Excitation Of The Nuclear Giant Dipole Resonance By Inelastic Electron Scattering

This is the most recent and complete review on giant resonances in nuclei. It includes electric as well as magnetic collective states and a detailed discussion on the excitation mechanisms and the decay properties is given.

Inelastic electron scattering experiments were performed with the Naval Postgraduate School 110 MeV Linac. The investigation included 238U, 140Ce, 89Y, 60Ni, 58Ni and 28Si, which combined with our previous studies of 208Pb, 197Au and 165Ho, form a survey of the giant resonances in many nuclei. The energy resolution of about 0.4% to 0.5%, was usually sufficient for studying these broad resonances; the excitation energy range covered was from 4 to 40 or 50 MeV, and showed giant resonances of energies from 6 to 33 MeV. Forward scattering angles were used resulting in only electric multipole resonances. The cerium experiment possibly revealed more than any other single nucleus studied. In addition to E2 Delta T =0) at 10 MeV and E1 at 15.3 MeV, the isovector E2 appears at 25 MeV. E3 resonances appear at 6.0 MeV, 22 MeV and 34638 MeV in general agreement with the model of Bohr and Mottelson. For Uranium, both quadrupole resonances were observed, but were low in strength unless a transition radius larger than the ground state radius was assumed. Systematics of the resonance at 53 cu.rt. (1/A) MeV showed a smooth and drastic decrease with strength as a function of decreasing A, a behavior not seen for the GQR at 63 cu.rt.(1/A) MeV. This suggests the former resonance is an oscillation of the excess neutron of a heavy nucleus.

Electron Scattering from Complex Nuclei, Part B is a three-chapter text that explores the excitation of the nucleus to bound levels and the nucleus breakup through particle emission from continuum states. The first chapter discusses the inelastic scattering to nuclear levels, the giant resonances, the concepts of radiative corrections, and the phase shift analysis for inelastic scattering. The subsequent chapter concerns the quasi-elastic continuum and the observations of the nuclear decay products. The last chapter presents special topics on electron scattering, such as dispersion and exchange corrections, sum rules, and isospin effects. Physicists, researchers, and graduate students will find this book invaluable.

Giant resonances in 165Ho were studied with inelastic scattering of electrons with 60 MeV to 105 MeV incident energy at a scattering angle of 75 degrees. From 5 MeV to 30 MeV excitation energy, five multipole resonances were observed of which only the dipole resonances have been previously reported. Reduced transition probabilities and multipolarity assignments have been made. The five resonances were observed at excitation energies of 9.6 (E0 or E2), 11.5 (E2), 12.3 (E1), 15.8 (E1), and 23.5 MeV (E2). The splitting of the dipole resonance observed in photonuclear reaction experiments with prolate spheroid nuclei are confirmed with inelastic electron scattering.

The results of recent measurements obtained by electron scattering on 018 are presented. Nuclear excitations, including the giant dipole resonance, were observed in the energy spectrum of 69 MeV electrons inelastically scattered through 180 degrees.

A review is presented of the basic theory of electron scattering from nuclei and of photonuclear processes, as well as a discussion of the analysis of electron scattering experiments. This includes cross sections in Born approximation, elastic scattering from nuclei for the study of nuclear moments, and continuum scattering. Particular attention is given to inelastic electron scattering with excitation of nuclear levels, both below and in the giant resonance region. A variety of theoretical models is discussed that describe excitations of nuclear states. (Author).

Matrix elements for the excitation of particle-hole states in Ca40 by inelastic electron scattering are calculated. Electric dipole transitions to T = 1 states are considered, taking into account both transverse and Coulomb contributions. The particle-hole matrix elements are evaluated for a zero-range residual interaction. with the help of angular momentum identities, these matrix elements are expressed in a form involving only two Clebsch-Gordan coefficients, thus eliminating the usual 9-j symbols. Wave functions for the excited states are obtained from the diagonalization of the secular matrix. As functions of momentum transfer, some of the matrix elements for the electro-excitation of the different energy levels exhibit characteristically different behavior, thus helping to identify these levels in the extended shell model scheme. Varying the parameters at the residual interaction over a reasonable range brings about minor modifications in this behavior, but the qualitative results do not depend critically on the choice of these parameters. The sum of the contributions from the four energy levels above threshold, as a function of momentum transfer, proves to be extremely insensitive to changes in the parameters of the residual interaction, thus exhibiting the effects of closure (auth).