B. L. Burks

Coulomb excitation of giant resonances in 208Pb by E = 84 MeV/Nucleon 17O projectiles

Abstract Inelastic scattering of 84 MeV/nucleon 17 O on 208 Pb has been measured between 1.5° ⩽ θ CM ⩽5.0°. The giant resonance structure near 12 MeV is excited with a differential cross section of more than 2b/sr and exhibits a peak-to-continuum ratio as large as 6 to 1. The major part of the cross section can be ascribed to Coulomb excitation of the isovector giant dipole and the giant quadrupole resonance. From the Coulomb excitation of the GQR we deduce a B (E2) fx = 0.53 ±0.11 e 2 b 2 which is that expected for a nearly pure isoscalar resonance which exhausts ≈ 60% of the EWSR.

Multipole matrix elements for 208Pb

New measurements of inelastic proton scattering to low‐lying states of 208Pb at 200 and 400 MeV are reported. Deformation lengths extracted from angular distributions for the 3− (2.614 MeV), 5−1 (3.198 MeV), 5−2 (3.209 MeV), 2+ (4.086 MeV) and 4+ (4.324 MeV) states are in good accord with values extracted at other incident proton energies. The fact that the deformation lengths are independent of incident proton energy within experimental uncertainty provides support for the validity of the collective DWBA for medium energy proton scattering to strongly excited states. Advantage is taken of this to extract statistically more precise values of the ratio of neutron to proton multipole matrix elements (Mn/Mp). Different methods of determining the appropriate average value of Mn/Mp are discussed.

Collective model distorted-wave Born approximation analysis of 500-MeV proton scattering from 40Ca.

A vibrational collective model has been used to analyze 15 bound states in /sup 40/Ca excited by inelastic scattering of 500 MeV polarized protons. It is shown that for those states which have surface peaked charge transition densities the collective model describes the shape and magnitude of the angular distributions quite well. The hadronic deformation lengths extracted are shown to be constant over the incident proton energy range of 25--800 MeV with the exception of data at 185 MeV. The average values for the hadronic deformation lengths are used to calculate the ratio of the neutron to proton multipole matrix elements for five states. Elastic scattering and the 3/sub 1//sup -/, 2/sub 1//sup +/, and 5/sub 1//sup -/ transitions have also been studied using the relativistic collective model.

T=1, spin-dipole strength in40Ca

Spin-dipole strength in40Ca has been studied by inelastic scattering of 500-MeV protons and the dipole response in40Ca is compared with the spin-dipole data from the40Ca(p, n) reaction and nonspin-dipole data from photonuclear studies.

Transfer reactions at high energy and ambiguities in heavy-ion potentials

The smaller impact parameters that contribute to transfer reactions between heavy ions at high energies make them more sensitive to different types of optical potentials than is the case at lower energies. This may allow one to distinguish between potentials that otherwise generate similar elastic scattering cross sections within the limited angular region over which typical elastic data are available. We cite as evidence results for nucleon transfers induced by18O +28Si at 352 MeV which rule out surface transparent potentials.

Investigation of the one-step direct contribution to the 28Si(18O, 18F)28Al reaction at 19.6 MeV/nucleon☆

Abstract Cross sections for the 28 Si( 18 O, 18 F) 28 Al reaction have been measured at 19.6 MeV/nucleon. Realistic microscopic DWA calculations using a double folding model with an M3Y effective N-N interaction account for a negligible fraction of the previously measured cross sections at ∼3 MeV/nucleon, but give ∼30% of those observed at 19.6 MeV/nucleon.