Spectra of the 9 Be(e,e) reaction have been measured at the Superconducting Darmstadt Electron Linear Accelerator at an electron energy of E 0 = 73 MeV and scattering angles of 93 • and 141 • with high-energy resolution up to excitation energies of E x = 8 MeV. The astrophysically relevant resonance parameters of the first excited 1/2 + state of 9 Be have been extracted in a one-level approximation of R-matrix theory, resulting in resonance energy E R = 1.748(6) MeV and width R = 274(8) keV, which are in good agreement with the latest 9 Be(γ ,n) experiment but with considerably improved uncertainties. However, the reduced B(E1) transition strength deduced from an extrapolation of the (e,e) data to the photon point is smaller by a factor of two. Implications of the new results for possible production of 12 C in neutron-rich astrophysical scenarios are discussed.
Fine structure in the region of the isoscalar giant quadrupole resonance (ISGQR) in 58Ni, 89Y, 90Zr, 120Sn, 166Er, and 208Pb has been observed in high-energy-resolution ( E1/2 35–50 keV) inelastic proton scattering measurements at E0 = 200 MeV at iThemba LABS. Calculations of the corresponding quadrupole excitation strength functions performed within models based on the random-phase approximation (RPA) reveal similar fine structure when the mixing of one-particle one-hole states with two-particle two-hole states is taken into account. A detailed comparison of the experimental data is made with results from the quasiparticle-phonon model (QPM) and the extended time-dependent Hartree-Fock (ETDHF) method. For 208Pb, additional theoretical results from second RPA and the extended theory of finite Fermi systems (ETFFS) are discussed. A continuous wavelet analysis of the experimental and the calculated spectra is used to extract dominant scales characterizing the fine structure. Although the calculations agree with qualitative features of these scales, considerable differences are found between the model and experimental results and amongst different models. Within the framework of the QPM and ETDHF calculations it is possible to decompose the model spaces into subspaces approximately corresponding to different damping mechanisms. It is demonstrated that characteristic scales mainly arise from the collective coupling of the ISGQR to low-energy surface vibrations
High-energy-resolution inelastic electron scattering (at the S-DALINAC) and proton scattering (at iThemba LABS) experiments permit a thorough test of the nature of proposed one- and two-phonon symmetric and mixed-symmetric 2+ states of the nucleus 94Mo. The combined analysis reveals the one-phonon content of the mixed-symmetry state and its isovector character suggested by microscopic nuclear model calculations. The purity of two-phonon 2+ states is extracted.
Dosimetric measurements in the field of secondary cosmic radiation were extensively made during the last years. Since the majority of these measurements were performed on-board passenger aircraft at altitudes between 10 and 12 km, measurements at higher altitudes are desirable for the verification of the legal dose assessment procedures for aircrew. A simple solution is to use a high-altitude balloon that reaches altitudes as high as 30 km. In this work, it is shown that the dose rate profile up to 30 km can be measured with acceptable uncertainties using a Si-detector.
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