Decay Strength Research Articles

Observation of the J≤7/2 low-spin states in Fr213 populated in the electron capture of the 1/2− ground state of Ra213

A detailed level scheme of Fr126213 following the EC/β+ decay of the 1/2−Ra213 parent ground state was built in an experiment performed at the ISOLDE Decay Station, CERN. The fragmented total β decay strength favours the direct population of several low-spin (J≤7/2) excited states. The analysis of the γ-singles spectrum and γ−γ coincidences allowed us to identify many new γ-ray transitions and excited states in Fr213 up to about 3.6 MeV excitation energy. The spins and parities of the newly established levels, on top of the (7/21−) state, were mainly assigned based on the systematics of the N=126 isotones and further compared with shell-model calculations. The level scheme displays a structural pattern, with several groups of states with negative parity, emerging from the well-defined, simple, π(h9/25), π(h9/24f7/21) configurations or from their configuration mixing. The strength of the 2 transitions within the multiplets is compared with shell-model theoretical calculations performed with the and 208 effective interactions. A new (3/2−) isomer with a half-life of 26(3) ns has been identified. An upper limit of 35 ps was determined for the half-life of the first excited state, 7/2−. The possibility of a mixed M1+E2 character is discussed for the 7/21−→9/2gs− decay in Fr213, which leads to an l-forbidden nature of the πf7/2→πh9/2 transition. Published by the American Physical Society 2024

Wood Degrading Enzymes and their Decay Strength: A Review

The degradation of wood is a major point of concern in the economy. The microbes that degrade the wood release various enzymes that decay the wood. In the present review article, we have collected the data for various decay strengths of different decay enzymes released by the various microbes from several peer-reviewed articles. The fungus basidiomycetes and some wood-degrading bacteria are responsible for the degradation of wood. The degraded wood is a major loss to the economy timber decay and many more. The degradation of wood or wood decay is also a major loss to the ecosystem by losing some precious plant species. Various data mining techniques have been used in this review to collect the data from the publications. The data in this article covers the various fields, the Name of the plant being degraded, the name of the wood degrading microbe, the Enzyme released by the microbe, the Decay strength of that enzyme, and the total loss to the economy by that decay. The unwanted decay of plant wood can be minimized if the causative agent and the enzyme released by it are found.

What can we learn from recent 2ν β β experiments?*

Abstract Recent measurements of the two neutrino double beta decay high precision electron spectra, combined with charge exchange or β-decay experimental data, have revealed severe constraints across current nuclear many body calculations. Our calculations show that the quasi-particle random phase approximation (QRPA) approach can adequately reproduce the measured spectra for the two open shell nuclei, Se and Mo. For the closed shell nucleus Xe, QRPA can also reproduce the spectra with proper treatments. Considering the high-lying state reduction, we also find that the nuclear shell model can also adequately reproduce the spectra and Gamow-Teller transition strength under a unique quenched axial-vector coupling constant . For Xe, we find that flipping the sign for the decay strength causes the spectra to go beyond the so-called high-lying state dominance hypothesis. These results call for future high precision measurements of charge-exchange reactions.

Gamow–Teller Beta Decay and Pseudo-SU(4) Symmetry

We report on recent experimental results on β decay into self-conjugate (N=Z) nuclei with mass number 58≤A≤70. Super-allowed β decays from the Jπ=0+ ground state of a Z=N+2 parent nucleus are to the isobaric analogue state through so-called Fermi transitions and to Jπ=1+ states by way of Gamow–Teller (GT) transitions. The operator of the latter decay is a generator of Wigner’s SU(4) algebra and as a consequence GT transitions obey selection rules associated with this symmetry. Since SU(4) is progressively broken with increasing A, mainly as a consequence of the spin–orbit interaction, this symmetry is not relevant for the nuclei considered here. We argue, however, that the pseudo-spin–orbit splitting can be small in nuclei with 58≤A≤70, in which case nuclear states exhibit an approximate pseudo-SU(4) symmetry. To test this conjecture, GT decay strength is calculated with use of a schematic Hamiltonian with pseudo-SU(4) symmetry. Some generic features of the GT β decay due to pseudo-SU(4) symmetry are pointed out. The experimentally observed GT strength indicates a restoration of pseudo-SU(4) symmetry for A=70.

Origin of the Reactor Antineutrino Anomalies in Light of a New Summation Model with Parametrized β^{-} Transitions.

We investigate the possible origins of the reactor antineutrino anomalies in norm and shape within the framework of a summation model where β^{-} transitions are simulated by a phenomenological model of Gamow-Teller decay strength. The general trends of divergence from the Huber-Mueller model on the antineutrino side can be reproduced in both norm and shape. From the exact electron-antineutrino correspondence of the summation model, we predict similar distortions in the electron spectra, suggesting that biases on the reference spectra of fission electrons could be the cause of the anomalies.

β decay of Ba141

The $\ensuremath{\beta}$-decay strength function of nuclides produced in fission is important as it dictates the distribution of decay energy between electrons, neutrinos, and $\ensuremath{\gamma}$ rays and so is critical for calculating decay heat in reactors and for estimating the reactor antineutrino spectrum. Several experimental techniques are available to determine this strength function, including electron spectroscopy, $\ensuremath{\gamma}$-ray calorimetry (TAGS spectroscopy), and detailed, high-resolution spectroscopy with modern large high-purity germanium arrays. This work investigates the decay of the well-known and strongly produced fission fragment $^{141}\mathrm{Ba}$. A beam of $^{141}\mathrm{Cs}$ was implanted at the target position of the Gammasphere and the subsequent decay of the daughter $^{141}\mathrm{Ba}$ was studied. Extensive decay spectroscopy was possible up to the decay $Q$ value of 3.197(7) MeV, including a significant extension of the level scheme and detailed angular correlation measurements for all levels with greater than $0.25%\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$ feeding. The distribution of the $\ensuremath{\beta}$-decay strength was then inferred and compared to previous calorimetric studies. The agreement was excellent and provides a benchmark for comparing strength function methods and data for a more detailed understanding of the structure of $^{141}\mathrm{La}$.

Quantum theory of nonradiative decay dependent on the coupling strength in a plexcitonic system

Revealing the quantum dynamics of plexciton, hybridized states produced by a quantum emitter and localized surface plasmon (LSP) in a strong coupling regime is of importance from fundamental and applied points of view. Photoluminescence (PL) spectrum is recognized for essentially reflecting the interaction between light and matter compared with extinction spectrum and scattering spectrum. However, there are still challenges to realize single-emitter plexciton in PL spectrum because of the unexpected nonradiative decay. In this paper, we develop a full-quantum method to describe the interaction between single emitter and a plasmonic nanocavity. By utilizing our model, we find that there is an optimum for surface-fluorescence enhancement near an intermediate coupling regime instead of a strong coupling regime. Furthermore, we show that strong electric-field enhancement will broaden plexciton’s linewidth covering the Rabi splitting in PL spectrum. The relation between nonradiative decay and coupling strength is given by a quantitative method, and we obtain the revised equation for PL spectrum. By comparing the revised PL spectrum with the scattering spectrum, we find that it is best to find optimal fluorescence splitting in the critical point between the intermediate coupling regime and strong coupling regime. Our method provides a theoretical method for explaining the nonradiative decay depending on coupling strength of a plexcitonic system in the PL spectrum and revealing single-emitter quantum optics.

Tensor force role in β decays analyzed within the Gogny-interaction shell model

Background: The half-life of the famous $^{14}$C $\beta$ decay is anomalously long, with different mechanisms: the tensor force, cross-shell mixing, and three-body forces, proposed to explain the cancellations that lead to a small transition matrix element. Purpose: We revisit and analyze the role of the tensor force for the $\beta$ decay of $^{14}$C as well as of neighboring isotopes. Methods: We add a tensor force to the Gogny interaction, and derive an effective Hamiltonian for shell-model calculations. The calculations were carried out in a $p$-$sd$ model space to investigate cross-shell effects. Furthermore, we decompose the wave functions according to the total orbital angular momentum $L$ in order to analyze the effects of the tensor force and cross-shell mixing. Results: The inclusion of the tensor force significantly improves the shell-model calculations of the $\beta$-decay properties of carbon isotopes. In particular, the anomalously slow $\beta$ decay of $^{14}$C can be explained by the isospin $T=0$ part of the tensor force, which changes the components of $^{14}$N with the orbital angular momentum $L=0,1$, and results in a dramatic suppression of the Gamow-Teller transition strength. At the same time, the description of other nearby $\beta$ decays are improved. Conclusions: Decomposition of wave function into $L$ components illuminates how the tensor force modifies nuclear wave functions, in particular suppression of $\beta$-decay matrix elements. Cross-shell mixing also has a visible impact on the $\beta$-decay strength. Inclusion of the tensor force does not seem to significantly change, however, binding energies of the nuclei within the phenomenological interaction.

Pulsating waves in a dissipative medium with Delta sources on a periodic lattice

This paper studies a dissipative heat equation with Delta sources of non-linear strength located on a periodic lattice. The model arises from intracellular waves in continuum excitable media with discrete release sites. Due to the presence of Delta sources, the solution of the model has discontinuous spatial derivatives. We focus on the bistable regime of the model, determined by the decay strength parameter a and the separation distance L between release sites, in which the model admits exactly three L-periodic steady states. We establish the existence of pulsating waves spatially connecting them. For the case of waves connecting two stable L-periodic steady states, the uniqueness and global exponential stability of pulsating waves are shown. Also a new technique is introduced to find the fine structure of the tails of pulsating waves.

Ground-state and decay properties of neutron-rich Nb106

The ground-state properties of neutron-rich 106Nb and its beta decay into 106Mo have been studied using the CARIBU radioactive-ion-beam facility at Argonne National Laboratory. Niobium-106 ions were extracted from a 252Cf fission source and mass separated before being delivered as low-energy beams to the Canadian Penning Trap, as well as the X-Array and SATURN beta-decay-spectroscopy station. The measured 106Nb ground-state mass excess of -66202.0(13) keV is consistent with a recent measurement but has three times better precision; this work also rules out the existence of a second long-lived, beta-decaying state in 106Nb above 5 keV in excitation energy. The decay half-life of 106Nb was measured to be 1.097(21) s, which is 8% longer than the adopted value. The level scheme of the decay progeny, 106Mo, has been expanded up to approximately 4 MeV. The distribution of decay strength and considerable population of excited states in 106Mo of J >= 3 emphasises the need to revise the adopted Jpi = 1- ground-state spin-parity assignment of 106Nb; it is more likely to be J => 3.

Evaluation of Decay and Shear Strength of Glued Laminated Timber Used Outdoors for 30 Years

Evaluation of Decay and Shear Strength of Glued Laminated Timber Used Outdoors for 30 Years

Experimental Measurement Method of Beta Decay Strength of Unstable Nuclei

The β decays of atomic nuclei refer to the transformation that the nuclei emit a β particle or capture an electron. The accurate measurements of the β transition strength functions Sβ(E) are of great significance in exploring the structure of unstable nuclei, revealing the process of stellar nucleosynthesis and also verifying the β decay theories. Experimentally, one way to determine the β transition strength is to directly measure the beta decay product using β-γ coincidence technique and/or total absorption spectroscopy. This method can give the transition information within the Qβ window. Another method to obtain the β decay strength is via the charge exchange reactions performed at the intermediate energy region (100~400 MeV/u), such as (p, n) or (3He, t). This is done by a high-precision measurement of the differential cross section. This method allows to access the transition strength that beyond the Qβ window, however, it is restricted by the beam intensity, and as a consequence hard to perform a systematical study of unstable nucleus with low yields. In view of this, in this paper we proposes a systematic measurement of the total charge exchange reaction cross section of the unstable nuclei. Combined with the well developed nuclear reaction theory, this method may set a constrain to the summed strength of the Gamow-Teller transition of the unstable nuclei within the proton separation threshold. Moreover, we introduce briefly the relevant work that has been carried out and planned.

Design considerations of grating couplers in directionally coupled waveguides.

The far-field pattern of an optical wave radiating from a grating coupler integrated in a directional coupler is discussed based on the coupled mode theory. It is shown that there are two types of intensity distributions with respect to the radiation angle. One type shows a simple single lobe, while the other has a deformed lobe or two lobes. Far-field patterns are discussed along with near-field patterns. They are determined by directional coupling strength as well as radiation decay strength. A parameter is introduced to indicate the type. The indicator is useful as a key parameter for device design.

Structure of beta-decay strength function Sβ(E) and quenching of axial-vector weak interaction constant in halo nuclei

Resonance structure of the beta decay strength function Sβ(E) for GT β--decay of halo nuclei6He and11Li is analyzed. Compare experimental total strength for β-transitions in gv2/4π units with the Ikeda sum rule (in(gAeff)2/4πunits) one can determine the squared ratio of axial-vector and vector weak interaction constants value (geff/gV)2. We obtained(geff/gv)1= 1.272 ± 0.010 for6He and (gAeff/gv)2= 1.5±0.2 for11Li β--decays. Quenching of the weak axial-vector constantgAeffin halo nuclei is discussed. Analysis of the evolution of EGTR- EIAStoward neutron-rich nuclei was done. It is shown that the valueZ/N≈ 0.6 corresponds to the SU(4) Wigner's spin-isospin symmetry region.

Recent Shell-model Calculations of \(\gamma \)-decay Strength Functions

We present recent shell-model calculations of the gamma-decay in sd-pf and pf-shell nuclei. We focus on the M1 part of the dipole strength which was shown to exhibit interesting low-energy effects, in particular a low-energy enhancement which can have a considerable impact on the radiative neutron capture. We discuss the persistence of the shell effects in the nuclear quasi-continuum and the relation between the shape of the strength function at low energy and nuclear deformation.

Decoherence effects on quantum Fisher information of multi-qubit W states

Quantum fisher information of a parameter characterizing the sensitivity of a state with respect to parameter changes. In this paper, we study the quantum fisher information of the W state for four, five, six and seven particles in decoherence channels, such as amplitude damping, phase damping and depolarizing channel. Using Krauss operators for decoherence channels components, we investigate the quantum fisher information quite analytically. We observe that for the W state, the amount of the quantum fisher information and consequently, the amount of entanglement are reduced by applying the quantum noises, which affect each particle in the same way. In some cases, a relative increase appears in the quantum fisher information for certain values of the decay strength p. We also show that the phase damping channel vanishes the value of the quantum fisher information for the W state.

Co69,71 β -decay strength distributions from total absorption spectroscopy

Background: The rapid neutron capture process is one of the main nucleosynthesis processes of elements heavier than Fe. Uncertainties in nuclear properties, such as masses, half-lives, and $\ensuremath{\beta}$-delayed neutron probabilities can cause orders of magnitude of variation within astrophysical $r$-process simulations. Presently, theoretical models are used to make global predictions of various nuclear properties for the thousands of nuclei required for these simulations, and measurements are required to benchmark these models, especially far from stability.Purpose: $\ensuremath{\beta}$-decay strength distributions can be used to not only inform astrophysical $r$-process simulations, but also to provide a stringent test for theoretical calculations. The aim of this work is to provide accurate strength distributions for $^{69,71}\mathrm{Co}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$ decay.Method: The technique of total absorption spectroscopy was used to measure the $\ensuremath{\beta}$ decay of $^{69,71}\mathrm{Co}$ for the first time at the National Superconducting Cyclotron Laboratory. The ions were implanted in a double-sided silicon strip detector at the center of the Summing NaI(Tl) detector and identified using standard particle identification methods. The response of the detection system to the $\ensuremath{\beta}$-decay electron and subsequent $\ensuremath{\gamma}$-ray radiation was fit to the observed experimental data using a ${\ensuremath{\chi}}^{2}$-minimization technique.Results: $\ensuremath{\beta}$-feeding intensities and Gamow-Teller strength distributions were extracted from the fits of the experimental data. The $\ensuremath{\beta}$-decay intensities show that there is a large percentage of feeding to levels above 2 MeV, which have not been observed in previous studies. The resultant $\ensuremath{\beta}$-feeding intensities and Gamow-Teller strength distributions were compared to shell model and quasiparticle random phase approximation (QRPA) calculations.Conclusions: Comparing experimentally determined $\ensuremath{\beta}$-decay strength distributions provides a test of models, which are commonly used for global $\ensuremath{\beta}$-decay properties for astrophysical calculations. This work highlights the importance of performing detailed comparisons of models to experimental data, particularly far from stability and as close to the $r$-process path as possible.

Suddenly shortened half-lives beyond Ni78:N=50 magic number and high-energy nonunique first-forbidden transitions

$\beta$-decay rates play a decisive role in understanding the nucleosynthesis of heavy elements and are governed by microscopic nuclear-structure information. A sudden shortening of the half-lives of Ni isotopes beyond $N=50$ was observed at the RIKEN-RIBF. This is considered due to the persistence of the neutron magic number $N=50$ in the very neutron-rich Ni isotopes. By systematically studying the $\beta$-decay rates and strength distributions in the neutron-rich Ni isotopes around $N=50$, I try to understand the microscopic mechanism for the observed sudden shortening of the half-lives. The $\beta$-strength distributions in the neutron-rich nuclei are described in the framework of nuclear density-functional theory. I employ the Skyrme energy-density functionals (EDF) in the Hartree-Fock-Bogoliubov calculation for the ground states and in the proton-neutron Quasiparticle Random-Phase Approximation (pnQRPA) for the transitions. Not only the allowed but the first-forbidden (FF) transitions are considered. The experimentally observed sudden shortening of the half-lives beyond $N=50$ is reproduced well by the calculations employing the Skyrme SkM* and SLy4 functionals. The sudden shortening of the half-lives is due to the shell gap at $N=50$ and cooperatively with the high-energy transitions to the low-lying $0^-$ and $1^-$ states in the daughter nuclei. The onset of FF transitions pointed out around $N=82$ and 126 is preserved in the lower-mass nuclei around $N=50$. This study suggests that needed is a microscopic calculation where the shell structure in neutron-rich nuclei and its associated effects on the FF transitions are selfconsistenly taken into account for predicting $\beta$-decay rates of exotic nuclei in unknown region.

First experimental constraint on the Os191(n,γ) reaction rate relevant to s -process nucleosynthesis

The nuclear level density and $\gamma$-decay strength of $^{192}$Os have been extracted using particle-$\gamma$ coincidence data from the $^{192}$Os($\alpha,\alpha^\prime\gamma$)$^{192}$Os reaction by means of the Oslo method. The level density is found to be a rather smooth function of excitation energy, approximately following the constant temperature model. The $\gamma$-decay strength is compared to photoneutron cross-section data above the neutron separation energy, and to $E1$ and $M1$ strengths for nuclei in this mass region derived from primary transitions following neutron capture. Our results are in good agreement with these previous data and draw a consistent picture of the $\gamma$-strength function in the range $E_\gamma \approx 1.5-6 $ MeV. Using the measured nuclear level density and $\gamma$-decay strength as input to the nuclear-reaction code TALYS, we provide the first experimentally constrained Maxwellian-averaged cross section (MACS) for the $^{191}$Os($n,\gamma$)$^{192}$Os reaction relevant to $s$-process nucleosynthesis. The systematic uncertainties introduced by the normalization procedure of the level density and $\gamma$-strength function were investigated and propagated to the calculated Maxwellian-averaged cross section. The obtained result of the Maxwellian-averaged cross section at $k_BT=30$ keV, $\langle \sigma \rangle_{n,\gamma}=1134\pm 375$ mb, is in very good agreement with the theoretical estimate provided by the KADoNiS project, giving experimental support to the adopted KADoNiS value. Good agreement is also found with MACS values obtained from other libraries, such as TENDL-2017, ENDF/B-VII.0, and JEFF.

Clarification of large-strength transitions in the β decay of Be11

The shape and normalisation of the beta-delayed alpha spectrum from 11Be was measured by implanting 11Be ions in a segmented Si detector. The spectrum is found to be dominated by a well-known transition to the 3/2+ state at Ex = 9.87MeV in 11B. A significant increase in the observed decay strength towards the higher end of the Q window means, however, that the 9.87MeV state cannot alone be responsible for the transition. Using the R-matrix framework we find that the inclusion of an extra 3/2+ state at Ex = 11.49(10)MeV is required in order to obtain a satisfactory description of the spectrum. Both states show large widths towards alpha decay, exhausting significant fractions of the Wigner limit, a typical signature of alpha clusterisation. The observed Gamow-Teller strength indicate large overlaps between the two states and the ground state of 11Be.