Α-decay Energy Research Articles

Micronuclear battery based on a coalescent energy transducer.

Micronuclear batteries harness energy from the radioactive decay of radioisotopes to generate electricity on a small scale, typically in the nanowatt or microwatt range1,2. Contrary to chemical batteries, the longevity of a micronuclear battery is tied to the half-life of the used radioisotope, enabling operational lifetimes that can span several decades3. Furthermore, the radioactive decay remains unaffected by environmental factors such as temperature, pressure and magnetic fields, making the micronuclear battery an enduring and reliable power source in scenarios in which conventional batteries prove impractical or challenging to replace4. Common radioisotopes of americium (241Am and 243Am) are α-decay emitters with half-lives longer than hundreds of years. Severe self-adsorption in traditional architectures of micronuclear batteries impedes high-efficiency α-decay energy conversion, making the development of α-radioisotope micronuclear batteries challenging5,6. Here we propose a micronuclear battery architecture that includes a coalescent energy transducer by incorporating 243Am into a luminescent lanthanide coordination polymer. This couples radioisotopes with energy transducers at the molecular level, resulting in an 8,000-fold enhancement in energy conversion efficiency from α decay energy to sustained autoluminescence compared with that of conventional architectures. When implemented in conjunction with a photovoltaic cell that translates autoluminescence into electricity, a new type of radiophotovoltaic micronuclear battery with a total power conversion efficiency of 0.889% and a power per activity of 139 microwatts per curie (μW Ci-1) is obtained.

α-decay properties of superheavy nuclei with 117 ≤ Z ≤ 120 from the systematics of decay chains and isotopic chains* *Supported by the National Natural Science Foundation of China (12075121), the Natural Science Foundation of Jiangsu Province (BK20190067), and the Fundamental Research Funds for the Central Universities (30922010312)

Recently, the synthesis of new elements above Z = 118 has been a hot topic in nuclear physics. Meanwhile, the α-decay chain is expected to be the unique tool to identify these heaviest nuclei. We have systematically calculated the α-decay energies and half-lives on the same footing for superheavy nuclei (SHN) within the cluster model along with a slightly modified Woods-Saxon (W.S.) potential as the nuclear potential. Based on the available experimental data, the key radius parameter (R) in the α-core potential is determined via the systematic trend from the α-decay and isotopic chains. The α-decay energy ( ) values and half-lives are then obtained simultaneously for those unknown SHN in the range of 117 ≤ Z ≤ 120, during which the decay width is obtained using a new treatment for the asymptotic behavior of the α-core wave function. The theoretical values and experimental data are found to be in excellent agreement for the nuclei 117 and 118 regardless of the method used to determine the R parameter. Predicting the α-decay chains for new elements Z = 119 and Z = 120 can be useful in ongoing or forthcoming experiments.

An improved α-decay energy formula for heavy and superheavy nuclei * *Supported by National Natural Science Foundation of China (Grant No. 12175100), the construct program of the key discipline in Hunan province, the Research Foundation of Education Bureau of Hunan Province, China (Grant No. 18A237), the Innovation Group of Nuclear and Particle Physics in USC, the Shandong Province Natural Science

Based on the liquid-drop model and using the first derivative of the normalized Gaussian function to consider the shell correction, a simple α-decay energy formula is proposed for heavy and superheavy nuclei. The values of corresponding adjustable parameters are obtained by fitting α-decay energies of 209 nuclei ranging from Z = 90 to Z = 118 with N ≥ 140. The calculated results are in good agreement with the experimental data. The average and standard deviations between the experimental data and theoretical results are 0.141 and 0.190 MeV, respectively. For comparison, the reliable formulae proposed by Dong T K et al (2010, Phys. Rev. C 82, 034 320), Dong J M et al (2010, Phys. Rev. C 81, 064 309) and the WS3+ nuclear mass model proposed by Wang N et al (2011, Phys. Rev. C 84, 051 303) are also used. The results indicate that our improved 7-parameter formula is superior to these empirical formulae and is largely consistent with the WS3+ nuclear mass model. In addition, we extend this formula to predict the α-decay energies for nuclei with Z = 117, 118, 119 and 120. The predicted results of these formulae are basically consistent.

Decay spectroscopy of Os171,172 and Ir171,172,174

We report on a study of the α-decay fine structure and the associated Eα−Eγ correlations in the decays of Os171,172 and Ir171,172,174. In total, 13 new α-decay energy lines have been resolved, and three new γ-ray transitions have been observed following the new decay branches to Re168 and W167. The weak α-decay branch from the bandhead of the νi13/2 band in Os171 observed in this work highlights an unusual competition between α, β, and electromagnetic decays from this isomeric state. The nucleus Os171 is therefore one of few nuclei observed to exhibit three different decay modes from the same excited state. The nuclei of interest were produced in Mo92(Kr83,xpyn) fusion-evaporation reactions at the Accelerator Laboratory of the University of Jyväskylä, Finland. The fusion products were selected using the gas-filled ion separator RITU and their decays were characterized using an array of detectors for charged particles and electromagnetic radiation known as GREAT. Prompt γ-ray transitions were detected and correlated with the decays using the JUROGAM II germanium detector array surrounding the target position. Results obtained from total Routhian surface (TRS) calculations suggest that α-decay fine structure and the associated hindrance factors may be a sensitive probe of even relatively small shape changes between the final states in the daughter nucleus.5 MoreReceived 13 October 2022Accepted 11 January 2023DOI:https://doi.org/10.1103/PhysRevC.107.014308Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayLow & intermediate energy heavy-ion reactionsNuclear structure & decaysProperties150 ≤ A ≤ 189Nuclear Physics

Study of α-Decay Energy by an Artificial Neural Network Considering Pairing and Shell Effects

We build and train an artificial neural network (ANN) model based on experimental α-decay energy (Qα) data. In addition to decays between the ground states of parent and daughter nuclei, decays from the ground states of parent nuclei to the excited states of daughter nuclei are also included. In this way, the number of samples is increased dramatically. The α particle is assumed to have a spherical symmetric shape. The root-mean-square deviation between the calculated results obtained from the ANN model and the experimental data is 0.105 MeV. It shows a good predictive power for α-decay energy with the ANN model. The influence of different inputs is investigated. It is found that both the shell effect and the pairing effect result in an obvious improvement of the predictive power of the ANN model, and the shell effect plays a more important role. The optimal result can be obtained when both the shell and pairing effects are considered simultaneously. The application of the ANN model in predicting α-decay energy indicates a neutron magic number at N=184 in the superheavy nuclei mass region.

Radioactive Thoron 220Rn Exhalation From Unfired Mud Building Material Into Room Air of Earthen Dwellings

Thoron (220Rn), an isotope of radon with a strong α-decay energy, and its short-lived metallic progeny can pose an elevated lung cancer hazard in room air when unfired-soil derived building materials are used in earthen dwellings. Changes in moisture content and density influencing the thoron exhalation rate from earthen materials into room air were studied in the laboratory with terra rossa from a village on the Ðồng Văn Karst Plateau Geopark, Việt Nam, where ethnic minorities construct traditional dwellings with unfired terra rossa walls and floors. Our results show that the thoron exhalation rate from mud surfaces depends on (i) the content of radioactive parental nuclides in mineral components; (ii) the moisture content of mud where ∼5–10 weight % water maximizes the 220Rn exhalation rate; and (iii) the density of dry mud as primarily controlled by internal macroscopic voids, fractures, and porosity. Additional time-series of 220Rn exhalation data from an interior mud wall of a terra rossa-built house under different seasonal and weather conditions show that the temperature is influencing thoron exhalation via the water vapor pressure deficit (VPD) in air and the associated amount of atmospheric moisture adsorbed onto indoor mud surfaces. Our data suggest that occupants of “mud house” earthen dwellings in northern Việt Nam are exposed to an increased thoron geohazard during cooler weather, low VPD, and high relative humidity in air. Detailed studies are needed to evaluate the thoron geohazard for inhabitants of mud-built dwellings in other climates and geological terrains.

Predictions on the α-cluster structure in 104Te

The present work analyzes the α + core structure in 104Te using the local potential model. The α + core interaction is described by a nuclear potential of (1 + Gaussian)×(W.S. + W.S.3) shape. The energy levels, total α widths and rms intercluster separations are determined for the ground state band and compared with a previous calculation which uses a double-folding potential. The two potential forms produce similar spectra between the 0+ and 14+ states. The antistretching effect is predicted for the 104Te ground state band, as is observed in previous α + core calculations in intermediate mass nuclei. An α-decay half-life T1/2,α ≈ 3 ns is predicted for 104Te in the α-decay energy Qα ≈ 5.36 MeV using an α preformation factor P = 1. The calculated T1/2,α value is compatible with the recently reported experimental result on α-decay of 104Te.

Systematic study of α-decay half-lives of super-heavy nuclei with 106≤Z≤118

The α-decay half-lives of the superheavy nuclei are systematically studied using different versions of proximity potential and a exact method to calculate Coulomb potential between spherical and deformed nuclei in the framework of the double folding model. To reproduce the α-decay half-life, the experimental α-decay energy and Wentzel-Kramers-Brillouin approximation have been used. It is found that the computed values by the Ngô 80 are in good compromise with the experimental half-lives in comparison with other versions. Also, by using this version and within QWS4 for determination α-decay energies for superheavy elements, we had predicted the α-decay half-lives for superheavy nuclei which have not been reported yet. The long half-lives with magnitude about 100 seconds are predicted for the superheavy nuclei which are not in stability islands which indicating remarkable stability in comparison with their neighbors. These results are also in good agreement with the predictions of other semi-empirical formulas.

Effect of choosing the [formula omitted]-values and daughter density distributions on the magic numbers predicted by [formula omitted] decays

We investigated the effects of choosing the α-decay energy (Qα) and particular density distributions of the daughter nuclei on predicting unknown magic numbers, or confirming some of them. The Qα values were calculated using three models, namely the finite-range droplet model (FRDM), the Weizsäcker–Skyrme (WS4) mass model, and a recent fitting formula. The α-decay half-lives (Tα) of superheavy nuclei of Z = 118–124 have been calculated within the generalized density-dependent cluster model. The double-folding α+core potential was determined based on the M3Y-Reid nucleon–nucleon interaction. We have used the two-parameter Fermi distribution to represent the nuclear density, with four sets of parameters that were determined based on electron scattering data and different microscopic calculations. Upon investigating the relative stability of the mentioned superheavy isotopic chains, we found that the Qα-values deduced from FRDM and WS4 models predict different neutron magic numbers. The examined fitting formula failed to predict any magic number larger than N= 162. Under normalization to the proton and neutron (N) numbers, the different choices of the density distributions showed almost no effect on the general behavior of Tα with N, but changed its values up to one order of magnitude. Even though the maxima and minima of Tα clearly follow the characteristic minima and maxima of Qα, respectively, the results showed that precise density distribution and deformations, in addition to a correct preformation probability, are necessarily required for estimating an accurate value of the half-life.

Nuclear properties for astrophysical and radioactive-ion-beam applications (II)

We tabulate the ground-state odd-proton and odd-neutron spins and parities, proton and neutron pairing gaps, one- and two-neutron separation energies, quantities related to β-delayed one- and two-neutron emission probabilities, average energy and average number of emitted neutrons, β-decay energy release and half-life with respect to Gamow–Teller decay with a phenomenological treatment of first-forbidden decays, one- and two-proton separation energies, and α-decay energy release and half-life for 9318 nuclei ranging from 16O to 339136 and extending from the proton drip line to the neutron drip line. This paper is a new and improved version of Atomic Data And Nuclear Data Tables [66 131 (1997)]. The starting point of our present work is the new study (FRDM(2012)) of nuclear ground-state masses and deformations based on the finite-range droplet model and folded-Yukawa single-particle potential published in a previous issue of Atomic Data And Nuclear Data Tables [109–110, 1 (2016)]. The β-delayed neutron-emission probabilities and Gamow–Teller β-decay rates are obtained from a quasi-particle random-phase approximation with single-particle levels and wave functions at the calculated nuclear ground-state shapes as input quantities. A development since 1997 is we now use a Hauser–Feshbach approach to account for (n, γ) competition and treat first-forbidden decay in a phenomenological approach.

Branching ratios of α-decay to ground and excited states of Fm, Cf, Cm and Pu

We use the well-known Wentzel–Kramers–Brillouin (WKB) barrier penetration probability to calculate α-decay branching ratios for ground and excited states of heavy even–even nuclei of Fermium (248–254Fm), Californium (244–252Cf), Curium (238–248Cm) and Plutonium (234–244Pu) with 94≤Zp≤100. We obtained the branching ratios for the excited states of daughter nucleus by the α-decay energy (Qα), the angular momentum of α-particle (ℓα), and the excitation probability of the daughter nucleus with the excitation energy of state ℓ in the daughter nucleus (i.e. Eℓ⁎). α-Decay half-lives have been evaluated by using the proximity potential model for the heavy even–even nuclei. We have reported the half-lives and compared the results with the experimental data. The theoretical branching ratios of α-transitions in our calculation are found to agree with the available experimental data well for 0→+ 0+, 0→+ 2+, 0→+ 4+, 0→+ 6+ and 0+ → 8+α-transitions.

Stability of super heavy nuclei associated with the updated nuclear data**Supported by National Natural Science Foundation of China (11675066, 11647306), Fundamental Research Funds for the Central Universities (lzujbky-2017-ot04) and Feitian Scholar Project of Gansu province

The stability of super heavy nuclei (SHN) from Z=104 to Z=126 is analyzed systematically, associated with the following theoretical mass tables: FRDM2012 [At. Data Nucl. Data Tables 109-110(2016)], WS2010 [Phys. Rev. C 82, 044304(2010)], WS-LZ-RBF [J. Phys. G: Nucl. Part. Phys. 42, 095107(2015)] and the updated experimental data AME2016 [Chinese Physics C 41, 040002(2017)]. The nucleus with the biggest mean binding energy in each isotopic chain shows systematic regular behavior, indicating that the mean binding energy is a good criterion to classify SHN by their stability. Based on binding energy, the α-decay energy Qα, two-proton separation energy S2p, and two-neutron separation energy S2n are extracted and analyzed. It is found that N=152 and N=162 are sub-magic numbers, N = 184 is a neutron magic number, and Z = 114 is a proton magic number, which may provide useful information for the synthesis and identification of SHN.

Study of neutron-deficient isotopes of Fl in the 239Pu, 240Pu + 48Ca reactions

The results of the experiments aimed at the synthesis of Fl isotopes in the 239Pu + 48Ca and 240Pu + 48Ca reactions are presented. The experiment was performed using the Dubna gas-filled recoil separator at the U400 cyclotron. In the 239Pu+48Ca experiment one decay of spontaneously fissioning 284Fl was detected at 245-MeV beam energy. In the 240Pu+48Ca experiment three decay chains of 285Fl were detected at 245 MeV and four decays were assigned to 284Fl at the higher 48Ca beam energy of 250 MeV. The α-decay energy of 285Fl was measured for the first time and decay properties of its descendants 281Cn, 277Ds, 273Hs, 269Sg, and 265Rf were determined more precisely. The cross section of the 239Pu(48Ca,3n)284Fl reaction was observed to be about 20 times lower than those predicted by theoretical models and 50 times less than the value measured in the 244Pu+48Ca reaction. The cross sections of the 240Pu(48Ca,4-3n)284,285Fl at both 48Ca energies are similar and exceed that observed in the reaction with lighter isotope 239Pu by a factor of 10. The decay properties of the synthesized nuclei and their production cross sections indicate rapid decrease of stability of superheavy nuclei with departing from the neutron number N=184 predicted to be the next magic number.

The structural and decay properties of Francium isotopes

We study the bulk properties such as binding energy (BE), root-mean-square (RMS) charge radius, quadrupole deformation etc. for Francium (Fr) isotopes having mass number A = 180–240 within the framework of relativistic mean field (RMF) theory. Systematic comparisons are made between the calculated results from RMF theory, Finite Range Droplet Model (FRDM) and the experimental data. Most of the nuclei in the isotopic chain shows prolate configuration in their ground state. The α-decay properties like α-decay energy and the decay half-life are also estimated for three different chains of 198 Fr , 199 Fr and 200 Fr . The calculation for the decay half-life are carried out by taking two different empirical formulae and the results are compared with the experimental data.

Ground State Properties of Ds Isotopes Within the Relativistic Mean Field Theory

The ground state properties of Ds (Z = 110) isotopes (N = 151–195) are studied in the framework of the relativistic mean field (RMF) theory with the effective interaction NL-Z2. The pairing correlation is treated within the conventional BCS approximation. The calculated binding energies are consistent with the results from finite-range droplet model (FRDM) and Macroscopic-microscopic method (MMM). The quadrupole deformation, α-decay energy, α-decay half-live, charge radius, two-neutron separation energy and single-particle spectra are analyzed for Ds isotopes to find new characteristics of superheavy nuclei (SHN). Among the calculated results it is rather distinct that the isotopic shift appears evidently at neutron number N = 184.

Discovery of 157W and 161Os

The nuclides 157W and 161Os have been discovered in reactions of 58Ni ion beams with a 106Cd target. The 161Os α-decay energy and half-life were 6890±12 keV and 640±60 μs. The daughter 157W nuclei β-decayed with a half-life of 275±40 ms, populating both low-lying α-decaying states in 157Ta, which is consistent with a 7/2− ground state in 157W. Fine structure observed in the α decay of 161Os places the lowest excited state in 157W with Iπ=9/2− at 318±30 keV. The branching ratio of 5.5−2.2+3.1% indicates that 161Os also has a 7/2− ground state. Shell-model calculations analysing the effects of monopole shifts and a tensor force on the relative energies of 2f7/2 and 1h9/2 neutron states in N=83 isotones are presented.

The new isotope 179Pb and α-decay properties of 179Tlm

The new isotope 179Pb has been produced in the complete fusion reaction 40Ca + 144Sm → 179Pb+5n at the velocity filter SHIP (GSI). Its α-decay energy of 7350(20) keV and half-life value of 3.5+1.4− 0.8 ms were deduced based on the recoil–α–α correlation technique. A spin parity of Iπ = (9/2−) was tentatively assigned to the ground state of 179Pb; thus, it is based on the 1h9/2 orbital. Improved measurements of the α-decay properties of 179Tlm and 175Aum are also presented.

ALPHA-DECAYS TO MEMBERS OF GROUND-STATE ROTATIONAL BAND OF HEAVY EVEN-EVEN NUCLEI

We apply a simple barrier penetration approach to calculate α-decay branching ratios to members of ground-state rotational band of heavy even-even nuclei. The influence of α-decay energy, the angular momentum of α-particle, and the excitation probability of the daughter nucleus is taken into account in our calculations. The theoretical branching ratios of α-transitions are found to agree with the available experimental data well.

Branching ratios of α-decay to excited states of even–even nuclei

We make a systematic calculation on α-decay branching ratios to members of ground-state rotational band and to excited 0 + states of even–even nuclei by a simple barrier penetration approach. The branching ratios to the excited states of daughter nucleus are determined by the α-decay energy, the angular momentum of α-particle, and the excitation probability of the daughter nucleus. Our calculation covers isotopic chains from Hg to Fm in the mass regions 180 < A < 202 and A ⩾ 224 . The calculated branching ratios of α-transitions are consistent with the experimental data. Some useful predictions are made for future experiments.

Description of α-decay half-lives of heaviest nuclei

The accuracy in describing α-decay half-lives T α of heavy and superheavy nuclei is studied. A simple five-parameter phenomenological formula, expressing T α as a function of the α-decay energy Q α, is considered. It is found that such a formula can describe measured values of T α within a factor of 1.3 for even-even, 2.1 for odd-even, 3.2 for even-odd, and 4.0 for odd-odd nuclei when measured values of Q α are taken. This accuracy is decreased by a factor of about 4 when theoretical values of Q α are used. The latter are obtained within a macroscopic-microscopic approach and reproduce the experimental values of Q α of the same nuclei with an average accuracy of about 190 keV for even-even, 270 keV for odd-even, 260 keV for even-odd, and 330 keV for odd-odd nuclei. In the analysis, 201 nuclei with proton number Z = 84–111 and neutron number N = 128–161, with measured values of both Q α and T α, are taken.