Radiative Capture Reactions Research Articles

Validity analysis of γ-ray strength function models for radiative capture reactions of heavy nuclei

Accurate simulation of radiative capture reactions (RCRs) requires precise modeling of [Formula: see text]-ray strength functions (GSF). Various GSF models exist but need normalization based on experimental total radiative width (TRW) data. This study found that current normalization methods fail for neutron-induced RCRs in [Formula: see text]U and [Formula: see text]Th nuclei. In this regard, re-normalization values are proposed in order to improve model consistency at low energies. The standard Lorentzian (SLO) model fits experimental data best with minimal normalization.

A study of the fine-structure constant dependence of radiative capture in Halo-EFT

We study the fine structure constant dependence of the rates of some selected radiative capture reactions within the framework of so-called Halo Effective Field Theory in order to assess the adequacy of some assumptions made on the Coulomb penetrability. We find that this dependence deviates from that implied by a parameterization of the cross sections of this effect via a simple penetration factor. Some features of this fine-structure dependence are discussed, in particular its potential impact on the abundances of the light elements in primordial nucleosynthesis.

Investigating the rate of $$^{10}$$Be(n,$$\gamma$$)$$^{11}$$Be radiative capture reaction within the FRDWBA framework

Investigating the rate of $$^{10}$$Be(n,$$\gamma$$)$$^{11}$$Be radiative capture reaction within the FRDWBA framework

The Astrophysical S Factor of the p + 7Be Radiative Capture Reaction

The Astrophysical S Factor of the p + 7Be Radiative Capture Reaction

Magnetic dipole transition in proton-deuteron radiative capture at BBN energies within potential model

The pd radiative capture reaction plays a vital role in Big Bang nucleosynthesis and stellar proton-proton chain. The study of the low-energy reaction is challenging in both experiments and theories. Using the framework of potential model, we analyze pd radiative capture below 1 MeV for both electric dipole (E1) and magnetic dipole (M1) transitions. The obtained astrophysical S factors agree well with recent results, especially at energies relevant to sensitive deuterium abundance. The calculated reaction rate shows good agreement, with less than a 5% difference compared to recent works. The extrapolated value for S(0) including both transitions is determined to be 0.211 ± 0.016 eV b. A comparison with experimental data using the χ 2 test reveals the sensitivity of the M1 cross section at low energies to the scattering potential depth.

Study on producing radioisotopes based on fission or radiative capture method in a high flux reactor

Radioisotopes tend to play important roles in many fields, such as industry, healthcare, agriculture, aerospace, etc. Radioisotope production is mainly through accelerators or research reactors, and high flux research reactor is one of the most effective approaches for radioisotope production. The physical basis of preparing radioisotope relies on nuclear reactions occurring in the reactor core, which includes fission, (n,γ), (n,α), and (n,p) reaction, etc. Among them, fission and (n,γ) reaction are most important in the nuclear reactor. For example, the 99Mo could be generated by uranium fission and extracting from the fission products, or through the radiative capture reaction from enriched 98Mo. As for the fission method, the irradiation target is gradually transitioning from high enriched uranium (HEU) target to low enriched uranium (LEU) target due to the requirement of non-proliferation. In this paper, studies on the impacts of different fission targets on radioisotope productions are conducted. Moreover, an optimized study on the radiative capture method is performed to improve the production efficiency. It is concluded that it is advantageous to use radiative capture method to generate radioisotopes in high flux reactor, which helps to improve the specific activity with environmental friendliness.

Astrophysical S-factor and reaction rate for 15N(p,γ)16O within the modified potential cluster model* *Supported by the Ministry of Science and Higher Education of the Republic of Kazakhstan (AP09259174)

We study radiative capture on the ground state of 16O at stellar energies within the framework of a modified potential cluster model (MPCM) with forbidden states, including low-lying resonances. The investigation of the 15N( )16O reaction includes the consideration of resonances due to transitions and the contribution of the scattering wave in the p + 15N channel due to the transition. We calculated the astrophysical low-energy S-factor, and the extrapolated turned out to be within 34.7−40.4 keV·b. The important role of the asymptotic constant (AC) for the 15N( )16O process with interfering (312) and (962) resonances is elucidated. A comparison of our calculation for the S-factor with existing experimental and theoretical data is addressed, and a reasonable agreement is found. The reaction rate is calculated and compared with the existing rates. It has negligible dependence on the variation of AC but shows a strong impact of the interference of (312) and (962) resonances in reference to the CNO Gamow windows, especially at low temperatures. We estimate the contribution of cascade transitions to the reaction rate based on the exclusive experimental data from Phys. Rev. C. 85, 065810 (2012). The reaction rate enhancement due to the cascade transitions is observed from and reaches the maximum factor ~ 1.3 at . We present the Gamow energy window and a comparison of rates for radiative proton capture reactions 12N( )13O, 13N( ) 14O, 14N( )15O, and 15N( )16O obtained in the framework of the MPCM and provide the temperature windows, prevalence, and significance of each process.

Calculation of Thermalized Component of Neutron Spectra in a D-D Neutron Generator

The results of the thermalized flux calculation that incorporate radiative capture reactions in the presence and absence of polyethylene blocks that form an enclosure for a deuteron-deuteron (D-D) neutron generator are presented. This method can be used to measure the moderated neutron flux component in a mixture of moderated and primary neutron spectra. Using 20-cm-thick polyethylene blocks to surround a D-D neutron generator, the moderation of primary neutrons was investigated using nine indium foils. In this paper, the relationship between the moderated neutron flux and the radiative capture rates in the presence and absence of polyethylene blocks is derived. This is compared to a MCNP simulation and a calculation of modulated flux that ignore the primary neutron components.

The astrophysical [formula omitted] factor of [formula omitted]9Be radiative capture reaction in a potential model

In this work, we calculate the S-factor for p+9Be Radiative Capture Reaction according to a modified potential model. We consider the sum of all possible electrical and magnetic transitions as a total cross-section. The zero-energy S-factor results are in good agreement with previously theoretical studies and the experimentally reported data.

Astrophysical S-Factor Analysis for 14N(p, γ)15O Radiative Capture Reaction Based on p + 14N Elastic Scattering at Low Energies

Astrophysical S-Factor Analysis for 14N(p, γ)15O Radiative Capture Reaction Based on p + 14N Elastic Scattering at Low Energies

Triton-alpha radiative capture reaction at astrophysical energies

Triton-alpha radiative capture reaction at astrophysical energies

Estimation of the S34(0) S-factor for 3He(α, γ)7Be reaction by using distorted wave born approximation and artificial neural network

The astrophysical S-factor and total cross-section of radiative capture reaction are analyzed using the first-order distorted wave born approximation and artificial neural network. To make estimations of S34(0) at energies going to zero, we have used an artificial neural network model as a new approximation in this area. First, we obtain distorted wave born approximation results using the Gaussian and Woods-Saxon potentials. After, we evaluate artificial neural network approximation to analyze reaction observables of the system. Our results show that artificial neural network model is a powerful candidate as an extrapolation model for astrophysical energies for estimating of the S-factor observable.

Estimation of radiative capture 13B(n, γ 0+1)14B reaction rate in the modified potential cluster model* *Supported by the Ministry of Science and Higher Education of the Republic of Kazakhstan (AP09259174)

We discuss current attempts to employ the modified potential cluster model to describe the available experimental data on the 13B(n, γ 0+1)14B total cross-sections. The estimated results of the M1 and E1 transitions from the n 13B scattering states to the ground and first excited states of 14B are presented. The 1st resonance at E x = 1. 275 MeV (1+) is revealed in both the cross-section and reaction rate. Within the variation in the asymptotic constant, a thermal cross-section interval of 5.1 – 8.9 mb is proposed. Based on the theoretical total cross-sections at energies of 0.01 eV to 5 MeV, we calculate the reaction rate in the temperature range of 0.01 to 10T 9. The ignition T 9 values of the 13B(n, γ 0+1)14B reaction depending on a neutron number density of ~ 1022 cm−3 are determined. The radiative neutron capture reaction rates on the boron 10-13B and carbon 12-14С isotopes are compared.

Continuum random-phase approximation for (n,γ) reactions on neutron-rich nuclei: Collective effects and resonances

We formulate a microscopic theory to calculate cross section of the radiative neutron capture reaction on neutron-rich nuclei using the continuum random-phase approximation (cRPA) to the time-dependent density functional theory (TDDFT). With an intention of applying to the $r$ process, for which the statistical reaction model may not be appropriate, we describe the transition between a initial state of incident neutron and a final state of the $\ensuremath{\gamma}$ decay by means of a single many-body framework of the cRPA-TDDFT. With the cRPA approach, it is possible to describe various excitation modes present in the $(n,\ensuremath{\gamma})$ reaction, including soft dipole excitation, the giant resonances, as well as noncollective excitations and the single-particle resonances. Furthermore, it enables us to describe the $(n,\ensuremath{\gamma})$ reaction where the the final states of the $\ensuremath{\gamma}$ transition are low-lying surface vibrational states. We demonstrate the theory by performing numerical calculation for the reaction $^{139}\mathrm{Sn}(n,\ensuremath{\gamma})^{140}\mathrm{Sn}$. We discuss various new features which are beyond the single-particle model: the presence of narrow and wide resonances originating from noncollective and collective excitations and roles of low-lying quadrupole and octupole vibrational states.

Advances in radiative capture studies at LUNA with a segmented BGO detector

Studies of charged-particle reactions for low-energy nuclear astrophysics require high sensitivity, which can be achieved by means of detection setups with high efficiency and low backgrounds, to obtain precise measurements in the energy region of interest for stellar scenarios. High-efficiency total absorption spectroscopy is an established and powerful tool for studying radiative capture reactions, particularly if combined with the cosmic background reduction by several orders of magnitude obtained at the Laboratory for Underground Nuclear Astrophysics (LUNA). We present recent improvements in the detection setup with the Bismuth Germanium Oxide (BGO) detector at LUNA, aiming to reduce high-energy backgrounds and increase the summing detection efficiency. The new design results in enhanced sensitivity of the BGO setup, as we demonstrate and discuss in the context of the first direct measurement of the 65 keV resonance (E x = 5672 keV) of the 17O(p,γ)18F reaction. Moreover, we show two applications of the BGO detector, which exploit its segmentation. In the case of complex γ-ray cascades, e.g. the de-excitation of E x = 5672 keV in 18F, the BGO segmentation allows to identify and suppress the beam-induced background signals that mimic the sum peak of interest. We demonstrate another new application for such a detector in form of in situ activation measurements of a reaction with β + unstable product nuclei, e.g. the 14N(p,γ)15O reaction.

$$^{3}\hbox{He} - \alpha $$ Radiative Capture Reaction by EFT

We have investigated the $$^3\hbox{He} (\alpha ,\gamma ) ^7\hbox{Be}$$ radiative capture reaction using the pionless Effective Field Theory (EFT). The amplitude, cross-section, and S-factor for the $$E_1$$ and $$E_2$$ transitions to the $$^{7}\hbox{Be}$$ ground state have been computed using the Faddeev equation approach up to Next-to Leading Order in the astrophysical energy range. Our aim has been the study of Coulomb interaction effects and the contribution of EFT higher-order calculations in optimizing the results. The computed S-factor for the reaction agrees with experimental data and previous theoretical calculations.

Cross sections of the Rb83(p,γ)Sr84 and Kr84(p,γ)Rb85 reactions at energies characteristic of the astrophysical γ process

We have measured the cross section of the $^{83}\mathrm{Rb}(p,\ensuremath{\gamma})^{84}\mathrm{Sr}$ radiative capture reaction in inverse kinematics using a radioactive beam of $^{83}\mathrm{Rb}$ at incident energies of 2.4 and $2.7\phantom{\rule{0.16em}{0ex}}A$ MeV. Prior to the radioactive beam measurement, the $^{84}\mathrm{Kr}(p,\ensuremath{\gamma})^{85}\mathrm{Rb}$ radiative capture reaction was measured in inverse kinematics using a stable beam of $^{84}\mathrm{Kr}$ at an incident energy of $2.7A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\ensuremath{\gamma}$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17--0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{84}\mathrm{Sr}$, caused by the reduced rate of the $^{84}\mathrm{Sr}(\ensuremath{\gamma},p)^{83}\mathrm{Rb}$ reaction derived from the present measurement.

The Big Bang nucleosynthesis abundances of the light elements using improved thermonuclear reaction rates

Big Bang nucleosynthesis (BBN) is an important stage of a homogeneous and isotropic expanding universe. The results of calculation of the synthesis of light elements during this epoch can then be compared with the abundances of the light elements. The theoretical calculation of the BBN model depends on the initial conditions of the early universe and reaction cross sections measured by the nuclear physics experiment. Recently, an update of the Nuclear Astrophysics Compilation of REactions database is presented. This improved compilation comprises thermonuclear reaction rates for 34 two-body reactions on light nuclides (fifteen are particle transfer reactions and nineteen are radiative capture reactions). In this work, we calculate the BBN abundances by using these updated thermonuclear reaction rates in the framework of the code AlterBBN. Our results suggest that the new numerical result of the primordial Lithium abundance is 7.1% larger than the previous calculation.

Recoil mass separators for nuclear astrophysics: The role of ERNA

The measurements of radiative capture reactions can be performed in inverse kinematic detecting directly the recoil produced in the nuclear reaction using a recoil mass separator (RMS). The development of RMS allows the possibility to overtake both the problems of gamma background signal and purity and production of target. The European Recoil Separator for Nuclear Astrophysics (ERNA) is a RMS designed with the main goal of determining the 12C(α, γ)16O, presently hosted at Center for Isotopics Research and Cultural hEritage laboratory of Department of Mathematics and Physics, University of Campania Luigi Vanvitelli, Caserta Italy (CIRCE-DMF). A general discussion on measurement techniques with recoil mass separator will be presented in this contribution with a focus on the ERNA one.

Determination of asymptotic normalization coefficients for the channel $$^{16}$$O$$\rightarrow \alpha +^{12}$$C: excited state $$^{16}$$O($$0^+; 6.05$$ MeV)

Asymptotic normalization coefficients (ANC) determine the overall normalization of cross sections of peripheral radiative capture reactions. In the present paper, we treat the ANC $C$ for the virtual decay $^{16}$O$(0^+; 6.05$ MeV)$\to \alpha+^{12}$C(g.s.), the known values of which are characterized by a large spread $(0.29-1.65)\times 10^3$ fm$^{-1/2}$. The ANC $C$ is found by analytic continuation in the energy of the $\alpha^{12}$C $s$-wave scattering amplitude, known from the phase-shift analysis of experimental data, to the pole corresponding to the $^{16}$O bound state and lying in the unphysical region of negative energies. To determine $C$, two different methods of analytic continuation are used. In the first method, the scattering data are approximated by the sum of polynomials in energy in the physical region and then extrapolated to the pole. The best way of extrapolation is chosen on the basis of the exactly solvable model. Within the second approach, the ANC $C$ is found by solving the Schr\"odinger equation for the two-body $\alpha^{12}$C potential, the parameters of which are selected from the requirement of the best description of the phase-shift analysis data at a fixed experimental binding energy of $^{16}$O$(0^+; 6.05$ MeV) in the $\alpha+^{12}$C channel. The values of the ANC $C$ obtained within these two methods lie in the interval (886--1139) fm$^{-1/2}$.