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The thermonuclear rate of the 7 Be( p , γ ) 8 B reaction was calculated using the effective field theory (EFT) and coupled-channel formalism, considering the contribution of the excited nuclei 7 Be* up to the N 2 LO. We also investigated how the 1 + resonance affects the reaction rate. Our conclusions from this process were consistent with the known experimental data and the results of other theoretical methods. [ABSTRACT FROM AUTHOR]

The 14C(p,γ)15N reaction is of considerable interest in nuclear astrophysics. This reaction is one of the reactions of 15N production in the stars. The rate of the 14C(p,γ)15N reaction plays an important role in the formation of nuclei with an atomic mass of more than 14. Currently, this reaction at low energies has not been studied well enough, both experimentally and theoretically. Therefore, in this work, within the framework of a modified potential cluster model with a classification of orbital states according to Young's diagrams and taking into account allowed and forbidden states, we examined the possibility of describing the available experimental data for the total cross sections of the radiative p14C capture to the ground state of the 15N nucleus. The calculations carried out take into account the wide resonance at 1.4 MeV in c.m. and performed at energies up to 5 MeV. It is shown that only on the basis of the E1 transition from the p14C scattering state, it is quite possible to explain the magnitude and shape of the experimental astrophysical S-factor. The work presents comparisons of the astrophysical S-factors of the radiative p14C capture to the ground state of the 15N nucleus found by us with the experimental data available in the literature. Based on the obtained total cross sections, the rate of this reaction was calculated in the temperature range from 0.01 to 10.0 T9. The calculated results for rates are approximated by a simple expression, which simplifies their use in applied thermonuclear and astrophysical research. [ABSTRACT FROM AUTHOR]

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Indirect experimental angular distributions data for protons elastically scattered from 14N target nuclei at low energies: 1.8, 2.2, 3.0, 3.3, and 3.8 MeV are extracted from the available experimental excitation functions for p + 14N. These extracted data are subjected to theoretical analysis within the framework of single folding optical potential (SFOP) model in order to obtain the optimal potential that could fairly reproduce the p + 14N elastic scattering angular distributions. The obtained potential parameters are then used to calculate the astrophysical S-factor for 14N(p, γ)15O radiative capture reaction at very low energies where no experimental data is available and compared with the available experimental data. [ABSTRACT FROM AUTHOR]

The 11B(p,γ)12C reaction is of considerable interest in the field of controlled thermonuclear fusion and in nuclear astrophysics. In thermonuclear reactors, structural elements containing boron can be used as neutron absorbers. This reaction is one of the reactions of 11B production in the starsю. The rate of the 11B(p,γ)12C reaction (occurring in the interiors of first-generation stars) can be of great importance for the amount of 11B and 10B observed today in the Earth's crust and in the interstellar medium. Therefore, in this work, within the framework of a modified potential cluster model with a classification of orbital states according to Young's diagrams and taking into account allowed and forbidden states, we examined the possibility of describing the available experimental data for the total cross sections of the radiative p11B capture to the ground state of the 12C nucleus at energies up to 1.5 MeV. It is shown that only on the basis of E1 and M1 transitions from the p11B scattering states, taking into account the first resonance for the ground state of the 12C nucleus, it is quite possible to explain the magnitude and shape of the experimental astrophysical S-factor. The work presents comparisons the astrophysical S-factors of the radiative p11B capture to the ground state of the 12C nucleus found by us with the experimental data available in the literature. Based on the obtained theoretical S-factor, the rate of this reaction was calculated in the temperature range from 0.01 to 1 T9. The calculated results for rates are approximated by a simple expression, which simplifies their use in applied thermonuclear and astrophysical research. [ABSTRACT FROM AUTHOR]

The isotope 1 6 O is one of the most abundant light isotopes, and therefore the process 1 6 O (n , γ) 1 7 O reaction plays a critical role in stellar nucleosynthesis. Reaction cross-sections and rates for neutron capture by 1 6 O at astrophysical energies have been calculated with special attention to low-lying, narrow resonances while implementing R -matrix formalism during integration. [ABSTRACT FROM AUTHOR]

Based on the framework of the modified potential cluster model (MPCM), with orbital states classified using Young diagrams, we consider the possibility of prediction absentee of experimental data for the total cross-sections of the radiative neutron capture on 1 1 B to the first excited state of 1 2 B at 0.95314 MeV (2 + ), to the second excited state of 1 2 B at 1.67365 MeV (2−), and prediction absentee of experimental data for the total cross-sections to the third and fourth excited states of 1 2 B at 2.6208 MeV (1−) and 2.723 MeV (0 + ), for a reaction energy of 10 meV to 7 MeV. We calculate the reaction rate for a temperature range of 0.01–10.0 T 9 on the basis of the obtained cross-sections, which take into account resonances up to 5 MeV. We then demonstrate that low-lying resonances have a significant impact on the reaction rate of capture. An approximation for the calculated reaction rate is derived based on an analytical formula. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with a classification of orbital states according to Young's diagrams, the possibility of predicting the missing experimental data for the total cross sections of radiative n11B capture on the first excited state of the 12B nucleus at 0.95 MeV (2+) for the reaction energies from 10 meV (1 meV = 10-3 eV) to 7 MeV is considered. Based on the obtained total cross sections that take into account resonances up to 5 eV, the reaction rate is calculated at temperatures from 0.01 to 10.0 Т9. It is shown that low-lying resonances have a significant effect on the capture reaction rate. [ABSTRACT FROM AUTHOR]

One of the critical aspects for the accurate determination of neutron capture cross sections when combining time-of-flight and total energy detector techniques is the characterization and control of systematic uncertainties associated to the measuring devices. In this work we explore the most conspicuous effects associated to harsh count rate conditions: dead-time and pile-up effects. Both effects, when not properly treated, can lead to large systematic uncertainties and bias in the determination of neutron cross sections. In the majority of neutron capture measurements carried out at the CERN n_TOF facility, the detectors of choice are the C 6 D 6 liquid-based either in form of large-volume cells or recently commissioned sTED detector array, consisting of much smaller-volume modules. To account for the aforementioned effects, we introduce a Monte Carlo model for these detectors mimicking harsh count rate conditions similar to those happening at the CERN n_TOF 20 m flight path vertical measuring station. The model parameters are extracted by comparison with the experimental data taken at the same facility during 2022 experimental campaign. We propose a novel methodology to consider both, dead-time and pile-up effects simultaneously for these fast detectors and check the applicability to experimental data from 197Au(n , γ), including the saturated 4.9 eV resonance which is an important component of normalization for neutron cross section measurements. [ABSTRACT FROM AUTHOR]

The reaction rate of the He 3 − α radiation capture process has been calculated in astrophysical energies using the pionless Effective Field Theory (EFT) and applying the Faddeev equation approach up to Next-to Leading Order (NLO) while taking Coulomb interaction into account. The findings for the E 1 and E 2 transitions to the Be 7 ground state have been normalized using NACRE 1999 experimental data and compared to the certain theoretical and experimental data. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with the classification of orbital states according to Young's diagrams, the possibility of describing the experimental data for the total cross sections of radiative n13C capture to the ground and first excited states of the 14C nucleus at energies from 10 meV (1 meV = 10–3 eV) to 5 MeV is considered. It is shown that it is quite possible to explain values of the known experimental cross sections only based on E1 transitions from some n13C scattering states, taking into account the first resonance at 153 keV. Based on theoretical total cross sections, the capture reaction rate has been calculated in the temperature range from 0.01 to 10.0 Т9, and its analytical parameterization has been performed. [ABSTRACT FROM AUTHOR]

The radiative p6Li capture process has been treated within the framework of the modified potential cluster model with forbidden states at energies from 10 keV to 10 MeV with allowance for the first excitation energy resonance at excitation energies exceeding the p6Li channel threshold by 7.2 or 1.6 MeV. The experimental data on the astrophysical S-factor are well reproduced based on the interaction potentials relevant to the bound state energies and the corresponding asymptotic coefficients. Based on the total cross sections calculated at energies from 1 keV to 5 MeV, the reaction rates of p6Li radiative capture have been calculated at temperatures in the range from 0.01 to 10 T9. The obtained reaction rates have been approximated by simple expressions easier to use in other works. [ABSTRACT FROM AUTHOR]

A potential model is applied for the analysis of the astrophysical direct nuclear capture process 16O(p, γ) 17 F. The phase-equivalent potentials of the Woods-Saxon form for the p − 16 O interaction are examined which reproduce the binding energies and the empirical values of ANC for the 17F(5/2+) ground and 17F(1/2+) (E ⁎ =0.495 MeV) excited bound states from different sources. The best description of the experimental data for the astrophysical S factor is obtained within the potential model which yields the ANC values of 1.043 fm−1/2 and 75.484 fm−1/2 for the 17F(5 / 2 +) ground and 17F(1 / 2 +) excited bound states, respectively. The zero-energy astrophysical factor S (0) = 9.321 KeV b is obtained by using the asymptotic expansion method of D. Baye. The calculated reaction rates within the region up to 1010 K are in good agreement with those from the R-matrix approach and the hierarchical Bayesian model in both absolute values and temperature dependence. [ABSTRACT FROM AUTHOR]

The article examines the features of the interaction of virtual and real α-particles with isotopes 6Li and 7Li with the formation of the ground and excited states of 10B and 11B nuclei. The multiparticle shell model is used to describe the structures of nuclei. The significant difference in the excitation spectra of 10B and 11B nuclei in the capture of real and virtual α-particles is explained by the structural features of these nuclei and different mechanisms of capture of α-particles. Real α-particles are captured in reactions (α, γ), and virtual ones -- in lithium cluster transfer reactions. In both boron isotopes, the first decay channel is the α-particle, then there is an energy range of several MeV until the next decay channel with the emission of particles. Moreover, in this energy range, the S-factors are anomalously small. If the excited levels lie above the threshold for the breakup of the nucleus with the emission of certain particles α, then the S-factors turn out to be related to the partial widths of the decay Гα. In contrast to spectroscopic factors, which do not depend on energy and are determined only by the structure of the initial and final states, the partial Γ-widths depend on the energy which the particles are emitted with. It is shown that, in a narrow energy range from the first threshold for the emission of particles to the second threshold, the cross sections for the excitation of residual nuclei by real and virtual α-particles differ significantly. Narrow beams of γ-quanta formed with large cross sections in reactions of radiative α-capture can be used for diagnostics of thermonuclear plasma. Keywords: virtual and real α-particles, excitation spectra of 6Li and 7Li, 10B and 11B nuclei, radiative capture, lithium transfer reactions. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with forbidden states, we have considered the astrophysical S-factor of radiative р13N capture at low energies. The S-factor is calculated on the basis of the E1 transition to the bound 3Р0 state of the 14O nucleus in the р13N channel from the 3S1 wave of р13N scattering in the energy range from 30 keV to 7 MeV, which includes a resonance at 0.545 (1–) MeV (c.m.). The S-factor in the energy range 30–70 keV proved to be practically stable and equal to 7.3(2) keV·b. Next, we obtained the reaction rate in the temperature range from 0.01 T9 to 10 T9, which is in general agreement with the results of works by Li (2006), Tang (2004), and Magnus (1994). However, the obtained reaction rate at some temperatures is up to two times greater than the results of Decrock (1993). The reaction rate is approximated by a simple analytical expression. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with forbidden states, radiative n12С capture at energies from 10–5 keV to 5 MeV has been considered with allowance for the wide resonance at Ex = 8.2 MeV. It has been shown that it is possible, with the help of potentials that have been matched with bound state energies, to accurately reproduce the available experimental data. Reaction rates of n12C capture have been calculated on the basis of the obtained total cross sections. Results for the reaction rates are approximated by simple expressions, which simplifies their use in applied studies. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with forbidden states, we consider radiative p2H capture at energies from 1 keV to 10 MeV. It is shown that on the basis of potentials that have been matched with the energy of the bound state and its asymptotic constant, it is possible to correctly reproduce the available experimental data. On the basis of the obtained total cross sections, a calculation of the reaction rate of p2H capture in the temperature range from 0.01 T9 to 10 T9 is performed. Results of this calculation are approximated by simple expressions, which simplifies their use in other studies. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with forbidden states, n2H radiative capture is considered at energies from 10 meV (0.01 eV) to 10 MeV. It is shown that on the basis of p2H-interaction potentials with small changes it is possible to correctly reproduce the available experimental data. On the basis of theoretical total cross sections, the reaction rate of n2H capture has been calculated in the temperature range from 0.01 T9 to 10 T9. The calculated reaction rate is approximated by a simple expression, which simplifies its use in other works. [ABSTRACT FROM AUTHOR]

Within the framework of the modified potential cluster model with forbidden states, radiative 3He3H capture at low and astrophysical energies is considered. It is shown that on the basis of potentials which are matched with scattering phase shifts and the energy of the bound state, overall success is obtained in reproducing the available experimental data. On the basis of the obtained total cross sections, a calculation of the astrophysical S-factor and the capture reaction rate has been performed. All of the obtained results are approximated by curves of a definite type, which simplifies their use in applied studies. [ABSTRACT FROM AUTHOR]

Some accelerator technologies are already used for commercial 9 9 Mo-99mTc production, as the economic criteria are considered representative of the main differences between diverse technologies including accelerators and reactors. This study has provided a review of known and potential 9 9 Mo production using conventional medical facilities. Accelerator-based method in 99mTc production via (p , 2 n) direct reaction on 1 0 0 Mo was simulated using 18 MeV proton beam. Meanwhile, a conceptual design for indirect 9 9 Mo production via 1 0 0 Mo(γ , n) 9 9 Mo and 1 0 0 Mo(n, 2n) 9 9 Mo reactions was investigated when an electron source of 35 MeV by accelerator is used. These indirect reactions were explored via inserted 1 0 0 Mo samples at different positions inside the lead region. Furthermore, Adiabatic Resonance Crossing (ARC) method based on proton accelerator via transmutation in 9 8 Mo(n , γ) 9 9 Mo was examined when the 30 MeV proton beam is used. Saturation activity and yield were investigated using alternative proposed methods. The potential proliferation risk associated with accelerator technetium production is minimal. While accelerators could be turned into neutron sources which could in turn be used to irradiate 2 3 8 U to breed plutonium, and centrifuges used to enrich 1 0 0 Mo for targets could conceivably be turned to enriching uranium, this would result in very tiny global production capability particularly compared with research or power reactors. The potential of the fresh methods could provide a replacement or complement over current reactor-based supply sources in various radioisotopes production purposes. [ABSTRACT FROM AUTHOR]

Review of calculation results for astrophysical S -factor of the 1 4 N (p , γ) 1 5 O capture reaction in the p 1 4 N channel of 1 5 O was presented. It was carried out in the frame of the modified potential cluster model (MPCM) taking into account resonances in the 1 5 O spectrum up to 3.2 MeV at energy of incident protons varying of 30 keV to 5 MeV. It is possible to describe experimental data for the astrophysical S -factors of the radiative proton capture on 1 4 N to five excited states of 1 5 O at excitation energies of 5.18 MeV to 6.86 MeV, only under assumption, that all five resonances are D scattering waves. Quality new physical interpretation of the capture mechanism is discussed in this channel to the ground state of 1 5 O. We assumed that the ground state of 1 5 O is determined by the p 1 4 N ∗ channel with excited 1 4 N ∗ cluster, which immediately allowed us to correctly describe order of values of the experimental S -factor for capture to this state. Taking into account these results, the total S -factor of the proton capture on 1 4 N and the reaction rates to the ground and five excited states of 1 5 O were determined at temperatures of 0.01 T 9 to 10 T 9 . The parametrization of the total reaction rate with a simple form is performed, which allows as to obtain χ 2 equal to 0.06 with 5% errors of the calculated rate. [ABSTRACT FROM AUTHOR]

The impact of exciton-vibrational coupling involving fast and slow vibrational modes on absorption and emission in molecular H-aggregates is investigated using a multimode Holstein Hamiltonian. For H-aggregates composed of rigid molecules the radiative decay rate is rigorously zero due to the asymmetry of the lowest energy exciton. Increasing the Huang–Rhys factors of the coupled modes results in an increase of the radiative efficiency through increased sideband emission. Coupling to a spectrally unresolved slow mode leads to an apparent increase in the 0-0 intensity of the vibronic progression of the fast mode, thereby mimicking a distribution of molecular transition frequencies (diagonal disorder). In the intermediate coupling regime, the radiative efficiency of the aggregate exceeds the sum of the fast-mode-only and slow-mode-only radiative efficiencies. The mechanism underlying the synergistic enhancement of the radiative yield is similar to that which causes spectral splitting in the absorption spectrum of quaterthiophene crystals. [L. Silvestri et al., J. Chem. Phys. 130, 234701 (2009)]. The results here qualitatively account for the robust emission efficiency of hexaphenyl microcrystallites where the slow torsional motion involving the interphenyl dihedral angle in conjunction with the fast ring breathing mode conspire to enhance the quantum yield. [ABSTRACT FROM AUTHOR]

The statistical model of atom–diatom insertion reactions is combined with coupled-channel capture theory and used to calculate differential cross sections for the reactions of C([sup 1]D), N([sup 2]D), O([sup 1]D) and S([sup 1]D) with H[sub 2]. In the case of C([sup 1]D) and S([sup 1]D), the resulting statistical differential cross sections are found to be in excellent agreement with the recent quantum reactive scattering calculations of Honvault and Launay. They are therefore also in good agreement with molecular beam experiments for the S([sup 1]D)+H[sub 2] reaction, in contrast to the results of earlier calculations based on a less rigorous statistical theory. However, because the exact quantum mechanical differential cross sections for N([sup 2]D) and O([sup 1]D) exhibit a slight forward–backward asymmetry, the agreement with the statistical model for these reactions is not quite so good. The difference between the two cases can be rationalized in terms of the greater exoergicities of the N([sup 2]D) and O([sup 1]D) reactions, which lead to broader resonances and hence to shorter lifetimes of the H[sub 2]O and NH[sub 2] collision complexes than those of CH[sub 2] and H[sub 2]S. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Proposes an effective medium treatment (EMT) to model the magnetic field around randomly distributed magnetic cylindrical fine wires and to calculate the capture radius of paramagnetic particles in a filter operating either in longitudinal or transverse design mode. Literature on the study of magnetic filtration theory; Equations of motions; Results and discussion.

We present a new calculation of the Li 6 (p , γ) 7 Be radiative capture astrophysical S -factor in a cluster model framework. We consider several intercluster potentials, adjusted to reproduce the Be 7 bound state properties and the p − 6 Li elastic scattering phase shifts. Using these potentials, we calculate the astrophysical S -factor, obtaining a good agreement with available data, and the photon angular distribution. Finally, we discuss the consequences of a hypothetical resonance-like structure on the S -factor. [ABSTRACT FROM AUTHOR]

Big Bang Nucleosynthesis (BBN) relevance reactions 3He(2H, γ)5Li, 3H(3He, γ)6Li, and 5Li(n , γ)6Li as a key to approach for scenario of 6Li formation are treated. The rates of reaction for these processes are analyzed. Comparison of the reactions rates and the prevalence of light elements leads to the assumption that the two-step process 2H + 3He → 5 Li + γ and n + 5Li → 6 Li + γ can make a significant contribution to the formation of 6Li at the BBN at least at temperatures T 9 of the order of unity. Calculations of the total cross sections, astrophysical S -factor, and reaction rates have been performed for 3He(2H, γ)5Li radiative capture within the modified potential cluster model with forbidden states, which follow from the classification of the orbital cluster states according to Young diagrams. Numerical data and corresponding parametrizations cover the energy range up to 5 MeV and temperature range T 9 < 10. An updated compilation of detailed data for the reaction 3He(2H, γ)5Li are presented. [ABSTRACT FROM AUTHOR]

Radiative convective equilibrium (RCE) describes a balance between the cooling of the atmosphere by radiation and the heating through latent heat release and surface heat fluxes. While RCE is known to provide an energetic constraint on the atmosphere at the global scale, little is known about the proximity of the atmosphere to RCE at smaller spatial and temporal scales, despite the common use of RCE in idealized modeling studies. Here we provide the first observational evaluation of the scales at which the atmosphere is near RCE. We further use observations of cloud characteristics to investigate the role played by organized convection in the RCE state. While the tropical atmosphere as a whole is near RCE on daily time scales and longer, this is not the case for any given location. Rather, areas in excess of 5,000 × 5,000 km2 must be considered to ensure the atmosphere remains near RCE at least 80% of the time, even for monthly averaged conditions. We confirm that RCE is established through the interplay of regions of active deep convection with high precipitation and weak radiative cooling and regions of subsiding motions leading to shallow cloud states that allow strong radiative cooling with no precipitation. The asymmetry in the maximum amount of radiative cooling and latent heating leads to the well‐known ratio of small areas of precipitation and large regions of subsidence observed in the tropics. Finally, we show that organized deep convection does not occur when regions smaller than 1,000 × 1,000 km2 are near RCE. Key Points: The scales of tropical radiative convective equilibrium (RCE) are assessed from observations for the first timeThe tropics as a whole are near RCE on a daily basisOrganized deep convection is a rare state for regions in RCE and is absent when small regions are in RCE [ABSTRACT FROM AUTHOR]