Beta decay studies of neutron-rich aluminum-30,31 and in-beam studies of neutron-rich aluminum-30.

摘要

Low-spin states were studied in 30Al following the beta decay of 30Mg produced in the fragmentation of 140 MeV/AMU 48Ca. Analysis of the beta-gamma and beta-gamma-gamma coincidences revealed a new 1+ state at 2413 keV, confirmation of the level scheme, and a more accurate half life measurement of 315(6) ms for the 30Mg ground state. Higher-spin states were investigated in the reaction of 14C on 18O at 22 MeV. Protons and deuterons were detected in a segmented E-DeltaE Si telescope in coincidence with one or two gamma rays in the FSU Ge detector array. A comparison of the resulting level and decay scheme with predictions of the sd shell model shows good agreement with all but 6 of the states in both excitation energy and gamma decay branching ratios. The RMS deviations in energy of these states using the older USD and newer USDA and USDB interactions were 265, 176, and 173 keV respectively. The remaining 6 states are well described as 4- to 7- states, similar in relative energy to those in 28Al but shifted down by about 1200 keV. These states also agree well with the predictions of shell model calculations using the WBP interaction. A comparison of the lowest 4- states in even A Na, Al, and P isotopes shows a systematic decrease in energy with increasing N and with decreasing Z. The energies of the 4- states are almost identical in nuclei with the same N - Z values.;In addition to the study of 30Al, 31Al was also produced following the beta decay of 31Mg in the fragmentation of 140 MeV/AMU 48Ca. The beta-gamma and beta-gamma-gamma coincidences were able to show all previously known work. However, no new transitions were observed.