Nuclear Decay Processes Research Articles

Understanding the puzzle of angular momentum conservation in beta decay and related processes

We ask the question of how angular momentum is conserved in electroweak interaction processes. To introduce the problem with a minimum of mathematics, we first raise the same issue in elastic scattering of a circularly polarized photon by an atom, where the scattered photon has a different spin direction than the original photon, and note its presence in scattering of a fully relativistic spin-1/2 particle by a central potential. We then consider inverse beta decay in which an electron is emitted following the capture of a neutrino on a nucleus. While both the incident neutrino and final electron spins are antiparallel to their momenta, the final spin is in a different direction than that of the neutrino-an apparent change of angular momentum. However, prior to measurement of the final particle, in all these cases angular momentum is indeed conserved. The apparent nonconservation of angular momentum arises in the quantum measurement process in which the measuring apparatus does not have an initially well-defined angular momentum, but is localized in the outside world. We generalize the discussion to massive neutrinos and electrons, and examine nuclear beta decay and electron-positron annihilation processes through the same lens, enabling physically transparent derivations of angular and helicity distributions in these reactions.

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

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

All orders factorization and the Coulomb problem

In the limit of large nuclear charge, Z≫1, or small lepton velocity, β≪1, Coulomb corrections to nuclear beta decay and related processes are enhanced as Zα/β and become large or even nonperturbative (with α the QED fine structure constant). We provide a constructive demonstration of factorization to all orders in perturbation theory for these processes and compute the all-orders hard and soft functions appearing in the factorization formula. We clarify the relationship between effective field theory amplitudes and historical treatments of beta decay in terms of a Fermi function. Published by the American Physical Society 2024

Updated evaluation of potential ultralow Q -value β -decay candidates

"Ultra-low" Q value $\beta$ decays are referred to as such due to their low decay energies of less than $\sim$1 keV. Such a low energy decay is possible when the parent nucleus decays into an excited state in the daughter, with an energy close to that of the Q value. These decays are of interest as potential new candidates for neutrino mass determination experiments and as a testing ground for studies of atomic interference effects in the nuclear decay process. In this paper, we provide an updated evaluation of atomic mass data and nuclear energy level data to identify potential ultra-low Q value $\beta$ decay candidates. For many of these candidates, more precise and accurate atomic mass data is needed to determine if the Q value of the potential ultra-low decay branch is energetically allowed and in fact ultra-low. The precise atomic mass measurements can be achieved via Penning trap mass spectrometry.

Tsallis Divergence as Strategy for Radioactive Source Search and Location

For the problem of searching radioactive sources in a certain area, a search method combining Tsallis divergence strategy with a particle filtering algorithm is proposed. The method this paper proposes for searching for radioactive sources is carried out by using a mobile platform equipped with a NaI(Tl) scintillator detector. The estimation model of the parameters of the radioactive source is constructed and is based on the inverse square law and the fact that the count values of the NaI(Tl) detector in nuclear decay processes obeys the Poisson distribution. The Tsallis divergence strategy is used as a reward function to control the movement of the platform. The posterior distribution of the parameters of the radioactive source is continuously and iteratively updated by using the particle filtering algorithm. The results of Monte Carlo simulations and practical experiments verify the effectiveness of the algorithm.

Isomers as a bridge between nuclear and atomic physics

The year 2021 marks exactly 100 years since Otto Hahn discovered the first example of nuclear isomerism. The existence of long-lived nuclear excited states opens a window on nuclear structure and applications. From isomers, the availability of electromagnetic decay pathways enables coupling to the atomic electrons, such that nuclear and atomic transitions become interdependent. The nuclear decay process of internal conversion is the most well known. However, observation of its inverse, nuclear excitation by free electron capture, is controversial and requires further research. In this work, the relationship between nuclear and atomic transitions is outlined, and examples are discussed of the use of external electromagnetic radiation to manipulate nuclear transitions associated with isomers.

Following nuclei through nucleosynthesis: A novel tracing technique

Astrophysical nucleosynthesis is a family of diverse processes by which atomic nuclei undergo nuclear reactions and decay to form new nuclei. The complex nature of nucleosynthesis, which can involve as many as tens of thousands of interactions between thousands of nuclei, makes it difficult to study any one of these interactions in isolation using standard approaches. In this work, we present a new technique, nucleosynthesis tracing, that we use to quantify the relative fraction of nuclear abundances that pass through individual nuclear reaction, decay, and fission processes at any point during nucleosynthesis. We apply this technique to study fission and ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay as they occur in the rapid neutron capture ($r$) process of nucleosynthesis.

First in-core gamma spectroscopy experiments in a zero power reactor

Gamma rays in nuclear reactors, arising either from nuclear reactions or decay processes, significantly contribute to the heating and dose of the reactor components. Zero power research reactors offer the possibility to measure gamma rays in a purely neutronic environment, allowing for validation experiments of dose estimates, computed spectra, and prompt to delayed gamma ratios. The resulting data can contribute to models, code validation and photo atomic/nuclear data evaluation. To date, most experiments have relied on flux measurements using TLDs, ionization chambers, or spectrometers set in low flux areas. The CROCUS reactor allows for flexible detector placement in and around the core, and has recently been outfitted with gamma detection capabilities to fulfill the need for in-core gamma spectroscopy, as opposed to flux. In this paper we report on the experiments and accompanying simulations of gamma spectrum measurements inside a zero power reactor core, CROCUS. It is a two-zone, uranium-fueled light water moderated facility operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology Lausanne (EPFL). Herein we also introduce, in detail, the new LEAF system: A Large Energy-resolving detection Array for Fission gammas. It consists of an array of four detectors – two large ø 127 254 mm Bismuth Germanate (BGO) and two smaller ø 12 50 mm Cerium Bromide (CeBr3) scintillators. We describe the calibration and characterization of LEAF followed by first in-core measurements of gamma ray spectra in a zero power reactor at different sub-critical and critical states, and different locations. The spectra are then compared to code results, namely MCNP6.2 pulse height tallies. We were able to distinguish prompt processes and delayed peaks from decay databases. We present thus experimental data from hitherto inaccessible core regions. We provide the data as validation means for codes that attempt to model these processes for energies up to 10 MeV. We finally draw conclusions and discuss the future uses of LEAF. The results indicate the possibility of isotope tracking and burn-up validation.

Erosion or decay? Conceptualizing causes and mechanisms of democratic regression

ABSTRACT Democratic regression has become a worrying phenomenon in the last years. Social science has provided a variety of explanations why democratic regimes have lost democratic regime quality. Against this backdrop, I take stock of the recent literature by putting forward two important analytical distinctions that we should make more explicit. First, I propose to classify our current explanations along the source where the cause for the malaise originated. By doing so, I introduce a distinction between erosion and decay type of arguments. While the former is a gradual process that is caused exogenously – like wind or water hitting a stone – the latter is caused endogenously – like the half-life in nuclear decay processes. Second, I draw a distinction between the endogenous or exogenous roots of the cause and the subsequent causal mechanism that connects the cause with the outcome. I outline the need for dissecting a causal mechanism into its constitutive components and highlight its underlying dimensions of temporality. Throughout the article, I use empirical case material as well as relevant secondary literature to illustrate these points.

Sensitive search for double electron capture on 124Xe in XMASS-I

Double electron capture is a rare nuclear decay process in which two orbital electrons are captured simultaneously in the same nucleus. We have conducted an improved search for two-neutrino double electron capture on 124Xe and 126Xe using 800.0 days of the XMASS-I data. As a result of fitting the observed energy spectra with the expected signal and background, no significant signal is found. Therefore, we set the most stringent lower limits on their half-lives at 2.1 × 1022 years for 124Xe and 1.9 × 1022 years for 126Xe at 90% confidence level. The limits get improved by a factor of 4.5 compared to the previous result.

Chernobyl’s Lesser Known Design Flaw: The Chernobyl Liquidator Medal—An Educational Essay

The honorary Chernobyl Liquidator Medal depicts pathways of alpha, gamma, and beta rays over a drop of blood, signifying the human health impacts of the Chernobyl accident. A relativistic analysis of the trajectories depicted on the Chernobyl Liquidator Medal is conducted assuming static uniform magnetic and electric fields. The parametric trajectories are determined using the energies of alpha (α) and beta (β) particles relevant to the Chernobyl nuclear power plant accident and compared with the trajectories depicted on the liquidator medal. For minimum alpha particle velocity of 0.0512c, the beta particle trajectory depicted on the medal is highly unlikely to have come from a naturally occurring nuclear decay process. The parametric equations are used to determine the necessary beta energies to reproduce the depicted trajectories. This article documents the unfortunate misrepresentation of a famous scientific experiment on an honorary medal and illustrates the importance of better communication between artists and scientists.

α decay in intense laser fields: Calculations using realistic nuclear potentials

We calculate the effect of intense laser fields on nuclear alpha decay processes, using realistic and quantitative nuclear potentials. We show that alpha decay rates can indeed be modified by strong laser fields to some finite extent. We also predict that alpha decays with lower decay energies are relatively easier to be modified than those with higher decay energies, due to longer tunneling paths for the laser field to act on. Furthermore, we predict that modifications to angle-resolved penetrability are easier to achieve than modifications to angle-integrated penetrability.

Identification and investigation of possible ultra-low Q value β decay candidates

Among the wide energy range of β decays, there can exist decays with Q values as low as a few hundred eV. These decays can occur when the parent decays to a excited state in the daughter nucleus. Such decays have been called “ultra-low” Q value β decays. Their application is mainly twofold: (1) they are of interest as potential candidates for neutrino mass determination experiments, and (2) they provide a testing ground for theoretical studies of atomic interference effects in the nuclear decay process. In this work we have identified a number of such potential candidates by analyzing the most recent atomic mass and nuclear energy level data. To determine if an ultra-low Q value β decay branch is energetically allowed for these candidates, more precise and accurate data for the Q value of the ultra-low decay branch is needed. In most cases, this requires more precise atomic mass measurements for the parent and/or daughter atoms. These requirements can be met using Penning trap mass spectrometry.

Quantitative electron spectroscopy of 125I over an extended energy range

Auger electrons emitted after nuclear decay have potential application in targeted cancer therapy. For this purpose it is important to know the Auger electron yield per nuclear decay. In this work we measure the ratio of the number of conversion electrons (emitted as part of the nuclear decay process) and the number of Auger electrons (emitted as part of the atomic relaxation process after the nuclear decay) for the case of 125I. Results are compared with Monte-Carlo type simulations of the relaxation cascade using the BrIccEmis code. With the appropriate choice of parameters this program describes the observed spectra quite well over the whole energy range.

Nuclear recoil spectroscopy of levitated particles

We propose a new method for the detection and characterization of nuclear decay processes. Specifically, we describe how nuclear decay recoil can be observed within small particles levitated in an optical trap with high positional resolution. Precise measurements of the magnitude of each recoil as well as their rate of occurrence can provide accurate information about the isotopic composition of a radioactive sample. We expect that this new technique for nuclear material characterization will be especially useful in the area of nuclear forensic analysis.

Radioactive Transition Metals for Imaging and Therapy.

Nuclear medicine is composed of two complementary areas, imaging and therapy. Positron emission tomography (PET) and single-photon imaging, including single-photon emission computed tomography (SPECT), comprise the imaging component of nuclear medicine. These areas are distinct in that they exploit different nuclear decay processes and also different imaging technologies. In PET, images are created from the 511 keV photons produced when the positron emitted by a radionuclide encounters an electron and is annihilated. In contrast, in single-photon imaging, images are created from the γ rays (and occasionally X-rays) directly emitted by the nucleus. Therapeutic nuclear medicine uses particulate radiation such as Auger or conversion electrons or β- or α particles. All three of these technologies are linked by the requirement that the radionuclide must be attached to a suitable vector that can deliver it to its target. It is imperative that the radionuclide remain attached to the vector before it is delivered to its target as well as after it reaches its target or else the resulting image (or therapeutic outcome) will not reflect the biological process of interest. Radiochemistry is at the core of this process, and radiometals offer radiopharmaceutical chemists a tremendous range of options with which to accomplish these goals. They also offer a wide range of options in terms of radionuclide half-lives and emission properties, providing the ability to carefully match the decay properties with the desired outcome. This Review provides an overview of some of the ways this can be accomplished as well as several historical examples of some of the limitations of earlier metalloradiopharmaceuticals and the ways that new technologies, primarily related to radionuclide production, have provided solutions to these problems.

Measurement of the intensity ratio of Auger and conversion electrons for the electron capture decay of 125I

Auger electrons emitted after nuclear decay have potential application in targeted cancer therapy. For this purpose it is important to know the Auger electron yield per nuclear decay. In this work we describe a measurement of the ratio of the number of conversion electrons (emitted as part of the nuclear decay process) to the number of Auger electrons (emitted as part of the atomic relaxation process after the nuclear decay) for the case of 125I. Results are compared with Monte-Carlo type simulations of the relaxation cascade using the BrIccEmis code. Our results indicate that for 125I the calculations based on rates from the Evaluated Atomic Data Library underestimate the K Auger yields by 20%.

ID2018 Radioisotope Enzymes And Cancer Study

Cancer is a pathological symptom, when abnormal cells appear in certain human tissues or organs. These cells can reproduce beyond the control of normal biological protection mechanism. Because they multiply themselves rapidly, the metabolic process is accelerated, which causes an extreme need for energy, substrate material and catalyzing enzyme. Bases on these needs, we can control the metabolic process by: • Stopping the supply of energy. • Stopping the supply of substrate materials to build up the cell’s structure. • Stopping the catalysis process by breaking out the enzyme’s structure and/or deactivating the catalytic function of existing enzymes. • Destroying the tumor cells by extraneous agents such as radiations and chemicals. All of these methods have been studied for a long time, with a lot of resources to be spent. Although we obtained some positive result, it is nowhere closed to satisfactory. There are many reasons for this situation but the main issue is the lack of information of the processes taking place in human’s cells and body. In this paper, we, however, would like to propose a method to break the structure and/or to deactivate the catalytic function of the enzyme by nuclear decay process.

Radioactivity: An Introduction to Mysterious Science

Materials that undergo decay process to attain a stable configuration followed by the emission of particles such as alpha, beta and gamma are termed as radioactive elements. Radioactivity is measured in Curie (Ci) and Becquerel (Bq) SI units. Though radioactive elements are abundant on Earth and constantly decays to produce stable nuclei but such nuclear decay process may pose serious health threats to living beings. Therefore, must be regulated when working in vitro. Biosafety levels should be strictly observed when engaged in radioactive experiments to minimize contamination exposure.

Search for two-neutrino double electron capture on 124Xe with the XMASS-I detector

Double electron capture is a rare nuclear decay process in which two orbital electrons are captured simultaneously in the same nucleus. Measurement of its two-neutrino mode would provide a new reference for the calculation of nuclear matrix elements whereas observation of its neutrinoless mode would demonstrate lepton number violation. A search for two-neutrino double electron capture on $^{124}$Xe is performed using 165.9 days of data collected with the XMASS-I liquid xenon detector. No significant excess above background was observed and we set a lower limit on the half-life as $4.7 \times 10^{21}$ years at 90% confidence level. The obtained limit has ruled out parts of some theoretical expectations. We obtain a lower limit on the $^{126}$Xe two-neutrino double electron capture half-life of $4.3 \times 10^{21}$ years at 90% confidence level as well.