected solar 3He abundance in Earth's deep mantle and Earth's D/H sea water ratios that shed light on the accretion time of the early protoplanets. Accretion scenarios that can explain the different isotope ratios, including a Moon-forming event after ca. 50 Myr, support the theory that the bulk of Earth's mass (>80%) most likely accreted within 10-30 Myr. From a combined analysis of the before mentioned isotopes, one finds that proto-Earth accreted 0.5-0.6 MEarth within the first ~4-5 Myr, the approximate lifetime of the protoplanetary disk. For Venus, the available atmospheric noble gas data are too uncertain for constraining the planet's accretion scenario accurately. However, from the available Ar and Ne isotope measurements, one finds that proto-Venus could have grown to 0.85-1.0 MVenus before the disk dissipated. Classical terrestrial planet formation models have struggled to grow large planetary embryos quickly from the tiniest materials within the typical lifetime of protoplanetary disks. Pebble accretion could solve this long-standing time scale controversy. Pebble accretion and streaming instabilities produce large planetesimals that grow into Mars-sized and larger planetary embryos during this early accretion phase. The later stage of accretion can be explained well with the Grand-Tack, annulus or depleted disk models. The relative roles of pebble accretion and planetesimal accretion/giant impacts are poorly understood and should be investigated with N-body simulations that include pebbles and multiple protoplanets.

Cluster radioactivity in superheavy nuclei 299-306122

Cluster radioactivity is an intermediate between alpha decay and spontaneous fission. It is also an exotic decay obtained in superheavy nuclei. When a cluster decay is detected in superheavy nuclei, the daughter nuclei is having near or equal to doubly magic nuclei. We have investigated cluster decay of isotopes of He, Li, Be, Ne, N, Mg, Si, P, S, Cl, Ar and Ca in the superhaevy nuclei region 299-306122. We have also compared the logarithmic half-lives of cluster decay with that of other models such as Univ [1], NRDX [2], UDL [3] and Horoi [4]. From this study it is concluded that cluster decay of 4He, 22Ne, 26Mg, 28Si 30Si, 34S, 40Ca and 46Ca are having shorter logarithmic half-lives compared to exotic cluster decay modes.

The old, unique C1 chondrite Flensburg – Insight into the first processes of aqueous alteration, brecciation, and the diversity of water-bearing parent bodies and lithologies

On September 12, 2019 at 12:49:48 (UT) a bolide was observed by hundreds of eye-witnesses from the Netherlands, Germany, Belgium, Denmark and the UK. One day later a small meteorite stone was found by accident in Flensburg. The presence of short-lived cosmogenic radionuclides with half-lives as short as 16 days proves the recent exposure of the found object to cosmic rays in space linking it clearly to the bolide event. An exceptionally short exposure time of ∼5000 years was determined. The 24.5 g stone has a fresh black fusion crust, a low density of <2 g/cm3, and a magnetic susceptibility of logχ = 4.35 (χ in 10−9 m3/kg). The rock consists of relict chondrules and clusters of sulfide and magnetite grains set in a fine-grained matrix. The most abundant phases are phyllosilicates. Carbonates (∼3.9 vol.%) occur as calcites, dolomites, and a Na-rich phase. The relict chondrules (often surrounded by sulfide laths) are free of anhydrous silicates and contain abundant serpentine. Lithic clasts are also surrounded by similar sulfide laths partly intergrown with carbonates. 53Mn-53Cr ages of carbonates in Flensburg indicate that brecciation and contemporaneous formation of the pyrrhotite-carbonate intergrowths by hydrothermal activities occurred no later than 4564.6 ± 1.0 Ma (using the angrite D'Orbigny as the Mn-Cr age anchor). This corresponds to 2.6 ± 1.0 or 3.4 ± 1.0 Ma after formation of CAIs, depending on the exact absolute age of CAIs. This is the oldest dated evidence for brecciation and carbonate formation, which likely occurred during parent body growth and incipient heating due to decay of 26Al.In the three oxygen isotope diagram, Flensburg plots at the 16O-rich end of the CM chondrite field and in the transition field to CV-CK-CR chondrites. The mass-dependent Te isotopic composition of Flensburg is slightly different from mean CM chondrites and is most similar to those of the ungrouped C2 chondrite Tagish Lake. On the other hand, 50Ti and 54Cr isotope anomalies indicate that Flensburg is similar to CM chondrites, as do the ∼10 wt.% H2O of the bulk material. Yet, the bulk Zn, Cu, and Pb concentrations are about 30% lower than those of mean CM chondrites. The He, Ne, and Ar isotopes of Flensburg show no solar wind contribution; its trapped noble gas signature is similar to that of CMs with a slightly lower concentration of 20Netr.Based on the bulk H, C, and N elemental abundances and isotopic compositions, Flensburg is unique among chondrites, because it has the lightest bulk H and N isotopic compositions of any type 1 or 2 chondrite investigated so far. Moreover, the number of soluble organic compounds in Flensburg is even lower than that of the brecciated CI chondrite Orgueil.The extraordinary significance of Flensburg is evident from the observation that it represents the oldest chondrite sample in which the contemporaneous episodes of aqueous alteration and brecciation have been preserved. The characterization of a large variety of carbonaceous chondrites with different alteration histories is important for interpreting returned samples from the OSIRIS-REx and Hayabusa 2 missions.