Studies of the Giant Dipole Resonance in ²⁷Al , ⁴⁰Ca , ⁵⁶Fe , ⁵⁸Ni and ²⁰⁸Pb with high energy-resolution inelastic proton scattering under 0°

A survey of the fine structure of the Isovector Giant Dipole Resonance (IVGDR) was performed, using the recently commissioned Zero-degree Facility of the K600 magnetic spectrometer at iThemba LABS. Inelastic proton scattering at an incident energy of 200MeV was measured on ²⁷Al , ⁴⁰Ca , ⁵⁶Fe , ⁵⁸Ni and ²⁰⁸Pb. A high energy-resolution (ΔE≃ 40 keV FWHM) could be achieved after utilising faint-beam and dispersion-matching techniques. A considerable fine structure is observed in the energy region of the IVGDR and characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The comparison with Quasiparticle-Phonon Model (QPM) calculations provides insight into the relevance of different giant resonance decay mechanisms. Photoabsorption cross sections derived from the data assuming a dominance of relativistic Coulomb excitation are in fair agreement with previous work using real photons.