Comparison of reaction theories for multilevel interference—the 14C + p reactions

1969 ◽  
Vol 47 (24) ◽  
pp. 2763-2777 ◽  
Author(s):  
C. T. Tindle ◽  
E. Vogt
Keyword(s):  
Compound Nucleus ◽  
Cross Sections ◽  
Curve Fitting ◽  
Low Energy ◽  
Analytic Method ◽  
R Matrix ◽  
Strong Interference ◽  
S Matrix ◽  
Fitting Procedures ◽  
Good Agreement

A comparison is made between the R-matrix and S-matrix theories of low-energy compound nucleus resonances for the particular case of two-level interference. The (p,γ) and (p,n) cross sections of 14C for proton energies between 0.7 and 1.5 MeV are analyzed using both theories. The 15N compound nucleus in this region exhibits strong two-level interference. The two theories provide equally good fits to the data, but the parameters describing the compound-nucleus levels are quite different. A general analytic method of relating the two sets of parameters is derived and shown to give good agreement with the results obtained by curve-fitting procedures. Remarks are made concerning the general behavior of the parameters under strong interference conditions and also on the inclusion of many channels into the analysis.

Theoretical photoionization study of Ti9+ ion

2020 ◽  
Author(s):  
Hongbin Wang ◽  
Gang Jiang
Keyword(s):  
Cross Sections ◽  
Energy Levels ◽  
Radiative Transition ◽  
High Energy ◽  
Low Energy ◽  
Transition Rates ◽  
Channel Coupling ◽  
R Matrix ◽  
Good Consistency ◽  
Good Agreement

Photoionization (PI) of Ti<sup>9+</sup> ion is investigated by the Dirac R-matrix method. Multi-Configuration Dirac-Fock (MCDF) calculations are performed to construct accurate target functions. Good agreement of energy levels and radiative transition rates indicate the accuracy of target functions. PI cross sections show good consistency between length and velocity forms. The results are consistent with the previous theoretical values in high-energy regions. Partial waves contribution to the total PI cross sections are discussed for the ground and metastable states. Moreover, the PI cross sections are dominated by many resonance structures and affected by the channel coupling effects in low-energy region. In addition to providing data for the Opacity Project TOPbase, the present work promotes plasma simulation and diagnosis.

Pseudopotential calculations of elastic scattering of low-energy electrons (< 20 eV) from neon atoms

1992 ◽  
Vol 70 (5) ◽  
pp. 305-310 ◽  
Author(s):  
Y. Frongillo ◽  
B. Plenkiewicz ◽  
P. Plenkiewicz ◽  
J.-P. Jay-Gerin
Keyword(s):  
Elastic Scattering ◽  
Energy Range ◽  
Cross Sections ◽  
Impact Energy ◽  
Theoretical Data ◽  
Low Energy ◽  
Pseudopotential Calculations ◽  
Low Energy Electrons ◽  
The Impact ◽  
Good Agreement

Pseudopotential calculations of phase shifts, differential, total, and momentum-transfer cross sections for electrons elastically scattered from neon atoms are reported in the impact energy range 0–20 eV. The results are found to be in very good agreement with existing experimental and other theoretical data.

scholarly journals Fast Neutron Cross Sections in the 2S–1D Shell

1972 ◽  
Vol 50 (20) ◽  
pp. 2385-2390 ◽  
Author(s):  
G. R. Norman ◽  
W. V. Prestwich ◽  
T. J. Kennett
Keyword(s):  
Fast Neutron ◽  
Compound Nucleus ◽  
Cross Sections ◽  
Nuclear Reactor ◽  
Low Energy ◽  
Fast Neutron Flux ◽  
Energy Data ◽  
Nucleus Formation ◽  
Compound Nucleus Formation ◽  
Neutron Cross Sections

Total neutron cross sections for six elements in the 2S–1D shell have been measured in the energy region 0.8–3.0 MeV using a new method. The experiment utilizes the fast neutron flux from a nuclear reactor with the neutron energies being determined by a measurement of their time of flight.From the present results the resonance parameters for aluminum have been determined and examined in the context of earlier low energy results for this element. The observed widths, which range to greater than 100 keV, are found to be consistent with compound nucleus formation when the reduced widths are compared with the corresponding low energy data. It is concluded that the observation of resonances with large widths is not sufficient to discount compound nucleus formation.

On threshold resonances

1970 ◽  
Vol 48 (15) ◽  
pp. 1747-1758 ◽  
Author(s):  
C. T. Tindle
Keyword(s):  
Cross Sections ◽  
Matrix Theory ◽  
Threshold Level ◽  
R Matrix ◽  
Neutral Particles ◽  
S Matrix ◽  
Energy Neutron ◽  
Square Well ◽  
Neutron Cross Sections ◽  
Threshold Resonances

A comparison is made of the way R-matrix and S-matrix theories analyze the threshold resonances which occur in the scattering of neutral particles by a square well. Both approaches are found to provide very good approximate formulas. However, modifications of the usual S-matrix expansions must first be made. The behavior of the energy of the threshold level is quite different in the two alternatives. By comparing the two theories in their interpretation of the low-energy neutron cross sections of 1H, 16O, and 208Pb it is concluded that.R-matrix theory provides a better interpretation for unbound levels and S-matrix theory is preferable when the threshold level is bound.

Reaction mechanism of the 16O + d reactions

1970 ◽  
Vol 48 (19) ◽  
pp. 2235-2253 ◽  
Author(s):  
N. E. Davison ◽  
W. K. Dawson ◽  
G. Roy ◽  
W. J. McDonald
Keyword(s):  
Experimental Data ◽  
Compound Nucleus ◽  
Cross Sections ◽  
Direct Interaction ◽  
Scattering Data ◽  
Orbit Potential ◽  
Spectroscopic Factors ◽  
Theoretical Predictions ◽  
Using Data ◽  
Good Agreement

The reactions 16O(d,d)16O, 16O(d,p)17O, and 16O(d,n)17F have been studied in the deuteron energy range 4.00–6.00 MeV in order to determine to what extent current theories can satisfactorily describe these reactions. It was found that the theoretical curves from both the optical and DWBA models fit the experimental data significantly better when the deuteron optical-model potentials had been obtained using a spin–orbit potential in the analysis of the elastic scattering data. Spectroscopic factors obtained for the ground and first-excited states of 17O and 17F using the DWBA theory are in satisfactory agreement with theoretical predictions and with values obtained by previous workers. Small, but nonzero, spectroscopic factors have been obtained for the states at 3.058 and 3.846 MeV excitation in 17O using data measured in this work and in previous experiments. The sum of the calculated direct interaction and compound-nucleus cross sections is in good agreement with experimental data for all states studied, whether they were populated primarily by direct or compound-nucleus reactions. The calculated compound-nucleus lifetimes are also in agreement with values obtained from an analysis of the fluctuations in the yield curves.

scholarly journals Excitation and ionisation cross-sections in condensed-phase biomaterials by electrons down to very low energy: application to liquid water and genetic building blocks

2021 ◽  
Vol 23 (9) ◽  
pp. 5079-5095
Author(s):  
Pablo de Vera ◽  
Isabel Abril ◽  
Rafael Garcia-Molina
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Condensed Phase ◽  
Electronic Excitation ◽  
Building Blocks ◽  
Low Energy ◽  
Wide Energy Range ◽  
Wide Energy ◽  
Energy Application ◽  
Good Agreement

A model is presented for computing electron-impact electronic excitation and ionisation cross-sections for arbitrary condensed-phase biomaterials in a wide energy range, showing a general good agreement with the available experimental data.

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.

Fission probability in the 232Th(p,p′xnf) reaction at low energy

1983 ◽  
Vol 61 (4) ◽  
pp. 646-648
Author(s):  
Chien Chung ◽  
James J. Hogan ◽  
Hans H. Muleer
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Low Energy ◽  
Incident Proton ◽  
Mass Ratio ◽  
Dispersion Data ◽  
Fission Probability ◽  
Comparison Of The Results ◽  
Good Agreement ◽  
Model Approach

In our recent works, a model was developed to calculate many of the features of 232Th(p,X) reactions with incident proton energies to 100 MeV. The model reproduced many properties such as spallation excitation functions, total fission cross sections, the symmetric/asymmetric mass ratio, and fission charge dispersion data. In this work, the model approach is extended to consider the fission probability in 232Th(p,p′xnf) fission channels. A comparison of the results calculated from the model to the experimental data shows very good agreement, and again justifies the approach of the model.

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