A new method for solving the configuration-space Faddeev equations for elastic p-d scattering below the deuteron-breakup threshold is described. Numerical solutions that demonstrate the convergence ...and accuracy of the method are given. The number of channels and the value of the matching radius required to obtain an accurate solution are also investigated. These calculations demonstrate that this method can efficiently solve the large matrix equations required for the three-body scattering problem.
Hyperfine intervals in light hydrogenic atoms and ions are among the most accurately measured quantities in physics. The theory of QED corrections has recently advanced to the point that uncalculated ...terms for hydrogenic atoms and ions are probably smaller than 0.1 parts per million (ppm), and the experiments are even more accurate. The difference of the experiments and QED theory is interpreted as the effect on the hyperfine interaction of the (finite) nuclear charge and magnetization distributions, and this difference varies from tens to hundreds of ppm. We have calculated the dominant component of the 1s hyperfine interval for deuterium, tritium, and singly ionized helium, using modern second-generation potentials to compute the nuclear component of the hyperfine splitting for the deuteron and the trinucleon systems. The calculated nuclear corrections are within 3% of the experimental values for deuterium and tritium, but are about 20% discrepant for singly ionized helium. The nuclear corrections for the trinucleon systems can be qualitatively understood by the invoking of SU(4) symmetry.
In high neutron flux environments where isomers can be strongly populated by nucleonic reactions, isotope abundances from reaction network chains can be affected by the population of nuclear isomers. ...At high temperatures and densities, there is the additional possibility of populating these isomers electromagnetically. Here, we examine the rates for electromagnetic excitation of the isotopes of several isomers of interest both in astrophysics and applied physics (e.g.,
235
U,
193
Ir, and
87,88
Y). We consider six possible electromagnetic processes, namely, photoabsorption, inverse internal conversion, inelastic electron scattering, coulomb excitation, and (γ,γ') and (e,e'γ) reactions. We find that for plasma temperatures kT ~ 1 to 10 keV, the electromagnetic reactions rates are negligible. Thus, we conclude that reaction network calculations do not need to include the possibility of electromagnetically exciting nuclear isomers. This is true in both stellar and terrestrial thermonuclear explosions, as well as in plasma conditions expected at the National Ignition Facility.
We examine the importance of conserving the vector current in calculating low-energy neutrino-nucleus interactions by implicitly invoking Siegert's Theorem in describing the vector transverse ...electric current. We find that at low neutrino energies (E? <50 MeV), Siegert's Theorem can change neutrino cross sections for normal-parity non-spin-flip excitations by about a factor of two.The same is true of muon capture rates. At higher neutrino energies the effect of Siegert's Theorem diminishes, and by about 100 MeV the effect is very small.
Alternative definitions of the Born approximation and the distorted-wave Born approximation within the framework of the configuration-space Faddeev equations are explored. The most natural definition ...does not correspond to the Born approximation derived from the Schrodinger equation, even though the exact T-matrices for both formalisms are equivalent. The Schrodinger form is optimal, although it is shown that the differences are numerically unimportant. The DWBA corresponding to the Faddeev equations is not channel symmetric, although numerically this is unimportant for the p-d (Coulomb) case. The place in the partial-wave series beyond which the Born approximation can be effectively substituted for the exact result is briefly investigated for p-d and n-d scattering below breakup threshold. PUBLICATION ABSTRACT
Leading-order three-nucleon forces that violate isospin symmetry are calculated in heavy-baryon chiral perturbation theory. The effect of the charge-symmetry-breaking three-nucleon force is ...investigated in the trinucleon systems using Faddeev calculations. We find that the contribution of this force to the {sup 3}He-{sup 3}H binding-energy difference is given by {delta}E{sub 3NF}{sup CSB}{approx_equal}5 keV.
Nuclear sizes and the isotope shift Friar, J. L.; Martorell, J.; Sprung, D. W. L.
Physical review. A, Atomic, molecular, and optical physics,
12/1997, Letnik:
56, Številka:
6
Journal Article
Odprti dostop
Darwin-Foldy nuclear-size corrections in electronic atoms and nuclear radii are discussed from the nuclear-physics perspective. The interpretation of precise isotope-shift measurements is formalism ...dependent, and care must be exercised in interpreting these results and those obtained from relativistic electron scattering from nuclei. We strongly advocate that the entire nuclear-charge operator be used in calculating nuclear-size corrections in atoms rather than relegating portions of it to the nonradiative recoil corrections. A preliminary examination of the intrinsic deuteron radius obtained from isotope-shift measurements suggests the presence of small meson-exchange currents (exotic binding contributions of relativistic order) in the nuclear charge operator, which contribute approximately 1/2%.
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