Low-multipolarity magnetic transitions in 30Si, 32S, and 34S studied by 180 degrees electron scattering.

Abstract

Low-multipolarity magnetic transitions of $^{30}\mathrm{Si}$, $^{32}\mathrm{S}$, and $^{34}\mathrm{S}$ were studied by 180\ifmmode^\circ\else\textdegree\fi{} inelastic electron scattering at low momentum transfers (q\ensuremath{\sim}0.3\char21{}0.5 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$). These measurements, made in the excitation energy region from 9 to 14 MeV, revealed several previous unreported levels. These are the first low-q results obtained by electron scattering for $^{30}\mathrm{Si}$ and $^{34}\mathrm{S}$. Multipolarities and transition strengths for all the observed transitions were determined in a model-independent analysis. A large fragmentation of M1 strength is observed in the 4N+2 nuclei $^{30}\mathrm{Si}$ and $^{34}\mathrm{S}$, while more strength is concentrated into fewer transitions in the self-conjugate nucleus $^{32}\mathrm{S}$. The experimental M1 strength distributions are compared with configuration-mixing shell-model calculations. The sums of the transition strengths are in good agreement with recent shell-model calculations using an effective M1 operator.