Radioactive Nuclei Research Articles

Unveiling radii and neutron skins of unstable atomic nuclei via nuclear collisions

Total reaction, interaction, and charge-changing cross sections, which are kinds of cross sections standing for total nuclear collision probability in medium-to high-energy region from a few to several hundred MeV, have been extensively utilized to probe nuclear sizes especially for unstable nuclei. In this mini review, experimental techniques and recent findings from these cross sections are briefly overviewed. Additionally, two new methods to extract neutron skin thickness solely from the above cross sections are explained: One is utilizing the energy and isospin dependence of the total reaction cross sections, and the other is the combination of the total reaction and charge-changing cross section measurements.

Monitoring partially observed average kiloelectron-volt emissions using exponentially weighted moving average chart

The average lifespan of particles is a key parameter in nuclear physics, critical for identifying different particle types. Modern particle detectors are highly effective at detecting the arrival of individual radioactive nuclei and observing their decay events. However, challenges arise when matching arrivals with departures, especially when departures are only partially observed. One inefficient approach involves conducting experiments with very low arrival rates to facilitate matching. The kiloelectron-volt E(keV) emission is obtained during this radioactive process. We propose a Modified Distance Weighted Exponentially Weighted Moving Average (MDE) control chart for monitoring kiloelectron-volt E(keV) data. Control charts are vital in quality control, offering real-time insights into process stability by distinguishing between normal (common-cause) and unusual (special-cause) variations. This capability enables precise decision-making, showing when a process is within control or requires intervention, thus preventing unnecessary adjustments and costly errors. By highlighting trends and shifts, control charts foster continuous improvement, identifying areas where processes can be optimized. The proposed control chart is developed for Weibull lifetimes under type-I censoring. For constructing an efficient control charting structure, we employed the conditional median (CM) methods. The goal is to detect changes in the mean of Weibull lifetimes with censored data under both known and estimated parameter conditions. The performance of the proposed MDE chart is evaluated by the average run length (ARL). Besides a simulation study, a real-life data set on kiloelectron-volt E(keV) related to the alpha decays of the 177 Lutetium isotope is also discussed. It is observed that the proposed chart is more efficient than existing control charts for monitoring kiloelectron-volt E(keV) censored data.

High-temperature 205Tl decay clarifies 205Pb dating in early Solar System

Radioactive nuclei with lifetimes on the order of millions of years can reveal the formation history of the Sun and active nucleosynthesis occurring at the time and place of its birth1,2. Among such nuclei whose decay signatures are found in the oldest meteorites, 205Pb is a powerful example, as it is produced exclusively by slow neutron captures (the s process), with most being synthesized in asymptotic giant branch (AGB) stars3–5. However, making accurate abundance predictions for 205Pb has so far been impossible because the weak decay rates of 205Pb and 205Tl are very uncertain at stellar temperatures6,7. To constrain these decay rates, we measured for the first time the bound-state β− decay of fully ionized 205Tl81+, an exotic decay mode that only occurs in highly charged ions. The measured half-life is 4.7 times longer than the previous theoretical estimate8 and our 10% experimental uncertainty has eliminated the main nuclear-physics limitation. With new, experimentally backed decay rates, we used AGB stellar models to calculate 205Pb yields. Propagating those yields with basic galactic chemical evolution (GCE) and comparing with the 205Pb/204Pb ratio from meteorites9–11, we determined the isolation time of solar material inside its parent molecular cloud. We find positive isolation times that are consistent with the other s-process short-lived radioactive nuclei found in the early Solar System. Our results reaffirm the site of the Sun’s birth as a long-lived, giant molecular cloud and support the use of the 205Pb–205Tl decay system as a chronometer in the early Solar System.

In vitro and in vivo study of 221Fr and 213Bi progeny release from the 225Ac-labelled TiO2 nanoparticles

BackgroundTargeted alpha therapy (TAT) is an effective option for cancer treatment. To maximize its efficacy and minimize side effects, carriers must deliver radionuclides to target tissues. Most of the nuclides used in TAT decay via the alpha cascade, producing several radioactive daughter nuclei with sufficient energy to escape from the original carrier. Therefore, studying these daughter atoms is crucial in the search for new carriers. Nanoparticles have potential as carriers due to their structure, which can prevent the escape of daughter atoms and reduce radiation exposure to non-target tissues. This work focuses on determining the released activity of 221Fr and 213Bi resulting from the decay of 225Ac labelled TiO2 nanoparticles. ResultsLabelling of TiO2 nanoparticles has shown high sorption rates of 225Ac and its progeny, 221Fr and 213Bi, with over 92 % of activities sorbed on the nanoparticle surface for all measured radionuclides. However, in the quasi-dynamic in vitro system, the released activity of 221Fr and 213Bi is strongly dependent on the nanoparticles concentration, ranging from 15 % for a concentration of 1 mg/mL to approximately 50 % for a nanoparticle concentration of 10 μg/mL in saline solution. The released activities of 213Bi were lower, with a maximum value of around 20 % for concentrations of 0.05, 0.025, and 0.01 mg/mL. The leakage of 225Ac and its progeny was tested in various biological matrices. Minimal released activity was measured in saline at around 10 % after 48 h, while the maximum activity was measured in blood serum and plasma at 20 %. The amount of 225Ac released into the media was minimal (<3 %). The in vitro results were confirmed in a healthy mouse model. The difference in %ID/g was clearly visible immediately after dissection and again after 6 h when 213Bi reached equilibrium with 225Ac. ConclusionThe study verified the potential release of 225Ac progeny from the labelled TiO2 nanoparticles. Experiments were performed to determine the dependence of released activity on nanoparticle concentration and the biological environment. The results demonstrated the high stability of the prepared 225Ac@TiO2 NPs and the potential release of progeny over time. In vivo studies confirmed our hypothesis. The data obtained suggest that the daughter atoms can escape from the original carrier and follow their own biological pathways in the organism.

JWST/NIRSpec WIDE survey: a z = 4.6 low-mass star-forming galaxy hosting a jet-driven shock with low ionization and solar metallicity

ABSTRACT We present NIRSpec/micro-shutter assembly observations from the JWST large-area survey WIDE, targeting the rest-frame UV–optical spectrum of Ulema, a radio-active galactic nucleus host at redshift $z=4.6348$. The low-resolution prism spectrum displays high equivalent width nebular emission, with remarkably high ratios of low-ionization species of oxygen, nitrogen, and sulphur, relative to hydrogen; auroral O$^+$ emission is clearly detected, possibly also C$^+$. From the high-resolution grating spectrum, we measure a gas velocity dispersion of $\sigma \sim 400$$\mathrm{km\, s^{-1}}$, broad enough to rule out star-forming gas in equilibrium in the gravitational potential of the galaxy. Diagnostics based on emission-line ratios suggest that the nebular emission is due to a shock which ran out of pre-shock gas. To infer the physical properties of the system, we model simultaneously the galaxy spectral energy distribution and shock-driven line emission under a Bayesian framework. We find a relatively low-mass, star-forming system ($M_\star = 1.4 \times 10^{10}~{\rm M}_\odot$, $\mathrm{SFR} = 70~{\rm M}_\odot ~{\rm yr^{-1}}$), where shock-driven emission contributes 50 per cent to the total H β luminosity. The nebular metallicity is near solar – three times higher than that predicted by the mass–metallicity relation at $z=4.6$, possibly related to fast-paced chemical evolution near the galaxy nucleus. We find no evidence for a recent decline in the star-formation rate of the galaxy, meaning that, already at this early epoch, fast radio-mode active galactic nucleus feedback was poorly coupled with the bulk of the star-forming gas; therefore, most of the feedback energy must end up in the galaxy halo, setting the stage for future quenching.

Investigating the average kiloelectron-volt emission of partially observed events in nuclear physics through distance weighted mean based censored control chart.

The average lifespan of particles, a crucial parameter in nuclear physics, is essential for identification purposes. Modern particle detectors excel at recognizing individual radioactive nuclei arrivals and their subsequent decay events. However, challenges arise when matching arrivals with departures, especially when departures are only partially observed. One inefficient approach involves conducting experiments with very low arrival rates to facilitate matching. The kiloelectron-volt E(keV) emission is obtained during this radio active process. This study focuses on the meticulous surveillance of the average keV emission from partially observed events within the domain of nuclear physics. To accomplish this, the methodology employs the statistical approach known as Distance Weighted Mean (DWM), integrated with the application of censored control charts. The utilization of censored control charts allows for the effective management of incomplete data, enabling researchers to make informed decisions despite potential limitations in observation. We propose a DWM based exponentially weighted moving average-cumulative sum (DWM-EC) control chart for monitoring kiloelectron-volt E(keV) data. The proposed charts is developed for Weibull lifetimes under type-I censoring. For the construction of an efficient control charting structure, we employed the conditional median (CM) methods. The goal is to find changes in the mean of Weibull lifetimes with censored data with known and estimated parameter conditions. The performance of the proposed DWM-EC chart is evaluated by the average run length (ARL). Besides a simulation study, a real-life data set on E(keV) related to the alpha decays of 177 Lutetium isotope is also discussed.

γ‐Ray Driven Aqueous‐Phase Methane Conversions into Complex Molecules up to Glycine

AbstractFundamental understanding of initial evolutions of molecules in the universe is of great interest and importance. CH4 is one of the abundant simple molecules in the universe. Herein we report γ‐ray, high‐energy photons commonly existing in cosmic rays and unstable isotope decay, as an external energy to efficiently drives aqueous‐phase CH4 conversions to various products with the presence of oxygen at room temperature. Glycine also forms with an additional introduction of ammonia. Both CH4 conversions and product distributions are modified by solid granules, and a CH3COOH selectivity as high as 82 % is obtained when SiO2 is added. Our results point to γ‐ray driven aqueous‐phase CH4 conversions as a likely formation network of initial complex organic compounds in the universe and offer an alternative strategy for efficiently utilizing CH4 as the carbon source to produce value‐added products at mild conditions, a long‐standing challenging task in heterogeneous catalysis.

Magnetically Aligned Grains as a Ubiquitous Source of Spin-polarized Electrons and Chiral-symmetry-breaking Agents

The unique biosignature of life on Earth is the homochirality of organic compounds, such as amino acids, proteins, and sugars. High-energy spin-polarized (spinup or spindown) electrons (SPEs) from the β decay of radioactive nuclei have been proposed as a source of symmetry breaking, leading to homochirality; however, their exact role is much debated. Here, we propose magnetically aligned dust grains as a new source of SPEs, due to the photoemission of electrons having aligned spins by the Barnett effect. For the interstellar UV radiation field of strength G UV, we find that the SPE emission rate is ΓpeSPE∼10−14GUV electrons per second per H, the fraction of spin-polarized to total photoelectrons is ∼10%, and the SPE yield (photoelectron number per UV photon) can reach ∼1%, using the modern theory of grain alignment. SPEs emitted from aligned grains could play an important role in chiral-induced spin-selectivity-driven reduction chemistry in the icy grain mantles, producing an enantiomer excess of chiral molecules formed on the grain mantle. Finally, we suggest magnetically aligned grains could directly impact the enantio-selectivity through the chiral-induced spin-selective adsorption effect and exchange interaction. We estimate the disalignment of electron spins and depolarization by elastic scattering using the Mott theory and find that these effects are negligible for low-energy SPEs, so that the spins of SPEs remain well aligned during their journey through dust grains and the gas. Our proposed mechanism might explain the chiral asymmetry of prebiotic molecules detected in numerous comets, asteroids, and meteorites.

The puzzle of suppression of nuclear level density in N ≈ Z Zn isotopes compared to N > Z

A systematic investigation of isospin dependence of nuclear level density (NLD) is performed for the Zn isotopes. Experimental level densities of 67Zn and 61Zn have been determined by analyzing the spectra of evaporated neutrons emitted from the excited 68Zn and 62Zn nuclei populated via 4He + 64Ni and 4He + 58Ni reactions, respectively. At the low excitation energies, the neutron spectra are predominantly contributed by the first-chance decay, leading to 67Zn and 61Zn as daughters for the two cases. A comparison of the present experimental data along with previously measured NLDs of 66Zn, 64Zn, and 60Zn is performed with state-of-the-art microscopic calculations. While the experimental NLDs of stable isotopes (i.e., 67Zn, 66Zn, and 64Zn) align excellently with theoretical predictions, a compelling contrast emerges for the unstable isotopes 61Zn and 60Zn, exhibiting NLDs an order of magnitude lower than predicted. The possible origins of the observed suppression of NLDs for the N ≈ Z isotopes are discussed. A significant reduction of level density for nuclei situated away from the stability line could have critical implications for the calculation of astrophysical reaction rates pertinent to heavy-element nucleosynthesis.

Production of neutron-rich nuclei in the vicinity of 78Ni: Fragmentation reactions of unstable 81Ga and 82Ge beams

The fragmentation reactions of neutron-rich unstable nuclei 81Ga and 82Ge at 250 MeV/nucleon have been studied in order to search the optimal mean for the production of very neutron-rich nuclei in the vicinity of 78Ni. The newly measured cross sections were compared with various calculations, showing a good agreement with EPAX3.01. The present work provides experimental insights into the two-step scheme—fragmentation following fission—as a method to produce very neutron-rich nuclei through a combination of ISOL and fragmentation of post-accelerated beams of unstable nuclei. Our results enable an evaluation of the potential of the two-step scheme in the production of very neutron-rich nuclei for the 78Ni region. The two-step scheme using fragmentation of a post-accelerated 81Ga beam could be an option to produce neutron-rich nuclei around 78Ni when the 81Ga beam intensity reaches 1.0×108 pps, compared to the one-step scheme with fission of 238U.

Monitoring kiloelectron-volt emission variability in partially observed nuclear events through distance weighted censored control charts

The variation in the lifespan of particles is a crucial parameter in nuclear physics and is essential for identification purposes. Modern particle detectors excel at recognizing individual radioactive nuclei arrivals and their subsequent decay events. However, challenges arise when matching arrivals with departures, especially when departures are only partially observed. One inefficient approach involves conducting experiments with very low arrival rates to facilitate matching. The kiloelectron-volt E(keV) emission is obtained during this radio active process. This study focuses on the meticulous surveillance of the standard deviation in keV emission from partially observed events within the domain of nuclear physics.The utilization of censored control charts allows for the effective management of incomplete data, enabling researchers to make informed decisions despite potential limitations in observation. To accomplish this, the methodology employs the statistical approach known as Distance Weighted Mean based Standard Deviation (DWMS) integrated with the application of censored control charts. We propose a DWMS based exponentially weighted moving (DWMS-E) control chart for monitoring kiloelectron-volt E(keV) data. The proposed charts is developed for Weibull lifetimes with type-I censored data. The goal is to find changes in the mean of Weibull lifetimes with known and estimated parameter conditions. The performance of the proposed DWMS-E chart is evaluated by the average run length (ARL). Besides a simulation study, a real-life data set on E(keV) related to the alpha decays of 177 Lutetium isotope is also discussed.

Static or dynamic pear shapes in radioactive nucleus 224Rn?

We report a comprehensive study on low-lying parity doublet states of 224Rn by mixing both quadrupole- and octupole-shaped configurations in multireference covariant density functional theory, in which broken symmetries in configurations are restored using projection techniques. The low-lying energy spectrum is reasonably reproduced when the shape fluctuations in both the quadrupole and octupole shapes are considered. Electric octupole transition strength in 224Rn is found to be B(E3;31-→01+)=43\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B(E3; 3^-_1 \\rightarrow 0^+_1)=43$$\\end{document} W.u., comparable to that in 224Ra, whose data are 42(3) W.u.. Our results indicate that 224Rn shares similar low-energy structure with 224Ra despite the excitation energy of first 3-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$3^-$$\\end{document} state of the former nucleus is higher than that of the latter. This study suggests 224Rn is a candidate for the search for permanent electric dipole moment.

Simplified efficiency calibration methods for scintillation detectors used in nuclear remediation

Our study introduces innovative methods to address waste reduction and enhance resource efficiency in nuclear cleanup processes. We focus on sustainable nuclear technology, aligning with goals for cleaner production and environmental protection. We developed two novel methods, termed “oversimplified” and “simplified,” for easily determining the photopeak efficiency of NaI(Tl) scintillation detectors. These methods, along with a “general” solution method, were validated with calibrated radioactive sources such as 241Am, 57Co, 133Ba, 137Cs, and 60Co, and were used to commission a NaI(Tl) scintillation detector system at Chalk River Laboratories (CRL) for nuclear remediation. The system demonstrated high accuracy, making it suitable for screening unstable isotopes at contaminated sites. This screening tool significantly reduces the number of soil samples requiring detailed characterization, thereby lowering operational costs. The NaI(Tl) detector system was calibrated for near-contact geometry, which is commonly used at CRLs. Detection limits were established for this configuration. By improving the efficiency calibration of scintillation detectors, our study advances sustainable nuclear remediation practices, promoting environmental sustainability and cleaner production processes.

Nuclear contacts of unstable nuclei

Nuclear contact is a key quantity to describe the nucleon-nucleon short-range correlations (SRCs). While they have been determined by electron scattering experiments for selected stable nuclei, nuclear contacts are largely unknown for unstable nuclei. In this work, we study nuclear contacts for a number of nuclei in the vicinity of the doubly magic 132Sn from the theoretical perspective, with special emphasis on unstable nuclei. We find that the proton-proton contact generally gets suppressed by the excess neutrons for the Sn isotopes, resembling the suppression of α-cluster formation reported recently for the same isotopic chain (J. Tanaka et al., 2021 [46]). This might suggest a hidden universal aspect of SRCs and α clustering, two different kinds of nuclear correlations. Moreover, we reveal a model-independent correlation between the proton-proton contact and the root-mean-square radius of proton density distributions for Sn isotopes. Meanwhile, a linear relation is found between the proton-proton contact and the proton number for the N=82 isotones. Our results can be helpful for future experimental studies of SRCs in unstable nuclei at advanced facilities worldwide.

Design and commissioning of the ISOL beamline at the RAON facility

The Rare isotope Accelerator complex for ON-line experiment (RAON) located at the Daejeon site of the Institute for Basic Science (IBS) is the first Radioactive Isotope (RI) beam facility in Korea. The RAON facility employs an in-flight method using RI beams produced using an Isotope Separator On-Line (ISOL) method to explore unstable nuclei in uncharted regions. A high-power ISOL facility is critical for providing the required high-quality, intense RI beams. The design, construction, and installation of the ISOL system have been completed, and the beam transport line commissioning with stable isotope beams has been conducted. As a result, all requirements, such as the transmission and the mass-resolving power, for the beamlines were satisfied, and the beams from the Target Ion Source (TIS) were transported to the end of the ISOL beamline, which is the entrance to the superconducting linear accelerator system. The ISOL beamline is now ready for the transport of RI beams.

Cryptography with stochastic photons

Quantum cryptography protocols are based on the use of quantum objects with at least two orthogonal states, for example, the polarization states of a photon. We propose a completely different cryptography protocol using a stochastic flow of single photons. Our method is based on the stochastic decay of an ensemble of radioactive nuclei randomly emitting a stream of γ-photons. We have experimentally demonstrated the transmission of classical information containing binary bits. Reading this information requires precise knowledge of the repetition rate of its sending. Otherwise, it is impossible to make the transmitted information visible, since it will be lost in the noise.

Electroweak Nuclear Properties from Single Molecular Ions in a Penning Trap.

We present a novel technique to probe electroweak nuclear properties by measuring parity violation (PV) in single molecular ions in a Penning trap. The trap's strong magnetic field Zeeman shifts opposite-parity rotational and hyperfine molecular states into near degeneracy. The weak interaction-induced mixing between these degenerate states can be larger than in atoms by more than 12 orders of magnitude, thereby vastly amplifying PV effects. The single molecule sensitivity would be suitable for applications to nuclei across the nuclear chart, including rare and unstable nuclei.

Signal processing analysis for detection of anomalies in numerical series

It might be instinctively assumed that the occurrence of the first digit of a randomly selected number is uniformly distributed among 1 to 9. However, the Newcomb–Benford law (NBL), also known as the first-digit law or Benford’s law, reveals a completely different fact: the distributions follows a logarithm-type law. This bias in the frequency of occurrence of the leading digits of numbers is evident in everything from the lengths of rivers, the areas of countries, stock prices, and population numbers. Omnipresence of NBL emerges in mathematics (the Fibonacci sequence, the distribution of prime numbers, etc.) and also in the field of physics (i.e. the half-lives of unstable nuclei). From the earliest years, a large bibliography has been developed and applied to many fields such as fraud detection in finances, international trade and election results analysis. Usually, the diagnosis of such works is reduced to a qualitative binary assessment (conformity or non-conformity). The present paper aims to establish a supervised methodology to address existing gaps and enhance the reliability of final decisions. These gaps include uncertainty about the minimum data volume required to validate Benford’s Law, the low sensitivity of current metrics (Euclidean distance or Mean Absolute Difference) to detect minor levels of adulteration, and the need to quantify both the level and nature of adulteration. Two new procedures have been established coming from Signal Analysis and Processing theory. The first relates the deconvolution between the empirical leading digit distribution and the Benford one. The second procedure consists of obtaining the generating functions (via Hilbert and Fourier transforms) to increase the contrast between both functions: the empirical under research and Benford’s as the reference. Based on calibrated datasets, we are able to quantify the magnitude of accidental errors or malicious fraud adulteration and make the discrimination between both. Finally, as benchmark, fifteen real-world datasets were studied. This study shows that most of datasets are suspicious of Fraud. Notably, in the field of human health, several datasets demonstrate significant fraudulent deviations, defying conventional patterns of fraud and error. This phenomenon has been termed Berserker Fraud.

Simulations on the performances of neutron shielding glass materials and secondary radiation risks

Glasses with neutron shielding properties are extremely important for nuclear industries. Neutron interactions with ten different neutron shielding glass types were simulated by using GEANT4 Monte Carlo simulation toolkit. Simulation results were evaluated in terms of shielding performances, deposited energy properties and produced secondary radiation. Important evaluations were made in view of radiation safety, especially on secondary particles and radioactivity resulting from interactions between neutrons and glass samples. All simulated glass samples were found to emit risky secondary particles and radioactive nuclei after interacting with fast neutrons.

Determination of the type of radioactive nuclei and gamma spectrometry analysis for radioactive sources

Determining the type of radioactive nuclei is the second activity after the inventory of radioactive waste in Kosovo, their location and the number of radioactive sources. Before starting any type of radioactive waste action, it is necessary to determine the content of their activity, the type of radioisotope, physical and chemical form and the risks associated with their management. The realization of this is achieved as a combination of quality assurance processes, the inventory of the radioisotope and its activity that is present in the waste, the composition of the waste material and direct measurements. This serious activity was carried out entirely in the field and was undertaken due to the lack of source certification or any other indication of their classification and activity. The process of determining the type of radioactive nuclei helps to realize a more effective characterization of them as well as to determine the path of waste management. The probability that a gamma radiation detector interacts with it to produce a pulse represents the effectiveness of the detector.