EPSRC Visiting Fellow
Alex Brown of Michigan State University spent six months of his sabbatical leave as an EPSRC Visiting Fellow with the nuclear orientation group of Nick Stone at Oxford. As an experienced nuclear shell model theorist, Brown's objectives were to set up detailed calculations in the 132Sn region to support interpretation of new magnetic dipole moment and decay data obtained by the Oxford group in recent nuclear orientation on-line studies at the OSIRIS facility, Studsvik in Sweden. Brown's other purpose was to work with Jirina Stone on testing the new Skyrme skx interaction using Hartree Fock models
In the work at 132Sn, Brown set up a basis for large scale shell model calculations in the model space where the neutrons fill the top of the (0g7/2,1d5/2,1d3/2,2s5/2,Oh11/2) shell and protons fill the bottom of this shell. A new G matrix hamiltonian to deal with proton-neutron interaction was developed in collaboration with N. Hjorth-Jensen of Oslo to complement existing proton-proton and neutron-neutron interactions.
Alex Brown collaborated with Ian Towner on full calculations of single-particle nuclear magnetic dipole moments based on his shell model wavefunctions. These calculations provide the basis for interpretation of new magnetic moment, excited state and transition properties of Sb, Te, Xe and I isotopes resulting from the work of the Oxford nuclear orientation group at the Studsvik laboratory. First papers have been written and the project is ongoing. Nuclear theory hand-in-hand with experiment in this region is vitally important in allowing extraction of sub-nucleon degrees of freedom (mesonic exchange current effects) from precisely measured nuclear dipole moments.
The 'pure theory' research concentrated on testing the SkX Skyrme interaction in predictions of properties of infinite isoscaler nuclear matter and pure neutron matter. This took the form of exploring the feasibility of making calculations on neutron stars (with density up to ten times that of nuclei) using the same interaction as that found acceptable in describing nuclei. This essential compatibility was shown to exist but to impose useful constraints on the theory. A second aspect of this work was an investigation of how nuclear radii calculated in spherical and deformed HF models compared with each other and with experiment. Both projects are on-going and will be published soon
During his time in the United Kingdom Brown gave invited seminars and colloquia at Universities of Liverpool, Manchester, Oxford and Surrey. He worked closely with graduate students of the nuclear orientation group. His detailed predictions of structure of Sb, Te, I and Xe isotopes will enhance a whole generation of theses!