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Title: A study of gadolinium isotopes around N = 90 utilizing particle-gamma coincidences
Author: Ross, Timothy Joseph
ISNI:       0000 0004 2747 015X
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2013
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Particle-γ coincidence data can be used as a strong tool for studying low energy nuclear structure. The STARS-LIBERACE array at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory was used to study gadolinium isotopes straddling the N = 90 shape change region. A 25 MeV proton beam was impinged upon 154Gd and 158Gd targets. The gadolinium isotopes 152,153,154,156,157,158Gd were studied following the (p,p'), (p,d) and (p,t) neutron transfer reactions. The primary focus of this work is to study the structure of and identify singleneutron quasi-particle states in the odd N Gd nuclei following the (p, d) reactions. Numerous new levels are observed in both 153Gd and 157Gd and multiple new γ rays have been observed and associated with these and other previously known levels. A large excitation energy gap between approximately 500 keV and 1500 keV is observed in the level schemes of both nuclei where very few states are populated. This gap appears to demonstrate the persisting influence of the N = 64 spherical sub-shell closure to intermediate deformations. It is striking that such an effect is apparent when probed from so far above (i.e. ~30 neutrons away). The secondary focus of this work is upon the angular momentum transferred to the statistical continuum region of these nuclei via different light ion transfer reactions, i.e. between approximately 2 MeV and the neutron separation energy. The angular momentum transferred via (p,d) and (p,t) reactions populating 157Gd and 156Gd respectively was measured using two independent techniques. The first technique involves studying the γ-ray decay path within the residual nucleus, the second technique involves measuring the angular distribution of the light ions following the reaction. The two techniques are in good agreement and appear to verify each other. The measured angular momentum transferred via the (p,t) reaction is measured to be a distribution centered around ΔL = 4-5 h. The angular momentum transferred via the (p,d) reaction is slightly lower and is closer to ΔL = 4 h.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available