Evolution of single-particle structure near the $N=20$ island of inversion

The single-particle properties of $^{29}$Mg have been investigated via a measurement of the $^{28}$Mg(d,p) 29Mg reaction, in inverse kinematics, using the ISOLDE Solenoidal Spectrometer. The negative-parity intruder states from the f p shell have been identified and used to benchmark modern shell-model calculations. The systematic data on the single-particle centroids along the $N = 17$ isotones show good agreement with shell-model predictions in describing the observed trends from stability toward $^{25}$O. However, there is also evidence that the effect of the finite geometry of the nuclear potential is playing a role on the behavior of the p orbitals near the particle-emission threshold.