Microscopic interpretation of inelastic electron scattering from even Ni isotopes.

Abstract

Transition charge densities of inelastic electron scattering for the excitation of 2{sup +} and 4{sup +} states in even-mass Ni isotopes are investigated in terms of the standard shell model of the ({ital p}{sub 3/2},{ital p}{sub 1/2},{ital f}{sub 5/2}){sup {ital n}} configurations. Effective transition operators pertinent to the model space are derived by considering particle-hole excitations up to 12{h bar}{omega} for {ital C}2 and 14{h bar}{omega} for {ital C}4 transitions within the framework of a first-order perturbation theory. It is shown that surface-peaked transition charge densities can be obtained for the first excited 2{sup +} and 4{sup +} states, being in agreement with experiment. Particle-hole excitations up to {lambda}{h bar}{omega}, e.g., {lambda}=2 for {ital C}2 transition, are most responsible for that feature. Higher {h bar}{omega} excitations appear relatively significant in the interior region of the nucleus: They enhance the peak around the surface, improving further agreement with experiment, but for {ital C}2 transition they tend to generate another peak inside the nucleus and thus seem to deteriorate agreement with experiment. Transition densities for the 0{sub g.s.}{sup +}{r arrow}2{sub 2,3}{sup +} and 0{sub g.s.}{sup +}{r arrow}4{sub 2}{sup +} transitions are also discussed.