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Abstract Titanium and calcium are both refractory lithophile elements. Significant stable isotopic variations on Ti and Ca have been documented within calcium, aluminum-rich inclusions (CAIs) in carbonaceous chondrites. To trace the condensation history of Ti in the solar nebula, we conducted a high-precision double-spike Ti stable isotopic study on a large set of chondrites. The studied chondrites have a homogeneous bulk Ti stable isotopic composition (δ 49/47Ti IPGP-Ti = −0.069 ± 0.018‰, 2se, n = 22, i.e., the per mil deviation of the 49Ti/47Ti ratios relative to the IPGP-Ti reference material). The homogeneity across eleven chondrite groups implies that chondrites have acquired, through the condensation sequence at equilibrium, the average stable isotopic composition of Ti in the refractory solids that condensed early in the solar nebula. In contrast, the light Ca stable isotopic compositions of bulk chondrites can be attributed to either the presence of CAIs (CV-, CM- and CO-type) or parent-body aqueous alteration (CR- and CI-type). [ABSTRACT FROM AUTHOR]

Previous studies have shown that CV and CM chondrites incorporated Ca, Al-rich inclusions (CAIs) with different isotopic characteristics, which may represent different snapshots in the isotopic evolution of the early Solar System. To better understand how the isotopic characteristics of CAIs vary between different chondrite groups, we have studied calcium and titanium isotopes in CAIs from CM, CO, and CR chondrites. We show that all three chondrite groups contain CAIs with large anomalies in 48 Ca and/or 50 Ti (10s of ‰ or 100s of ε -units) as well as CAIs with no anomalies resolved beyond measurement uncertainties. Isotopically, the anomalous CO and CR chondrite CAIs resemble the platy hibonite crystals (PLACs) from CM chondrites, but they are more mineralogically complex. The new data are consistent with the well-established mutual exclusivity relationship between incorporation of 26 Al and the presence of large anomalies in 48 Ca and 50 Ti. The two highly anomalous CO chondrite CAIs have correlated anomalies in 46 Ti and 50 Ti, while most other highly anomalous CAIs do not. This result could indicate that the reservoir with coupled 46 Ti and 50 Ti that was sampled by bulk meteorites and CV chondrite CAIs already existed before arrival and/or homogeneous distribution of 26 Al in the protoplanetary disk. Among the studied CM chondrite CAIs are ten spinel-hibonite inclusions (SHIBs) with known oxygen isotopic compositions. Our results show that these objects sampled a reservoir that was well-mixed in oxygen, calcium, and titanium isotopes. We further show that SHIBs tend to be slightly enriched in the heavy calcium isotopes, suggesting that their formation history was different from CV chondrite CAIs. [ABSTRACT FROM AUTHOR]

Measured and modeled Ca and Ti isotopic fractionation effects in a diverse suite of refractory inclusions are used to understand processes of condensation in the solar protoplanetary disk where they and their precursor materials formed. This coordinated approach reveals largely decoupled isotopic signatures and implies that few, if any, of the studied inclusions can be considered primary condensates. All studied inclusions are enriched in light Ca isotopes (∼−0.2 to − 2.8 ‰ / amu ), but only two show correspondingly light Ti isotopes. Studied inclusions exhibit both heavy and light Ti isotope enrichments (∼0.3 to − 0.4 ‰ / amu ). These refractory element isotopic signatures, therefore, suggest admixture and reprocessing of earlier formed materials with distinct condensation histories. Along with coordinated measurements of 50 Ti isotopic anomalies, which span a range from ∼0 to ∼40 epsilon-unit excesses, the comparison of measured and modeled fractionation of Ca and Ti isotopes provides a powerful approach to understanding primitive nebular processes and environments in the protoplanetary disk. Remarkable evidence for Ca isotopic zoning within a typical Type B1 inclusion exemplifies the potential record of the earliest solar nebula that is likely lost and/or overprinted in the isotopic compositions of more volatile elements (e.g., Mg, Si, and O) by later modification processes. [ABSTRACT FROM AUTHOR]

PLACs (platy hibonite crystals) and related hibonite-rich calcium-, aluminum-rich inclusions (CAIs; hereafter collectively referred to as PLAC-like CAIs) have the largest nucleosynthetic isotope anomalies of all materials believed to have formed in the solar system. Most PLAC-like CAIs have low inferred initial 26 Al/ 27 Al ratios and could have formed prior to injection or widespread distribution of 26 Al in the solar nebula. In this study, we report 26 Al– 26 Mg systematics combined with oxygen, calcium, and titanium isotopic compositions for a large number of newly separated PLAC-like CAIs from the Murchison CM2 chondrite (32 CAIs studied for oxygen, 26 of these also for 26 Al– 26 Mg, calcium and titanium). Our results confirm (1) the large range of nucleosynthetic anomalies in 50 Ti and 48 Ca (our data range from −70‰ to +170‰ and −60‰ to +80‰, respectively), (2) the substantial range of Δ 17 O values (−28‰ to −17‰, with Δ 17 O = δ 17 O − 0.52 × δ 18 O), and (3) general 26 Al-depletion in PLAC-like CAIs. The multielement approach reveals a relationship between Δ 17 O and the degree of variability in 50 Ti and 48 Ca: PLAC-like CAIs with the highest Δ 17 O (∼−17‰) show large positive and negative 50 Ti and 48 Ca anomalies, while those with the lowest Δ 17 O (∼−28‰) have small to no anomalies in 50 Ti and 48 Ca. These observations could suggest a physical link between anomalous 48 Ca and 50 Ti carriers and an 16 O-poor reservoir. We suggest that the solar nebula was isotopically heterogeneous shortly after collapse of the protosolar molecular cloud, and that the primordial dust reservoir, in which anomalous carrier phases were heterogeneously distributed, was 16 O-poor (Δ 17 O ⩾ −17‰) relative to the primordial gaseous (CO + H 2 O) reservoir (Δ 17 O < −35‰). However, other models such as CO self-shielding in the protoplanetary disk are also considered to explain the link between oxygen and calcium and titanium isotopes in PLAC-like CAIs. [ABSTRACT FROM AUTHOR]

We report oxygen, calcium, titanium and 26 Al– 26 Mg isotope systematics for spinel-hibonite inclusions (SHIBs), a class of calcium–aluminum-rich inclusions (CAI) common in CM chondrites. In contrast to previous studies, our analyses of 33 SHIBs and four SHIB-related objects obtained with high spatial resolution demonstrate that these CAIs have a uniform Δ 17 O value of approximately −23‰, similar to many other mineralogically pristine CAIs from unmetamorphosed chondrites (e.g., CR, CV, and Acfer 094). Five SHIBs studied for calcium and titanium isotopes have no resolvable anomalies beyond 3 σ uncertainties. This suggests that nucleosynthetic anomalies in the refractory elements had been significantly diluted in the environment where SHIBs with uniform Δ 17 O formed. We established internal 26 Al– 26 Mg isochrons for eight SHIBs and found that seven of these formed with uniformly high levels of 26 Al (a multi-CAI mineral isochron yields an initial 26 Al/ 27 Al ratio of ∼4.8 × 10 −5 ), but one SHIB has a smaller initial 26 Al/ 27 Al of ∼ 2.5 × 10 −5 , indicating variation in 26 Al/ 27 Al ratios when SHIBs formed. The uniform calcium, titanium and oxygen isotopic characteristics found in SHIBs with both high and low initial 26 Al/ 27 Al ratios allow for two interpretations. (1) If subcanonical initial 26 Al/ 27 Al ratios in SHIBs are due to early formation, as suggested by Liu et al. (2012), our data would indicate that the CAI formation region had achieved a high degree of isotopic homogeneity in oxygen and refractory elements before a homogeneous distribution of 26 Al was achieved. (2) Alternatively, if subcanonical ratios were the result of 26 Al– 26 Mg system resetting, the clustering of SHIBs at a Δ 17 O value of ∼−23‰ would imply that a 16 O-rich gaseous reservoir existed in the nebula until at least ∼0.7 Ma after the formation of the majority of CAIs. [ABSTRACT FROM AUTHOR]

Isotope fractionations associated with high temperature evaporation provide important constraints on the physicochemical processes that affected planetary materials at the birth of the solar system. Previous evaporation experiments have focused on isotopic fractionation of moderately to highly volatile elements. Here, we investigate the isotope fractionation behavior of two highly refractory elements, calcium and titanium, during evaporation of perovskite (CaTiO3) in a vacuum furnace. In our experiments, isotope fractionation during evaporation follows the Rayleigh law, but not the commonly used exponential law, with the dominant evaporating species being Ca(g) and TiO2(g). If isotope fractionations in early solar system materials did follow the Rayleigh law, the common practice of using an exponential fractionation law to correct for mass-dependent fractionation in the study of mass-independent fractionations may introduce significant artificial isotope anomalies. [ABSTRACT FROM AUTHOR]

The article presents brief information on the correlations and neutrinoless β βdecay nuclear matrix elements (NMEs) of p f- shell nuclei. It mentions about the determination of nuclear matrix elements (NMEs) for neutrinoless using shell model (SM) and energy density functional (EDF) methods. Topics discussed include systematic study of the radioactive decays of calcium, titanium and others, and Fermi contribution of the NMEs, is offered.

The 40Ca(α,γ)44Ti reaction is believed to be the main production channel for the radioactive nuclide 44Ti in core-collapse Supernovae. Radiation from decaying 44Ti has been observed so far for two supernova remnants, and precise knowledge of the 44Ti production rate may help improve supernova models. The 40Ca(α,γ)44Ti astrophysical reaction rate is determined by a number of narrow resonances. Here, the resonance triplet at Eα = 4497,4510, and 4523 keV is studied both by activation, using an underground laboratory for the γ counting, and by in-beam γ spectrometry. The target properties are determined by elastic recoil detection analysis and by nuclear reactions. The strengths of the three resonances are determined to be ωγ = (0.92 ± 0.20), (6.2 ± 0.5), and (1.32 ±0.24) eV, respectively, a factor of 2 more precise than before. The strengths of this resonance triplet may be used in future works as a point of reference. In addition, the present new data directly affect the astrophysical reaction rate at relatively high temperatures (above 3.5 GK). [ABSTRACT FROM AUTHOR]

The giant dipole resonance (GDR) in N = 28 isotones (48Ca, 50Ti, 52Cr, 54Fe) is analyzed in the framework of the Skyrme random-phase-approximation (RPA). Three Skyrme forces, SkM*, SLy6 and SV-bas, are used. The effects beyond RPA are simulated by the double folding procedure. We show that dipole strength exhibits a large collective shift, which testifies to a strong impact of the residual interaction and signals on considerable anharmonic effects. In 52Cr, a significant pairing impact is found. For exception of 50Ti, an acceptable agreement with the experiment data is obtained, which justifies the ability of Skyrme forces to describe GDR in light nuclei. [ABSTRACT FROM AUTHOR]

The relatively short-lived radionuclide 44Ti is of considerable importance for the interpretation of nucleosynthesis in core-collapse supernova environments. Production is predominantly through the 40Ca(α,γ)44Ti reaction, which has been studied in this work over the energy range Ecm = 2.73--4.18 MeV, via direct γ counting and the 4π-summing technique, utilizing a previously characterized 12 inch × 12 inch single Nal crystal. The inferred reaction rate is compared here to both current experimental measurements and theoretical model calculations [ABSTRACT FROM AUTHOR]

The Recoil Distance Doppler-Shift method has been used to measure the lifetime of the first 3- state in the N = Z 44Ti nucleus, populated via the 40Ca(6Li, pn)44Ti reaction. State-of-the-art analysis techniques have been employed to determine the experimental lifetime, resulting in a B(Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed.) ≈ 3 W.u. [ABSTRACT FROM AUTHOR]

Excited states of the N=32 nucleus 54Ti have been studied, via both inverse-kinematics proton scattering and one-neutron knockout from 55Ti by a liquid hydrogen target, using the GRETINA γ-ray tracking array. Inelastic proton-scattering cross sections and deformation lengths have been determined. A low-lying octupole state has been tentatively identified in 54Ti for the first time. A comparison of (p,p') results on low-energy octupole states in the neutron-rich Ca and Ti isotopes with the results of random phase approximation calculations demonstrates that the observed systematic behavior of these states is unexpected. [ABSTRACT FROM AUTHOR]