C.K. Bockelman

Excitation of two-particle-one-hole states by the 208Pb(d, p)209Pb reaction

Abstract The weak transitions in the 208 Pb(d, p) 209 Pb reaction leading to two-particle-one-hole (2p-1h) states in 209 Pb have been studied at a bombarding energy of 20 MeV. These transfers exhibit typical stripping-type angular distributions and were analyzed using standard DWBA for l -values and spectroscopic factors. Arguments are presented which support an interpretation of these results as one-step transfer reactions proceeding in some cases via single-particle admixtures in the final states and in other cases via 2p-2h correlations in the 208 Pb ground state. The results imply a departure of 208 Pb from shell closure in qualitative agreement with the magnitude and character predicted by RPA calculations. Four fragments which exhaust most of the available j 15 2 single-particle strength are observed. Evidence is also obtained for fragments of single-particle strength from the N > 184 shell mixed into low-lying states of primary 2p-1h configuration. The observed levels are compared with the 209 Pb level structure predicted by calculations based on a hole coupled to the multipole pairing states in 210 Pb and a particle coupled to particle-hole excitations in 208 Pb.

Anomalous electron scattering from 142, 146, 150Nd

Abstract Properties of the ground state charge distributions and some low-lying states in 142, 146, 150 Nd have been investigated using the Yale University Electron Accelerator. The incident energy was varied between 15 MeV and 60 MeV while angular distribution measurements were obtained at angles between 70° and 150° inclusive. If the ground state charge distribution is described in terms of a half-density radius and a skin thickness, a conventional phase-shift analysis of the present results, in the context of spherically symmetric static charge distributions, indicates anomalously small values of the skin thickness in all three neodymium isotopes. Measured cross sections differ by as much as 40 % from those expected for these nuclei on the basis of the results of muonic X-ray and high-energy electron scattering experiments. Estimates by Rawitscher of the effect of virtual nuclear excitations suggest that these excitations (neglected in the analysis) may be responsible for the observed anomalies. Reduced γ-transition probabilities have been deduced for the following low-lying levels: 142 Nd, 1.57 MeV (2 + ), 2.09 MeV (3 − , (2 + ?)); 146 Nd, 0.45 MeV (2 + ); 150 Nd, 0.13 MeV (2 + ).

The scattering of 60 MeV electrons from 90Zr

Abstract The rms radius of the charge distribution of 90 Zr is measured to be 4.12±0.05 fm by elastic electron scattering. Reduced transition probabilities and transition radii for the 2.18 MeV (2 + ), 2.74 MeV (3 − ) and 3.84 MeV (2 + ) states are deduced from a distorted-wave analysis of inelastic scattering. The results for B (E L ↑) are discussed briefly in the light of current theories.

Gamma rays from thermal and resonance neutron capture in gold

Abstract A lithium-drifted germanium detector has been used to measure the high-energy gamma rays following thermal and resonance neutron capture in gold. In the region E γ ≧ 5.08 MeV , many new transitions are resolved, and transition intensities as well as level excitations are given. A level scheme deduced from these data does not agree with one proposed on the basis of low-energy, gamma-ray measurements. A comparison of the spectrum following capture in the 4.9 eV resonance with that following thermal neutron capture shows that no significant change in the relative intensity of individual gamma rays occurs.