90 research outputs found
8Be Nuclear Data Evaluation
An R-matrix analysis of experimental nuclear data on the reactions
4He(alpha,alpha), 4He(alpha,p), 4He(alpha,d), 7Li(p,alpha), 7Li(p,p), 7Li(p,n),
7Be(n,p), 6Li(d,alpha), 6Li(d,p), 6Li(d,n) and 6Li(d,d), leading to the 8Be
intermediate state, has been completed in the last two years. About 4700 data
points from 69 experimental references are included. The excitation energy
above the 8Be ground state is 25-26 MeV for all reactions except
4He(alpha,alpha) and 7Be(n,p). The data for the reactions 4He(alpha,alpha) and
6Li(d,d) do not fit well, but the other reactions fit with a chi^2/(point) of
less than the overall value of 7.9. Most of the 19 resonances found in the
R-matrix analysis correspond to resonances formerly known from experiment.
Evaluated integrated 4He(alpha,p), 4He(alpha,d), 7Li(p,alpha), 7Li(p,n),
7Be(n,p), 6Li(d,alpha), 6Li(d,p) and 6Li(d,n) reaction cross-sections are
presented. Evaluated cross-section and angular dependence files in ENDF format
were prepared for the twelve reactions p 7Li, n 7Be, d 6Li -> alpha 4He, p 7Li,
n 7Be, d 6Li. Maxwellian averaged temperature-dependent cross-sections in NDI
format were prepared for the six reactions 7Li(p,alpha), 7Li(p,n), 7Be(n,p),
6Li(d,alpha), 6Li(d,p) and 6Li(d,n).Comment: Published in proceedings of International Conference on Nuclear Data
for Science and Technology (ND2004), Santa Fe, NM, 26 September - 1 October
2004, LaTeX, 4 pages, 8 encapsulated postscript figure
Recommended from our members
Phenomenology of light systems using R-matrix theory.
Over the last 30 years, a program of R-matrix analyses has been carried out at Los Alamos in the mass range 2 {le} A {le} 18 that gives useful information about the light systems. These analyses provide data for astrophysics, as well as for neutronic and thermonuclear applications, and can yield important constraints from the experimental measurements on the nature of few-body interactions. Following a brief introduction to R-matrix theory, I will describe recent work on reactions in the A=2 (NN) and A=4 systems. Finally, some comments will be made about extending the theory to complex energies in order to obtain information about resonances and other types of S-matrix singularities
Monotonic properties of the shift and penetration factors
We study derivatives of the shift and penetration factors of collision theory
with respect to energy, angular momentum, and charge. Definitive results for
the signs of these derivatives are found for the repulsive Coulomb case. In
particular, we find that the derivative of the shift factor with respect to
energy is positive for the repulsive Coulomb case, a long anticipated but
heretofore unproven result. These results are closely connected to the
properties of the sum of squares of the regular and irregular Coulomb
functions; we also present investigations of this quantity.Comment: 13 pages, 1 figur
Synthesis of the elements in stars: forty years of progress
Forty years ago Burbidge, Burbidge, Fowler, and Hoyle combined what we would now call fragmentary evidence from nuclear physics, stellar evolution and the abundances of elements and isotopes in the solar system as well as a few stars into a synthesis of remarkable ingenuity. Their review provided a foundation for forty years of research in all of the aspects of low energy nuclear experiments and theory, stellar modeling over a wide range of mass and composition, and abundance studies of many hundreds of stars, many of which have shown distinct evidence of the processes suggested by B2FH. In this review we summarize progress in each of these fields with emphasis on the most recent developments
- …