Magnetic multipole excitations inC12by inelastic electron scattering

Abstract

Magnetic excitations in $^{12}\mathrm{C}$ have been measured by inelastic electron scattering at backward scattering angles for momentum transfers between $q=0.5 \mathrm{and} 3.3$ ${\mathrm{fm}}^{\ensuremath{-}1}$. Data for $M1$, $M2$, $M3$, and $M4$ transitions are compared to shell model calculations. In general, the excitation energies are reasonably predicted, as are the momentum transfer dependences of the form factors. However, the form factor magnitudes often exceed measurements by factors of more than 2. Candidates for ${2}^{\ensuremath{-}}$ states are seen at excitation energies of 18.2 and 22.7 MeV. It is shown how structure effects may reduce estimates of isospin mixing matrix elements from ($\ensuremath{\pi}$,${\ensuremath{\pi}}^{\ensuremath{'}}$) ratios.