Isospin asymmetries in pion scattering to isoscalar giant quadrupole states in Ni isotopes

Inelastic scattering of 180 MeV {pi}{sup {minus}} and {pi}{sup +} from {sup 58,60,62,64}Ni shows a prominent quadrupole feature near 65{ital A}{sup {minus}1/3} MeV, identified as the familiar isoscalar giant quadrupole resonance. For the heavier two isotopes, the {pi}{sup {minus}} scattering cross sections greatly exceed those for {pi}{sup +}, the same effect previously noted in pion scattering on heavy nuclei. Since these four nickel targets contain a range of single-nucleon binding energies, these new data demonstrate the influence of these single-particle effects on the apparent isospin response, increasingly neutronlike for the heavier isotopes.