Non- Resonant Reaction Rate for <sup>15</sup>N (p,γ)<sup>16</sup>O Reaction

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.

The radiative proton capture reactions 12C(p, γ)13N, 14N(p, γ)15O, and 17O(p, γ)18F have been investigated within the framework of a direct capture model employing Woods - Saxon potentials. These reactions play a fundamental role in hydrogen burning through the carbon-nitrogen-oxygen (CNO) cycles in stellar interiors. Nuclear structure inputs constrained by experimental data have been used to calculate astrophysical S factors and scattering phase shifts. The calculated results show good agreement with available measurements, accurately reproducing both non-resonant contributions and narrow resonance features in the 12C(p, γ)13N and 17O(p, γ)18F reactions. The rate-limiting behavior of the 14N(p, γ)15O reaction in the CNO-I cycle has also been described with satisfactory precision. The findings provide improved inputs for stellar nucleosynthesis modeling and contribute to the understanding of low-energy nuclear capture processes relevant to astrophysics.

In stars, four hydrogen nuclei are converted into a helium nucleus by two competing nuclear fusion processes: the proton - proton chain (p-p) and the carbon - nitrogen - oxygen (CNO) cycle. At temperatures higher than 2 · 107 K, the CNO cycle dominates the energy production. In particular, its rate is determined by the slowest reaction: 14N(p, γ)15O. Direct measurement in a laboratory at the surface of the Earth is hampered by the background due to the cosmic rays. Here we report on an experiment performed with the LUNA (Laboratory for Underground Nuclear Astrophysics) accelerator placed deep underground in the Gran Sasso laboratory (Italy). Thanks to the cosmic ray suppression provided by the mountain shield, we could measure the 14N(p, γ)15O cross section for the first time directly at energies corresponding to stellar temperatures and with unprecedented accuracy. The results are strictly related to carbon stars formation, an independent lower limit on the age of the universe and solar neutrinos flux. The 13N and 15O neutrinos coming from the CNO cycle are strictly correlated to the 14N(p, γ)15O S-factor and their flux will play an important role in some future solar neutrino experiment, such as Borexino.

Gaseous fusion reactions are divided into two main classes: e thermonuclear and the pycnonuclear. In a gas of low density and high temperature the Coulomb-barrier penetration probability is only slightly affected by electron screening, and the main contribution to the reaction probability comes from the relatively few fast-moving nuclei at the energy E0 of the Gamow peak. These are the temperature-sensitive thermonuclear reactions. As the density increases and the temperature decreases, the potential barriers are depressed by electron screening and the Gamow peak is increased in height and displaced towards a lower energy. At high densities and low temperatures, when the potential barriers are depressed by an amount larger than E0, the Gamow peak is shifted across the origin and only its tail-end remains. The reaction probability is now density sensitive, and the main contribution comes from the relatively abundant slow-moving nuclei. These reactions are no longer thermonuclear and are more aptly described as `pycnonuclear' (after Cameron). At still higher densities and lower temperatures the nuclear gas becomes degenerate and the reaction probability is independent of the temperature of the gas; these reactions are referred to as `cryonuclear'. The present results for pycnonuclear reactions differ in detail from those obtained by previous authors. Although the results can be readily adapted and extended in the case of astrophysical applications, the main emphasis is on hydrogen-isotope reactions with the possibility in mind of achieving the controlled release of nuclear energy from dense media in the laboratory. For example, in the typical thermonuclear working region of 1014 < n < 1016 cm-3, 108 < T < 109 °K (where n is the ion number density and T is the temperature) the burn-up time of the nuclear fuel is the same as in the cryonuclear working region of 3 × 104 < ρ < 105 g cm-3, T < 105 °K (where ρ is the density of the gas). A proposed classification of the gaseous fusion reactions, based on the form of the reaction probability, is as follows. The first class (a) consists of the thermonuclear or temperature-sensitive reactions, and is subdivided into (i) the araeonuclear reactions which are density independent, and (ii) the pycno-thermonuclear reactions which are density dependent. The second class (b) consists of the pycnonuclear or density-sensitive reactions, and is subdivided into (iii) the thermo-pycnonuclear reactions which are temperature dependent, and (iv) the cryonuclear reactions which are temperature independent and occur only in degenerate nuclear gases.

We predict the sterile neutrino spectrum of some of the key solar nuclear reactions and discuss the possibility of these being observed by the next generation of solar neutrino experiments. By using an up-to-date standard solar model with good agreement with current helioseismology and solar neutrino flux data sets, we found that from solar neutrino fluxes arriving on Earth only 3–4% correspond to the sterile neutrino. The most intense solar sources of sterile neutrinos are the pp and ^7Be nuclear reactions with a total flux of 2.2times 10^{9} and 1.8times 10^{8};{{mathrm{cm}}^2 {mathrm{s}}^{-1}}, followed by the ^{13}N and ^{15}O nuclear reactions with a total flux of 1.9times 10^{7} and 1.7times 10^{7};{mathrm{cm}}^2, {mathrm{s}}^{-1}. Moreover, we compute the sterile neutrino spectra of the nuclear proton–proton nuclear reactions – pp, hep and ^8B and the carbon–nitrogen–oxygen – ^{13}N, ^{15}O and ^{17}F and the spectral lines of ^7Be.

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.

The ring current during the magnetic storm period of September 4-6, 1984 is investigated with the AMPTE/CCE Medium Energy Particle Analyzer. Within the L-shells of ≈2.5 to 5 in the dusk sector (≈ 16 MLT) near the equatorial plane, flux in the lowest energy channel of the carbon, nitrogen, oxygen (CNO) group (137 to 365 keV) shows the largest enhancement factor (2 × 10³), followed by the helium (≈ 10² in the 72 to 240 keV channel) and then by the protons (≈ 10 in the 56 to 190 keV channel). Flux ratios of helium and CNO to all ions at equal total energies also show significant increases in the same L-shell ranges. The radial profile of the current density for the ring current particles sampled is also evaluated, showing current density enhancement of about 0.5 nA/m² over the L range of 3.5 to 6 during the main phase of this magnetic storm. The major contribution to the computed current density is due to the pressure gradient current of the protons.

Reaction rate of radiative n6Li capture in the temperature range from 0.01 to 10 T9

Valence-doorway model for radiative capture

The 12 C( α , γ ) 16 O reaction plays a key role in the evolution of stars with masses of M > 0.55 M ⊙ . At the Gamow peak ( E c.m. = 300 ke V, T 9 = 0.2), the cross section of the 12 C( α , γ ) 16 O reaction is so small (about 10 −17 barn) that the direct measurement in ground laboratory is not feasible with the existing technology. Up to now, the cross sections at lower energies can only be extrapolated from the data at higher energies. However, two subthreshold resonances, locating at E x = 7.117 MeV and E x = 6.917 MeV, make this extrapolation more complicated. In this work the 6.917 MeV subthreshold resonance in the 12 C( α , γ ) 16 O reaction was investigated via the 12 C( 11 B, 7 Li) 16 O reaction. The experiment was performed using the Q3D magnetic spectrograph at HI-13 tandem accelerator. We measured the angular distribution of the 12 C( 11 B, 7 Li) 16 O transfer reaction leading to the 6.917 MeV state. Based on DWBA analysis, we derived the square of ANC of the 6.917 MeV level in 16 O to be (2.45± 0.28) ×10 10 fm −1 , with which the reduced- α width can be computed. Finally, we calculated the astrophysical S E 2 factor of the 6.917 MeV resonance to be 67.6 ± 7.7 ke V b.

Cross section of 3He( 3He,2p) 4He measured near the Gamow peak

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 capture $p + {}^{13}\mathrm{C}\rightarrow {}^{14}\mathrm{N}+\gamma $ at energies bearing astrophysical consequences is one of the important processes in the CNO cycle. We focus on the possibility of describing the main contribution to the total cross section of the radiative capture process in the framework of the single-particle potential model without separation into direct and resonant transitions. In case where the single-particle potential model fails to describe other partial components, we use the R-matrix approach. The partial components of the astrophysical S-factor are calculated for all possible electric dipole transitions. The calculated value of the total S-factor at zero energy is in good agreement with earlier reported values. Based on the value of total astrophysical S-factor depending on the collision energy, we calculate the nuclear reaction rates for ${p} + {^{13}\mathrm{C}} \rightarrow {^{14}\mathrm{{N}}}+\gamma $ .

Alginate, a biocompatible and biodegradable natural polymer, has been widely used as a drug molecular carrier using ionic gelation methods (crosslinking). One of the factors that must be taken into account in its preparation is the mechanical effect. The purpose of this study was to explain the preparation process and the characteristics of the calcium alginate crosslinkers as dexamethasone sodium phosphate carriers with low energy and high energy techniques. Nanosuspension is made in six formulas using 3 techniques: low energy (aeration), high energy (ultrasonication), low and high energy (aeration and ultrasonication) with a fixed concentration of dexamethasone sodium phosphate and sodium alginate, that is 0,2% and 0,1%, with 0,02% and 0,2% of calcium chloride. Determination of particle size, zeta potential, and morphology of nanoparticles using Particle Size Analyzer (PSA) and Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM). Determination of encapsulation efficiency using UV/Vis spectrophotometer and statistical analysis using MANOVA test. Synthesis of nanosuspension using a combination of low and high energy (aeration and ultrasonication) results in the most optimal characteristics with particle size value of 352.90 ± 6.10 nm, homogenized polydispersity index (0,52 ± 0,04), optimal potential zeta -44,40 ± 0,4 mV, the encapsulation efficiency of 49,5 - 74,8% and spherical particle shape. It can be concluded that the preparation using a combination of low and high energy is the most optimal preparation result.

Folding model approach to the elastic p+12,13C scattering at low energies and radiative capture 12,13C(p,γ) reactions