High spin structure and intruder configurations in 31P

Abstract

The nucleus 31 P has been studied in the 24 Mg ( 16 O ,2𝛼⁢𝑝) reaction with a 70-MeV 16 O beam. A complex level scheme extended up to spins 17/2+ and 15/2−, on positive and negative parity, respectively, has been established. Lifetimes for the new states have been investigated by the Doppler shift attenuation method. Two shell-model calculations have been performed to describe the experimental data, one by using the code ANTOINE in a valence space restricted to the sd shell, and the other by applying the Monte Carlo shell model in a valence space including the 𝑠𝑑−𝑓𝑝 shells. The latter calculation indicates that intruder excitations, involving the promotion of a 𝑇=0 proton-neutron pair to the fp shell, play a dominant role in the structure of the positive-parity high-spin states of 31 P .