1− and 2+ discrete states in Zr90 populated via the (O17,O′17γ) reaction

International audience; 2+ and 1− states in Zr90 were populated via the (O17,O′17γ) reaction at 340 MeV. The γ decay was measured with high resolution using the AGATA (advanced γ tracking array demonstrator array). Differential cross sections were obtained at few different angles for the scattered particle. The results of the elastic scattering and inelastic excitation of 2+,3−, and 1− states are compared with distorted-wave Born approximation (DWBA) calculations, using both the standard collective form factor and a form factor obtained by folding microscopically calculated transition densities. This allowed to extract the isoscalar component of the 1− state at 6.424 MeV. The comparison of the present (O17,O′17γ) data with existing (γ,γ′) and (p,p′) data in the corresponding region of the γ continuum (6–11 MeV), characterized by a large E1 component, shows completely different behaviors of the cross section as a function of the nuclear excitation energy. The comparison of the data with DWBA calculations suggests a decrease of the isoscalar strength in the cross section with increasing excitation energy.