Cluster states and isoscalar monopole transitions ofMg24

Abstract

Background: Isoscalar monopole transition has been suggested as a key observable to search for exotic cluster states. Recently, excited 0+ states with strong isoscalar monopole transition strengths were experimentally reported in Mg24, but their structures were not revealed because of the lack of theoretical analysis. Purpose: We study the structure of the excited 0+ states of Mg24 populated by isoscalar monopole transition from the ground state, and identify their cluster configurations. Method: The 0+ states of Mg24 and their isoscalar monopole transition strengths from the ground state are calculated with antisymmetrized molecular dynamics combined with the generator coordinate method using the Gogny D1S interaction. Results: The calculated isoscalar monopole strength function shows reasonable agreement with experiment and is consistent with other theoretical calculations. The structures of the excited 0+ states with pronounced isoscalar monopole transitions are analyzed. It is found that the 02+, 03+, and 05+ states have mixed nature of mean-field and cluster, and that the 08+ state is dominated by a C12+C12 cluster configuration. In addition, it is predicted that 5α-pentagon+α states appear around 23 MeV. Conclusions: The excited 0+ states which appear as the prominent peaks in the calculated strength function are associated with Ne20+α, C12+C12, and 5α-pentagon+α cluster states.