Radiative Proton Capture Research Articles

Stellar Thermonuclear Reaction Rates of Proton Radiative Capture by Closed Light Shell Isotopes

Light isotopes, especially closed shell nuclei, have significance in thermonuclear reactions of the Carbon-Nitrogen-Oxygen (CNO) cycle in stars. In this research, 12C(p, γ) 13N and 14N(p, γ) 15O reactions have been calculated by means of Matlab codes to find the reaction rate across a temperature range of 0.006 to 10 GK using non-resonant parts, as well as the astrophysical S- factor S(E) at low energies. It was concluded that the high binding energy of 12C and 14N nuclei make the reaction less probable thus enabling other competitive processes to develop, which enhances the probability of other competitive proton reactions in the CNO cycle.

ANC and SF of bound states in 15N→14C+p, 16O→15N+p, 19F→18O+p, 32S→31P+p

Asymptotic normalization coefficients (ANCs) and spectroscopic factors (SFs) for proton binding in the ground states of the [Formula: see text]N, [Formula: see text]O, [Formula: see text]F and [Formula: see text]S nuclei were extracted from an analysis of available literature data on the (3He[Formula: see text]) and ([Formula: see text]) reactions. Modified DWBA and ADWA analyses showed that the proton transfer process is more peripheral in (3He,d) reactions and therefore more reliable for determining the ANCs. As a result of the comparative analysis of peripheral (3He,d) and nonperipheral ([Formula: see text]) reactions, the uncertainties in the extracted values of SFs were reduced. The data obtained are to be used in calculating astrophysical S-factors for radiative proton capture.

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.

Systematic study of the radiative proton capture including the compound, pre-equilibrium, and direct mechanisms

Systematic study of the radiative proton capture including the compound, pre-equilibrium, and direct mechanisms

Radiative capture of proton through the 14N(p,γ)15O reaction at low energy

The CNO cycle is the main source of energy in stars more massive than our Sun. This process defines the energy production, the duration of which can be used to determine the lifetime of massive stars. The cycle is an important tool for determining the age of globular clusters. Radiative proton capture via , at energies of astrophysical interest, is an important process in the CNO cycle. In this project, we apply a potential model to describe both non-resonant and resonant reactions in the channels where radiative capture occurs through electric transitions. We employed the R-matrix method to describe the ongoing reactions via resonant transitions, when it was not possible to correctly reproduce the experimental data using the potential model. The partial components of the astrophysical S-factor are calculated for all possible electric and magnetic dipole transitions in 15O. The linear extrapolated S-factor at zero energy (S(0)) agrees well with earlier reported values for all transition types considered in this work. Based on the value of the total astrophysical S-factor, depending on the collision energy, we calculate the nuclear reaction rates for . The computed rates agree well with the results reported in the NACRE II Collaboration and most recent existing measurements.

Reaction rate of radiative capture of proton by 11B nucleus

Reaction rate of radiative capture of proton by 11B nucleus

Ab initio informed evaluation of the radiative capture of protons on 7Be

The radiative capture of protons by 7Be, which is the source of 8B that β-decays emitting the majority of higher-energy solar neutrinos measured on earth, has not yet been measured at astrophysically relevant energies. The recommended value for its zero-energy S-factor, S17(0)=20.8±(0.7)exp±(1.4)theory eV⋅b, relies on theoretical extrapolations from higher-energy measurements, a process that leads to significant uncertainty. We performed a set of first-principle (or, ab initio) calculations of the 7Be(p,γ)8B reaction to provide an independent prediction of the low-energy S-factor with quantified uncertainties. We demonstrate underlying features in the predicted S-factor allowing the combination of theoretical calculations and measurements to produce an evaluated S-factor of S17(0)=19.8±0.3 eV⋅b. We expect the calculations and uncertainty quantification process described here to set a new standard for the evaluation of light-ion astrophysical reactions.

Cross section measurement of the ^{12}C(p,gamma )^{13}N reaction with activation in a wide energy range

The CNO cycle is one of the fundamental processes of hydrogen burning in stars. The first reaction of the cycle is the radiative proton capture on ^{12}C and the rate of this ^{12}C(p,gamma )^{13}N reaction is related to the ^{12}C/^{13}C ratio observed e.g. in the Solar System. The low-energy cross section of this reaction was measured several times in the past, however, the experimental data are scarce in a wide energy range especially around the resonance at 1.7 MeV. In the present work the ^{12}C(p,gamma )^{13}N cross section was measured between 300 and 1900 keV using the activation method. This method was only used several decades ago in the low-energy region. As the activation method provides the total cross section and has uncertainties different from those of the in-beam gamma -spectroscopy technique, the present results provide a largely independent data set for future low-energy extrapolations and thus for astrophysical reaction rate calculations.

Контроль наносекундных сгустков протонов в магнитоизолированном ионном диоде по резонансным ядерным реакциям радиационного захвата протонов

To calibrate the detection efficiency of a plastic scintillator that detects prompt gamma quanta from the 19F(p,αγ)16O resonant reaction of radiative proton capture and is used to control the dynamics of the arrival of protons with an energy of about 340 keV accelerated by a magnetically isolated pulsed ion diode, a change the polarity of the diode electrodes to the reverse was used, at which electron bunches were accelerated in the geometry of the Luce diode, forming virtual cathodes. The virtual cathodes in the Luce diode collectively accelerated protons to an energy of about 500 keV, the value of which was determined from the drift velocity of these virtual cathodes, while the number of such protons was determined from the activity of the 13N radionuclide induced by the 457 keV resonance of the 12C(p,γ)13N reaction.

Control of nanosecond proton bunches in a magnetically insulated ion diode by resonant nuclear reactions of radiative proton capture

To calibrate the detection efficiency of a plastic scintillator that detects prompt gamma quanta from the 19F(p,αγ)16O resonant reaction of radiative proton capture and is used to control the dynamics of the arrival of protons with an energy of about 340 keV accelerated by a magnetically isolated pulsed ion diode, a change the polarity of the diode electrodes to the reverse was used, at which electron bunches were accelerated in the geometry of the Luce diode, forming virtual cathodes. The virtual cathodes in the Luce diode collectively accelerated protons to an energy of about 500 keV, the value of which was determined from the drift velocity of these virtual cathodes, while the number of such protons was determined from the activity of the 13N radionuclide induced by the 457 keV resonance of the 12C(p,γ)13N reaction. Keywords: intense pulsed ion beam, organic scintillator, prompt gamma spectrometry.

Radiative proton capture on N15 within effective field theory

The astrophysical $S$ factor for the radiative proton capture process on the $^{15}\mathrm{N}$ nucleus, i.e., $^{15}\mathrm{N}(p, \gamma)^{16}\mathrm{O}$, at stellar energies are studied within the framework of the cluster effective field theory. The thermonuclear $^{15}\mathrm{N}(p, \gamma)^{16}\mathrm{O}$ reaction links the type-I to type-II cycles of the carbon-nitrogen-oxygen cycle and affects the abundances of elements in the univere. For investigating this reaction in the effective field theory formalism, we first construct an effective Lagrangian that is appropriate for this reaction at low-energies. Since the intermediate excited states of the $^{16}\mathrm{O}$ nucleus have a crucial role in this reaction, we include these resonances in the formalism. The corresponding radiative capture amplitudes and cross section are calculated, which lead to the astrophysical $S$ factor. The low energy constants introduced in the effective Lagrangian are determined by fitting the theoretical results to the observed $S$ factors in the range of $130~\mathrm{keV} < E_p < 2500~\mathrm{keV}$ using three different experimental data sets. Considering the recent data sets, we obtain $S(0) = 29.8\mbox{-}34.1~\mathrm{keV\ b}$, which is in a good agreement with the estimates from $R$-matrix approaches in the literature. The values of $S$ at the Gamow energy are found to be larger than $S(0)$ values by about $10\%$.

Magnetic dipole transitions in 9Be(p,γ)10B

The proton radiative capture reactions are crucial in nuclear astrophysics. 9Be(p,γ)10B is important in stellar and primordial nucleosynthesis. In the present work, we compute the astrophysical S-factor for 9Be(p,γ)10B by employing the potential model (PM) for the magnetic transitions. Moreover, we revised the nuclear structure features and spectroscopic properties of the 10B nucleus under the PM approach.

Re-analysis of radiative capture11C(p, γ)12N at low energy

Within the framework of the modified potential model, we computed the astrophysical S-factor of the proton radiative capture p + 11C → 12N + γ. At energies bearing astrophysical importance, radiative capture is a key process in the spectroscopic study of 12N. In this work, we consider the radiative capture cross-section for the proton capture by 11C within the framework of the potential model. For the possible electric and magnetic dipole transitions, we computed the partial components of the astrophysical S-factor within the energy range E = (0.01–0.8) MeV. The computed value of the S-factor at zero energy shows satisfactory agreement with the reported results. Furthermore, we computed the radiative capture rates for the selected reaction, which shows a better comparison with the reported data.

Stable nickel production in type Ia supernovae: A smoking gun for the progenitor mass?

Context. At present, there are strong indications that white dwarf (WD) stars with masses well below the Chandrasekhar limit (MCh ≈ 1.4 M⊙) contribute a significant fraction of SN Ia progenitors. The relative fraction of stable iron-group elements synthesized in the explosion has been suggested as a possible discriminant between MCh and sub-MCh events. In particular, it is thought that the higher-density ejecta of MCh WDs, which favours the synthesis of stable isotopes of nickel, results in prominent [Ni II] lines in late-time spectra (≳150 d past explosion). Aims. We study the explosive nucleosynthesis of stable nickel in SNe Ia resulting from MCh and sub-MCh progenitors. We explore the potential for lines of [Ni II] in the optical an near-infrared (at 7378 Å and 1.94 μm) in late-time spectra to serve as a diagnostic of the exploding WD mass. Methods. We reviewed stable Ni yields across a large variety of published SN Ia models. Using 1D MCh delayed-detonation and sub-MCh detonation models, we studied the synthesis of stable Ni isotopes (in particular, 58Ni) and investigated the formation of [Ni II] lines using non-local thermodynamic equilibrium radiative-transfer simulations with the CMFGEN code. Results. We confirm that stable Ni production is generally more efficient in MCh explosions at solar metallicity (typically 0.02–0.08 M⊙ for the 58Ni isotope), but we note that the 58Ni yield in sub-MCh events systematically exceeds 0.01 M⊙ for WDs that are more massive than one solar mass. We find that the radiative proton-capture reaction 57Co(p, γ)58Ni is the dominant production mode for 58Ni in both MCh and sub-MCh models, while the α-capture reaction on 54Fe has a negligible impact on the final 58Ni yield. More importantly, we demonstrate that the lack of [Ni II] lines in late-time spectra of sub-MCh events is not always due to an under-abundance of stable Ni; rather, it results from the higher ionization of Ni in the inner ejecta. Conversely, the strong [Ni II] lines predicted in our 1D MCh models are completely suppressed when 56Ni is sufficiently mixed with the innermost layers, which are rich in stable iron-group elements. Conclusions. [Ni II] lines in late-time SN Ia spectra have a complex dependency on the abundance of stable Ni, which limits their use in distinguishing among MCh and sub-MCh progenitors. However, we argue that a low-luminosity SN Ia displaying strong [Ni II] lines would most likely result from a Chandrasekhar-mass progenitor.

Examining measuring the degree of linear photon-beam polarization in the energy range up to 100 MeV with the use of He4(γ⃗,p)H3 and He4(γ⃗,n)He3 reactions

The paper gives physical justification of a new method for measuring the degree of linear photon-beam polarization, which relies on the experimental data for the total cross section of spin $S$ = 1 transitions in the $^{4}\mathrm{He}(\ensuremath{\gamma},p)^{3}\mathrm{H}$ and $^{4}\mathrm{He}(\ensuremath{\gamma},n)^{3}\mathrm{He}$ reactions. The experimental information on the cross section was obtained from both the mentioned reactions and the reactions of radiative capture of protons by tritium nuclei. The total cross section for transitions with spin $S$ = 1 is $\ensuremath{\approx}1%$ of the total cross section for the reaction. The ratio of the differential cross section in the collinear geometry, specified by the $S$ = 1 transitions, to the differential reaction cross section at the nucleon emission angle ${\ensuremath{\theta}}_{N}={90}^{\ensuremath{\circ}}$ in the energy range 20 $\ensuremath{\le}{E}_{\ensuremath{\gamma}}\ensuremath{\le}$ 100 MeV is independent of the photon energy within the experimental error. The total cross section for the $S$ = 1 transitions can be also determined from the experimental data on the cross-section asymmetry of the reaction with linearly polarized photons $\mathrm{\ensuremath{\Sigma}}({\ensuremath{\theta}}_{N})$. However, the total cross section for transitions with spin $S$ = 1, calculated from the asymmetry of the cross section $\mathrm{\ensuremath{\Sigma}}({\ensuremath{\theta}}_{N})$, is several times greater than that calculated from the differential cross section. This inconsistency of the experimental data may be due, in particular, to the overestimate of the degree of linear photon-beam polarization. The above-mentioned reactions seem to be more convenient for measuring the degree of linear photon-beam polarization than the deuteron photodisintegration reactions.

Radiative capture of proton by 9Be(p, γ)10B at low energy

Radiative capture p + 9Be → 10B + γ at energies bearing astrophysical importance is a key process for the spectroscopic study of 10B. In this work, we consider the radiative capture cross-section for the 9Be(p, γ)10B within the framework of the potential model and the R-matrix method for the multi-entrance channel cases. In certain cases, when the potential fails, therefore, the R-matrix approach is better to use for the description of partial components of the cross-section that have sharp or broad resonances. For all possible electric and magnetic dipole transitions, partial components of the astrophysical S-factor are computed. The computed value of the total S-factor at zero energy is consistent with the reported results.

Radiative proton–capture reactions with 112,114Cd at astrophysically important energies

The reaction network in the neutron-deficient part of the nuclear chart around A ≈ 100 contains several nuclei of importance to astrophysical processes, such as the p–process. This work reports on the results from recent experimental studies of the radiative proton–capture reactions 112,114Cd(p, γ)113,115 In. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched 112Cd and 114Cd targets. Two different techniques, the in–beam γ–ray spectroscopy and the activation method have been implemented, where the latter is considered mandatory to account for the presence of low–lying isomers in 113In (E ≈ 392 keV, t1/2 ≈ 100 min), and 115In (E ≈ 336 keV, t1/2 ≈ 4.5 h). Following the measurement of the cross sections, the astrophysical S factors have been subsequently

New anomaly observed in He4 supports the existence of the hypothetical X17 particle

Energy-sum and angular correlation spectra of $e^+e^-$ pairs produced in the $^{3}$H(p,$\gamma$)$^{4}$He nuclear reaction have been studied at $E_p$=510, 610 and 900 keV proton energies. The main features of the spectra can be understood by taking into account the internal and external pair creations following the direct proton radiative capture by $^{3}$H. However, these processes cannot account for the observed peak around 115$^\circ$ in the angular correlation spectra. This anomalous excess of $e^+e^-$ pairs can be described by the creation and subsequent decay of a light particle during the direct capture process. The derived mass of the particle is $m_\mathrm{X}c^2$=16.94$\pm0.12 (stat) \pm 0.21 (syst)$~MeV. According to the mass and branching ratio ($B_x=5.1(13)\times10^{-6}$), this is likely the same X17 particle, which we recently suggested [Phys. Rev. Lett. 116, 052501 (2016)] for describing the anomaly observed in the decay of $^8$Be.

Reaction rate of the 7Li(p,γ)8Be radiative capture at low energies

Within the framework of the modified potential cluster model with the classification of orbital states according to Young diagrams, the possibility of description experimental data for S-factor of the proton radiative capture on 7Li to the ground state of 8Be is considered. It was shown that taking into account E1 and M1 transitions from the state of p7Li scattering to the ground state of 8Be in the p7Li channel it is possible to explain the value of the S-factor at energies up to 10 MeV. Based on the calculated total cross sections, the reaction rate in the temperature range of 0.01 to 10.0 T9 is obtained. It is demonstrated that the inclusion of low-lying resonance states gives some contribution into the reaction rate at high temperatures.

An investigation of radiative proton–capture reactions in the Cd–In mass region

The reaction network in the neutron–deficient part of the nuclear chart around A∼100 contains several nuclei of importance to astrophysical processes, such as the p–process. This work reports on the results from recent experimental studies of the radiative proton-capture reactions 112,114Cd(p,γ)113,115In. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched 112Cd and 114Cd targets. Two different techniques, the in–beam γ–ray spectroscopy and the activation method have been employed, with the latter considered necessary to account for the presence of low–lying isomers in 113In (Eγ≈392 keV, t1/2≈100 min), and 115In (Eγ≈336 keV, t1/2≈4.5 h). Following the measurement of the total reaction cross sections, the astrophysical S factors have been additionally deduced. The experimental results are compared with Hauser–Feshbach theoretical calculations carried out with the most recent version of TALYS. The results are discussed in terms of their significance to the various parameters entering the models.