scholarly journals Study of nonlocality effects in direct capture reactions with Lagrange-mesh R-matrix method

2021 ◽  
Author(s):  
Nguyen Hoang Phuc ◽  
Nguyen Tri Toan Phuc ◽  
Do Cong Cuong
Keyword(s):  
Matrix Method ◽  
Radiative Capture ◽  
Potential Model ◽  
Nonlocal Potential ◽  
Direct Capture ◽  
R Matrix ◽  
Local Potentials ◽  
The Difference ◽  
Good Agreement ◽  
Nonlocal Potentials

We apply the Lagrange-mesh [Formula: see text]-matrix method to calculate the [Formula: see text]-factor for the [Formula: see text]C[Formula: see text]N and [Formula: see text]O[Formula: see text]F direct radiative capture reactions. By comparing the astrophysical [Formula: see text]-factors calculated with nonlocal and local potentials, we investigate the nonlocality effects coming from the nuclear potentials in the direct capture reactions. Our calculations are in good agreement with the experimental data and indicate a nonnegligible difference in the results of local and nonlocal potentials. The use of small diffuseness narrow potentials also provides a remarkably good fit in the case with multiple broad resonances. Our findings suggest that the nonlocal potential improves the calculated results although the difference between the local and nonlocal potentials is smaller than uncertainties from other sources. We propose the nonlocality potential should be used in the potential model calculation of future astrophysics rates evaluation.

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

2022 ◽  
Author(s):  
Abdul Kabir ◽  
Jameel-Un Nabi
Keyword(s):  
Cross Section ◽  
Capture Cross Section ◽  
Radiative Capture ◽  
Potential Model ◽  
Low Energy ◽  
Capture Cross ◽  
Zero Energy ◽  
R Matrix ◽  
S Factor ◽  
Radiative Capture Cross Section

Abstract 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.

CROSS SECTIONS FOR NUCLEAR ASTROPHYSICS

2008 ◽  
Vol 17 (10) ◽  
pp. 2165-2170
Author(s):  
PIERRE DESCOUVEMONT
Keyword(s):  
Cross Sections ◽  
Matrix Method ◽  
Potential Model ◽  
Nuclear Astrophysics ◽  
Reaction Rates ◽  
Low Energy ◽  
R Matrix ◽  
General Properties ◽  
Microscopic Models

General properties of low-energy cross sections and of reaction rates are presented. We describe different models used in nuclear astrophysics: microscopic models, the potential model, and the R-matrix method. Two important reactions, 7 Be ( p ,γ)8 B and 12 C (α,γ)16 O , are then briefly discussed.

ESTIMATES OF THE ASTROPHYSICAL S-FACTORS FOR PROTON RADIATIVE CAPTURE BY 10B AND 24Mg NUCLEI USING THE ANCs FROM PROTON TRANSFER REACTIONS

2010 ◽  
Vol 19 (05n06) ◽  
pp. 1102-1108 ◽  
Author(s):  
S. V. ARTEMOV ◽  
S. B. IGAMOV ◽  
A. A. KARAKHODZHAEV ◽  
G. K. NIE ◽  
R. YARMUKHAMEDOV ◽  
...  
Keyword(s):  
Ground State ◽  
Radiative Capture ◽  
Transfer Reactions ◽  
Matrix Formalism ◽  
Zero Energy ◽  
Direct Capture ◽  
R Matrix ◽  
S Factor ◽  
Low Energies ◽  
Proton Transfer Reactions

The contribution of the direct radiative capture of protons by 10 B and 24 Mg nuclei at low energies to the astrophysical S -factors in the reactions 10 B (p,γ)11 C and 24 Mg (p,γ)25 Al have been calculated within the R-matrix formalism by using empirical proton asymptotical normalization coefficients (ANC). The ANCs for bound proton configurations {10 B +p} and {24 Mg +p} were obtained from the analysis of the reactions (3 He , d). The ANCs were also estimated from the values of the neutron ANCs in the mirror nucleus 25 Mg following the suggestion that the neutron and the proton in the mirror states have equivalent nuclear potentials. It has been found that the S -factor for the reaction 10 B (p,γ)11 C extrapolated to zero energy contributes ~100 keV b to the radiative capture to the ground state of 11 C . For the reaction 24 Mg (p,γ)25 Al the value S(0) gives 58 keV b with a direct capture contribution of 41 keV b .

Explaining the magnetism of gold

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Gas Phase ◽  
Computational Study ◽  
Formation Enthalpy ◽  
Gold Atom ◽  
Orbital Energy ◽  
Knudsen Effusion ◽  
Energy Diagram ◽  
Unpaired Electrons ◽  
The Difference ◽  
Good Agreement

<p>In the present work, a computational study is performed in order to clarify the possible magnetic nature of gold. For such purpose, gas phase Au<sub>2</sub> (zero charge) is modelled, in order to calculate its gas phase formation enthalpy. The calculated values were compared with the experimental value obtained by means of Knudsen effusion mass spectrometric studies [5]. Based on the obtained formation enthalpy values for Au<sub>2</sub>, the compound with two unpaired electrons is the most probable one. The calculated ionization energy of modelled Au<sub>2</sub> with two unpaired electrons is 8.94 eV and with zero unpaired electrons, 11.42 eV. The difference (11.42-8.94 = 2.48 eV = 239.29 kJmol<sup>-1</sup>), is in very good agreement with the experimental value of 226.2 ± 0.5 kJmol<sup>-1</sup> to the Au-Au bond<sup>7</sup>. So, as expected, in the specie with none unpaired electrons, the two 6s<sup>1</sup> (one of each gold atom) are paired, forming a chemical bond with bond order 1. On the other hand, in Au<sub>2</sub> with two unpaired electrons, the s-d hybridization prevails, because the relativistic contributions. A molecular orbital energy diagram for gas phase Au<sub>2</sub> is proposed, explaining its paramagnetism (and, by extension, the paramagnetism of gold clusters and nanoparticles).</p>

Effect of leakage and blockage on the acoustic behavior of particle filters

2019 ◽  
Vol 67 (6) ◽  
pp. 483-492
Author(s):  
Seonghyeon Baek ◽  
Iljae Lee
Keyword(s):  
Transfer Matrix ◽  
Particle Filters ◽  
Acoustic Analysis ◽  
Transmission Loss ◽  
One Dimensional ◽  
Filter System ◽  
The Difference ◽  
The One ◽  
Analytical Approaches ◽  
Good Agreement

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.

scholarly journals Relativistic B-Spline R-Matrix Calculations for Electron Collisions with Ytterbium

Atoms ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 47
Author(s):  
Kathryn R. Hamilton ◽  
Klaus Bartschat ◽  
Oleg Zatsarinny
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Cross Sections ◽  
Matrix Method ◽  
Model Potential ◽  
Electron Collisions ◽  
R Matrix ◽  
B Spline ◽  
Potential Approach

We have applied the full-relativistic Dirac B-Spline R-matrix method to obtain cross sections for electron scattering from ytterbium atoms. The results are compared with those obtained from a semi-relativistic (Breit-Pauli) model-potential approach and the few available experimental data.

Effect of Magnetic Fields on the Resistance and Microstructure of Al-Cu Alloy during Solidification Processing

2011 ◽  
Vol 287-290 ◽  
pp. 2916-2920
Author(s):  
Chun Yan Ban ◽  
Peng Qian ◽  
Xu Zhang ◽  
Qi Xian Ba ◽  
Jian Zhong Cui
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Turning Points ◽  
Probe Method ◽  
Solidification Processing ◽  
Ac Magnetic Field ◽  
Dc Magnetic Field ◽  
Cu Alloy ◽  
The Difference ◽  
Good Agreement

The resistance of Al-21%Cu alloy under no magnetic field, DC magnetic field and AC magnetic field from liquid to solid was measured by a four-probe method. The difference of resistance versus temperature curves (R-T curves) was analyzed. It is found that the R-T curves of Al-21%Cu alloy are monotone decreasing and have two obvious turning points. Under DC magnetic field, the liquidus and solidus temperatures of the alloy both decrease, while under AC magnetic field, the liquidus and solidus temperatures both increase. There is a good agreement between the microstructure of quenching sample and R-T curves. The mechanism of the effect of magnetic fields was discussed.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

The derivation of the rotational potential function from atom–atom potentials. III. Borohydride compounds

1988 ◽  
Vol 66 (4) ◽  
pp. 791-793 ◽  
Author(s):  
David Smith
Keyword(s):  
Transition Temperature ◽  
Experimental Method ◽  
Potential Function ◽  
Ground Level ◽  
Potential Functions ◽  
The Difference ◽  
Level Degeneracy ◽  
Entropy Of Transition ◽  
Good Agreement

The rotational potential functions for the borohydride ion embedded in potassium and rubidium halides are derived from atom–atom potentials of the Buckingham (exp-6) type. The librational frequencies computed from the potential functions are in good agreement with the observed frequencies. The potential functions for rubidium and potassium borohydrides derived from the atom–atom potentials yield librational frequencies that are about 10% higher than the observed values. Since the entropy of transition for potassium and rubidium borohydrides is less than expected, there is a possibility that there is some ordering of the borohydride ions above the transition temperature. An experimental method is presented for studying the ordering of the borohydride ions based on the difference in the ground level degeneracy of a tetrahedral ion in ordered and disordered states.

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