Decay Half-lives Research Articles

Delving into uncharted isotones demonstrating neutron shell closure at N=126

In our research, we have extensively investigated various decay modes including alpha, beta, proton, and spontaneous fission decay modes, focusing particularly on isotones characterized by [Formula: see text] and Z spanning from 53 to 100. Alpha-decay, one and two proton-decay half-lives were evaluated using an effective liquid drop model. Beta-decay and spontaneous fission half-lives have been evaluated using semi-empirical formulae. We observed notably shorter [Formula: see text] half-lives within the Z range of 53 to 81 and [Formula: see text]Pb is observed to be more stable. The prevalence of [Formula: see text]-decay half-lives was prominent for Z values ranging from 83 to 98, with the exception of [Formula: see text]At nuclei. Moreover, we identified two spontaneous fission emitters exhibiting half-lives ranging from microseconds to nanoseconds. Our analysis revealed significant neutron shell gaps at [Formula: see text], 66, 82 and 98 for [Formula: see text], pronounced shell structure indicative of relatively stable nuclei. Additionally, certain nuclei such as [Formula: see text]I, [Formula: see text]Au and [Formula: see text]U were found to exhibit lower stability compared to their neighboring nuclei. Our investigation led to the identification of 29 new isotones, comprising 22 [Formula: see text] emitters, five [Formula: see text] emitters and two spontaneous emitters. These newly identified isotones, synthesizable through fusion reactions, significantly contribute to advancing our comprehension of nuclear decay processes and isotonic behavior with [Formula: see text].

-decay half-life predictions with support vector machine

In this study, we investigate the application of support vector machines utilizing a radial basis function kernel for predicting nuclear -decay half-lives. Our approach integrates a comprehensive set of physics-derived features, including characteristics derived from nuclear structure, to systematically evaluate their impact on predictive accuracy. In addition to traditional parameters such as proton and neutron numbers, as well as terms based on the liquid drop model (e.g., volume, surface, Coulomb features), we incorporate decay energies and orbital angular momentum quantum numbers for both parent and daughter nuclei. Our analysis of 2232 nuclear data points demonstrates that the use of the radial basis function kernel yields predictive models with root mean square errors of 0.819 (for set1) and 0.352 (for set2), aligning with results obtained from comparable machine learning methodologies. Furthermore, Shapley additive explanations values highlight the predominant role of parent nuclei in predicting -decay half-lives within the support vector machines. These results highlight the effectiveness of machine learning in nuclear structure research, opening up new possibilities for predicting the -decay half-lives of previously unstudied nuclei.

Enhanced empirical formulas for α-decay for heavy and superheavy nuclei: Incorporating deformation effects of daughter nuclei

Abstract The latest experimental data of $\alpha$-decay half-lives for 573 nuclei within the range of $52 \leq Z \leq 118$ have been utilized to enhance empirical formulas with updated coefficients. These formulas were enhanced by analyzing the contributions of orbital angular momentum and isospin asymmetry. The effect of deformation of daughter nuclei on the $\alpha$-decay half-life is modeled by incorporating two additional terms, dependent on the quadrupole and hexadecapole deformation parameters, into the empirical formulas for $\alpha$-decay half-lives. Incorporating these deformation-dependent terms, along with angular momentum and isospin asymmetry, improved the standard deviation by approximately $17\%$. The revised empirical formulas for $\alpha$-decay half-lives demonstrated better agreement with experimental data when deformation factors were included. Validation of the modified formulas was conducted through comparisons with recent experimental results and further theoretical predictions. This study presents and compares $\alpha$-decay half-life predictions for several isotopes of superheavy nuclei with $Z = 120-126$, which are yet to be experimentally synthesized. For various isotopes of each element, the variation of $\log_{10} T_{\alpha}$ with changes in neutron number is also explored.

Noise-aware dynamic image denoising and positron range correction for Rubidium-82 cardiac PET imaging via self-supervision

Rubidium-82 (82Rb) is a radioactive isotope widely used for cardiac PET imaging. Despite numerous benefits of 82Rb, there are several factors that limits its image quality and quantitative accuracy. First, the short half-life of 82Rb results in noisy dynamic frames. Low signal-to-noise ratio would result in inaccurate and biased image quantification. Noisy dynamic frames also lead to highly noisy parametric images. The noise levels also vary substantially in different dynamic frames due to radiotracer decay and short half-life. Existing denoising methods are not applicable for this task due to the lack of paired training inputs/labels and inability to generalize across varying noise levels. Second, 82Rb emits high-energy positrons. Compared with other tracers such as 18F, 82Rb travels a longer distance before annihilation, which negatively affect image spatial resolution. Here, the goal of this study is to propose a self-supervised method for simultaneous (1) noise-aware dynamic image denoising and (2) positron range correction for 82Rb cardiac PET imaging. Tested on a series of PET scans from a cohort of normal volunteers, the proposed method produced images with superior visual quality. To demonstrate the improvement in image quantification, we compared image-derived input functions (IDIFs) with arterial input functions (AIFs) from continuous arterial blood samples. The IDIF derived from the proposed method led to lower AUC differences, decreasing from 11.09% to 7.58% on average, compared to the original dynamic frames. The proposed method also improved the quantification of myocardium blood flow (MBF), as validated against 15O-water scans, with mean MBF differences decreased from 0.43 to 0.09, compared to the original dynamic frames. We also conducted a generalizability experiment on 37 patient scans obtained from a different country using a different scanner. The presented method enhanced defect contrast and resulted in lower regional MBF in areas with perfusion defects. Lastly, comparison with other related methods is included to show the effectiveness of the proposed method.

Cluster radioactivity of heavy elements within an improved Coulomb and Proximity potential model

The Coulomb and Proximity potential Model (CPPM) is improved by introducing an accurate empirical expression for the nuclear surface diffuseness parameter in the expression for the proximity potential. Within the improved CPPM, the decay half-lives of experimentally detected cluster emissions from heavy elements are calculated. The results of the calculations using the Universal Decay Law (UDL) [Qi et al., Phys. Rev. Lett. 103 (2009) 072501], the improved empirical formula of Sahu et al. (ImSahuB) [Wang et al., Chin. Phys. C 45 (2021) 044111], and the empirical formula of Horoi [J. Phys. G. Nucl. Part. Phys. 30 (2004) 945] are compared with the predictions of the improved CPPM. The lowest standard deviation is obtained for the predictions using the improved CPPM. The model’s predictive power increases significantly when the proximity potential is modified by including the diffuseness parameter. Furthermore, improved CPPM is employed to calculate the decay half-lives of undiscovered cluster emissions from heavy elements, a valuable information for upcoming experimental investigations. The calculated values are compared with the predictions of the UDL, Horoi formula and the improved empirical formula of Sahu et al. (ImSahuB). There is a high degree of agreement between the improved CPPM, UDL, and Horoi formula predictions. The ImSahuB formula predict decay half-life one or two order magnitudes lower than the predictions of the other models.

Calculation of α-decay half-lives of 186−218Po isotopes and actinide nuclei using a new phenomenological potential

This paper is devoted to the calculations of alpha decay half-lives of [Formula: see text]Po [Formula: see text] isotopes and actinide nuclei between the atomic numbers Z = 90 and Z = 102, using an energy-dependent potential model. The [Formula: see text]-nucleus effective potential employed in this study includes a Coulomb potential, a centrifugal barrier potential, and a nuclear potential. The nuclear potential is chosen to be the energy-dependent singularized harmonic potential, typical of nuclear interactions. The role of the energy-dependent potential is very significant in this study. Indeed, when compared to the experimental data, our results are found to be improved when energy-dependent interaction potential is employed compared to when energy-independent interactions are used, especially for small values of the parameter [Formula: see text] as evidenced by the values of the root mean square deviation.

Research on compound amidohydroxysulfobetaine foamer for high-temperature and high-salinity clastic reservoirs

A high-quality foaming agent should exhibit excellent solubility in formation water and strong foaming ability, while also meeting the requirements of stability under high-temperature and high-salinity conditions, as well as low adsorption capacity. This study explores the potential of amidohydroxysulfobetaine surfactant as a foaming agent in sandstone reservoirs under specific reservoir conditions of 110 ℃ and 25.0×104 mg/L salinity. The findings indicate that compounding EHSB with a small amount of LHSB to form LA13 significantly reduces the Krafft point of EHSB. Furthermore, LA13 demonstrates outstanding solubility in 25.0×104 mg/L brine and exhibits an overall adsorption capacity on quartz sand surfaces lower than 0.6 mg/g when its concentration is below 1.0 wt%. Performance evaluation of bulk foam for LA31 at concentrations ranging from 0.05 wt% to 0.4 wt% suggests that using a foaming agent concentration of 0.05 wt% results in relatively low foaming volume and foam decay half-life; however, consistent foaming performance is observed across other concentrations, leading to highly stable foam due to the compound system's higher surface dilational modulus being the primary factor contributing to foam stability. Flow experiments reveal that the foam generated in cores with permeabilities of 46.5 mD, 185.5 mD, 632.0 mD, and 2005.3 mD exhibits a high resistance factor when the concentration of LA13 exceeds 0.1 wt%, while also demonstrating commendable gas-channeling regulation capability. Therefore, it is recommended to use LA13 as a foaming agent for field applications when its concentration surpasses 0.1 wt%. Additionally, comparing the mobility of foam formed by concentrations of 0.1 wt% and 0.2 wt% LA13 in cores with varying permeabilities shows that LA13 exhibits selective mobility regulation specifically in cores with permeabilities lower than 632.0 mD.

Accessing the Characteristics of Nuclear Reactions: A Radioactive Decay and Half-Life Measurement Study

This study investigates the impact of external environmental factors, specifically electromagnetic fields and pressure variations, on the decay constants and half-lives of three radioactive isotopes: 60Co, 137Cs, and 226Ra. By conducting controlled laboratory experiments, the research aimed to quantify the extent to which these factors influence decay rates, challenging the traditional assumption of invariant half-lives. The isotopes were exposed to varying levels of electromagnetic fields (0-100 Gauss) and pressure (1-10 atm), with decay rates measured using high-resolution gamma-ray spectrometers. The results revealed that while 137Cs exhibited the most significant sensitivity, with a 13.04% increase in decay constant under extreme conditions, 60Co and 226Ra showed moderate and minimal changes, respectively. These findings have important implications for fields such as nuclear medicine, radiometric dating, and nuclear waste management, where precise knowledge of decay rates is crucial. The study contributes to a deeper understanding of nuclear decay processes and highlights the need for further research on the effects of other environmental factors, such as temperature and chemical composition, on radioactive decay.

An alpha decay study of superheavy nuclei within a Coulomb and proximity potential model including a Q-value dependent surface diffuseness parameter

Using the Coulomb and Proximity Potential Model (CPPM) and a Q-value dependent surface diffuseness parameter in the proximity potential, the alpha decay half-lives of 75 experimentally synthesized superheavy nuclei were determined. Comparisons are made between the obtained results and experimentally determined alpha decay half-lives, as well as the predictions of Yang et al.’s recent study [Nucl. Phys. A 1014 (2021) 122250], which is based on the Unified Fission Model (UFM) with a new preformation parameter. The lowest standard deviation of 0.621 is obtained for CPPM calculations with Q-value-dependent surface diffuseness parameter. The calculation is extended further to estimate the alpha decay half-lives [Formula: see text]119 and [Formula: see text]120 superheavy isotopes and compared with the predictions of UFM. Finally, the results of the calculations are compared to the predictions of the UDL formula [Phys. Rev. Lett. 103 (2009) 072501] and the modified Hutsukawa formula [Nucl. Part. Phys. Proc. 339 (2023) 92].

Hydroxysulfobetaine foamer for potential mobility control application in high-temperature and ultra-high salt reservoirs

A good foamer should have good solubility in the formation of water, strong foaming ability, and also meet the requirements of thermal stability and low adsorption capacity under high temperature and high salinity conditions. The foam properties of hydroxylsulfobetaine surfactant with different carbon chain lengths were measured at 130 °C, 30 MPa, and in brine with a salinity of 22 × 104 mg·L−1. The results showed that hydroxylsulfobetaine surfactant with long carbon chains exhibited strong foam stability, with foam decay half-lives reaching 13 days for 0.4 wt% EHSB (erucamide propyl hydroxysulfobetaine) and 2.9 days for 0.4 wt% HSB18 (octadecyl dimethyl hydroxypropyl sulfobetaine), respectively. Hydroxysulfobetaine surfactant with short carbon chains had a foam decay half-life of less than 10 h. Considering the poor thermal stability of EHSB at 130 °C, HSB18 was primarily chosen as the foamer. HSB18 and HSB12 (dodecyl dimethyl hydroxypropyl sulfobetaine) were combined in a ratio of 3:1 to form the compound hydroxysulfobetaine MHSB31, which demonstrated good solubility in saline solution with KP (Krafft point) lower than 30 °C. The evaluation, using different concentrations of MHSB31, showed that the foam decay half-life ranged from 88 h for 0.03 wt% MHSB31 compared to 42 h for 0.1 wt% MHSB31. The excellent foaming performance of the compound system is attributed to its high surface dilational modulus and the formation of wormlike micelles. The adsorption capacity test demonstrated that when the concentration was less than 1 wt%, the adsorption capacity of MHSB31 on quartz sand surface was less than 1 mg·g−1, satisfying oilfield requirements. The results of the flow experiment at 130 °C and 10 MPa, in brine with a salinity of 22 × 104 mg·L−1, show that when the concentration of MHSB31 is greater than 0.1 wt%, the foam formed in the core with permeability of 632 mD and 2005 mD has a higher apparent viscosity and resistance factor. Additionally, the relative mobility of the foam formed in the core with a permeability of 2005 mD is lower than that formed in the core with a permeability of 632 mD. This indicates a certain selective reduction effect on mobility. Due to the influence of ultimate capillary pressure, both foam resistance factor and apparent viscosity are lower for the 47 mD core injected with different concentrations of MHSB31 ranging from 0.05 wt% to 0.5 wt%. The evaluation data presented in this paper regarding bulk foam and flow foam, using hydroxysulfobetaine surfactant under high temperature, high pressure, and high salinity conditions, have significant guiding significance for selecting and applying foamers in reservoirs with such harsh conditions.

Impact of recent updates to neutrino oscillation parameters on the effective Majorana neutrino mass in 0νββ decay

We investigate how recent updates to neutrino oscillation parameters and the sum of neutrino masses influence the sensitivity of neutrinoless double-beta (0νββ) decay experiments. Incorporating the latest cosmological constraints on the sum of neutrino masses and laboratory measurements on oscillations, we determine the sum of neutrino masses for both the normal hierarchy (NH) and the inverted hierarchy (IH). Our analysis reveals a narrow range for the sum of neutrino masses, approximately 0.06 eV/c2 for NH and 0.102 eV/c2 for IH. Utilizing these constraints, we calculate the effective Majorana masses for both NH and IH scenarios, establishing the corresponding allowed regions. Importantly, we find that the minimum neutrino mass is nonzero, as constrained by the current oscillation parameters. Additionally, we estimate the half-life of 0νββ decay using these effective Majorana masses for both NH and IH. Our results suggest that upcoming ton-scale experiments will comprehensively explore the IH scenario, while 100-ton-scale experiments will effectively probe the parameter space for the NH scenario, provided the background index can achieve 1 event/kton-year in the region of interest. Published by the American Physical Society 2024

Controlling 229Th isomeric state population in a VUV transparent crystal

The radioisotope thorium-229 (229Th) is renowned for its extraordinarily low-energy, long-lived nuclear first-excited state. This isomeric state can be excited by vacuum ultraviolet (VUV) lasers and 229Th has been proposed as a reference transition for ultra-precise nuclear clocks. To assess the feasibility and performance of the nuclear clock concept, time-controlled excitation and depopulation of the 229Th isomer are imperative. Here we report the population of the 229Th isomeric state through resonant X-ray pumping and detection of the radiative decay in a VUV transparent 229Th-doped CaF2 crystal. The decay half-life is measured to 447(25) s, with a transition wavelength of 148.18(42) nm and a radiative decay fraction consistent with unity. Furthermore, we report a new “X-ray quenching” effect which allows to de-populate the isomer on demand and effectively reduce the half-life. Such controlled quenching can be used to significantly speed up the interrogation cycle in future nuclear clock schemes.

Measurement of the Isolated Nuclear Two-Photon Decay in ^{72}Ge.

The nuclear two-photon or double-gamma (2γ) decay is a second-order electromagnetic process whereby a nucleus in an excited state emits two gamma rays simultaneously. To be able to directly measure the 2γ decay rate in the low-energy regime below the electron-positron pair-creation threshold, we combined the isochronous mode of a storage ring with Schottky resonant cavities. The newly developed technique can be applied to isomers with excitation energies down to ∼100 keV and half-lives as short as ∼10 ms. The half-life for the 2γ decay of the first-excited 0^{+} state in bare ^{72}Ge ions was determined to be 23.9(6)ms, which strongly deviates from expectations.

Empirical relations for α -decay half-lives: The effect of deformation of daughter nuclei

The influence of the daughter nuclei deformations on the α decay's half-life is modeled by adding the term depending on the quadrupole deformation parameter value to the empirical relations for the α-decay half-lives. It is shown that the addition of the deformation-dependent term led to a better description of the experimental data by the empirical expressions for the half-lives of the α decay than the ones without it. A new empirical expression for a description of the α-decay half-lives is proposed. The empirical relation for the α decay half-lives for the transitions from the ground state to the ground state and the lowest 2+ state of the even-even nuclei is discussed. Published by the American Physical Society 2024

Searching for 76Ge neutrinoless double beta decay with the CDEX-1B experiment* *Supported by the National Key Research and Development Program of China (2017YFA0402201, 2022YFA1604701, 2022YFA1605000) and the National Natural Science Foundation of China (12322511, 12175112, 12005111, 11725522)

We operated a p-type point contact high purity germanium (PPCGe) detector (CDEX-1B, 1.008 kg) in the China Jinping Underground Laboratory (CJPL) for 500.3 days to search for neutrinoless double beta ( ) decay of 76Ge. A total of 504.3 kg day effective exposure data was accumulated. The anti-coincidence and the multi/single-site event (MSE/SSE) discrimination methods were used to suppress the background in the energy region of interest (ROI, 1989–2089 keV for this work) with a factor of 23. A background level of 0.33 counts/ (keV kg yr) was realized. The lower limit on the half life of 76Ge decay was constrained as , corresponding to the upper limits on the effective Majorana neutrino mass: 3.2–7.5 .

Separation of terbium as a first step towards high purity terbium-161 for medical applications.

Terbium-161 is a medical radiolanthanide that has a beta decay energy and half-life similar to that of lutetium-177, which makes it a promising alternative for therapeutic purposes. The production route using an enriched gadolinium-160 target necessitates the purification of terbium-161 from the untransmuted target material as well as from its stable decay product, dysprosium-161. The separation of neighbouring lanthanides is challenging due to their similar chemical properties and prominent trivalent oxidation states. In this work, the aim is to change the oxidation state of terbium, resulting in the altering of chemical properties that ease the intragroup separation. To this end, a novel separation method is investigated, involving the electrochemical oxidation of terbium (3+) to terbium (4+) followed by anion exchange chromatography. The electrolysis conditions are set to the highest achievable conversion rate, followed by a dilution step during which the pH and electrolyte concentration are slightly lowered to obtain conditions that are compatible with the separation method. XAS analysis is done to characterize the carbonato complex of both oxidation states and to further elucidate the separation mechanism. The results show that the separation approach of combining electrochemical oxidation with anion exchange chromatography is promising for the purification of 161Tb for medical use.

Structural and decay properties of even–even trans-lead nuclei

A systematic study of the ground-state properties of even–even Po, Rn, Ra and Th isotopes is conducted using the self-consistent Skyrme-Hartree–Fock–Bogoliubov (HFB) theory. Different Skyrme interactions are employed in the study. The bulk properties such as binding energy, two-neutron separation energies, two-proton separation energies and neutron skin thickness are investigated. The obtained results from the Skyrme-HFB formalism are compared with the calculated results from the Finite Range Droplet Model (FRDM) and the available experimental data. Our theoretical values were found to be consistent with their counterparts. In addition, the density-dependent cluster model is utilized to estimate [Formula: see text]-decay half-lives. A good agreement is achieved between the calculated results and the recent experimental data.

Decay Characteristics of Neutron Excess Scandium Nuclei

In neutron star mergers, neutron excess nuclei and the r-process are important factors governing the production of heavier nuclear systems. A single-particle model evaluation of Scandium nuclei suggests that the heaviest Z = 21 nucleus will have mass 71 with filling of the 1g9/2 neutron shell. A = 59 – 71 scandium isotopes have limited experimental half-life data, but the model predicts beta decay half-lives in the range of 0.312 – 7.60 ms. Based on previous calculations for Z = 9 - 20, 26, and 30 systems and comparisons to the 59Sc – 67Sc calculations, summarized in the Japanese Nuclear Data Compilation, the single-particle model results likely overestimate the half-lives of A = 59 – 71 neutron excess scandium nuclei.

Effects of deformation on the cluster and the [formula omitted]-decay half-lives for isotopes of the Trans-lead and the undetected superheavy nuclei

In the present investigation, based on the Wentzel–Kramers–Brillouin (WKB) approximation, and by considering deformation of the cluster and the daughter nuclei, the cluster radioactivity half-lives of 22 Trans-lead isotopes ranging from 221Fr to 242Cm are calculated. Also, the α-decay half-lives of even–even isotopes for the superheavy nuclei with Z in the range 104≤Z≤118 are computed. For the cluster radioactivity, a preformation factor, Pc depending on the atomic numbers of the cluster and the daughter nuclei is used according to the Santhosh and Jose (2021). The α preformation factor, Pα is evaluated based on the cluster-formation model (CFM). A universal decay law (UDL) proposed by Qi et al. (2009), was used to obtain the decay half-lives of the cluster and the α-decay for checking the credibility of our approach. The effects of the deformation of decay products on the half-lives of the cluster and the α-decay have also been investigated by comparing the obtained half-lives considering deformation with ones of the spherical nuclei and the results of the UDL as well as the available experimental data. Comparison indicates that our calculated cluster and α-decay half-lives considering deformation reproduce the experimental data more accurately than the UDL and the spherical nuclei. Furthermore, the cluster radioactivity half-lives of some isotopes that whose cluster radioactivity is energetically allowed but not observed preciously yet, are predicted. Also, the cluster and the α-decay half-lives and the branching ratios between them for some not yet discovered superheavy isotopes with Z=122 and Z=124 are obtained.

Bifunctional octadentate pseudopeptides as Zirconium-89 chelators for immuno-PET applications

BackgroundPositron emission tomography (PET) is a highly sensitive method that provides fine resolution images, useful in the field of clinical diagnostics. In this context, Zirconium-89 (89Zr)-based imaging agents have represented a great challenge in molecular imaging with immuno-PET, which employs antibodies (mAbs) as biological vectors. Indeed, immuno-PET requires radionuclides that can be attached to the mAb to provide stable in vivo conjugates, and for this purpose, the radioactive element should have a decay half-life compatible with the time needed for the biodistribution of the immunoglobulin. In this regard, 89Zr is an ideal radioisotope for immuno-PET because its half-life perfectly matches the in vivo pharmacokinetics of mAbs.ResultsThe main objective of this work was the design and synthesis of a series of bifunctional octadentate pseudopeptides able to generate stable 89Zr complexes. To achieve this, here we investigated hydroxamate, N-methylhydroxamate and catecholate chelating moieties in complexing radioactive zirconium. N-methylhydroxamate proved to be the most effective 89Zr-chelating group. Furthermore, the increased flexibility and hydrophilicity obtained by using polyoxyethylene groups spacing the hydroxamate units led to chelators capable of rapidly forming (15 min) stable and water-soluble complexes with 89Zr under mild reaction conditions (aqueous environment, room temperature, and physiological pH) that are mandatory for complexation reactions involving biomolecules. Additionally, we report challenge experiments with the competitor ligand EDTA and metal ions such as Fe3+, Zn2+ and Cu2+. In all examined conditions, the chelators demonstrated stability against transmetallation. Finally, a maleimide moiety was introduced to apply one of the most promising ligands in bioconjugation reactions through Thiol-Michael chemistry.ConclusionCombining solid phase and solution synthesis techniques, we identified novel 89Zr-chelating molecules with a peptide scaffold. The adopted chemical design allowed modulation of molecular flexibility, hydrophilicity, as well as the decoration with different zirconium chelating groups. Best results in terms of 89Zr-chelating properties were achieved with the N-methyl hydroxamate moiety. The Zirconium complexes obtained with the most effective compounds were water-soluble, stable to transmetallation, and resistant to peptidases for at least 6 days. Further studies are needed to assess the potential of this novel class of molecules as Zirconium-chelating agents for in vivo applications.