Radioactive Nuclei Research Articles

Theoretical investigation on double- α decay from radioactive nuclei

Theoretical investigation on the concept of double-\ensuremath{\alpha} (2\ensuremath{\alpha}) decay is studied in the framework of the modified generalized liquid drop model with different preformation parameters. Comparison of 2\ensuremath{\alpha} and $^{8}\mathrm{Be}$ emission from various nuclei reveals that 2\ensuremath{\alpha} emission is more probable than $^{8}\mathrm{Be}$ emission, and $^{8}\mathrm{Be}$ emission does not occur due to its highly unstable nature. Probable 2\ensuremath{\alpha} emitters are investigated for nuclei in the natural isotopic compositions of elements with atomic numbers varying from 60 to 92 and our predictions on half-lives are in agreement with the values reported by Tretyak [Nucl. Phys. At. Energy. 22, 121 (2021)] using the semiempirical formula for cluster decays. The computed 2\ensuremath{\alpha} half-life of $^{209}\mathrm{Bi}$ using the SemFIS formula is found to be $1.926\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.16em}{0ex}}\mathrm{yr}$ and is compared with the first reported experimental limit $({T}_{1/2}>2.9\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{0.16em}{0ex}}\mathrm{yr})$ estimated from the experimental data of de Marcillac et al. [Nature (London) 422, 876 (2003)]; and this observation demonstrates the possibility of the detection of 2\ensuremath{\alpha} decay from the $^{209}\mathrm{Bi}$ isotope. We have also predicted 2\ensuremath{\alpha} half-lives for various isotopes $^{191\text{--}226}\mathrm{At}$, $^{193\text{--}228}\mathrm{Rn}$, $^{197\text{--}232}\mathrm{Fr}$, $^{201\text{--}235}\mathrm{Ra}$, $^{205\text{--}237}\mathrm{Ac}$, Th, $^{212\text{--}241}\mathrm{Pa}$, $^{215\text{--}243}\mathrm{U}$, and $^{219\text{--}245}\mathrm{Np}$, and most of the decay half-lives are below the measurable upper limit thereby promising chances to enhance experimental investigations on 2\ensuremath{\alpha} decay in the future.

An Enhancement of Formation of Unstable 8Be Nucleus with the Growth of α-Particle Multiplicity in Fragmentation of Relativistic Nuclei

In this paper, the correlation between the formation of the unstable $^{8}$Be nucleus and accompanying $\alpha$ particles in the fragmentation of relativistic $^{16}$O, $^{22}$Ne, $^{28}$Si, and $^{197}$Au nuclei in a nuclear track emulsion is investigated. The $^{8}$Be decays are identified in a wide energy range by invariant masses calculated from 2$\alpha$-pair opening angles. The adopted approximations are verified by data on fragmentation of $^{16}$O nuclei in a hydrogen bubble chamber in a magnetic field. An increase in the $^{8}$Be contribution to the dissociation with the growth of $\alpha$-particle multiplicity is found.

Measurement of cosmogenic neutron production in SK-Gd

The Super-Kamiokande-Gd (SK-Gd) experiment has started after adding the gadolinium (Gd) into ultra-pure water in the SK detector. SK-Gd dramatically improves the sensitivity to supernova relic neutrino searches by tagging neutrons. Cosmic-ray muons penetrating into the SK detector induce hadronic showers. Such muon often break oxygen nuclei in water and produce unstable radioactive isotopes and neutrons, which are major background sources for supernova relic neutrino searches. On the other hand, the cosmogenic neutrons produced by muons can be used for the detector calibration source. Since cosmic-ray muons penetrate into the SK detector continuously with the rate of 2 event/s, the cosmogenic neutrons can be used to monitor the stability and uniformity of the Gd concentration in water. In this proceeding, we report the progress of cosmogenic neutron measurement in SK-Gd.

26Aluminum from Massive Binary Stars. II. Rotating Single Stars Up to Core Collapse and Their Impact on the Early Solar System

Abstract Radioactive nuclei were present in the early solar system (ESS), as inferred from analysis of meteorites. Many are produced in massive stars, either during their lives or their final explosions. In the first paper of this series (Brinkman et al. 2019), we focused on the production of 26Al in massive binaries. Here, we focus on the production of another two short-lived radioactive nuclei, 36Cl and 41Ca, and the comparison to the ESS data. We used the MESA stellar evolution code with an extended nuclear network and computed massive (10–80 M ⊙), rotating (with initial velocities of 150 and 300 km s−1) and nonrotating single stars at solar metallicity (Z = 0.014) up to the onset of core collapse. We present the wind yields for the radioactive isotopes 26Al, 36Cl, and 41Ca, and the stable isotopes 19F and 22Ne. In relation to the stable isotopes, we find that only the most massive models, ≥60 and ≥40 M ⊙ give positive 19F and 22Ne yields, respectively, depending on the initial rotation rate. In relation to the radioactive isotopes, we find that the ESS abundances of 26Al and 41Ca can be matched with by models with initial masses ≥40 M ⊙, while 36Cl is matched only by our most massive models, ≥60 M ⊙. 60Fe is not significantly produced by any wind model, as required by the observations. Therefore, massive star winds are a favored candidate for the origin of the very short-lived 26Al, 36Cl, and 41Ca in the ESS.

Radioactive isotopes: astrophysics answers in abundance

Radioactive isotopes: astrophysics answers in abundance The ERC Consolidator Grant project “RADIOSTAR: Radioactivities form Stars to Solar Systems” uses radioactive nuclei produced by nuclear reactions inside stars and supernovae to understand the history of the chemical matter that builds up our Sun, our planet and ourselves, generating a new understanding of our solar system and the life within it.

Global Microscopic Description of Nucleon-Nucleus Scattering with Quantified Uncertainties.

We develop for the first time a microscopic global nucleon-nucleus optical potential with quantified uncertainties suitable for analyzing nuclear reaction experiments at next-generation rare-isotope beam facilities. Within the improved local density approximation and without any adjustable parameters, we begin by computing proton-nucleus and neutron-nucleus optical potentials from a set of five nuclear forces from chiral effective field theory for 1800 target nuclei in the mass range 12≤A≤242 for energies between 0 MeV<E≲150 MeV. We then parameterize a global optical potential for each chiral force that depends smoothly on the projectile energy as well as the target nucleus mass number and isospin asymmetry. Uncertainty bands for elastic scattering observables are generated from a full covariance analysis of the parameters entering in the description of our global optical potential and benchmarked against existing experimental data for stable target nuclei. Since our approach is purely microscopic, we anticipate a similar quality of the model for nucleon scattering on unstable isotopes.

Direct Measurement of the ^{13}C(α,n)^{16}O Cross Section into the s-Process Gamow Peak.

One of the main neutron sources for the astrophysical s process is the reaction ^{13}C(α,n)^{16}O, taking place in thermally pulsing asymptotic giant branch stars at temperatures around 90MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230keV energy window (Gamow peak). At these sub-Coulomb energies, cross section direct measurements are severely affected by the low event rate, making us rely on input from indirect methods and extrapolations from higher-energy direct data. This leads to an uncertainty in the cross section at the relevant energies too high to reliably constrain the nuclear physics input to s-process calculations. We present the results from a new deep-underground measurement of ^{13}C(α,n)^{16}O, covering the energy range 230-300keV, with drastically reduced uncertainties over previous measurements and for the first time providing data directly inside the s-process Gamow peak. Selected stellar models have been computed to estimate the impact of our revised reaction rate. For stars of nearly solar composition, we find sizeable variations of some isotopes, whose production is influenced by the activation of close-by branching points that are sensitive to the neutron density, in particular, the two radioactive nuclei ^{60}Fe and ^{205}Pb, as well as ^{152}Gd.

Neutron capture cross sections of light neutron-rich nuclei relevant for r -process nucleosynthesis

The measurements of neutron capture cross sections of neutron-rich nuclei are challenging but essential for understanding nucleosynthesis and stellar evolution processes in the explosive burning scenario. In the quest of r -process abundances, according to the neutrino-driven-wind model, light neutron-rich unstable nuclei may play a significant role as seed nuclei that influence the abundance pattern. Hence, experimental data for neutron capture cross sections of neutron-rich nuclei are needed. Coulomb dissociation of radioactive ion beams at intermediate energy is a powerful indirect method for inferring capture cross section. As a test case for validation of the indirect method, the neutron capture cross section ( n , γ ) for C 14 was inferred from the Coulomb dissociation of C 15 at intermediate energy ( 600 A MeV). A comparison between different theoretical approaches and experimental results for the reaction is discussed. We report for the first time experimental reaction cross sections of Na 28 ( n , γ ) Na 29 , Na 29 ( n , γ ) Na 30 , Mg 32 ( n , γ ) Mg 33 , and Al 34 ( n , γ ) Al 35 . The reaction cross sections were inferred indirectly through Coulomb dissociation of Na 29 , 30 , Mg 33 , and Al 35 at incident projectile energies around 400–430 A MeV using the FRS-LAND setup at GSI, Darmstadt. The neutron capture cross sections were obtained from the photoabsorption cross sections with the aid of the detailed balance theorem. The reaction rates for the neutron-rich Na, Mg, Al nuclei at typical r -process temperatures were obtained from the measured ( n , γ ) capture cross sections. The measured neutron capture reaction rates of the neutron-rich nuclei, Na 28 , Na 29 , and Al 34 are significantly lower than those predicted by the Hauser-Feshbach decay model. A similar trend was observed earlier for C 17 and N 19 but in the case of C 14 ( n , γ ) C 15 the trend is opposite. The situation is more complicated when the ground state has a multi-particle-hole configuration. For Mg 32 , the measured cross section is about 40 – 90 % higher than the Hauser-Feshbach prediction.

HARM3D+NUC: A New Method for Simulating the Post-merger Phase of Binary Neutron Star Mergers with GRMHD, Tabulated EOS, and Neutrino Leakage

Abstract The first binary neutron star merger has already been detected in gravitational waves. The signal was accompanied by an electromagnetic counterpart including a kilonova component powered by the decay of radioactive nuclei, as well as a short γ-ray burst. In order to understand the radioactively powered signal, it is necessary to simulate the outflows and their nucleosynthesis from the post-merger disk. Simulating the disk and predicting the composition of the outflows requires general relativistic magnetohydrodynamical (GRMHD) simulations that include a realistic, finite-temperature equation of state (EOS) and self-consistently calculating the impact of neutrinos. In this work, we detail the implementation of a finite-temperature EOS and the treatment of neutrinos in the GRMHD code HARM3D+NUC, based on HARM3D. We include formal tests of both the finite-temperature EOS and the neutrino-leakage scheme. We further test the code by showing that, given conditions similar to those of published remnant disks following neutron star mergers, it reproduces both recombination of free nucleons to a neutron-rich composition and excitation of a thermal wind.

Relativistic Fock space coupled-cluster study of bismuth electronic structure to extract the Bi nuclear quadrupole moment

We report the value of the electric quadrupole moment of $^{209}$Bi extracted from the atomic data. For this, we performed electronic structure calculations for the ground $^4S^o_{3/2}$ and excited $^2P^o_{3/2}$ states of atomic Bi using the Dirac-Coulomb-Breit Hamiltonian and the Fock space coupled cluster method with single, double, and full triple amplitudes for the three-particle Fock space sector. The value of the quadrupole moment of $^{209}$Bi, $Q(^{209}$Bi$)=-418(6)$~mb, derived from the resulting electric field gradient values and available atomic hyperfine splittings is in excellent agreement with molecular data. Due to the availability of the hyperfine constants for unstable isotopes of Bi, current atomic calculation allows also to correct their quadrupole moments.

Description of elastic scattering induced by the unstable nuclei 9,10,11,13,14C * *Supported by the National Natural Science Foundation of China (11405099, 11575291, 12065003), Scientific and Technological Innovation Programs of Higher Education Institutions (STIP) in Shanxi of China (2019L0743) and Science Foundation for General in Shanxi of China (201901D111317). This work is also supported by the Open Project of Guangxi Key

The elastic-scattering angular distributions and total reaction cross sections of projectiles were predicted using the obtained and global optical model potentials, respectively. The predictions were analyzed in detail by comparison with the available experimental data. The results indicate that the and global optical model potentials provide a satisfactory description of the elastic scattering data for the reactions induced by the . For the neutron-rich carbon isotope , the elastic scattering can be well described by changing the real part radius parameter of the global optical model potential. Possible physical explanations for the observed differences are further discussed.

Systematic study of two-proton radioactivity with a screened electrostatic barrier * *Supported in part by the National Natural Science Foundation of China (11205083, 11505100, 11705055), the Construct Program of the Key Discipline in Hunan Province, the Research Foundation of Education Bureau of Hunan Province, China (18A237), the Natural Science Foundation of Hunan Province, China (2018JJ3324), the Innovation Group of Nuclear

In this study, a phenomenological model is proposed based on Wentzel-Kramers-Brillouin (WKB) theory and applied to investigate the two-proton ( ) radioactive half-lives of nuclei near or beyond the proton drip line. The total diproton-daughter nucleus interaction potential is composed of the Hulthen-type electrostatic term and the centrifugal term. The calculated radioactive half-lives can accurately reproduce the existing 10 experimental datasets of five true radioactive nuclei with σ = 0.736. In addition, we extend this model to predict the half-lives of possible radioactive nuclei whose radioactivity is energetically allowed or observed but not yet quantified in NUBASE2016. The predicted results are in agreement with those obtained using the Gamow-like model, generalized liquid drop model, Sreeja formula, and Liu formula.

Theoretical Calculations of the Cross-sections for (n,α) and (n,xα) reactions on the Structural Material for Fusion Reactor 46-50Ti

The biggest problem of structural materials for fusion reactor is the damage caused by the fusion product neutrons to the structural material. If this problem is overcomed, an important milestone will be left behind in fusion energy. One of the important problems of the structural material is that nuclei forming the structural material interacting with fusion neutrons are transmuted to stable or radioactive nuclei via (n, x) (x; alpha, proton, gamma etc.) reactions. In particular, the concentration of helium gas in the structural material increases through deuteron- tritium (D-T) and (n, α) reactions, and this increase significantly changes the microstructure and the properties of the structural materials. Therefore, in this study, the effects of the different nuclear level density models on the excitation functions of the (n, α) reactions on 46-50Ti isotopes, an attractive candidate for the structural material for fusion reactors, have been investigated for the first time. Also, the differential cross-sections with respect to alpha energy for the emission of alpha particles of the 46-50Ti (n, xα) reactions have been investigated at 14.1 MeV incident neutron energy. The calculations are performed using the two-component exciton model in the TALYS 1.9 code, and the results are compared with available experimental data. The results of this study will contribute to nuclear database as required for improving, design and operations of the important facilities as ITER (International Thermonuclear Experimental Reactor), DEMO (The demonstration power plant) and ENS (European Nuclear Society).

Radioactive Planet Formation

Abstract Young stellar objects are observed to have large X-ray fluxes and are thought to produce commensurate luminosities in energetic particles (cosmic rays). This particle radiation, in turn, can synthesize short-lived radioactive nuclei through spallation. With a focus on 26Al, this paper estimates the expected abundances of radioactive nuclei produced by spallation during the epoch of planet formation. In this model, cosmic rays are accelerated near the inner truncation radii of circumstellar disks, r X ≈ 0.1 au, where intense magnetic activity takes place. For planets forming in this region, radioactive abundances can be enhanced over the values inferred for the early solar system (from meteoritic measurements) by factors of ∼10−20. These short-lived radioactive nuclei influence the process of planet formation and the properties of planets in several ways. The minimum size required for planetesimals to become fully molten decreases with increasing levels of radioactive enrichment, and such melting leads to loss of volatile components, including water. Planets produced with an enhanced radioactive inventory have significant internal luminosity, which can be comparable to that provided by the host star; this additional heating affects both atmospheric mass loss and chemical composition. Finally, the habitable zone of red dwarf stars is coincident with the magnetic reconnection region, so that planets forming at those locations will experience maximum exposure to particle radiation and subsequent depletion of volatiles.

Kilonovae Across the Nuclear Physics Landscape: The Impact of Nuclear Physics Uncertainties on r-process-powered Emission

Abstract Merging neutron stars produce “kilonovae”—electromagnetic transients powered by the decay of unstable nuclei synthesized via rapid neutron capture (the r-process) in material that is gravitationally unbound during inspiral and coalescence. Kilonova emission, if accurately interpreted, can be used to characterize the masses and compositions of merger-driven outflows, helping to resolve a long-standing debate about the origins of r-process material in the Universe. We explore how the uncertain properties of nuclei involved in the r-process complicate the inference of outflow properties from kilonova observations. Using r-process simulations, we show how nuclear physics uncertainties impact predictions of radioactive heating and element synthesis. For a set of models that span a large range in both predicted heating and final abundances, we carry out detailed numerical calculations of decay product thermalization and radiation transport in a kilonova ejecta with a fixed mass and density profile. The light curves associated with our models exhibit great diversity in their luminosities, with peak brightness varying by more than an order of magnitude. We also find variability in the shape of the kilonova light curves and their color, which in some cases runs counter to the expectation that increasing levels of lanthanide and/or actinide enrichment will be correlated with longer, dimmer, redder emission.

Binary and Ternary Fragmentation Analysis of 252Cf Nucleus using Different Nuclear Radii

Pioneering study reveals that a radioactive nucleus may split into two or three fragments and the phenomena are known as binary fission and ternary fission respectively. In order to understand the nuclear stability and related structure aspects, it is of huge interest to explore the fragmentation behavior of a radioactive nucleus in binary and ternary decay modes. In view of this, Binary and ternary fission analysis of 252Cf nucleus is carried out using quantum mechanical fragmentation theory (QMFT). The nuclear potential and Coulomb potential are estimated using different versions of radius vector. The fragmentation structure is found to be independent to the choice of fragment radius for binary as wellas ternary decay paths. The deformation effect is included up to quadrupole (β2) with optimum cold orientations and their influence is explored within binary splitting mode. Moreover, the most probable fission channels explore the role of magic shell effects in binary and ternary fission modes.

The $^{135}$Cs(n,$\gamma$) cross section at 30 and 500 keV

The neutron capture cross section of the unstable isotope $^{135}$Cs was measured relative to that of gold by means of the activation method. The sample was produced by ion implantation in a high resolution mass separator and irradiated with quasi-monoenergetic neutrons at 30 keV and 500 keV, using the $^{7}$Li(p,n)$^{7}$Be reaction. After the irradiations at the above energies, one more irradiation with thermal neutrons was used for defining the sample mass and for measuring the half-life of $^{136}$Cs. The neutron capture cross section was determined as 164 $\pm$ 10 mbarn and 34.8 $\pm$ 3.0 mbarn at 30 keV and 500 keV, respectively, and were used to normalize the theoretically derived cross section shape.

Numerical Solution of Radioactive Core Decay Activity Rate of Actinium Series Using Matrix Algebra Method

The Actinium 235 series is one of the radioactive series which is widely used as a raw material for reactors and nuclear activities. The existence of this series is found in several countries such as West USA, Canada, Australia, South Africa, Russia, and Zaire. The purpose of this study was to determine the activity value and the number of radioactive nucleus decay atoms on the actinium 235 rendered in a very long decay time of 4.3 x 109 years. The decay count in this study uses an algebraic matrix method to simplify the chain decay solution, which generally uses the concept of differential equations. The solution using this method can be computationally simulated using the Matlab program. This study indicates that the value of the decay activity experienced by each element in this series is the same, which is equal to 2,636 x 1011 Bq. This condition causes the actinium 235 series to experience secular equilibrium because the half-life of the parent nuclide is greater than the nuclide derivatives. The decay activity of the radioactive nucleus under the actinium 235 series is strongly influenced by the half-life of the nuclides, the decay constants, and the number of atoms after decay

Direct measurement of the resonance strengths and branching ratios of low-energy (p, γ) reactions on Mg isotopes * *Supported by the National Natural Science Foundation of China (11490563, 11961141003) and the Continuous Basic Scientific Research Project (WDJC-2019-13)

Proton capture reactions on Mg isotopes are significant in the Mg-Al cycle in stellar H-burning. In particular, the resonance strengths and branching ratios of low-energy resonances in 25Mg( )26Al reactions determine the production of 26Al, which is one of the most important long-lived radioactive nuclei in nuclear astrophysics. In this article, we report our first experiment using the intense proton beam of approximately 2 mA provided by the JUNA accelerator ground laboratory and a new technique that can minimize the composition change of targets under intense beam irradiation. The resonance strengths and branching ratios of E = 214, 304, and 326 keV resonances in the reactions of 24Mg( )25Al, 25Mg( )26Al, and 26Mg( )27Al, respectively, were measured with high accuracy. The success of this experiment provides a good calibration for the nuclear astrophysical experiment at the Jinping underground laboratory.

Correlation in formation of 8Be nuclei and α-particles in fragmentation of relativistic nuclei

In the events of peripheral dissociation of relativistic nuclei in the nuclear track emulsion, it is possible to study the emerging ensembles of He and H nuclei, including those from decays of unstable 8Be and 9B nuclei, as well as the Hoyle state. These extremely short-lived states are identified by invariant masses calculated from the angles in 2α-pairs, 2αp- and 3α-triplets in the approximation of conservation of momentum per nucleon of the primary nucleus. In the same approach, it is possible to search for more complex states. This paper explores the correlation between the formation of 8Be nuclei and the multiplicity of accompanying α-particles in the dissociation of relativistic 16O, 22Ne, 28Si, and 197Au nuclei. On the above basis, estimates of this correlation are presented for the unstable 9B nucleus and the Hoyle state. The enhancement in the 8Be contribution to dissociation with the α-particle multiplicity has been found. Decays of 9B nuclei and Hoyle states follow the same trend.