Scissors Modes and Spin Excitations in Light Nuclei including N=2 excitations: Behaviour of 8Be and 10Be
Abstract
Shell model calculations are performed for magnetic dipole excitations in 8Be and 10Be in which all valence configurations plus 2ω excitations are allowed (large space). We study both the orbital and spin excitations. The results are compared with the `valence space only' calculations (small space). The cumulative energy weighted sums are calculated and compared for the J=0+ T=0 to J=1+ T=1 excitations in 8Be and for J=0+ T=1 to both J=1+ T=1 and J=1+ T=2 excitations in 10Be. We find for the J=0+ T=1 to J=1+ T=1 isovector spin transitions in 10Be that the summed strength in the large space is less than in the small space. We find that the high energy energy-weighted isovector orbital strength is smaller than the low energy strength for transitions in which the isospin is changed, but for J=0+ T=1 to J=1+ T=1 in 10Be the high energy strength is larger. We find that the low lying orbital strength in 10Be is anomalously small, when an attempt is made to correlate it with the B(E2) strength to the lowest 2+ states. On the other hand a sum rule of Zheng and Zamick which concerns the total B(E2) strength is reasonably satisfied in both 8Be and 10Be. The Wigner supermultiplet scheme is a useful guide in analyzing shell model results. In 10Be and with a Q · Q interaction the T=1 and T=2 scissors modes are degenerate, with the latter carrying 5/3 of the T=1 strength.
Turn this paper into a full lesson
ArcXiv compiles a staged curriculum from this paper: 8-12 lessons across beginner → advanced, synthesised section guides, visuals, flashcards, a quiz, exercises, and on-demand deep dives per section. Grounded in the abstract, never invented.