Type of Document	Dissertation
Author	Bender, Peter C.
URN	etd-08032011-134836
Title	Nuclear Structure of Neutron Rich 34P using In-Beam Gamma Ray Spectroscopy
Degree	Doctor of Philosophy
Department	Physics, Department of
Advisory Committee	Advisor Name Title Samuel Tabor Committee Chair Alexandr Volya Committee Member Grigory Rogachev Committee Member Maitri Warusawithana University Representative Munir Humayun University Representative
Keywords	34P gamma-ray spectroscopy nuclear structure gammasphere shell model
Date of Defense	2011-06-20
Availability	unrestricted
Abstract Increasing dominance of negative parity intruder states in neutron-rich nuclei in the sd shell as $N$ approaches $20$ shows evidence of evolving shell structure. Systematically examining the structure of isotopes with increasing $N$ while filling the $ u d_{3/2}$ level highlights a large number of intruder configurations. These intruder configurations come from the decrease in energy to promote a neutron across the $N = 20$ shell gap. Such studies are needed to help in the refinement of the shell model and increase its predictive power for nuclei far from stability. The presented work chronicles a series of $^{18}$O($^{18}$O,$pn$) experiments conducted around the world to study high spin states in $^{34}$P, a nucleus in the $sd$ shell bordering the ``island of inversion'. One of these experiments which was conducted at Argonne National Laboratory where a 24 MeV neutron rich $^{18}$O beam impinged on a Ta backed $^{18}$O target, is presented here in great detail. The evaporated charged particles were detected with {sc microball} while the $gamma$ rays emitted were detected with {sc gammasphere}. A brief discussion of the theory of analysis techniques used in in-beam $gamma$-ray spectroscopy is presented followed by an in depth discussion of the analysis of this experiment. From the analysis of excited states populated in $^{34}$P, a number of candidate states including $0p0h$ and $1p1h$ configurations are found and identified. A few states are also observed that have strong evidence pointing towards a more exotic $2p2h$ configuration. One state, the highest ever observed in $^{34}$P at 7917 keV may even be of the extremely exotic $3p3h$ type though the evidence is very speculative. Spins and parities of all levels have been assigned through arguments based on lifetime measurements of individual states measured with Doppler shift attenuation techniques and full $gamma$-ray angular distributions whenever possible. Model dependent assignments have also been used in some spin assignments. %mainly for reassurance. In total, 10 newly observed levels are presented along with 23 newly observed transitions. Detailed shell model calculations using both the $WBP-a$ and $sdpfnow$ interactions are also presented. A comparison of theoretically predicted properties of individual states, including occupations, branching ratios and electromagnetic transition strengths is made to the experimentally observed states when applicable. Both interactions show fairly reliable predictive power for the both $0p0h$ and $1p1h$ configurations with an approximate root mean squared deviation of 150 keV in energies. States involving $2p2h$ configurations are discussed, though the current shell model calculations are much less reliable for them.
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