Nature of mixed symmetry 2⁺ states in ⁹⁴Mo from high resolution electron and proton scattering and line shape of the first excited 1/2⁺ state in ⁹Be

The present work contains two parts. The first one is devoted to the investigation of mixed-symmetry structure in ⁹⁴Mo and the second one to the astrophysical relevant line shape of the first excited 1/2⁺ state in ⁹Be. In the first part of the thesis the nature of one- and two-phonon symmetric and mixed-symmetric 2⁺ states in ⁹⁴Mo is investigated with high-resolution inelastic electron and proton scattering experiments in a combined analysis. The (e,e') experiments were carried out at the 169 magnetic spectrometer at the S-DALINAC. Data were taken at a beam energy E e=70 MeV and scattering angles Θ_e=93 -165 . In dispersion-matching mode an energy resolution Δ_E=30-45 keV (full width at half maximum) was achieved. The (p,p') measurements were performed at iThemba LABS, South Africa, using a K600 magnetic spectrometer at a proton energy E p=200 MeV and scattering angles Θ_p=4.5 -26 . Typical energy resolutions were Δ_E≅35 keV. The combined analysis reveals a dominant one-phonon structure of the transitions to the first and third 2⁺ states, as well as an isovector character of the transition to the one-phonon mixed-symmetric state within the valence shell. Quantitatively consistent estimates of the one-phonon admixtures are obtained from both experimental probes when two-step contributions to the proton scattering cross sections are taken into account. In the second part of the thesis the line shape of the first excited 1/2⁺ state in ⁹Be is studied. Spectra of the ⁹Be(e,e') reaction were measured at the S-DALINAC at an electron energy E e=73 MeV and scattering angles of 93 and 141 with high energy resolution up to excitation energies E_x=8 MeV. The form factor of the first excited state has been extracted from the data. The astrophysical relevant ⁹Be(γ,n) cross sections have been extracted from the (e,e') data. The resonance parameters of the first excited 1/2⁺ state in ⁹Be are derived in a one-level R-matrix approximation. The deduced resonance parameters averaged over all available (e,e') data are E_R=1.748(6) MeV and Γ_R=274(8) keV However, the extracted B(E1) strength is a factor of two smaller than found in the latter indicating a violation of Siegert's theorem at the photon point. (orig.)