Mirror and Triplet spectroscopy in the fp shell with SeGA and GRETINA

In this thesis, data relevant to isospin-non conserving effects in the fp shell are presented. The data are interpreted in terms of the shell model and use empirically derived isospin non-conserving terms. Understanding the empirically derived isospin-non conserving terms is the main motivation for this research. The J = 2 anomaly is a term that has been introduced into shell
model calculations to reproduce mirror energy difference (MED) data in the f7/2 shell.

The first of the two experiments in this thesis examines the Tz = −3 nucleus 51Co. Excited states were identified through gamma ray spectroscopy with SeGA at the NSCL facility using the A1900+S800 setup. The transitions were identified using mirror symmetry arguments. The results show that the f7/2 MED calculation approach is still accurate when the states relevant to the MED are unbound to proton emission in the negative Tz nucleus.

A second experiment is presented which is the main focus of this thesis. The experimental setup was much the same except for higher mass beams and GRETINA was used in place of SeGA. The experiment used a 66As beam, and isotonic contaminants of 65Ge and 64Ga to populate excited states in fp shell nuclei. Results and discussion are presented for the following nuclide and pairs of mirror nuclei: 62Ga; 63Ge and 63Ga; 65As and 65Ge.

The conclusions drawn from the results of these two experiments are as follows:
• No additional isospin non-conserving effects are observed when states in one of the mirror nuclei are as much as 1.5 MeV unbound to proton emission.
• The A = 63 MED show that one of the expected terms (Vcr) does not function in the upper-fp shell.
• The implication from the presented data is that states in 65As undergo proton emission.
• A study of triplet energy difference (TED) systematics is presented along side data from 62Ga to produce a new candidate for the anomalous T = 1, 2+ state in 62Ga.