scholarly journals Calculation of the 13N(p, ?)14O Cross Section at Low Energies

1985 ◽  
Vol 38 (5) ◽  
pp. 657 ◽  
Author(s):  
FC Barker
Keyword(s):  
Experimental Data ◽  
Excited State ◽  
Shell Model ◽  
Cross Section ◽  
Energy Region ◽  
Model Calculations ◽  
R Matrix ◽  
Considerable Uncertainty ◽  
First Excited State ◽  
Low Energies

R-matrix formulae are used to calculate the 13N(p, ?) 140 cross section in the energy region of astrophysical interest. Values of the R-matrix parameters are determined by fitting experimental data in 14C and 14N as well as 140, and by making use of shell model calculations where necessary. With the presently available data, there is considerable uncertainty in the predicted cross section, but this could be reduced appreciably by a measurement of the lifetime of the first excited state of 14C. With the preferred channel radius of about 5 fm, the predicted cross section is lower than those found in two previous calculations, which are discussed in some detail.

The first excited state of 9Be

1983 ◽  
Vol 61 (10) ◽  
pp. 1371-1373 ◽  
Author(s):  
F. C. Barker
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Reasonable Agreement ◽  
R Matrix ◽  
First Excited State

An R-matrix fit to recent 9Be(γ,n)8Be cross-section measurements just above the neutron threshold gives parameters that are in reasonable agreement with those obtained from fits to data from other reactions.

scholarly journals The 12C(p, g)13N Cross Section near the Ep = 0·46 MeV Peak

1992 ◽  
Vol 45 (6) ◽  
pp. 749 ◽  
Author(s):  
S Hinds ◽  
FC Barker
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Thick Target ◽  
R Matrix ◽  
Best Value ◽  
First Excited State ◽  
Target Data

The I2C(p,'Y?3N cross section in the neighbourhood of the Ep = 0�46 MeV peak has been measured using thin and thick targets, and fitted using R-matrix formulae. The best value for the radiation width of the first excited state of I3N is 0�53�0�05 eV. eanalysis of earlier thick-target data gives values consistent with this result.

scholarly journals 8Be Level Properties from the Low-energy 7Li(p, γo)8Be Cross Section

1996 ◽  
Vol 49 (6) ◽  
pp. 1081 ◽  
Author(s):  
FC Barker
Keyword(s):  
Shell Model ◽  
Cross Section ◽  
Low Energy ◽  
Cross Section Data ◽  
Model Calculations ◽  
R Matrix ◽  
Section Data ◽  
Extensive Data

R-matrix fits to 7Li(p, γo)8Be cross section data for Ep ≤ 1500 keV give reduced width amplitudes of the 1+ levels of 8Be at 17.64 and 18.15 MeV having signs in agreement with shell model calculations, contrary to previous fits to less-extensive data.

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 0+ States of 8Be

1968 ◽  
Vol 21 (3) ◽  
pp. 239 ◽  
Author(s):  
FC Barker ◽  
HJ Hay ◽  
PB Treacy
Keyword(s):  
Excited State ◽  
Excited States ◽  
Cross Section ◽  
Scattering Data ◽  
Excitation Energies ◽  
R Matrix ◽  
Channel Radius

The light even nuclei with A ;;;. 10 have 0+ excited states near 6 MeV, probably with large (X-particle reduced widths. A similar state in BBe would be very broad. Evidence for 0+ excited states in BBe has been obtained here using many-level R-matrix fits to known (X-(X scattering data, but the excitation energies depend strongly on the assumed channel radius. For a simultaneous fit to the 9Be(p, d)BBe cross section, assuming these higher states are not strongly populated, the channel radius is restricted to (7~~) fm, implying a 0+ excited state at (6=f3) MeV of width (9=f4) MeV.

scholarly journals p-Wave Strength in the Low-energy 7Li(p,?0)8Be Cross Section

1995 ◽  
Vol 48 (5) ◽  
pp. 813 ◽  
Author(s):  
FC Barker
Keyword(s):  
Angular Distribution ◽  
Shell Model ◽  
Cross Section ◽  
Low Energy ◽  
P Wave ◽  
Model Calculations ◽  
Energy Data

Recent fits to low-energy 7Li(p, "Yo)8Be angular distribution and analysing power data suggested a large p-wave strength. It is shown that acceptable fits to the data can be obtained by attributing the p-wave Ml contributions to the tails of the 17 �64 and 18 �15 MeV 1+ levels of 8Be, with p-wave strengths much less than those obtained previously, but only if some of the spectroscopic amplitudes have signs opposite to those suggested by shell model calculations and/or a fit to higher-energy data.

scholarly journals GDR Contribution to Coulomb Excitation. II. 17O

1982 ◽  
Vol 35 (3) ◽  
pp. 301 ◽  
Author(s):  
FC Barker
Keyword(s):  
Excited State ◽  
Shell Model ◽  
Excited States ◽  
Giant Dipole Resonance ◽  
Coulomb Excitation ◽  
Dipole Resonance ◽  
First Excited State ◽  
Virtual Excitation

The contribution to the Coulomb excitation of the first excited state of 170 due to virtual excitation of the giant dipole resonance (GDR) is calculated, using shell model wavefunctions for the ground and first excited states. A large value is obtained.

scholarly journals No-core shell model calculations of the photonuclear cross section of 10B

2019 ◽  
Vol 55 (12) ◽  
Author(s):  
M. K. G. Kruse ◽  
W. E. Ormand ◽  
C. W. Johnson
Keyword(s):  
Shell Model ◽  
Cross Section ◽  
Core Shell ◽  
Model Calculations

scholarly journals Absolute cross section measurements of 238U(n,f) and 237Np(n,f) in the neutron energy range 1-2.4 MeV

2019 ◽  
Vol 211 ◽  
pp. 03009
Author(s):  
Paula Salvador-Castiñeira ◽  
Franz-Josef Hambsch ◽  
Alf Göök ◽  
Marzio Vidali ◽  
Nigel P. Hawkes ◽  
...  
Keyword(s):  
Cross Section ◽  
Neutron Energy ◽  
Cross Sections ◽  
Energy Region ◽  
Power Plants ◽  
National Physical Laboratory ◽  
Absolute Cross Section ◽  
Neutron Energy Range ◽  
Physical Laboratory ◽  
Low Energies

New standard (n,f) cross sections other than 235U are important to study the relevant cross sections for Generation-IV power plants. A specific need for such standards is for performing new experiments with quasimonoenergetic neutron beams, such as those produced by Van de Graaf accelerators. Neutrons down-scattered to low energies in the experimental environment, so called room-return, become relevant for this type of measurements. Hence, a standard (n,f) cross section with a fission threshold is of great interest, in order to suppress the contribution from room-return background. For this reason we have performed two experiments at the VDG of the National Physical Laboratory to measure absolutely the (n,f) cross sections of 235U, 238U and 237Np in the fast neutron energy region. Our preliminary results are in agreement with the most up-to-date evaluations.

Structure of 12B from measurement and R-matrix analysis of σ(θ) for 11B(n, n)11B and 11B(n, n')11B∗(2.12 MeV), and shell-model calculations

1983 ◽  
Vol 394 (1-2) ◽  
pp. 221-244 ◽  
Author(s):  
P.E. Koehler ◽  
H.D. Knox ◽  
D.A. Resler ◽  
R.O. Lane ◽  
D.J. Millener
Keyword(s):  
Shell Model ◽  
Matrix Analysis ◽  
Model Calculations ◽  
R Matrix
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