Abstract

The Search for Πf_7/2 Intruder States in ⁷³As

Student: Amelia Doetsch (Wayne State University)
Faculty Mentor: Robert Haring-Kaye (OWU Department of Physics and Astronomy)

Arsenic-73 (⁷³As) belongs to a region of atomic nuclei known as the “Wild West.” This name stems from the fact that these nuclei have structural properties that are not as predictable as their heavier neighbors. In particular, certain isotopes in the Wild West have exhibited evidence for strongly deformed shapes (resembling American footballs) based on a rather unique configuration of their constituent protons. The goal of this study was to search for the “fingerprint” of a similar structure in ⁷³As. Although none was found, this result can help inform contemporary theoretical models as to why some isotopes exhibit this structure while others do not.

Proton occupation of the f_7/2 orbital (the Πf_7/2 configuration) in the mass A ~ 70 region is rare since it would require large prolate shape deformation (β₂ ≥ 0.4). So far, there are only two known cases of such an occupation in this region (⁷¹As and ⁶⁷Cu). The aim of this study was to search for evidence of Πf_7/2 states in ⁷³As. High-spin states in ⁷³As were populated using the ¹⁴C(⁶²Ni, p2n) reaction at 50 MeV performed at Florida State University. A Compton-suppressed Ge detector array made up of three Clover detectors and seven single-crystal detectors was used to record γ-γ coincidences. Directional correlation of oriented nuclei ratios (R_DCO) were used to assign spins. Coincidence data showed no evidence of a f_7/2 band structure. Furthermore, a state at 577 keV that was previously thought to have a spin of 7/2 (and which could be the head of a Πf_7/2 band) was instead determined to have a spin of 5/2 based on R_DCO measurements. These results suggest that there is no Πf_7/2 orbital occupation in ⁷³As.