0000000000010919
AUTHOR
N. Voegler
Shell structure and the fluctuation of the nuclear density distribution
We investigate the relation between the density-fluctuations in nuclei and their description by single-particle models, i.e. the shell model and the Hartree-Fock method; the question is whether every shell-structure necessarily leads to those fluctuations. We demonstrate the flexibility of the single-particle models by constructing a shell-model potential and an effective Hartree-Fock potential, respectively, which produce completely flat distributions without any density fluctuation; this means that “shell structure” is not sufficient an explanation for the fluctuations. Only the additional requirement that the dynamical features of nuclei are also met selects a subclass of “reasonable” po…
Distribution of electric multipole strengths in58Ni
Inelastic electron scattering of 124 and 180 MeV electrons from58Ni has been measured for momentum transfers of 0.4 fm−1≤q≤1.2 fm−1 with an energy resolution of 110 keV. Using DWBA form factors with Tassie transition densities, we have extracted the electric multipole strength forL≤4 residing in 28 discrete states and in the inelastic continuum below 22.5 MeV of excitation.
Determination of the total photo-absorption cross section of 197Au from () reaction cross sections
Abstract Cross sections for the reactions 197Au ( γ, ℩ n ) (x ⩽ 12) have been measured for bremsstrahlung end-point energies in the range 60–340 MeV. From these dominant cross sections, the total photon absorption cross section is determined using a cascade-evaporation calculation to account for the missing reaction channels. The enhancement factor for the classical E1 sum rule is found to be 0.93 ± 0.10.
Radiation tail in electron scattering: Approximations in the calculation and comparison to measurements
Abstract Different approximations to the calculation of the radiation tail in electron scattering experiments are investigated with particular emphasis on problems related to the peaking approximation and to the convolution of the different contributions to the tail. The calculations are compared to measurements on C and W targets.
Violation of Siegert's theorem in the electro-excitation of the (1−, T = 0)-level at 7.117 MeV in 16O
Abstract Cross sections are measured for the electro-excitation of the first 1−-level in 16O at extremely small momentum transfer. The model-independent interpretation with a Fourier-Bessel expansion of the transition charge density reveals an incompatibility with the life-time measurement at the photon point, i.e. a violation of Siegert's theorem.
Direct measurement of the radiative tail in electron scattering from atomic nuclei
We have made a direct measurement of the radiative tail of the eleastic peak from several tungsten targets. The measured data have been compared to the results expected for both internal and external bremsstrahlung contributions. Even for targets as thick as 4% of a radiation length of tungsten, agreement between the results of the experiment and the predictions of the theory has been found to be unexpectedly good.
Charge Distribution ofPb208and the Difference inρ(r)for Pb and Tl Investigated by by Elastic Electron Scattering
Elastic electron-scattering cross sections from $^{208}\mathrm{Pb}$ have been measured for $0.5 {\mathrm{fm}}^{\ensuremath{-}1}lql2.24 {\mathrm{fm}}^{\ensuremath{-}1}$. The charge distribution for this nucleus is determined by a "model-independent" method; it exhibits a bump in the center of the nucleus which is also a characteristic feature of Hartree-Fock calculations. The influence of the $3s$ protons on $\ensuremath{\rho}(r)$ has been investigated by a difference measurement between lead and thallium isotones.
Measurement of magnetic monopole transition in electron scattering fromO16as direct test of dispersive effects
For the first time an experiment has been performed to measure a magnetic monopole transition in inelastic electron scattering. In {sup 16}O the 0{sup +}{r arrow}0{sup {minus}} transition to the level at {ital E}{sub {ital x}}=10.957 MeV has been observed with a cross section of {ital d}{sigma}/{ital d}{Omega}=(5.4{plus minus}3.8){times}10{sup {minus}37} cm{sup {minus}2}/sr. Measurement of this transition is a direct signature of two-step contributions in electron scattering. Our measurement is in good agreement with the strength calculated for this transition.
What can be learnt about nuclear polarization from a consistency analysis ofe ? cross sections and muonic X-rays for208Pb and the isotone pair209Bi/208Pb?
A joint analysis of recent electron scattering cross sections and muonic atom X-ray energies is performed for208Pb and the isotone pair209Bi/208Pb. From the compatibility of the experimental data one can learn about the nuclear polarisation correction. However, we find this information not to be as accurate as other authors claimed when we take into consideration the ambiguities in the treatment of the corrections of the higher levels.