scholarly journals LEMA: A PROGRAM FOR CALCULATING NEUTRON CROSS SECTIONS WITH THE R-MATRIX FORMALISM AND WITH THE COMPLEX POLE EXPANSION OF THE COLLISION MATRIX.

1967 ◽  
Author(s):  
D.B. Adler ◽  
F.T. Adler
Keyword(s):  
Cross Sections ◽  
Matrix Formalism ◽  
R Matrix ◽  
Neutron Cross Sections

R-matrix analysis of Cl neutron cross sections up to 1.2 MeV

2006 ◽  
Vol 73 (4) ◽  
Author(s):  
R. O. Sayer ◽  
K. H. Guber ◽  
L. C. Leal ◽  
N. M. Larson ◽  
T. Rauscher
Keyword(s):  
Cross Sections ◽  
Matrix Analysis ◽  
R Matrix ◽  
Neutron Cross Sections

R-matrix analysis of the239Pu neutron cross sections

1986 ◽  
Vol 96 (1-4) ◽  
pp. 293-296 ◽  
Author(s):  
G. de Saussure ◽  
R. B. Perez ◽  
R. L. (Roger) Macklin
Keyword(s):  
Cross Sections ◽  
Matrix Analysis ◽  
R Matrix ◽  
Neutron Cross Sections

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.

scholarly journals ELASTIC BACKSCATTERED CROSS-SECTIONS OF 14N(P,P0)14N AT HIGH ANGLES

2020 ◽  
Vol 20 (3) ◽  
pp. 749-754
Author(s):  
MOHAMED ELTAYEB M. EISA ◽  
JOHAN ANDRE MARS ◽  
MUSTAFA J. ABUALREISH ◽  
MARWA L. WAREGH
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ion Beam ◽  
Region Of Interest ◽  
Laboratory Frame ◽  
Matrix Formalism ◽  
Cross Section Data ◽  
R Matrix ◽  
Section Data ◽  
Elastic Backscattering

The importance and present needs of proton cross section data of nitrogen needed by the Ion Beam Analysis (IBA) community are briefly reviewed. Previous experimental data presently used for the theoretical determination of the proton cross-sections are discussed. The Azure code based on the R-matrix formalism was then used to evaluate the data and to determine the nitrogen cross section in the previous and presently desired angular domain and energy region of interest. The experimental elastic backscattering cross section data, as spectra, for back-scattering analysis determined at angles in the laboratory frame of reference, θi,lab, of 165o, 170o and 176o are presented.

scholarly journals Developments regarding three-body reaction channels within the R-matrix formalism

2020 ◽  
Vol 239 ◽  
pp. 03002
Author(s):  
Benedikt Raab ◽  
Thomas Srdinko ◽  
Helmut Leeb
Keyword(s):  
Cross Sections ◽  
Matrix Theory ◽  
Resonance Region ◽  
Reaction Cross ◽  
Resonance Structure ◽  
Matrix Formalism ◽  
Matrix Formulation ◽  
R Matrix ◽  
Reaction Channels ◽  
Three Body

At low incident energies of nucleon-induced reaction cross sections exhibit a striking resonance structure which cannot properly be described by (semi-) microscopic models. Usually R-matrix theory is applied which provides a sufficiently accurate but phenomenological description of the resonance region. However, standard R-matrix theory is only suited for two-particle channels. Three- and many-particle channels which may occur at rather low incident energies and are usually treated in approximative or effective way. In this contribution an extension to unequal masses of the R-matrix formulation of Glockle based on the Faddeev equation is performed and proper expressions for numerical implementation are given.

scholarly journals Multi-photon above threshold ionization of multi-electron atoms and molecules using the R-matrix approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jakub Benda ◽  
Zdeněk Mašín
Keyword(s):  
Cross Sections ◽  
Outer Region ◽  
Angular Distributions ◽  
Matrix Formalism ◽  
Computationally Efficient ◽  
Threshold Ionization ◽  
R Matrix ◽  
Atoms And Molecules ◽  
Above Threshold Ionization ◽  
Transition Matrix Elements

AbstractWe formulate a computationally efficient time-independent method based on the multi-electron molecular R-matrix formalism. This method is used to calculate transition matrix elements for the multi-photon ionization of atoms and molecules under the influence of a perturbative field. The method relies on the partitioning of space which allows us to calculate the infinite-range free-free dipole integrals analytically in the outer region, beyond the range of the initial bound wave function. This approach is valid for an arbitrary order, that is, any number of photons absorbed both in the bound and the continuum part of the spectrum (below- and above-threshold ionization). We calculate generalized multi-photon cross sections and angular distributions of different systems (H, He, $$\hbox {H}_{{2}}$$ H 2 , $$\hbox {CO}_{{2}}$$ CO 2 ) and validate our approach by comparison with data from the literature.

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