Decay Scheme Research Articles

New fermionic dark matters, extended Standard Model and cosmic rays

Three generations of leptons and quarks correspond to the lepton charges (LCs) in this work. Then, the leptons have the electric charges (ECs) and LCs. The quarks have the ECs, LCs and color charges (CCs). Three heavy leptons and three heavy quarks are introduced to make the missing third flavor of EC. Then the three new particles which have the ECs are proposed as the bastons (dark matters) with the rest masses of 26.121 eV/c2, 42.7 GeV/c2 and 1.9 × 10[Formula: see text] eV/c2. These new particles are applied to explain the origins of the astrophysical observations like the ultra-high energy cosmic rays and supernova 1987A anti-neutrino data. It is concluded that the 3.5 keV X-ray peak observed from the cosmic X-ray background spectra is originated not from the pair annihilations of the dark matters but from the X-ray emission of the Q1 baryon atoms which are similar in the atomic structure to the hydrogen atom. The presence of the 3.5 keV cosmic X-ray supports the presence of the Q1 quark with the EC of −4/3. New particles can be indirectly seen from the astrophysical observations like the cosmic ray and cosmic gamma ray. In this work, the systematic quantized charges of EC, LC and CC for the elementary particles are used to consistently explain the decay and reaction schemes of the elementary particles. Also, the strong, weak and dark matter forces are consistently explained.

β-decay scheme ofTe140toI140: Suppression of Gamow-Teller transitions between the neutronh9/2and protonh11/2partner orbitals

We report for the first time the β-decay scheme of Te140 (Z=52) to I140 (Z=53), with a specific focus on the Gamow-Teller strength along N=87 isotones. These results were obtained in an experiment performed at the Radioactive Ion Beam Factory (RIBF), RIKEN, where the parent nuclide, Te140, was produced through the in-flight fission of a U238 beam at 345 MeV per nucleon impinging on a Be9 target. Based on data from the high-efficiency γ-ray spectrometer, EUROBALL-RIKEN Cluster Array (EURICA), we constructed a decay scheme of I140. The half-life of Te140 has been determined to be 350(5) ms. A level at 926 keV has been assigned as a (1+) state based on the logft value of 4.89(6). This (1+) state, commonly observed in odd-odd nuclei, can be interpreted in terms of the πh11/2νh9/2 configuration formed by the Gamow-Teller transition between a neutron in the h9/2 orbital and a proton in the h11/2 orbital. We observe a sharp contrast to this type of β-decay branching to the lower-lying 1+ states between I140 and I136, where we see a large reduction as the number of neutrons increases. This is in contrast to the prediction by large-scale shell model calculations. To investigate this type of the suppression, results of the Nilsson model calculations will be discussed. Along the isotones with N=87, we discuss a characteristic feature of the Gamow-Teller distributions at 1+ states with respect to the isospin difference.

Concept design of a time-of-flight spectrometer for the measurement of the energy of alpha particles

The knowledge of the energies of the alpha particles emitted in the radioactive decay of a nuclide is a key factor in the construction of its decay scheme. Virtually all existing data are based on a few absolute measurements made by magnetic spectrometry (MS), to which most other MS measurements are traced. An alternative solution would be the use of time-of-flight detectors. This paper discusses the main aspects to be considered in the design of such detectors, and the performances that could be reasonably expected. Based on the concepts discussed here, it is estimated that an energy resolution about 2.5keV may be attainable with a good quality source.

Improved calculations of electron capture transitions for decay data and radionuclide metrology

Electron capture properties are crucial to establish the decay schemes of numerous radionuclides. The present modelling aims at improving the theoretical estimates of these decays, which are needed when no measurement is available. Allowed and forbidden unique transitions are calculated on the basis of precise relativistic wave functions of the atomic electrons, determined in previous work. In this context, correcting for atomic effects is of high importance. The two common approaches from Bahcall and Vatai to correct for the overlap and exchange effects have been extended to every subshell in a unified formulation, with the electron occupation precisely taken into account. The shake-up and shake-off effects, which create secondary vacancies, and the influence of the hole due to the capture process, have been considered. Uncertainties are also estimated. Relative capture probabilities and their ratios, including capture-to-positron ratios, have been found to be in good agreement with a selection of precise measurements. This modelling was then applied to the third forbidden unique transition of 40K decay, with an update of the recommended values for the branching ratios and the total decay half-life.

Determination of the absolute photon emission intensities of some gamma rays of 166mHo

This paper presents the results of the absolute measurement of some photon emission intensities in the decay of 166mHo. Point sources from a reference solution standardized in the frame of the EURAMET.RI (II)-K2. Ho-166m activity comparison were measured by gamma spectrometry. The detection efficiency was obtained by Monte Carlo calculations including the complete decay scheme. Results obtained for 27 gamma and X-ray emissions are compared to reference values.

Determining concentrations of elements with different reaction channels in photon activation

In photon activation, same element may be activated by the bremsstrahlung beam through different nuclear reaction channels and produce different radioisotopes. These radioisotopes follow their own decay schemes and generate characteristic gamma rays. This phenomenon usually is an interference in spectra analysis, but it also offers a theoretical feasibility to determine the concentration of one element through different reaction channels.To realize this theoretical feasibility, we conducted series of photon activation experiments with sample and reference of known concentrations. Irradiation of the samples and the references were conducted with electronic LINAC with different photon converters at a peak energy around 30MeV. Several elements and their corresponding reaction channels were chosen to validate this procedure. Calculations of PAA were based on the internal monitor method. Our results have confirmed the advantages of current PAA reaction channel selection, and show that it might be beneficial to calculate the concentration of same elements with different reaction channels in some certain occasions. N-values, which indicate the relative intensity of reaction channels, were calculated and compared with those values generated from the photon activation at the Federal Institute for Materials Research and Testing in Germany (BAM). Results suggested that N values are impacted by several parameters of electron beam, and the design of electron-gamma converter may play a dominant role in determining N values.

New systematic features in the neutron-deficient Au isotopes

A recently developed portable, on-line capability for γ-ray and conversion-electron spectroscopy, HIGH-TATRA is demonstrated with its application to the study of 183Hg 183Au at ISOLDE. Key details of the low-energy level scheme of the neutron-deficient nuclide 183Au populated in this decay are presented. A broad energy germanium detector is employed to achieve this (the first-ever use of such a device in decay-scheme spectroscopy), by way of a combination of high-gain γ-ray singles spectroscopy and γ–γ coincidence spectroscopy. Further, by combining the γ-ray detectors with a liquid-nitrogen-cooled Si(Li) detector operated under high vacuum, conversion-electron singles and e–γ coincidences are obtained. These data lead to the determination of transition multipolarities and the location of a highly converted (E0 + M1 + E2) transition in the 183Au decay scheme, suggesting a possible new shape coexisting structure in this nucleus. Identification of new intruder and normal states fixes their relative energies in 183Au for the first time. New systematic features in the odd-Au isotopes are presented.

Modeling of wave processes in blocky media with porous and fluid-saturated interlayers

The wave processes in blocky media are analyzed by applying different mathematical models, wherein the elastic blocks interact with each other via pliant interlayers with the complex mechanical properties. Four versions of constitutive equations are considered. In the first version, an elastic interaction between the blocks is simulated within the framework of linear elasticity theory, and the model of elastic–plastic interlayers is constructed to take into account the appearance of irreversible deformation of interlayers at short time intervals. In the second one, the effects of viscoelastic shear in the interblock interlayers are taken into the consideration using the Poynting–Thomson rheological scheme. In the third option, the model of an elastic porous material is used in the interlayers, where the pores collapse if an abrupt compressive stress is applied. In the fourth case, the model of a fluid-saturated material with open pores is examined based on Biot's equations. The collapse of pores is modeled by the generalized rheological approach, wherein the mechanical properties of a material are simulated using four rheological elements. Three of them are the traditional elastic, viscous and plastic elements, the fourth element is the so-called rigid contact, which is used to describe the behavior of materials with the different resistance to tension and compression. It was shown that the thermodynamically consistent model is provided, which means that the energy balance equation is fulfilled for an entire blocky structure, where the kinetic and potential energy of the system is the sum of the kinetic and potential energies of the blocks and interlayers. Under numerical implementation of the interlayers models, the dissipationless finite difference Ivanov's method was used. The splitting method by spatial variables in the combination with the Godunov gap decay scheme was applied in the blocks. As a result, robust and stable computational algorithms are built and tested. Using MPI technology, the parallel software was designed for the modeling of wave processes in 2D setting. The numerical results are presented, discussed and future studies are outlined.

Identification of excited states and collectivity in Se88

The $\ensuremath{\gamma}$ decays of excited states in the very neutron-rich nucleus $^{88}\mathrm{Se}$ have been observed following the neutron-induced fission of $^{235}\mathrm{U}$. The measurement was performed using the EXILL array of Ge detectors at the PF1B cold-neutron beam facility of the Institut Laue-Langevin, Grenoble. The level scheme of $^{88}\mathrm{Se}$ was established using $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences. A low $({2}_{1}^{+})$ energy hints at the onset of quadrupole deformation, and the identification of possible members of a $({2}_{2}^{+})$ band provide evidence for $\ensuremath{\gamma}$ vibrations. Shell-model calculations using a $^{78}\mathrm{Ni}$ core reproduce the decay scheme well. Equivalent deformation and $B(E2)$ values have previously been predicted for $^{88}\mathrm{Se}$ using pseudo-SU(3), shell-model, and beyond mean-field frameworks implying that interactions between particles in the $\ensuremath{\pi}{f}_{5/2}p$ and $\ensuremath{\nu}sd$ orbits are mostly responsible for the collectivity present.

Reexamining the nuclear structure of Gd154 in the dynamic pairing plus quadrupole model

In a previous study of the collective multiphonon bands in $^{154}\mathrm{Gd}$, using the microscopic dynamic pairing plus quadrupole model, data for eight $K$ bands were analyzed. In the last four decades, its decay scheme is significantly revised and the nuclear theory has undergone a significant change. Special focus is on new weak intensity transitions in several bands and on the reassigned levels in its decay scheme. The present study represents a detailed revised analysis of the collective even parity bands below 2.1 MeV. Also, a discussion is given on the nature of the ${K}^{\ensuremath{\pi}}={0}^{+}$ excited bands, validity of band mixing approach, and of the assumption of shape coexistence of \ensuremath{\beta} band with ground band. Comparison is made with the $X$(5) analytical symmetry and the algebraic interacting boson model predictions. Discussion of the $2n$ transfer reactions is given. The validity of the multiphonon view of the ${K}^{\ensuremath{\pi}}={4}^{+}$ and ${2}_{2}^{+}$ bands is also studied.

Direct measurement of alpha emission probabilities in the decay of 226Ra

High-resolution alpha-particle spectrometry was performed to determine the main alpha-particle emission probabilities in the decay of 226Ra. Thin, homogeneous sources were prepared by electrodeposition on stainless steel disks. Alpha spectra with an energy resolution of 20keV were obtained in three laboratories and analysed with different deconvolution algorithms. In two set-ups, a magnet system was used to deflect conversion electrons to avoid their coincidental detection with the alpha particles. Spectra taken at close range without a magnet system yielded biased results which cannot be fully compensated by statistical corrections for coincidence summing. The derived emission probabilities of the three main alpha decays are 94.07 (1)%, 5.93 (1)%, and 0.0059 (15)%, respectively. They are in excellent agreement with calculated values derived from the P(γ+ce) decay scheme balance, which solves the existing discrepancy problem with two previous direct measurements published in literature.

Nuclear Data Sheets for A=189

Evaluated experimental data are presented for 13 known mass 189 nuclides (Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po). Since the 2003Wu02 publication, structure and decay data from 25 new and primary publications have been incorporated in the current work, while adding a new 189Hf nuclide. New data have been added for all nuclides except 189Au and 189Hg. Moreover, several previous datasets were modified for β-decay Q values and conversion coefficients even when no new publications appeared since 2003Wu02.In spite of large amounts of data available for A=189 nuclides, several deficiencies remain, which are pointed out below in the hope that further experimental work may improve our knowledge of structure of these nuclides. For 189Hf and 189Ta, ground-state half-lives, and their decay schemes are unknown. An isomer in 189Ta has recently been established but its decay characteristics are unknown, even though several gamma rays were connected with its decay. No excited states are known in 189W and only one in 189Po. The decay scheme of 189W is known poorly with most gamma rays left as unassigned. The decay schemes of 189Au and 189Pb g.s. suffer from incompleteness, while those for the g.s. and isomer of 189Tl are almost absent. The decay schemes of g.s. and isomer of 189Hg are very complex as apparent from the study by 1996Wo04. Evaluators feel that these two decay schemes could be improved with modern gamma-ray detector arrays. While several isomers are known in many of the A=189 nuclides, there is in general lack of information of level half-lives, thus limiting the knowledge of transition probabilities. High-spin structures, including SD bands in 189Hg and 189Tl, are known in 189Re, 189Ir, 189Pt, 189Au, 189Hg, 189Tl, 189Pb and 189Bi. Single-particle transfer data are available for 189Re, 189Os, and 189Pt; and two-neutron transfer data for 189Ir.

β decay studies of n-rich Cs isotopes with the ISOLDE Decay Station

Neutron-rich Ba isotopes are expected to exhibit octupolar correlations, reaching their maximum in isotopes around mass A = 146. The odd-A neutron-rich members of this isotopic chain show typical patterns related to non-axially symmetric shapes, which are however less marked compared to even-A ones, pointing to a major contribution from vibrations. In the present paper we present results from a recent study focused on 148–150Cs β-decay performed at the ISOLDE Decay Station equipped with fast-timing detectors. A detailed analysis of the measured decay half-lives and decay scheme of 149Ba is presented, giving a first insight in the structure of this neutron-rich nucleus.

Simulation of decay processes and radiation transport times in radioactivity measurements

The Fortran subroutine package pennuc, which simulates random decay pathways of radioactive nuclides, is described. The decay scheme of the active nuclide is obtained from the nucleide database, whose web application has been complemented with the option of exporting nuclear decay data (possible nuclear transitions, branching ratios, type and energy of emitted particles) in a format that is readable by the simulation subroutines. In the case of beta emitters, the initial energy of the electron or positron is sampled from the theoretical Fermi spectrum. De-excitation of the atomic electron cloud following electron capture and internal conversion is described using transition probabilities from the LLNL Evaluated Atomic Data Library and empirical or calculated energies of released X rays and Auger electrons. The time evolution of radiation showers is determined by considering the lifetimes of nuclear and atomic levels, as well as radiation propagation times. Although pennuc is designed to operate independently, here it is used in conjunction with the electron-photon transport code penelope, and both together allow the simulation of experiments with radioactive sources in complex material structures consisting of homogeneous bodies limited by quadric surfaces. The reliability of these simulation tools is demonstrated through comparisons of simulated and measured energy spectra from radionuclides with complex multi-gamma spectra, nuclides with metastable levels in their decay pathways, nuclides with two daughters, and beta plus emitters.

Petrochronology of Zircon and Baddeleyite in Igneous Rocks: Reconstructing Magmatic Processes at High Temporal Resolution

Zircon (ZrSiO4) and baddeleyite (ZrO2) are common accessory minerals in igneous rocks of felsic to mafic composition. Both minerals host trace elements substituting for Zr, among them Hf, Th, U, Y, REEs and many more. The excellent chemical and physical resistivity of zircon makes this mineral a perfect archive of chemical and temporal information to trace geological processes in the past, utilizing the outstanding power and temporal resolution of the U–Pb decay schemes. Baddeleyite is a chemically and physically much more fragile mineral. It preserves similar information only where it is shielded from dissolution and physical fragmentation as an inclusion in other minerals or in a fine-grained or non-reactive rock matrix. It offers the potential for dating the solidification of mafic rocks with high-precision through its crystallization in small pockets of Zr-enriched melt, after extensive olivine and pyroxene fractionation. Zircon and baddelelyite U–Pb dates are, for an overwhelming majority of cases and where we can assume a closed system, considered to reflect the time of crystallization. The development of the U–Pb dating tool CA-ID-TIMS (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) since 2005 has led to unprecedented precision of better than 0.1% in 206Pb/238U dates (Bowring et al. 2005). Increased sensitivity of mass spectrometers and low laboratory blanks due to reduction of acid volumes allow routine U–Pb age determinations of micrograms of material at sufficiently high radiogenic/common lead ratios (see Schoene and Baxter 2017, this volume). In situ U–Pb age analysis using laser ablation or primary ion beam sputtering allows analysis of sub-microgram quantities of zircon material from polished internal sections or zircon surfaces with spot diameters ranging from ~30 μm for laser-ablation, inductively coupled plasma mass spectrometry (LA-ICP-MS) to 10 μm for secondary ion mass spectrometry (SIMS), lateral resolutions of 2–5 μm for NanoSIMS …

Standardization of 68Ge-68Ga using 4πβ(LS)-γ coincidence counting system for activity measurements

68Ga has great scope for use in future for positron emission tomography (PET) imaging due to its very fast blood clearance and fast target localization, even though at present 18F is widely used. 68Ge in equilibrium with 68Ga (68Ge-68Ga) can also be used as a surrogate for 18F calibration, as 18F source standardization can be done at national metrology institute (NMI) but, these standards cannot be sent to nuclear medicine centers (NMCs) across India for calibration of isotope calibrators, due to the short half-life of 18F (110min). Providing 68Ge-68Ga standards to NMCs requires that first standardization must be carried out at NMI (BARC in India) to provide traceability to the measurements carried out at NMCs. In the present work, standardization of 68Ge-68Ga was carried out using 4πβ(LS)-γ coincidence counting system and CIEMAT/NIST efficiency tracing technique. The decay scheme correction factors for two gamma windows were calculated by Monte Carlo technique using general purpose code FLUKA. The activity concentration values were normalized by the activity concentration obtained by 4πβ(LS)-γ coincidence counting system using window-1. The final result reported to BIPM for 4πβ(LS)-γ coincidence counting was calculated by taking arithmetic mean of activity concentrations obtained for two gamma windows. The normalized activity concentration obtained by 4πβ(LS)-γ coincidence counting was 0.998±0.005 and that obtained using CIEMAT/NIST efficiency tracing was 1.002±0.007 which are in excellent agreement within uncertainty limits.

Full-Energy peak efficiency of an NaI(Tl) detector with coincidence summing correction showing the effect of the source-to-detector distance

The coincidence summing effect is considered to be one of the most important problems in γ-ray spectrometry. It has played an important role in the detector calibration process, especially at low source-to-detector distances, which are the typical conditions when the environmental samples have to be measured. In this work, the γ–γ coincidence summing correction factors (CSCF) for a 3″× 3″ NaI(Tl) γ-ray detector have been calculated at different distances from the detector end cap. These factors with NaI(Tl) γ-ray detectors have rarely been discussed in the previous literature, due to the lack of the separation process of the close gamma energy lines in the scintillation detector spectrum. The γ–γ CSCF were calculated for 60Co, 133Ba and 152Eu radioactive point sources, which show the simple and the complex decay scheme of several radionuclides. In order to obtain the CSCF, the following parameters must be estimated by the numerical simulation method (NSM): the total efficiency (εT), the full-energy peak efficiency (εP) and the effective solid angle (Ωeff). These parameters were calculated numerically depending on the direct mathematical method and efficiency transfer method. The obtained CSCF was used to correct the measured efficiency curves, which were measured at different distances, then compared to the ETNA and EFFTRAN programs, as well as the CSCF. The results show a good agreement, especially at large source-to-detector distances.

Dissemination and visualisation of reference decay data from Decay Data Evaluation Project (DDEP)

As a primary laboratory in the field of ionising radiation metrology, the Laboratoire National Henri Becquerel (LNE-LNHB), CEA Saclay, is involved in measurements, evaluations and dissemination of radioactive decay data. Data measurements undertaken by various laboratories are evaluated by an international commission of experts (Decay Data Evaluation Project) coordinated by LNHB staff in order to establish a set of recommended decay scheme data. New nuclide evaluations are regularly added to our website, the Nucleide database, published in the BIPM-5 Monographie series and uploaded to our web application Laraweb, a dedicated tool for alpha and gamma spectrometry. The Mini Table of Radionuclides is produced from time-to-time with data extracted from our database. Various publications are described, along with new search criteria and decay scheme visualisation in Laraweb.

High-resolution study of the113Cd(n,γ) spectrum by statistical decay model with discrete levels and transitions

The gamma-ray spectrum and the decay scheme of 114 Cd obtained from a radiative neutron capture experiment on 113 Cd samples are modelled in the framework of extreme statistical model. The unfolding of the experimental spectrum with proper normalization yields a total capture cross section of 21640 b and an average gamma-ray multiplicity of 4.1. Using the extreme statistical model the development of the low energy decay scheme of 114 Cd is in progress. In the model the constant-temperature level density is used, where the temperature parameter was very sensitive to the shape of the modelled gamma-ray spectrum. Using this sensitivity T = 0.62 MeV was obtained with the constraint of good description of low energy level density and the level density at the binding energy. This is in full agreement with our earlier publication. For the description of the continuum shape of the unfolded spectrum the inclusion of low energy enhancement for the photon strength function was an important new addition.

A metallic magnetic calorimeter dedicated to the spectrometry of L X-rays emitted by actinides

Many actinides emit intense L X-rays consecutively to their decay. However the intensities of these X-rays are not well known: they are generally calculated with relatively large uncertainties and do not always agree with existing measurements. The latter ones are obtained with semiconductor spectrometers, but due to their insufficient energy resolution, these detectors are not able to separate the many X-ray lines and to give detailed emission intensities. So new measurements of precise and detailed L X-ray emission intensities are required. These would be beneficial on the one hand for the knowledge of the decay schemes and on the other hand as reference data for end-users of X-ray spectrometry. Therefore a spectrometer with a high energy resolution has been developed based on the technology of metallic magnetic calorimeters. The L X-ray spectra from $^{241}$Am and $^{210}$Pb decays show a FWHM energy resolution of 26 eV associated with a constant detection efficiency between 5 and 26 keV. With such performance, about 30 relative L X-ray intensities can be determined for $^{241}$Am and $^{210}$Pb. The measured emission intensities of L X-ray groups are compared with those published as obtained with conventional techniques; the good agreement between the data validated our technique.