Electron Capture Probability Research Articles

Determination of Fractional Electron Capture Probabilities of 59Ni by Means of Metallic Magnetic Calorimeters

Determination of Fractional Electron Capture Probabilities of 59Ni by Means of Metallic Magnetic Calorimeters

Liquid scintillation efficiencies, gamma-ray emission intensities, and half-life for Gd-153

Gadolinium-153 was standardized for activity by live-timed anticoincidence counting and an ampoule was submitted to the international reference system (SIR). Absolute emission intensities for the main γ rays were determined with calibrated high-purity germanium (HPGe) and lithium-drifted silicon (Si(Li)) detectors. A revised decay scheme is indicated, with no probability of direct electron capture to the 153Eu ground state. Triple-to-double coincidence ratio (TDCR) efficiency curves indicate that the revised decay scheme is consistent with experiment. Half-life measurements agree with a previous NIST determination and show no sensitivity to chemical environment.

Multifunctional Thiophene Cascading SnO2/Perovskite Interfaces for Efficient and Stable MAPbI3 Photovoltaics.

The power conversion efficiency (PCE) and stability of n-i-p perovskite solar cells (PSCs) are significantly affected by inherent defects of SnO2 and perovskite layers. In this work, we incorporate 2-bromo-3-thiophenic acid (BrThCOOH) as a multifunctional passivant to simultaneously passivate the defects of SnO2 surface and perovskite layer. BrThCOOH permeates evenly into the MAPbI3 and coordinates with Pb2+ and iodine vacancies (VI+) to reduce surface defect density and inhibit the decomposition of MAPbI3. Carboxylic acid effectively passives the oxygen vacancy on the surface of SnO2 through coordination bonds, reducing the probability of electron capture by SnO2 surface defects, thus contributing to electron transport in device. The interaction of BrThCOOH with MAPbI3 and SnO2 surfaces leads to an upward shift in energy levels, reducing energy loss during charge migration. The optimal MAPbI3 device with BrThCOOH-modified SnO2 (T-SnO2) reveals an improved PCE of 21.12%, much higher than that of the control one (19.12%). The hydrophobicity of BrThCOOH-modified MAPbI3 is also improved, which is beneficial to the durability of the device. After 100 h of storage in the environment, the generated PSCs maintain their initial PCE of 75%, demonstrating excellent long-term stability without any encapsulation.

Shake-off in the Er164 neutrinoless double-electron capture and the dark matter puzzle

Traditionally neutrinoless double-electronic capture is considered as a resonance process. Degeneracy of the initial and daughter nuclei is the main factor mastering the decay rate. We have fulfilled shake-off probability calculations. Allowance for the shake-off loosens the need for resonance, leading to a radical increase of the capture rate in the nonresonance nuclei. In the case of $^{164}\mathrm{Er}$, the contribution of the new mechanism increases the capture rate by a factor of 5.6. It also increases the probability of electron capture from higher shells. The influence of the shake-off is also expected to manifest itself in the other $\ensuremath{\beta}$ processes which are used in the studies of the neutrino nature, its mass and role in the dark matter puzzle.

Shakeoff Effect on the Rate of Neutrinoless Double-Electron Capture in $${}^{{164}}$$Er

Traditionally double neutrinoless electronic capture is considered as a resonance process. We have fulfilled shake-off probability calculations, leading to ionization of the electron shell, in the case of $^{164}$Er. Allowance for the shake-off removes the requirement of resonance, leading to an increase of the capture rate. The contribution of the new mechanism increases the capture rate by a factor of 5.6 compared to the conventional resonance fluorescence mechanism. It also increases the probability of electron capture from higher shells, which must be foreseen in an experimental study. Moreover, effect of the shake-off can potentially expand the list of candidate nuclei for experiments.

Theoretical and experimental studies on the captured electron population probability of hydrogen-like O and N ions in collision with Al surface

The study of the interaction between highly charged ions and solid surfaces not only has great significance for basic scientific research such as atomic physics, astrophysics, and high energy density physics but also has promising application prospects in biomedicine, nanotechnology, surface analysis, and microelectronics. In this paper, the intermediate Rydberg states formed during highly charged O<sup>7+</sup> and N<sup>6+</sup> ions incident on Al surface are studied theoretically by using the two-state vector model. Both the probability of electron capture into different Rydberg states (<i>n<sub>A</sub></i> = 2 − 7) and the most probable neutralization distances are given. The calculation shows that the larger principal quantum number <i>n<sub>A</sub></i> is relevant to smaller probability. Therefore, the X-rays emitted by O<sup>7+</sup> and N<sup>6+</sup> ions incident on the Al surface come mainly from the de-excitation of the smaller <i>n<sub>A</sub></i> to the ground state. In order to confirm the calculations, we measured the X-ray emission spectra of O<sup>7+</sup> and N<sup>6+</sup> ions in collisions with the Al surface in the energy range of 3-20 keV/q. The experiments were performed at an ECR ion source located in Institute of modern physics. We also calculated the transition energies (n<i>p</i>-1<i>s</i>) from different high Rydberg states to the ground state by using the FAC code. The center of the measured <i>K</i> X-ray peak is close to the calculated transition energy from the principal quantum number n=2 to n=1, it is consistent with our results obtained by the two-state vector model as well. In addition, we found the experimental <i>K</i> X-ray yield for O<sup>7+</sup> ions incidence at lower energy collisions is almost the same with N<sup>6+</sup> ions, but larger at higher energy collisions. When the ion incident kinetic energy is low, the X-ray emission is mainly owing to the decay of “above the surface”hollow atoms. Because of the small difference in the critical distances for the capture of electrons by O<sup>7+</sup> and N<sup>6+</sup> to form hollow atoms, the X-ray yields produced in both cases are almost the same at low energy collisions. In contrast, as increasing the incident energy, the ions have a long-range in the target, so the contribution from the decay of “above the surface” and “below the surface”hollow atoms need to be considered at the same time.

^{159}Dy Electron-Capture: A New Candidate for Neutrino Mass Determination.

The ground state to ground state electron-capture Q value of ^{159}Dy (3/2^{-}) has been measured directly using the double Penning trap mass spectrometer JYFLTRAP. A value of 364.73(19)keV was obtained from a measurement of the cyclotron frequency ratio of the decay parent ^{159}Dy and the decay daughter ^{159}Tb ions using the novel phase-imaging ion-cyclotron resonance technique. The Q values for allowed Gamow-Teller transition to 5/2^{-} and the third-forbidden unique transition to 11/2^{+} state with excitation energies of 363.5449(14)keV and 362.050(40)keV in ^{159}Tb were determined to be 1.18(19)keV and 2.68(19)keV, respectively. The high-precision Q value of transition 3/2^{-}→5/2^{-} from this work, revealing itself as the lowest electron-capture Q value, is used to unambiguously characterize all the possible lines that are present in its electron-capture spectrum. We performed atomic many-body calculations for both transitions to determine electron-capture probabilities from various atomic orbitals and found an order of magnitude enhancement in the event rates near the end point of energy spectrum in the transition to the 5/2^{-} nuclear excited state, which can become very interesting once the experimental challenges of identifying decays into excited states are overcome. The transition to the 11/2^{+} state is strongly suppressed and found unsuitable for measuring the neutrino mass. These results show that the electron-capture in the ^{159}Dy atom, going to the 5/2^{-} state of the ^{159}Tb nucleus, is a new candidate that may open the way to determine the electron-neutrino mass in the sub-eV region by studying electron-capture. Further experimental feasibility studies, including coincidence measurements with realistic detectors, will be of great interest.

Electron cascades and secondary electron emission in graphene under energetic ion irradiation

Highly energetic ions traversing a two-dimensional material such as graphene produce strong electronic excitations. Electrons excited to energy states above the work function can give rise to secondary electron emission, reducing the amount of energy that remains the graphene after the ion impact. Electrons can either be emitted (kinetic energy transfer) or captured by the passing ion (potential energy transfer). To elucidate this behavior that is absent in three-dimensional materials, we simulate the electron dynamics in graphene during the first femtoseconds after ion impact. We employ two conceptually different computational methods: a Monte Carlo (MC) based one, where electrons are treated as classical particles, and time-dependent density functional theory (TDDFT), where electrons are described quantum-mechanically. We observe that the linear dependence of electron emission on deposited energy, emerging from MC simulations, becomes sublinear and closer to the TDDFT values when the electrostatic interactions of emitted electrons with graphene are taken into account via complementary particle-in-cell simulations. Our TDDFT simulations show that the probability for electron capture decreases rapidly with increasing ion velocity, whereas secondary electron emission dominates in the high velocity regime. We estimate that these processes reduce the amount of energy deposited in the graphene layer by 15\,\% to 65\,\%, depending on the ion and its velocity. This finding clearly shows that electron emission must be taken into consideration when modelling damage production in two-dimensional materials under ion irradiation.

Change in 7Be half-life in host media

First-principle calculations within the density functional theory framework are used to study the probability of electron capture for the 7Be nucleus. For this purpose, electron density at the 7Be nucleus is computed in Al, Au, Pd, Pt, and Pb environments. Our results show that the half-life of 7Be is changed by implanting 7Be in host environments. Electron affinity of the media and confinement effects are responsible for the change in the half-life of 7Be nucleus. Moreover, electric potential at the 7Be nucleus is calculated. Results show that variations in electric potential are usually consistent with those in electron density at the 7Be nucleus.

Calculation of electron capture probability of energetic protons colliding with rare-gas atoms: A comparison study on four methods

We calculate the probability of electron capture of energetic protons colliding with rare-gas atoms, comparing four methods based on time-dependent density-functional theory (TDDFT). By approximating the pair-correlation function of the system with an explicit dependence on the fractional number of bound electrons, a new effective model of pair-correlation function is built up. Benchmark calculations are given over a wide range of impact energy, demonstrating that the new designed read-out functional reproduces quite accurately the single-electron capture cross sections and the double-electron capture features which were not properly described by previous TDDFT calculations.

MetroMMC: Electron-Capture Spectrometry with Cryogenic Calorimeters for Science and Technology

Accurate decay data of radionuclides are necessary for many fields of science and technology, ranging from medicine and particle physics to metrology. However, data that are in use today are mostly based on measurements or theoretical calculation methods that are rather old. Recent measurements with cryogenic detectors and other methods show significant discrepancies to both older experimental data and theory in some cases. Moreover, the old results often suffer from large or underestimated uncertainties. This is in particular the case for electron-capture (EC) decays, where only a few selected radionuclides have ever been measured. To systematically address these shortcomings, the European metrology project MetroMMC aims at investigating six radionuclides decaying by EC. The nuclides are chosen to cover a wide range of atomic numbers Z, which results in a wide range of decay energies and includes different decay modes, such as pure EC or EC accompanied by gamma - and/or beta ^{+}-transitions. These will be measured using metallic magnetic calorimeters (MMCs), cryogenic energy-dispersive detectors with high-energy resolution, low-energy threshold and high, adjustable stopping power that are well suited for measurements of the total decay energy and X-ray spectrometry. Within the MetroMMC project, these detectors are used to obtain X-ray emission intensities of external sources as well as fractional EC probabilities of sources embedded in a 4pi absorber. Experimentally determined nuclear and atomic data will be compared to state-of-the-art theoretical calculations which will be further developed within the project. This contribution introduces the MetroMMC project and in particular its experimental approach. The challenges in EC spectrometry are to adapt the detectors and the source preparation to the different decay channels and the wide energy range involved, while keeping the good resolution and especially the low-energy threshold to measure the EC from outer shells.

Predicting the performance of the inter-Coulombic electron capture from single-electron quantities

The probability of the inter-Coulombic electron capture (ICEC) is studied for nanowire-embedded quantum-dot pairs where electron capture in one dot leads to electron emission from the other. Previous studies pointed to an interdependence of several ICEC pathways which can enhance the ICEC reaction probability. To identify favorable criteria for such synergies in a qualitative and quantitative manner, we conducted a considerable amount of simulations scanning multiple geometrical parameters. The focus of the paper is not only to find the geometries which are most favorable to ICEC but most importantly to explain the basic principles of the ICEC probability. We have thus derived a number of energy relations among solely single-electron level energies that explain the mechanisms of the multiple reaction pathways. Among them are direct ICEC, both slowing or accelerating the outgoing electron, as well as resonance-enhanced ICEC which captures into a two-electron resonance state that decays thereafter. These pathways may apply simultaneously for just one single geometric configuration and contribute constructively leading to an enhancement of the reaction probability. Likewise some conditions are found that clearly turn down the ICEC probability to zero. The results based on single-electron relations are so general that they can as well be used to predict the ICEC probability from the electronic structure in arbitrary physical systems such as atoms or molecules.

Direct determination of the La138β -decay Q value using Penning trap mass spectrometry

Background: The understanding and description of forbidden decays provides interesting challenges for nuclear theory. These calculations could help to test underlying nuclear models and interpret experimental data. Purpose: Compare a direct measurement of the $^{138}$La $\beta$-decay $Q$ value with the $\beta$-decay spectrum end-point energy measured by Quarati et al. using LaBr$_3$ detectors [Appl. Radiat. Isot. 108, 30 (2016)]. Use new precise measurements of the $^{138}$La $\beta$-decay and electron capture (EC) $Q$ values to improve theoretical calculations of the $\beta$-decay spectrum and EC probabilities. Method: High-precision Penning trap mass spectrometry was used to measure cyclotron frequency ratios of $^{138}$La, $^{138}$Ce and $^{138}$Ba ions from which $\beta$-decay and EC $Q$ values for $^{138}$La were obtained. Results: The $^{138}$La $\beta$-decay and EC $Q$ values were measured to be $Q$ = 1052.42(41) keV and $Q_{EC}$ = 1748.41(34) keV, improving the precision compared to the values obtained in the most recent atomic mass evaluation [Wang, et al., Chin. Phys. C 41, 030003 (2017)] by an order of magnitude. These results are used for improved calculations of the $^{138}$La $\beta$-decay shape factor and EC probabilities. New determinations for the $^{138}$Ce 2EC $Q$ value and the atomic masses of $^{138}$La, $^{138}$Ce, and $^{138}$Ba are also reported. Conclusion: The $^{138}$La $\beta$-decay $Q$ value measured by Quarati et al. is in excellent agreement with our new result, which is an order of magnitude more precise. Uncertainties in the shape factor calculations for $^{138}$La beta-decay using our new $Q$ value are reduced by an order of magnitude. Uncertainties in the EC probability ratios are also reduced and show improved agreement with experimental data.

Low energy secondary electron induced damage of condensed nucleotides.

Radiation damage and stimulated desorption of nucleotides 2'-deoxyadenosine 5'-monophosphate (dAMP), adenosine 5'-monophosphate (rAMP), 2'-deoxycytidine 5'-monophosphate (dCMP), and cytidine 5'-monophosphate (rCMP) deposited on Au have been measured using x-rays as both the probe and source of low energy secondary electrons. The fluence dependent behavior of the O-1s, C-1s, and N-1s photoelectron transitions was analyzed to obtain phosphate, sugar, and nucleobase damage cross sections. Although x-ray induced reactions in nucleotides involve both direct ionization and excitation, the observed bonding changes were likely dominated by the inelastic energy-loss channels associated with secondary electron capture and transient negative ion decay. Growth of the integrated peak area for the O-1s component at 531.3 eV, corresponding to cleavage of the C-O-P phosphodiester bond, yielded effective damage cross sections of about 23 Mb and 32 Mb (1 Mb = 10-18 cm2) for AMP and CMP molecules, respectively. The cross sections for sugar damage, as determined from the decay of the C-1s component at 286.4 eV and the glycosidic carbon at 289.0 eV, were slightly lower (about 20 Mb) and statistically similar for the r- and d- forms of the nucleotides. The C-1s component at 287.6 eV, corresponding to carbons in the nucleobase ring, showed a small initial increase and then decayed slowly, yielding a low damage cross section (∼5 Mb). Although there is no statistical difference between the sugar forms, changing the nucleobase from adenine to cytidine has a slight effect on the damage cross section, possibly due to differing electron capture and transfer probabilities.

Probability of Electron Capture by 3He2+ Ions from Argon Atoms at Different Impact Parameters

Probability of Electron Capture by 3He2+ Ions from Argon Atoms at Different Impact Parameters

Quantum-Chemical Analysis of the Electron Transfer in the MgTiF6+12MgCl2 Molten System By Frontier Molecular Orbital Method

Investigation of the electrochemical charge transfer mechanism in molten salts containing transition metal complexes is a challenging task. Such studies could be facilitated by analysis of the corresponding model systems by quantum-chemical methods. However, in practice, a direct search for the transition state in such systems requires enormous computational time. In this work, we suggest to use an approach that allows us to qualitatively characterize possible variants of electron transfer and, thus, to sharply narrow the search for the transition state. We mean the use of the frontier molecular orbital method. The method is traditionally employed to evaluate the reactivity of species. However, when applied to electrochemical systems, the method can also provide extremely useful information on whether a certain electron transfer mechanisms is possible or impossible In this work, we were interested in the state of the complex TiF6 2- near the cathode surface. For this reason, on one side of the molten system, a flat boundary layer consisting of 17 chlorine and magnesium ions was formed. In general, the boundary ions of chlorine and magnesium are not in the same plane. The mutual displacement of these ions was determined from the computation in the model system C96H24+7MgCl2, where C96H24 is a flat carbon cluster simulating the surface of the cathode; hydrogen atoms close the broken bonds of carbon atoms to prevent artifacts. After optimization of this system, the chlorine anions shifted by 0.3 Å relative to the magnesium cations (Δd) in the direction opposite to the surface of the carbon cluster. The direction of this displacement corresponds to the effect of the electric field on the chlorine anions. Thus, the equilibrium shift Δd is 0.3 Å. The model system MgTiF6+12MgCl2 with such shift value will be considered referent. A systematic study of the influence of the Δd value and the length of Ti-F bonds (Δr) on the lowest unoccupied molecular orbital (LUMO) character showed the following: 1) the group of lower free MOs, the main contribution to which gives the TiF6 2- complex, is destabilized with increasing of Ti-F bond contraction; 2) when the shift Δd increases, this MO group is also destabilized and simultaneously free MOs belonging to the boundary ions become more stable. In particular, when the Ti-F bonds are compressed on Δr = 0.05 Å, the critical value of the shift Δd is 0.6 Å. That is, at Δd ≥ 0.6 Å and Δr = 0.05 Å, LUMO is delocalized between the complex and the bridge cation. At excessively large values of Δd and Δr, LUMO is completely localized on the boundary ions, but this is undesirable. The combination of the parameters Δd = 0.6, 0.7 Å and Δr = 0.05 Å is optimal. At these values, LUMO is delocalized between the complex and the bridge cation and the activation energy (~18 kJ mol-1) is close to the experimental value (21±4 kJ mol-1). An increase in the parameter Δr leads to a rapid increase in the activation energy, a contraction value of 0.05 Å is optimal. An equally important characteristic is the highest occupied molecular orbital (HOMO) type of the structure after electron transfer (ET). Theoretically, there may exist three main types of HOMO for our structures (after ET): 1) HOMO is completely localized on the boundary ions; 2) HOMO is delocalized between the boundary ions and the complex; 3) HOMO is completely localized on the complex. In the first case, probability of electron capture by the complex is very small. After diffusion of the complex into the depth of the melt, electron remains on the boundary ions and then returns to the cathode. In the second case, there is a significant probability of ET to the complex through the bridge cation. In the latter case, the probability of electron capture by the complex is close to 100%, if the complex is in contact with the surface of the electrode.

Classical simulation of differential single charge transfer in fast proton-helium collisions

Three-body classical trajectory Monte Carlo method is employed to simulate the differential single electron capture process in fast proton-helium collisions. For the considered collisional system, by means of an independent particle model, both electron capture and electron excitation probabilities are evaluated in terms of the classical impact parameter and the related discussions are presented. The method is also applied to calculate the projectile-angular distribution of the cross sections in energy range of 50–630 keV. The obtained results are compared to the available precise data due to the cold-target recoil ion momentum spectroscopy and good overall agreement found with these experimental data. Also, within a classical-trajectory framework, the correlation between the impact parameter and the projectile scattering angle is examined through the simulation of the collision process.

Comparison of Intersubband Quantum-Well and Interband Graphene-Layer Infrared Photodetectors

We compare the characteristics of the intersubband quantum-well infrared photodetectors (QWIPs) based on the traditional semiconductor materials and the interband graphene-layer infrared photodetectors (GLIPs) based on van der Waals heterostructures. We show that the responsivity and dark-current-limited detectivity of GLIPs exceed those of QWIPs. This is because of a stronger radiation interband absorption in the GLs, a smaller capture probability of electrons into the GLs, and a higher activation energy of the electron thermionic and tunneling escape from the GLs in comparison with those in the QWs.

Total, state-selective and differential cross sections for single electron capture in He+–He collisions

The total, state-selective and angular-differential cross sections for single electron capture in He+–He collisions are investigated by using the two-center atomic orbital close-coupling method in the energy range 0.2–650 keV/u. The angular-differential cross sections for electron capture to the ground state of He are calculated at collision energies of 0.625, 1.25, 7.5, 25, 60, and 150 keV/u within the eikonal approximation for the scattering amplitude. Both total and differential cross sections are compared with the available experimental and theoretical data. The calculated differential cross sections exhibit oscillatory structures with exponentially decreasing amplitude and frequency decreasing with increasing the collision energy. They show good agreement with the experimental data for scattering angles where decreases with increasing the collision energy ( for E = 0.625 keV/u, for E = 150 keV/u). We found out that for a given collision energy, the oscillatory structure of angular-differential cross section is strongly correlated with the oscillatory structure of the impact parameter dependence of electron capture probability.

Measurement of the electron capture probabilities of 55Fe with a metallic magnetic calorimeter

The ratios of the electron capture probabilities PK, PL and PM of 55Fe have been measured with a metallic magnetic calorimeter, a specific type of cryogenic detector. The 55Fe source was enclosed in the detector absorber, whose dimensions were chosen such that the detection efficiency for Mn K X-rays was larger than 99.99%. Since all electrons and photons emitted by the source are absorbed in the detector, the detection efficiency is virtually 100% for K, L and M captures. The energy threshold was low enough to allow for clear separation of the M captures (~ 80eV) from noise. The capture probability ratios were translated to capture probabilities using the recommended value for the probability of the undetected N captures. The resulting values are in agreement both with the recommended values of PK, PL and PM and with the experimental data of Pengra and coworkers.