Isospin character of low-lying pygmy dipole states in Pb208 via inelastic scattering of O17 ions

The properties of pygmy dipole states in Pb208 were investigated using the Pb208(O17, O17’γ) reaction at 340 MeV and measuring the γ decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted γ rays and of the scattered particles were measured. The results are compared with (γ, γ′) and (p, p′) data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2+ and 3− states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first time. This has allowed us to extract the isoscalar component of the 1− excited states from 4 to 8 MeV.