Exploring the Nuclear Structure of the A = 39 Isobars

Investigation of nuclei with neutron and proton imbalance is at the forefront of nuclear physics research today, along with how the nuclear structure varies with the movement of the nucleons. Experimental data and theoretical models work hand-in-hand to understand the structure of these nuclei. Two of the A = 39 isobars, residing in limbo between the sd- and fp-shells are the isotopes of interest for this study. With 24 neutrons, eight neutrons more than the stable isotope of phosphorous, ³⁹P is considered a neutron-rich exotic nucleus, one of which has not been extensively studied until now. Since the late 1990s only two experiments have been conducted, producing the three known gamma-rays and one tentative gamma-ray for ³⁹P. Except for half-life measurements and mass measurements, no further studies of ³⁹P have been done prior to a beta-gamma coincidence experiment conducted in this study at the National Superconducting Cyclotron Laboratory (NSCL) using the Beta Counting System. Continuing up the isobaric chain from ³⁹P toward stability, ³⁹Ar is reached. Unlike ³⁹P, ³⁹Ar is nested between two of the stable isotopes of argon. Being closer to stability, it has been studied more extensively using transfer reactions, however, limited information on high-spin states is produced from only two prior experiments. Despite the more extensive study of ³⁹Ar, the observed gamma transitions are only well known for low-spin states except for one band of high-spin states which have been studied heavily using the gamma spectroscopy setup at the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University. Results for both isotopes, along with comparisons to Shell Model calculations will be presented.