Deformation effects on isoscalar giant resonances in Mg 24

Abstract

Strength distributions for isoscalar giant resonances with multipolarity L≤2 have been determined in Mg24 from "instrumental background-free" inelastic scattering of 386-MeV α particles at extreme forward angles, including 0. The isoscalar E0, E1, and E2 strengths are observed to be 57±7%, 111.1-7.2+10.9%, and 148.6±7.3%, respectively, of their energy-weighted sum rules in the excitation energy range of 6 to 35 MeV. The isoscalar giant monopole (ISGMR) and quadrupole (ISGQR) resonances exhibit a prominent K splitting which is consistent with microscopic theory for a prolate-deformed ground state of Mg24. For the ISGQR it is due to splitting of the three K components, whereas for the ISGMR it is due to its coupling to the K=0 component of the ISGQR. Deformation effects on the isoscalar giant dipole resonance are less pronounced, however.