Decay Half-lives Research Articles

Revisiting cross sections for proton induced reactions on natural lead between 10 and 80 MeV

Abstract This work is focused on the natPb(p,xn)207Bi reaction to extend earlier works on proton induced reactions for the determination of cross sections of residual nuclides. 207Bi decay (half-life 31.55 years) was measured by γ-ray spectrometry in 42 lead foils which had been irradiated by high proton fluxes 20 years ago. Since then, all short-lived radionuclides produced during the irradiation have decayed, so the background is strongly reduced and the cross section could be measured more precisely than during the original measurements. The results are found to be in very good agreement with the historical record. Additionally, theoretical calculations with modern Monte Carlo based codes were performed to compare the calculations of various Bi, Tl and Pb reactions with the historical data and with additional data from literature. The deviations of the new data from both theoretical calculations using EMPIRE and TALYS are discussed.

Two-delta shell resonance description of α-decay: analytic expression of half-life via energy derivative of phase-shift

The process of α-decay being intrinsically quantum mechanical originates from the resonance state of the α + daughter nucleus two-body system where the scattering phase-shifts vary rapidly in a small energy range of the size of the resonance width in the presence of narrow resonance. We model this physical phenomenon and derive a clear expression for the decay width, Γ, in terms of energy derivative of phase-shift obtained by properly matching the exact solutions within the segments of a shell of two delta potentials generating resonance with the pure Coulomb wave functions in the Coulomb–nuclear scattering phenomenon. With this decay width Γ, using the standard relation, T 1/2 = ln 2 , the decay half-life, T 1/2, is expressed analytically and the computed results successfully explain the experimental results of α-decay half-lives ranging from 10−7 s–1025 s in the cases of many light, heavy and super heavy radioactive nuclei with proton number Z = 52–120 and mass number A = 106–299.

Radiochemistry, Production Processes, Labeling Methods, and ImmunoPET Imaging Pharmaceuticals of Iodine-124.

Target-specific biomolecules, monoclonal antibodies (mAb), proteins, and protein fragments are known to have high specificity and affinity for receptors associated with tumors and other pathological conditions. However, the large biomolecules have relatively intermediate to long circulation half-lives (>day) and tumor localization times. Combining superior target specificity of mAbs and high sensitivity and resolution of the PET (Positron Emission Tomography) imaging technique has created a paradigm-shifting imaging modality, ImmunoPET. In addition to metallic PET radionuclides, 124I is an attractive radionuclide for radiolabeling of mAbs as potential immunoPET imaging pharmaceuticals due to its physical properties (decay characteristics and half-life), easy and routine production by cyclotrons, and well-established methodologies for radioiodination. The objective of this report is to provide a comprehensive review of the physical properties of iodine and iodine radionuclides, production processes of 124I, various 124I-labeling methodologies for large biomolecules, mAbs, and the development of 124I-labeled immunoPET imaging pharmaceuticals for various cancer targets in preclinical and clinical environments. A summary of several production processes, including 123Te(d,n)124I, 124Te(d,2n)124I, 121Sb(α,n)124I, 123Sb(α,3n)124I, 123Sb(3He,2n)124I, natSb(α, xn)124I, natSb(3He,n)124I reactions, a detailed overview of the 124Te(p,n)124I reaction (including target selection, preparation, processing, and recovery of 124I), and a fully automated process that can be scaled up for GMP (Good Manufacturing Practices) production of large quantities of 124I is provided. Direct, using inorganic and organic oxidizing agents and enzyme catalysis, and indirect, using prosthetic groups, 124I-labeling techniques have been discussed. Significant research has been conducted, in more than the last two decades, in the development of 124I-labeled immunoPET imaging pharmaceuticals for target-specific cancer detection. Details of preclinical and clinical evaluations of the potential 124I-labeled immunoPET imaging pharmaceuticals are described here.

Predictions for the α decay of proton-rich nuclei in the range of 86⩽Z⩽98

The α decay half-lives of odd-A and odd-odd nuclei ranging in 65⩽Z⩽112 are investigated by employing the modified universal decay law and the unified fission model, both of them take into account the contribution of centrifugal potential. The good agreement with the experimental data indicates that the modified universal decay law and the unified fission model are useful tools to investigate these α-decays when they contain the effect of centrifugal potential. Relatively long half-lives are predicted by using the new mass table WS2016+RBFs to determine the Qα for many unknown proton-rich nuclei between Rn and Cf, sufficient to detect them if synthesized in a laboratory.

Exploring the uncertainties in theoretical predictions of nuclear β-decay half-lives * *Partly supported by the National Natural Science Foundation of China under (11805004, 11875070), the Key Research Foundation of Education Ministry of Anhui Province (KJ2020A0485), and the Open fund for Discipline Construction, Institute of Physical Science and Information Technology, Anhui University

Nuclear -decay half-lives are predicted based on an empirical formula and the mass predictions from various nuclear models. It is found that the empirical formula can reproduce the nuclear -decay half-lives well, especially for short-lived nuclei with s. The theoretical half-life uncertainties from -decay energies and the parameters of the empirical formula are further investigated. It is found that the uncertainties of the half-lives are relatively large for heavy nuclei and nuclei near the neutron-drip line. For nuclei on the r-process path, the uncertainties for those with are about one order of magnitude, which are much larger than the uncertainties for those with and . However, theoretical uncertainties from the parameters of the empirical formula are relatively small for the nuclei on the r-process path, which indicates that the empirical formula is very suitable for predicting the -decay half-lives in r-process simulations.

Screening amendment to the universal decay law for alpha decay

By generalizing the electrostatic interaction by means of a screening effect, one proposed a new empirical formula for the $$\alpha $$ decay half lives. In the absence of screening, the formula recovers the universal decay law. The impact of the screening is found to be important only for even Z nuclei and highly sensitive to shell effects, when applied to nuclei with $$Z\ge 84$$ . The proposed empirical formulas are also used for the prediction of the half-lives for even Z superheavy nuclei.

Simulating the Production of Medical Radioisotopes in a Fast Thorium-Cycle ADS with SERPENT

Radiopharmaceuticals are used in nuclear medicine for diagnostic or therapeutic acts. The short decay half-lives of medical radioisotopes, especially those used for diagnostics, imply that they should be produced continuously and transported as quickly as possible to the medical units where they are used. Neutron-rich medical radioisotopes are generally produced in research reactors, like technetium-99m, lutetium-177, holmium-166 and iodine-131. On the other hand, proton-rich radioisotopes are produced via reactions with charged particles from accelerators like fluorine-18, gallium-67, iodine-123 and thallium-201. Beside this, innovative nuclear reactors are advocated as solutions to the issues of nuclear waste production and proliferation threats. Fast neutron, thorium-cycle and accelerator-driven subcritical (ADS) reactors are some of the most promising of them, proposed as safer fuel breeders and “waste burners”. This article examines the use of a fast thorium-cycle ADS with liquid lead-bismuth eutectic coolant for the production of molybdenum-99/technetium-99m and lutetium-177. Burnup simulation has been made with the Monte-Carlo (MC) code SERPENT. It is demonstrated that MC codes can advantageously be used to determine the optimal irradiation time for a given radioisotope in a realistic reactor core. It is also shown that fast thorium-cycle ADS is an economical option for the production of medical radioisotopes.

Systematic of alpha decay half-lives: role of quantization condition

Using the semiclassical WKB method and considering the WKB quantization condition, the alpha decay half-lives of 420 alpha emitters were calculated with eight forms of the proximity and Woods–Saxon type potentials. The effect of quantization condition on the nuclear potential, effective potential, assault frequency, tunneling probability, alpha decay half-life, and root mean square deviation between theory and the experiment were investigated. Significant differences between calculated half-lives with and without inclusion of the quantization condition were observed specially for proximity potentials. By including the quantization, the Woods–Saxon potential was found as the best potential for even–even, even–odd, odd–even, odd–odd, and all alpha emitters. The quantization condition normalized the nuclear potentials. Therefore, by considering this condition, the thirteen forms of the prox77 potential with different sets of the surface energy and surface asymmetry constants gave the same results. This result was justified with two sets of parameters.

Upgrade of the MAGNEX spectrometer toward the high-intensity phase of NUMEN

The NUMEN experimental activity with accelerated beams is performed at INFN–Laboratori Nazionali del Sud (LNS) in Catania using the Superconducting Cyclotron and the MAGNEX magnetic spectrometer. The scientific motivation of NUMEN is to extract experiment-driven information on the nuclear matrix elements entering in the expression of the 0νββ decay half-life. The reaction cross sections involved, especially for the double charge exchange process, are very low, thus limiting the present exploration to a few selected isotopes of interest in the context of typically low-yield experimental runs. In order to make feasible a systematic study of all the candidate nuclei, a major upgrade of the LNS facility is foreseen to increase the experimental yield by more than two orders of magnitude. To this purpose, frontier technologies are being developed for the accelerator and the detection systems. An updated description of the choices derived from the recent R&D activity on the target system and MAGNEX focal plane detector is given.

Recent experimental activity on heavy-ion induced reactions within the NUMEN project

The possibility to use a special class of heavy-ion induced direct reactions, such as double charge exchange reactions, is discussed in view of their application to extract information that may be helpful to determinate the nuclear matrix elements entering in the expression of neutrinoless double beta decay half-life. The strategies adopted in the experimental campaigns performed at INFN - Laboratori Nazionali del Sud are briefly described, emphasizing the advantages of the multi-channel approach to nuclear reaction data analysis.

Calculations of the Alpha Decay Half-lives of Some Polonium Isotopes Using the Double Folding Model

The calculations of the alpha decay half-lives of some Polonium isotopes in the mass range 186 - 218 have been carried out using the Wentzel-Kramers-Brillouin (WKB) semiclassical approximation. The alpha-nucleus effective potential used contains the Coulomb potential, centrifugal potential, and the nuclear potential. The nuclear potential is obtained via the double folding model, with the microscopic NN effective interactions derived from relativistic mean field theory Lagrangian (termed R3Y). Different parametrizations of the R3Y interactions have been employed in the computation of the nuclear potentials. The results obtained using the R3Y NN interactions are compared with the ones obtained using the famous Michigan-3-Yukawa (M3Y) interactions. The use of density-dependent NN interaction is also considered. When compared to available experimental data, there are improvements in the results when density-dependent interaction potentials are used compared to when density-independent interactions are employed.

Nuclear fission in intense laser fields

Rapid-advancing intense laser technologies enable the possibility of a direct laser-nucleus coupling. In this paper the effect of intense laser fields on a series of nuclear fission processes, including proton decay, alpha decay, and cluster decay, is theoretically studied with the help of nuclear double folding potentials. The results show that the half-lives of these decay processes can be modified by non-negligible amounts, for example on the order of 0.01 or 0.1 percents in intense laser fields available in the forthcoming years. In addition to numerical results, an approximate analytical formula is derived to connect the laser-induced modification to the decay half-life and the decay energy.

Final Results of GERDA on the Search for Neutrinoless Double-β Decay.

The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-β (0νββ) decay of ^{76}Ge, whose discovery would have far-reaching implications in cosmology and particle physics. By operating bare germanium diodes, enriched in ^{76}Ge, in an active liquid argon shield, GERDA achieved an unprecedently low background index of 5.2×10^{-4} counts/(keV kg yr) in the signal region and met the design goal to collect an exposure of 100kg yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2kg yr of total exposure. A limit on the half-life of 0νββ decay in ^{76}Ge is set at T_{1/2}>1.8×10^{26} yr at 90%C.L., which coincides with the sensitivity assuming no signal.

Systematic study of α decay half-lives within the Generalized Liquid Drop Model with various versions of proximity energies * *Support by National Natural Science Foundation of China (10775061, 11175054, 11675066, 11665019, 11947229), the Fundamental Research Funds for the Central Universities (lzujbky-2017-ot04, lzujbky-2020-it01), and Feitian Scholar Project of Gansu province

It is universally acknowledged that the Generalized Liquid Drop Model (GLDM) has two advantages over other α decay theoretical models: introduction of the quasimolecular shape mechanism and proximity energy. In the past few decades, the original proximity energy has been improved by numerous works. In the present work, the different improvements of proximity energy are examined when they are applied to the GLDM for enhancing the calculation accuracy and prediction ability of α decay half-lives for known and unsynthesized superheavy nuclei. The calculations of α half-lives have systematic improvements in reproducing experimental data after choosing a more suitable proximity energy for application to the GLDM. Encouraged by this, the α decay half-lives of even-even superheavy nuclei with Z=112-122 are predicted by the GLDM with a more suitable proximity energy. The predictions are consistent with calculations by the improved Royer formula and the universal decay law. In addition, the features of the predicted α decay half-lives imply that the next double magic nucleus after 208Pb is 298Fl.

New look at Geiger-Nuttall law and α clustering of heavy nuclei * *Supported by the National Natural Science Foundation of China (12075121, 11605089, 11975167, 11535004, 11761161001), the Natural Science Foundation of Jiangsu Province (BK20150762, BK20190067), the National Major State Basic Research and Development Program of China (2016YFE0129300)

The Geiger-Nuttall (GN) law of α decay is commonly explained in terms of the quantum tunneling phenomenon. In this study, we show that such an explanation is actually not enough regarding the α particle clustering. Such a conclusion is drawn after exploring the involved coefficients of the GN law based on the conventional description of α decay, namely the formation of an α cluster and its subsequent penetration. The specific roles of the two former processes, in the GN law, manifest themselves via the systematical analysis of the calculated and experimental α decay half-lives versus the decay energies across the and shell closures. The α-cluster preformation probability is then found to behave in a GN-like pattern. This previously ignored point is explicitly demonstrated as the product of an interplay between the mean-field and pairing effect, which in turn reveals the structural influence on the formation of the α cluster in a simple and clear manner. In addition to providing an effective method to evaluate the amount of surface α clustering in heavy nuclei, the present conjecture supports other theoretical treatments of the α preformation probability.

Search for neutrinoless double-beta decays in Ge-76 in the LEGEND experiment

The search for neutrinoless double-beta decay is the most sensitive technique to establish the Majorana nature of neutrinos. Two operating experiments that look for such decays in Ge-76, GERDA and MAJORANA DEMONSTRATOR have achieved the lowest backgrounds and the best energy resolution in the signal region. These are two of the most important detector characteristics for sensitive searches of this undiscovered decay. The Large Enriched Germanium Experiment for Neutrinoless Double-Beta Decay (LEGEND) Collaboration has been formed to pursue a tonne-scale Ge-76 experiment that integrates the best technologies from these two experiments and others in the field. The Collaboration is developing a phased experimental program that uses existing resources as appropriate to expedite physics results, with the ultimate discovery potential at a decay half-life beyond 1028 years.

Alpha and heavy cluster radioactivity of superheavy nuclei 100 ⩽ Z ⩽ 120

Using Cubic plus Yukawa plus Exponential (CYE) model, half lives of alpha decay and heavy cluster radioactivity of Superheavy nuclei have been systematically investigated for even-even, even-odd, odd-even and odd-odd nuclei with 100 ⩽ Z ⩽ 120. We have done our calculations by considering the Coulomb, centrifugal and Yukawa plus exponential potentials as an interacting barrier for separated fragments and the cubic potential for the overlapping region.The predicted half life time values by including deformation effects on parent and parent cluster have been compared with theAnalytical Super Asymmetric Fission (ASAF) model of D.N.Poenaru et.al. In this work, we have compared the half life time values of alpha and heavy cluster radioactivity of Super heavy nuclei leading to 208Pb. This study suggests that heavy-cluster radioactivity may be comparable to or even dominant over a decay for some of the isotopes with Z ⩾ 118. Furthermore, branching ratio calculations have been performed to find out the probable cluster emitters. The predictions for cluster emitters are in agreement with CPPM model by Santhosh et. al.,and Wentzel-Kramers-Brillouin (WKB) method by A.Soylu et. al. We hope that this study will help in future measurements on α-decay and cluster radioactivity half-lives of SHN.

Proton Radioactivity of Heavy Nuclei of Atomic Number Range 72 < Z < 88

We have studied proton radioactivity of heavy nuclei of atomic number range 72 < Z < 88. We have calculated the energy released during the proton decay (QP) and half-lives of proton decay. To study the competition between different decay modes, we have compared the proton decay half lives with that of the decay modes such as alpha decay, beta decay, cluster decay and spontaneous fission. To check the Geiger–Nuttall law for proton decay, we have plotted the logarithmic proton decay half-lives versus 1/sqrt(Q). We have also highlighted possible proton emitters with the corresponding energies and half-lives in the atomic number range 72 < Z < 88.

Recent results on heavy-ion induced reactions of interest for neutrinoless double beta decay at INFN-LNS

The NUMEN project aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0νββ). In this view measurements of Heavy Ion (HI) induced Double Charge Exchange (DCE) reaction cross sections are performed with high-accuracy. In particular, the (18O,18Ne) and (20Ne,20O) reactions are used as tools for β+β+ and β-β- decays, respectively. In the experiments, performed at INFN - Laboratory Nazionali del Sud (LNS) in Catania, the beams are accelerated by the Superconducting Cyclotron (CS) and the reaction ejectiles are detected the MAGNEX magnetic spectrometer. The measured cross sections are challengingly low (a few nb), being the total reaction cross section much larger (a few b), thus a high sensitivity and a large rejection capability are demanded to the experimental set-up. This limits the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is under way in order to increase the experimental dataset of more than two orders of magnitude, still preserving the high sensitivity of the present set-up. When accomplished this effort will make the INFN-LNS as the state-of-the-art research infrastructure for the systematic study of all the cases of interest for 0νββ. In this view, frontiers technologies are going to be adopted for the accelerator and the detection systems. In parallel, advanced theoretical models are being developed in order to extract the nuclear structure information from the measured cross sections.

Double beta decay and the quest for Majorana neutrinos

The observation of neutrinoless double beta (0νββ) decay remains crucial for understanding lepton number violation. The inverse half-life for 0νββ-decay is given by the product of a phase space factor (PSF), a nuclear matrix element (NME), which both rely on theoretical description, and a function f containing the physics beyond the standard model. Phase space factors and nuclear matrix elements have been evaluated, or are under evaluation, systematically for all processes of interest. The nuclear matrix elements have been calculated within the framework of the microscopic interacting boson model (IBM-2), and phase space factors have been evaluated using exact Dirac electron wave functions. The current situation is then discussed by combining the theoretical results with experimental limits on the half-life of neutrinoless double beta decay. The extracted limits on the average light neutrino mass are addressed, complemented with a discussion of other possible 0νββ-decay mechanisms and scenarios.