B(E2) Measurements in the Yrast Band of 28Mg: Implications on the N=20 Island of Inversion

In nuclei near the N=20 island of inversion, deformation and non-central tensor components of the nuclear interaction drive preferential occupation of pf-shell orbitals over the sd-shell orbitals predicted by the spherical shell model. High precision, excited state lifetime measurements in nuclei along the Mg isotopic chain provide a means to study the evolution of neutron shells systematically and better understand the onset of the island of inversion. In a recent experiment performed at TRIUMF, both the Doppler shift attenuation and recoil distance methods were used to measure excited state lifetimes in ²⁸Mg, including the (6⁺₁) -> 4⁺₁ -> 2⁺₁ -> 0⁺_g.s. yrast band. In this talk, I will discuss the results of this work and the implications on neutron shell evolution in Mg isotopes and the onset of the N=20 island of inversion.