scholarly journals Interference Between Levels in Nuclear Reactions

1967 ◽  
Vol 20 (3) ◽  
pp. 341 ◽  
Author(s):  
FC Barker
Keyword(s):  
Nuclear Reaction ◽  
Cross Section ◽  
Nuclear Reactions ◽  
Matrix Theory ◽  
R Matrix ◽  
Single Level ◽  
The Cross

In this note we consider the cross section for a nuclear reaction in which one of the product nuclei is unstable, with two or more levels contributing to its decay. Previously a formula had been derived from R-matrix theory for the case where contributions come from only a single level of the nucleus with a given spin and parity.

scholarly journals The Boundary Condition Parameter in R-Matrix Theory

1972 ◽  
Vol 25 (4) ◽  
pp. 341 ◽  
Author(s):  
FO Barker
Keyword(s):  
Boundary Condition ◽  
Finite Number ◽  
Cross Sections ◽  
Nuclear Reactions ◽  
Matrix Theory ◽  
R Matrix ◽  
The Cross

In the general R-matrix theory of nuclear reactions, all measurable quantities such as the cross sections scc' should be independent of the choice of the boundary condition parameters Bc although the values of the level parameters E? and ??c depend on the Bc. For applications involving only a finite number of levels ?, it is not obvious that this is still the case as completeness arguments can no longer be used. It is shown here that scc' can be made independent of the choice Bc of for any finite number of levels and any number of channels, and the resulting formulae giving the dependence of E? and ??c on Bc are derived. An application is made to the pair of 5/2- levels of 7Li near 7 MeV excitation.

From resonances to fluctuations: A microscopic analysis of the cross-section for inelastic neutron scattering to a definite state

2014 ◽  
Vol 23 (03) ◽  
pp. 1450009
Author(s):  
F. W. K. Firk
Keyword(s):  
Inelastic Scattering ◽  
Neutron Scattering ◽  
Cross Section ◽  
Nuclear Reactions ◽  
Matrix Theory ◽  
Inelastic Neutron Scattering ◽  
Microscopic Analysis ◽  
Resonance Region ◽  
Inelastic Neutron ◽  
The Cross

Thomas' approximation to the general R-matrix theory of Wigner and Eisenbud is used to study the development of fluctuations in the cross-section for inelastic neutron scattering, to a definite state, in the transition from the resonance region to the continuum. In standard analyses of Ericson fluctuations, averaging of all resonance parameters is carried out from the beginning. Here, no averaging is performed; it is therefore possible to study, in detail, the effects of variations in both the random distributions of the phases of interfering amplitudes associated with elastic and inelastic scattering and the statistical distributions of parameters of the underlying resonances. The present microscopic model is not limited to the study of nuclear reactions; studies of inelastic scattering associated with quantum dots in semiconductors at low temperature and electron–atom interactions that involve many overlapping resonances, require analyses of the kind reported.

scholarly journals Anthony Milner Lane. 27 July 1928—9 February 2011

2020 ◽  
Vol 68 ◽  
pp. 297-314
Author(s):  
Charles Clement
Keyword(s):  
Nuclear Physics ◽  
Collective Motion ◽  
Nuclear Reactions ◽  
Matrix Theory ◽  
Nuclear Data ◽  
Theoretical Physics ◽  
R Matrix ◽  
Good Account ◽  
Advanced Knowledge

Tony Lane came from humble beginnings to become one of the world's leading theoretical nuclear physicists. His career in the Theoretical Physics Division at the Atomic Energy Research Establishment (AERE) at Harwell was characterized by his outstanding successes in explaining experimental nuclear data. He pioneered the understanding of the important nucleon capture reactions by introducing new mechanisms of direct and semi-direct capture and, together with colleagues, he greatly advanced knowledge of nuclear analogue states, and the role of isospin in nuclear physics. With R. G. Thomas, he wrote a comprehensive review of R-matrix theory, applied to analyse resonances in nuclear reactions, which became one of the most cited papers in physics. His book Nuclear theory gave a good account of the use of pairing force theory in nuclear physics, and its application to nuclear collective motion.

Energy dependence of the cross section of the nuclear reaction O16(γ, n)O15

1961 ◽  
Vol 23 ◽  
pp. 513-517 ◽  
Author(s):  
L. Keszthelyi ◽  
I. Berkes ◽  
I. Demeter ◽  
I. Fodor
Keyword(s):  
Nuclear Reaction ◽  
Energy Dependence ◽  
Cross Section ◽  
The Cross

PECULIARITIES OF NUCLEAR REACTIONS INDUCED BY 6He AND 6Li NUCLEI NEAR THE COULOMB BARRIER

2008 ◽  
Vol 17 (10) ◽  
pp. 2349-2353 ◽  
Author(s):  
YU. E. PENIONZHKEVICH ◽  
R. KALPAKCHIEVA ◽  
A. A. KULKO ◽  
S. M. LUKYANOV ◽  
V. A. MASLOV ◽  
...  
Keyword(s):  
Statistical Model ◽  
Cross Section ◽  
Coulomb Barrier ◽  
Nuclear Reactions ◽  
Transfer Reactions ◽  
Excitation Functions ◽  
Model Calculations ◽  
The Cross ◽  
Evaporation Residues

Excitation functions for evaporation residues in the reactions 206,208 Pb (6,4 He,2n 210 Po , as well as for the transfer reactions in the interaction of 6 He and 6 Li projectiles with Au and Pt were measured at the energies near the Coulomb barrier. Studied reactions were characterized by an increase in the cross-section compared to statistical model calculations.

A new empirical formula for cross-sections of (n,nα) reactions

2020 ◽  
Vol 29 (08) ◽  
pp. 2050062
Author(s):  
Mustafa Yiğit
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Empirical Formula ◽  
Nuclear Reactions ◽  
Measured Cross Section ◽  
Future Studies ◽  
Present Formalism ◽  
The Cross ◽  
Neutron Cross Sections ◽  
Good Agreement

Studies on the cross-sections of (n,n[Formula: see text]) reactions which are energetically possible, about 14 MeV neutrons are quite scarce. In this paper, the cross-sections of (n,n[Formula: see text] nuclear reactions at [Formula: see text]14–15 MeV are analyzed by using a new empirical formula based on the statistical theory. We show that neutron cross-sections are closely related to the [Formula: see text]-value of nuclear reaction, in particular for (n,n[Formula: see text]) channels. Results obtained with this empirical formula show good agreement with the available measured cross-section values. We hope that the estimations on the cross-sections using the present formalism may be helpful in future studies in this field.

scholarly journals Study of the (n,γf) process on 239Pu

2019 ◽  
Vol 211 ◽  
pp. 02004 ◽  
Author(s):  
Esther Leal-Cidoncha ◽  
Gilles Noguere ◽  
Olivier Bouland ◽  
Olivier Serot
Keyword(s):  
Cross Section ◽  
Matrix Theory ◽  
Fission Cross Section ◽  
Neutron Multiplicity ◽  
Prompt Neutron ◽  
Neutron Resonance ◽  
Fission Reactions ◽  
R Matrix

In the neutron resonance range, fission cross section of 239Pu can be seen as a sum of the immediate (n,f) and the two-step (n,γf) fission reactions. In that case, five channel widths should be considered for a proper evaluation, those are: two opened fission channels for Jπ = 0+, one opened fission channel for Jπ = 1+ and two J-dependent for the (n,γf) reaction. The sizeable contribution of the (n,γf) process should have an impact on the determination of the capture and fission widths involved in the Reich-Moore approximation of the R-matrix theory. The present work aims to investigate this impact by using the CONRAD code and the Γγf available from literature. Prompt neutron multiplicity (νp) has been also reproduced including the contributions of the (n,γf) process.

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