Cross sections and thermonuclear reaction rates for the 24Mg(α,n)27Si, 25Mg(p,n)25Al, 27Al(p,n)27Si, and 28Si(α,n)31S reactions

1980 ◽  
Vol 58 (5) ◽  
pp. 697-702 ◽  
Author(s):  
C. W. Cheng ◽  
J. D. King
Keyword(s):  
Statistical Model ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Reaction Rates ◽  
Model Calculations ◽  
Model Predictions ◽  
Low Energies ◽  
Positron Decay ◽  
Γ Rays ◽  
Good Agreement

Cross sections for the 24Mg(α,n)27Si, 25Mg(p,n)25Al, 27Al(p,n)27Si, and 28Si(α,n)31S reactions have been measured at energies from near threshold to 3 to 4 MeV above threshold by detection of 0.511 MeV γ-rays in coincidence following positron decay of the product nuclei. Comparison with the theoretical calculations of Woosley, Fowler, Holmes, and Zimmerman shows good agreement between experiment and theory except at low energies where the statistical model calculations tend to overestimate the cross section. Reaction rates have been calculated for temperatures of interest in explosive nucleosynthesis and found to be in good agreement with the statistical model predictions for temperatures above 2 × 109 K.

scholarly journals Thermonuclear Reaction Rates for Reactions Leading to N = 28 Nuclei

1995 ◽  
Vol 48 (1) ◽  
pp. 125
Author(s):  
A.J Morton ◽  
DG Sargood
Keyword(s):  
Statistical Model ◽  
Nuclear Reaction ◽  
Cross Sections ◽  
Optical Model ◽  
Reaction Rates ◽  
Reaction Cross ◽  
Model Parameters ◽  
Thermonuclear Reaction ◽  
Model Calculations ◽  
Reaction Cross Sections

Nuclear reaction cross sections derived from statistical-model calculations have been used in the calculation of thermonuclear reaction rates for 36 nuclei at temperatures that are representative of the interiors of evolving stars and supernovae as nucleosynthesis approaches the production of nuclei with N = 28. The statistical-model calculations used optical-model parameters in the particle channels which had been selected to give the best overall agreement between theoretical and experimental cross sections for reactions on stable target nuclei in the mass and energy ranges of importance for the stellar conditions of interest. The optical-model parameters used, and the stellar reaction rates obtained, are tabulated. Comparisons are made between these stellar rates and those from other statistical-model calculations in the literature.

scholarly journals Statistical-model calculations for α-capture reactions relevant to the p process

2019 ◽  
Vol 26 ◽  
pp. 228
Author(s):  
C. Fakiola ◽  
I. Karakasis ◽  
I. Sideris ◽  
A. Khaliel ◽  
T. J. Mertzimekis
Keyword(s):  
Experimental Data ◽  
Statistical Model ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Reaction Network ◽  
Reaction Cross ◽  
Model Parameters ◽  
Model Calculations ◽  
Reaction Channels ◽  
Reaction Cross Sections

About 35 nuclides which lie on the neutron deficient side of the isotopic chart cannot be created by the two basic nucleosynthetic processes, the sand the rprocess. Due to scarce experimental data and the vast complexity of the reaction network involved, cross sections and reactions are estimated theoretically, using the Hauser–Feshbach statistical model. In the present work, theoretical calculations of cross sections of radiative α-capture reactions on the neutron–deficient Erbium and Xenon isotopes are presented in an attempt to make predictions inside the astrophysically relevant energy window (Gamow). The particular reactions are predicted to be sensitive branchings in the γprocess path.The most recent versions of TALYS (v1.9) and Fresco codes were employed for all calculations, initially focusing on investigating the influence of the default eight (8) α–nucleus optical potential models of TALYS on reaction cross sections. The theoretical results of both codes are compared and for the reactions where experimental data exist in literature, the optical model parameters were adjusted appropriately to best describe the data and were subsequently used for estimating (α,γ) reaction cross sections. Predictions for the (α,n) reaction channels have also been calculated and studied.

45Sc(p, p')45Sc and the Attainment of a Thermal Distribution of States in an Astrophysical Environment

1981 ◽  
Vol 34 (1) ◽  
pp. 105 ◽  
Author(s):  
MR Anderson ◽  
SR Kennett ◽  
ME Sevior ◽  
DG Sargood
Keyword(s):  
Statistical Model ◽  
Energy Range ◽  
Excited States ◽  
Cross Section ◽  
Cross Sections ◽  
Model Calculations ◽  
Thermal Distribution ◽  
Model Cross Section ◽  
Superelastic Scattering ◽  
Good Agreement

Cross sections for inelastic scattering of protons by 45SC have been measured over the energy range Ep = 1?2-2? 5 MeV for protons leading to the second, third, fourth, sixth and eighth excited states of 45SC. Statistical model calculations are' in good agreement with the data. Further statistical model cross section calculations are used in an investigation of the part played by inelastic and superelastic scattering of protons in bringing about a thermal distribution of states in 45SCin a stellar interior under the conditions of explosive silicon burning. This mechanism is found to be effective for temperatures above 4? ?x 109 K

Cross sections and thermonuclear reaction rates for the 28Si(α, p)31P and 54Fe(α, p)57Co reactions

1984 ◽  
Vol 62 (2) ◽  
pp. 134-140 ◽  
Author(s):  
M. A. Buckby ◽  
J. D. King
Keyword(s):  
Statistical Model ◽  
Cross Sections ◽  
Ground State ◽  
Reasonable Agreement ◽  
Reaction Rates ◽  
Parametric Equation ◽  
Thermonuclear Reaction ◽  
Model Calculations ◽  
Experimental Cross

Absolute cross sections for the 28Si(α, p)31P and 54Fe(α, p)57Co reactions have been measured for laboratory bombarding energies over the range 5.52 ≤ Eα ≤ 12.00 MeV, using targets of approximately 4-keV thickness. Ground state reaction rates were then deduced from these cross sections and stellar rates were deduced by multiplying by the ratio of stellar-to-ground state rates obtained from statistical model calculations. Stellar rates for the reverse reactions have been determined and are fitted by a parametric equation for ease of interpolation. The experimental cross sections and rates have been compared with statistical model calculations and are in reasonable agreement for the 54Fe(α, p)57Co reaction but deviate by as much as a factor of three for the 28Si(α, p)31P reaction.

scholarly journals The 55Mn(p,?)56Fe and 55Mn(p,n)55Fe Cross Sections

1983 ◽  
Vol 36 (1) ◽  
pp. 1 ◽  
Author(s):  
LW Mitchell ◽  
DG Sargood
Keyword(s):  
Statistical Model ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Reaction Rates ◽  
Significant Part ◽  
Thermonuclear Reaction ◽  
Model Calculations ◽  
The Cross

The cross section of the reaction 55Mn(p, y)56Pe has been measured in the energy range 0�80-2�04 MeV and of the reaction 55Mn(p, n)55Pe from threshold to 2� 04 MeV. Statistical model calculations reproduce the (p, n) cross section to within a factor of 1� 4, but with the (p, y) reaction they fail by a factor ;;;:2 over a significant part of the energy range. Thermonuclear reaction rates are calculated from the data for temperatures in the range (1-5) x 109 K.

scholarly journals The 7Be(p, ?)8B Cross Section at Low Energies

1980 ◽  
Vol 33 (2) ◽  
pp. 177 ◽  
Author(s):  
FC Barker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Solar Neutrinos ◽  
Model Calculations ◽  
Spectroscopic Factors ◽  
Low Energies ◽  
Standard Values ◽  
Experimental Values ◽  
Parameter Values ◽  
Potential Parameters

The nonresonant part of the 7Be(p, )I)8B cross section at low energies is recalculated by means of a direct-capture potential model, using parameter values determined by fitting 7Li(n, n)7Li and 7Li(n, )I)8Li data. Standard values of the potential parameters and spectroscopic factors give values of the 7Li(n,)I) cross section that are too large. Modified values that fit the thermal-neutron capture cross section predict 7Be(p,)I) cross sections that are much less than the experimental values. Also, shell model calculations predict resonant 7Be(p,)I) cross sections that are smaller than the experimental values. It is suggested that the accepted experimental values of the 7Be(p, )I) cross section may be too large, perhaps due partly to an overlarge accepted value for the 7Li(d, p)8Li cross section, which has been used for normalization purposes. A decrease in the 7Be(p,)I) cross section would reduce the calculated detection rate of solar neutrinos and lessen the discrepancy with the measured value.

scholarly journals Statistical model calculations of 72,73Ge(n,p) and 72,74Ge(n,α) reactions on natural Ge

2020 ◽  
Vol 15 ◽  
pp. 104
Author(s):  
S. Galanopoulos ◽  
R. Vlastou ◽  
P. Demetriou ◽  
M. Kokkoris ◽  
C. T. Papadopoulos ◽  
...  
Keyword(s):  
Statistical Model ◽  
Energy Range ◽  
Neutron Energy ◽  
Cross Sections ◽  
Reaction Cross ◽  
Model Calculations ◽  
Monoenergetic Neutron ◽  
Theoretical Investigations ◽  
Equilibrium Emission ◽  
Reaction Cross Sections

Systematic experimental and theoretical investigations of the 72,73Ge(n,p)72,73 Ga and 72,74Ge(n,α)69,71Znm reaction cross sections are presented in the energy range from thresh- old to about 17 MeV neutron energy. The above reaction cross sections were measured from 8.8 to 11.4 MeV by using the activation method, relative to the 27Al(n,α)24Na refer- ence reaction. The quasi-monoenergetic neutron beams were produced via the 2H(d,n)3He reaction at the 5 MV VdG Tandem T11/25 accelerator of NCSR “Demokritos”. Statisti- cal model calculations using the code EMPIRE-II (version 2.19) taking into consideration pre-equilibrium emission were performed on the data measured in this work as well as on data reported in literature.

scholarly journals Experimental measurement of the 12C+16O fusion cross sections at astrophysical energies

2018 ◽  
Vol 178 ◽  
pp. 04008
Author(s):  
X. Fang ◽  
W. P. Tan ◽  
M. Beard ◽  
R. J. deBoer ◽  
G. Gilardy ◽  
...  
Keyword(s):  
Cross Sections ◽  
Center Of Mass ◽  
Model Calculations ◽  
Center Of Mass Energy ◽  
Pure Graphite ◽  
S Factor ◽  
Hpge Detectors ◽  
Low Energies ◽  
The University

The total cross sections of the 12C+16O fusion have been experimentally determined at low energies to investigate the role of this reaction during late stellar evolution burning phases. A high-intensity oxygen beam was produced by the 5MV pelletron accelerator at the University of Notre Dame impinging on a thick ultra-pure graphite target. Protons and γ-rays were measured simultaneously in the center-of-mass energy range from 3.64 to 5.01 MeV, using strip silicon and HPGe detectors. Statistical model calculations were employed to interpret the experimental results. A new broad resonance-like structure is observed for the 12C+16O reaction, and a decreasing trend of its S-factor towards low energies is found.

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