A Study of Neutron Rich Isomers and Masses Using a Storage Ring.

Utilising the SIS-18 synchrotron at GSI, the fragmentation of 238U was carried out on a 4g/cm2 9Be target at 670 MeV per nucleon. The aim was to investigate long-lived high-spin isomers while also testing the feasibility of using an experimental storage ring for this purpose. The neutron-rich fragments created, were separated by the FRS then stored and cooled in the ESR where their masses were measured. Through this technique the masses of seven ground and four isomeric states have been measured with an average uncertainty of 51 keV. Of these masses, one (174Er) is experimentally measured for the first time and three (190gRe,190mlRe and 195Os) have their uncertainties reduced by 100-450keV. The newly measured mass of 174Er is used to extend the S2n line and calculate ẟVpn values in the surrounding region, with evidence for a subshell closure at N ~ 108 discussed in relation to these two values. The ground and isomeric state masses of 190Re represent not only the first direct measurement of the isomeric energy, but also highlights the self-consistent nature through which excitation energies can be found using this analysis technique. Multi-quasiparticle calculation have been carried out and are compared with the published level scheme in light of the new measurement. The mass of 195Os is directly measured for the first time, decreasing the uncertainty to which the mass is known by an order of magnitude. The accuracy of various microscopic and macroscopic mass models are discussed in relation to this value, as are the ground-state masses of the other isotopes measured. Finally, initial findings on 184Hf, found using the same experimental technique as described in this thesis, are presented and the reasons for the differing degrees of success discussed