[en] Low-lying collective vibrational excitations in ⁹⁴Mo have previously been investigated with electron scattering experiments at the 130 MeV superconducting electron accelerator S-DALINAC. The evaluation of the measured form factors as a function of momentum transfer had supported the one-phonon interpretation of symmetric and mixed-symmetric states (MSSs) which have been defined in the framework of IBM-2. In the neighbouring even-even isotone ⁹²Zr formed by N=52 neutrons with two valence neutrons and Z=40 with no protons occupying the π(g_9/2) sub-shell a stronger configurational isospin polarization of the one-phonon states than in ⁹⁴Mo is expected. In order to verify this expectation, a new electron scattering experiment at the S-DALINAC has been performed. Our data and a comparison to the momentum-transfer dependence of the form factor of the 2⁺ states are presented. The E2 transition strength of the one-quadrupole phonon states and the E3 transition strength of the one-octupole phonon state have been extracted and are compared to previously derived spectroscopic data on MSSs of ⁹²Zr.

[en] The electric dipole (E1) response of ²⁰⁸Pb has been precisely determined by measuring Coulomb excitation induced by proton scattering at very forward angles. The electric dipole polarizability, defined as inverse energy-weighted sum rule of the E1 strength, has been extracted as α_D = 20.1 ± 0.6 fm³. The data can be used to constrain the neutron skin thickness of ²⁰⁸Pb to Δr_np = 0.165 ± (0.009)_expt ± (0.013)_theor ± (0.021)_est fm, where the subscript ''expt'' refers to the experimental uncertainty, ''theor'' to the theoretical confidence band and ''est'' to the uncertainty associated with the estimation of the symmetry energy at the saturation density. In addition, a constraint band has been extracted in the plane of the symmetry energy (J and its slope parameter L) at the saturation density. (orig.)

[en] The light odd-even nucleus ⁹Be has the lowest neutron threshold (S_n 1.665 MeV) of all stable nuclei. Already the first excited J^π = 1/2⁺ state lies at an excitation energy of several tens of keV above the ⁸Be + n threshold. Parameters of this resonance are of great astrophysical importance. The description of this unbound level is long-standing problem. Due to its closeness to the neutron threshold the resonance has a strongly asymmetric line shape but despite a large number of different experiments there still exist discrepancies between the various deduced resonance parameters. We present high-resolution ⁹Be(e,e') experiments performed at the S-DALINAC and a reanalysis of our old electron scattering data. (orig.)

[en] Studies of the ²H(e,e') reaction of Θ = 180 were performed at the S-DALINAC at an incident electron energy E₀ = 27.8 MeV and 74 MeV. At such low momentum transfers (q = 0.28 fm^-1 and 0.72 fm^-1, respectively) magnetic dipole transitions are expected to give the dominant contributions to the breakup cross sections. An energy resolution of ΔE = 45 keV (FWHM) was achieved at the lower incident energy. Thus, the measured deuteron-electrodisintegration cross section at threshold can be used to obtain the cross section for the np → dγ reaction applying the principle of detailed balance. Accurate information about this process is of great interest in nuclear astrophysics, specifically with regard to Big-Bang nucleosynthesis. The experimental data are in excellent agreement with theoretical calculations based on a nucleon-nucleon potential model, after the inclusion of meson-exchange and isobar effects. (orig.)

[en] Low-lying collective vibrational excitations of ⁹²Zr have been investigated with electron scattering at the S-DALINAC. The form factors of isospin polarized one-quadrupole phonon states of ⁹²Zr at the Z = 40 proton subshell closure have been measured and the momentum-transfer dependence of the form factors for the one-quadrupole phonon states have been compared to the prediction of the Quasiparticle Phonon Model. The E2 transition strengths of the one-quadrupole phonon states and the E3 transition strength of the one-octupole phonon state have been extracted. A comparison to the data on ⁹⁴Mo and previous spectroscopic information on mixed-symmetric states (MSSs) of ⁹²Zr will be given.

[en] Modern experiments allow to unravel the fine structure of giant resonances even in heavy nuclei. High energy resolution along with excellent selectivity achieved by a proper choice of the kinematics give a possibility to extract spin- and parity-separated level densities by means of an autocorrelation analysis. A novel method using the discrete wavelet transform provides a nearly model-independent determination of the non-resonant background which is crucial for the applicability of this technique. Results for 1⁺ states in ⁵⁸Cu and ⁹⁰Nb, 2^- and 2⁺ states in ⁵⁸Ni and ⁹⁰Zr as well as 2⁺ states in a broad range of nuclei are presented in comparison with the predictions of state-of-the-art theoretical models applied in astrophysical network calculations. An emphasis is placed on a possible parity dependence and shell effects in nuclear level densities. (orig.)

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[en] A topic of high current interest are investigations of exotic electric dipole modes at energies well below the GDR. Recent (γ, γ') experiment and theoretical QPM calculations predict the existence of such dipole modes like the toroidal E1 mode in ²⁰⁸Pb with vortex transition current distribution between 6 and 11 MeV. Recent experimental progress at RCNP Osaka, Japan, allows measurements of intermediate-energy polarized inelastic proton scattering at and near 0 combined with high energy resolution. This new experimental opportunity was applied for an investigation of the toroidal mode. Measurements of the angular distribution and polarization transfer coefficients for E1 excitations might provide direct evidence of the toroidal mode. First results from the experiments will be presented. (orig.)

[en] Inclusive inelastic electron scattering off the deuteron under 180 deg. has been studied at the S-DALINAC close to the breakup threshold at momentum transfers q=0.27 fm^-1 and 0.74 fm^-1 with good energy resolution sufficient to map in detail the spin flip M1 response, which governs the starting reaction pn→dγ of big-bang nucleosynthesis over most of the relevant temperature region. Results from potential model calculations and (for q=0.27 fm^-1) from pionless nuclear effective field theory are in excellent agreement with the data