C. R. Brune

Alternative parametrization of R-matrix theory

An alternative parametrization of

The three-nucleon system near the N-d threshold

\mathit{R}

The [sup 3]He([rvec d],p)[sup 4 Breve; ]He reaction at low energies

-matrix theory is presented which is mathematically equivalent to the standard approach, but possesses features that simplify the fitting of experimental data. In particular, there are no level shifts and no boundary-condition constants which allow the positions and partial widths of an arbitrary number of levels to be easily fixed in an analysis. These alternative parameters can be converted to standard

New constraints on the 18F(p,α) 15O rate in novae from the (d, p) reaction

\mathit{R}

Low-energy p d scattering: High precision data, comparisons with theory, and phase shift analyses

-matrix parameters by a straightforward matrix diagonalization procedure. In addition, it is possible to express the collision matrix directly in terms of the alternative parameters.

R-matrix description of particle energy spectra produced by low-energy 3H + 3H reactions

Abstract The three-nucleon system is studied at energies a few hundred keV above the N-d threshold. Measurements of the tensor analyzing powers T 20 and T 21 for p-d elastic scattering at E c.m. = 432 keV are presented together with the corresponding theoretical predictions. The calculations are extended to very low energies since they are useful for extracting the p-d scattering lengths from the experimental data. The interaction considered here is the Argonne V18 potential plus the Urbana three-nucleon potential. The calculation of the asymptotic D- to S -state ratio for 3 H and 3 He, for which recent experimental results are available, is also presented.

γ-strength functions in 60Ni from two-step cascades following proton capture

Angular distributions of cross sections and complete sets of analyzing powers for the [sup 3]He([rvec d],p)[sup 4]He reaction have been measured at five energies between E[sub d]=60 and 641 keV. The energy dependence of the cross section was also measured from 245 to 685 keV, and the absolute cross section was determined at E[sub d]=426thinspkeV. The data have been included in an [ital R]-matrix analysis of the [sup 5]Li system. The bare-nuclear cross section derived from the [ital R]-matrix parametrization was used to determine the electron screening potential. [copyright] [ital 1999] [ital The American Physical Society]

Level density of Fe 56 and low-energy enhancement of γ-strength function

The degree to which the (p,gamma) and (p,alpha) reactions destroy 18F at temperatures 1-4x10^8 K is important for understanding the synthesis of nuclei in nova explosions and for using the long-lived radionuclide 18F, a target of gamma-ray astronomy, as a diagnostic of nova mechanisms. The reactions are dominated by low-lying proton resonances near the 18F+p threshold (E_x=6.411 MeV in 19Ne). To gain further information about these resonances, we have used a radioactive 18F beam from the Holifield Radioactive Ion Beam Facility to selectively populate corresponding mirror states in 19F via the inverse d(18F,p)19F neutron transfer reaction. Neutron spectroscopic factors were measured for states in 19F in the excitation energy range 0-9 MeV. Widths for corresponding proton resonances in 19Ne were calculated using a Woods-Saxon potential. The results imply significantly lower 18F(p,gamma)19Ne and 18F(p,alpha)15O reaction rates than reported previously, thereby increasing the prospect of observing the 511-keV annihilation radiation associated with the decay of 18F in the ashes ejected from novae.

Proton-deuteron elastic scattering at low energies

Angular distributions of

Development of an inertial confinement fusion platform to study charged-particle-producing nuclear reactions relevant to nuclear astrophysics

\ensuremath{\sigma}(\ensuremath{\theta}),