Showing papers by "Achim Richter published in 1985"
TL;DR: In this paper, the roles of spin and convection currents are studied by inelastic proton and electron scattering to the low-lying 1+ state at 4319 MeV in the f 7 2 -shell nucleus 46Ti.
66 citations
TL;DR: The study of electric quadrupole transitions from the ground state into symmetric states and into states of mixed symmetry in the deformed nucleus /sup 156/Gd by inelastic electron scattering has been used to derive effective neutron and proton boson charges for the E2 operator in the framework of the interacting-boson model.
Abstract: The study of electric quadrupole transitions from the ground state into symmetric states and into states of mixed symmetry in the deformed nucleus /sup 156/Gd by inelastic electron scattering has been used to derive effective neutron and proton boson charges for the E2 operator in the framework of the interacting-boson model. The values for e/sub ..pi../ and e/sub ..nu../ differ at most by 30% in the rotational limit.
33 citations
TL;DR: The M1 strength investigated in the energy region E/sub x/approx.
Abstract: Results of a search for M1 strength in the N=28 isotones $^{50}\mathrm{Ti}$, $^{52}\mathrm{Cr}$, and $^{54}\mathrm{Fe}$ by means of high-resolution electron scattering are presented. The M1 strength investigated in the energy region ${E}_{x}$\ensuremath{\simeq}7\char21{}12 MeV is found to be strongly fragmented and considerably suppressed with respect to results from shell-model calculations which include up to 2p-2h excitations. The theoretical model is also compared with recent results using other experimental probes.
27 citations
TL;DR: In this paper, it was suggested that the splitting of the magnetic giant dipole resonance observed in 164 Dy and 174 Yb could be explained by assuming a triaxial deformation, with a value of the γ-parameter of a few degrees.
26 citations
TL;DR: In this article, a brief reminder of the definition of a giant resonance, its strength and fragmentation and the method to determine reduced transition strengths which are the testing grounds for any comparison with a model is presented.
26 citations
TL;DR: The relative weight of proton and neutron spin-flip contributions to the M1 excitation of the recently discovered J/sup ..pi../ = 1/sup +/ state at E/sub x/ = 5.846 MeV has been determined by comparison of the momentum-transfer dependence of the measured electron-scattering form factor.
Abstract: The relative weight of proton and neutron spin-flip contributions to the M1 excitation of the recently discovered J/sup ..pi../ = 1/sup +/ state at E/sub x/ = 5.846 MeV has been determined by comparison of the momentum-transfer dependence of the measured electron-scattering form factor (q/sub eff/ = 0.44--1.59 fm/sup -1/) to results from a simple two-state model and from random-phase-approximation calculations using a spin- and spin-isospin--dependent effective separable interaction. The M1 transition is shown to be predominantly of isoscalar nature.
25 citations
TL;DR: In this paper, a sum rule approach is proposed for investigating the effects of triaxiality on the splitting of the M1 isovector rotational state, and the explicit dependence of the energy and M1 strength of these states on the deformation parameters ϵB and γ is derived.
21 citations
TL;DR: In this paper, the effects of ground state tensor correlations with a phenomenological two body correlation function on the spin-isospin modes of excitations in nuclei were studied.
Abstract: We study the effects of ground state tensor correlations with a phenomenological two body correlation function on the spin-isospin modes of excitations in nuclei. The correlation function is of Jastrow type with a tensor term. The energy weighted strength is drastically enhanced because of these correlations. We predict considerable amount of strength in the region of 60–70 MeV excitations if the sum is evaluated in a two-state model. Our results are also sensitively dependent on the strength of the tensor term in the phenomenological Jastrow function.
8 citations
TL;DR: In /sup 20/Ne, the isovector M2 strength distribution in the excitation region of E/sub x/ = 11--24 MeV was investigated by inelastic electron scattering and it was shown that orbital contributions are non-negligible in these transitions.
Abstract: In /sup 20/Ne, the isovector M2 strength distribution in the excitation region of E/sub x/ = 11--24 MeV was investigated by inelastic electron scattering. Two transitions to levels at E/sub x/ = 11.62 and 12.1 MeV were observed with strengths of B(M2,k)up-arrow = 64 +- 13 and 56 +- 13 ..mu../sub N//sup 2/fm/sup 2/, respectively. A comparison with the analogous (..pi../sup -/,..gamma..) reaction shows that orbital contributions are non-negligible in these transitions. The data are compared to model predictions.
5 citations
TL;DR: In this paper, a variational approach to magnetic dipole core polarization is discussed which goes beyond the usual perturbative treatment and takes the coupling between the collective M1 state and single particle states into account.
5 citations
TL;DR: In inelastic electron scattering, form factors are measured for the 1.115 MeV level and the M1 strength is deduced to be B(M1,k)\ensuremath{\uparrow}=0.3\ifmmode\pm\else\textpm\fi{}0.4 meV.
Abstract: In inelastic electron scattering, form factors are measured for the 1.115 MeV level (${J}^{\ensuremath{\pi}}$${=(5/2)}^{\mathrm{\ensuremath{-}}}$) in $^{65}\mathrm{Cu}$. This transition from the ground state (${J}^{\ensuremath{\pi}}$${=(3/2)}^{\mathrm{\ensuremath{-}}}$) is predominantly longitudinal, with B(E2,k)\ensuremath{\uparrow} =290\ifmmode\pm\else\textpm\fi{}20 ${e}^{2}$${\mathrm{fm}}^{4}$. In the framework of a model calculation, the M1 strength is deduced to be B(M1,k)\ensuremath{\uparrow}=0.12\ifmmode\pm\else\textpm\fi{}0.03${\ensuremath{\mu}}_{\mathrm{N}}$ 2 [${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}$(M1)=1.3\ifmmode\pm\else\textpm\fi{}0.4 meV].