Splitting of the Dipole and Spin-Dipole Resonances

Cross sections for the 90,92,94Zr(p,n) reactions were measured at energies of 79.2 and 119.4 MeV. A phenomenological model was developed to describe the variation with bombarding energy of the position of the L=1 peak observed in these and other (p,n) reactions. The model yields the splitting between the giant dipole and giant spin dipole resonances. Values of these splittings are obtained for isotopes of Zr and Sn and for 208Pb.Comment: 14 pages, 4 figure

Neutrino capture by r-process waiting-point nuclei

We use the Quasiparticle Random Phase Approximation to include the effects of low-lying Gamow-Teller and first forbidden strength in neutrino capture by very neutron-rich nuclei with N = 50, 82, or 126. For electron neutrinos in what is currently considered the most likely r-process site the capture cross sections are two or more times previous estimates. We briefly discuss the reliability of our calculations and their implications for nucleosynthesis.Comment: 9 pages, 4 figure

Solar Neutrino Detector GT Strength Distributions Via (p,n) Reactions

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

Hadronic Excitation of the Giant Dipole Resonance in 208-Pb and 40-Ca at E_p = 200 MeV

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

(p,n) Experiments at IUCF

This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit

Gamow-Teller strength distributions for nuclei in pre-supernova stellar cores

Electron-capture and $\beta$-decay of nuclei in the core of massive stars play an important role in the stages leading to a type II supernova explosion. Nuclei in the f-p shell are particularly important for these reactions in the post Silicon-burning stage of a presupernova star. In this paper, we characterise the energy distribution of the Gamow-Teller Giant Resonance (GTGR) for mid-fp-shell nuclei in terms of a few shape parameters, using data obtained from high energy, forward scattering (p,n) and (n,p) reactions. The energy of the GTGR centroid $E_{GT}$ is further generalised as function of nuclear properties like mass number, isospin and other shell model properties of the nucleus. Since a large fraction of the GT strength lies in the GTGR region, and the GTGR is accessible for weak transitions taking place at energies relevant to the cores of presupernova and collapsing stars, our results are relevant to the study of important $e^-$-capture and $\beta$-decay rates of arbitrary, neutron-rich, f-p shell nuclei in stellar cores. Using the observed GTGR and Isobaric Analog States (IAS) energy systematics we compare the coupling coefficients in the Bohr-Mottelson two particle interaction Hamiltonian for different regions of the Isotope Table.Comment: Revtex, 28 pages +7 figures (PostScript Figures, uuencoded, filename: Sutfigs.uu). If you have difficulty printing the figures, please contact [email protected]. Accepted for publication in Phys. Rev. C, Nov 01, 199

Weak Interaction Matrix Elements and (p,n) Cross Sections

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Spin Transfer Measurements for (p,n) Reactions at Intermediate Energy

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Gamow Teller Strength Obtained in the 52,54-Cr(p,n)52,54-Mn Reactions

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Electromagnetic Decay of Giant Resonances

Coincidence experiments were done to investigate the photon and neutron emission from the giant resonance regions of /sup 208/Pb and /sup 90/Zr using the ORNL Spin Spectrometer, a 72-segment NaI detector system. We have determined the total gamma-decay probability, the ground-state gamma branching ratio, and the branching ratios to a number of low-lying states as a function of excitation energy in /sup 208/Pb to approx.15 MeV. Similar data were also obtained on /sup 90/Zr. The total yield of ground-state E2 gamma radiation in /sup 208/Pb and the comparative absence of such radiation in /sup 90/Zr can only be understood if decay of compound (damped) states is considered. Other observations in /sup 208/Pb include the absence of a significant branch from the giant quadrupole resonance (GQR) to the 3/sup -/ state at 2.6 MeV, a strong branch to a 3/sup -/ state at 4.97 MeV from the same region, and transitions to various 1/sup -/ states between 5 to 7 MeV from the E* approx. 14 MeV region (EO resonance)