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HK: Physik der Hadronen und Kerne
HK 10: Poster Session: Nuclear Physics/Spectroscopy
HK 10.20: Poster
Tuesday, March 12, 2002, 10:30–12:45, Foyer Chemie
M1 and M2 modes in 180∘ electron scattering at the S-DALINAC⋆ — •Y. Kalmykov1, A. Dzhioev2, N. Goncharova2, F. Hofmann1, H. Lenske3, P. von Neumann-Cosel1, B. Reitz4, A. Richter1, and J. Wambach1 — 1Institut für Kernphysik, Technische Universität Darmstadt — 2Institute of Nuclear Physics, Moscow State University, Russia — 3Institut für Theoretische Physik, Universität Giessen — 4Jefferson Lab., Newport News, USA
Electron scattering at 180∘ is a proven technique for
investigating
magnetic excitations of nuclei. Two projects have been performed recently
with
the 180∘ system at the S-DALINAC: investigations of M1 and M2
transitions
in self-conjugate sd-shell nuclei and M2 transitions in the medium-heavy
nucleus 58Ni. The high experimental sensitivity allows studies of
subtle
effects like isospin mixing in isoscalar M1 transitions [1].
The deduced M2 strength distributions in 24Mg, 28Si and
32S are compared to a particle core coupling-type of shell model
calculation. The comparison of the extracted M2 strength distribution
in 58Ni and the spin-dipole strength deduced
from a (p→,p→ ′) experiment at KVI
indicates the presence of large orbital contributions which are interpreted
as
the twist mode in nuclei [2]. This finding is corroborated by QPM
calculations including the coupling to complex degrees of freedom.
⋆ Supported by the DFG under contract FOR 272/2-1.
F. Hofmann et al.,
Phys. Rev. C , in press.
B. Reitz et al.,
Phys. Lett. B , submitted.