Coulomb Excitation with Heavy Ions

Summary: The work for this thesis began with a study, on the ORNL 200-kev Cockcroft-Walton, of the possible use of the radio frequency ion source for multiply charged heavy ion production. When the results of this seemed unfavorable for the intended research, a PIG type ion source was designed and tested. It was capable of supplying usable quantities of Ne3+ ions, and was installed and used in the ORNL 5.5 Mv Van de Graaff accelerator. Multiply-charged components from the PIG source were not as copious as those from several larger PIG sources that had been reported as having been used in entirely different environments. In attempting to increase these components in the present design, a number of difficulties were mapped out. Ac and pulsed operation were briefly studied, and it appears that additional work in this area would be of interest. Anode extraction of the ion source was not attempted but this might provide increased multiple charge components. The difficulties of such extraction in conventional Van de Graaff were pointed out. However, the usefulness of a much increased Ne3+ beam or a usable Ne4+ beam would be considerable, and might warrant a study of this. The Ne2+ and Ne3+ beams in this work were used for Coulomb exciting low lying levels in eighteen nuclei from Li7 to Th232. The ϵB(E2) were extracted from these yields and compared with published data. There were specific deviations, but generally there was agreement with the large body of Coulomb excitation data which has been obtained mostly with lighter ions. Heavy ions are able to provide Coulomb excitation yields and angular distributions which are generally freer for complexities than those obtained with protons and helium ions. This is particularly the case for lighter nuclei. In the present research, the character of transitions from Coulomb excitation of eight odd-A nuclei from Ti47 to As75 were studied in detail. The angular distribution measurements provided strong evidence for the unique spin assignments for four of the levels which were excited. Two of these assignments (in Zn67) conflict with accepted values, and two of them confirm accepted values. The E2 matrix elements were determined for 14 transitions in the eight nuclei, and M1 matrix elements were determined for 10 transitions. Existing applications of the paring correlation theory to V51 and Ni61 were considered further. The enhanced transitions suggest that a collective approach in the framework of this theory might be useful for these nuclei. Specific observations were made on the bearing of the present data on shell model and collective aspects of the low energy structure of some of the nuclei. It is concluded that additional Coulomb excitation with lighter ions or more energetic heavy ions would be particularly useful for these nuclei. This should provide an informative adjunct to the present results, which yield relatively uncomplicated data about the lowest levels. Furthermore, some of the questionable aspects of the present data might be checked