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Betty Tsang Professor (NSCL) Nuclear Chemistry   PhD, Nuclear Chemistry, University of Washington, Seattle 1980 Joined NSCL in December 1980 Phone (517) 908-7386 Fax (517) 353-5967 Office W110   tsang at nsclmsuedu Professional homepage

As an experimentalist, I study collisions of nuclei at energies at approximately half the speed of light. From the collisions of nuclei, we can create environments, which resemble the first moments of the universe after the big bang. Properties of extra terrestrial objects such as neutron stars can be obtained from studying collisions of a variety of nuclei with different compositions of protons and neutrons. One important research area of current interest is the density dependence of the symmetry energy, which governs the stability as well as other properties of neutron stars. Symmetry energy also determines the degree of stability in nuclei. We have an active program to study the symmetry energy term in the nuclear equation of state. In one experiment, which measured the isotope yields from the collisions of different tin isotopes, 112Sn+112Sn (light tin systems), 124Sn+124Sn (heavy tin systems with more neutrons), we discovered that the ratios of the yields of specific isotopes between two different tin systems follow a nice systematic. The yield ratios depend exponentially on the neutron number N and proton number Z of the specific isotopes as shown in the figure. This phenomenon is coined “isoscaling” and has been observed in various types of reactions. Through model simulations, we have related the slopes of the lines to the symmetry energy. Experiments are planned at NSCL, as well as RIKEN, Japan, to further understand the symmetry energy observables at different nuclear densities created in nuclear collisions. Transport simulations of nuclear collisions carried out at the high performance computing center at MSU also help us in our quest to understand the role of symmetry energy in nuclear collisions, nuclear structure and neutron stars. By studying particles emitted in nuclear collisions, we also gain knowledge about the structure of nuclei. Single nucleon transfer reactions, when either a proton or neutron is transferred from the projectile to the target or vice versa, have been used successfully in the study of nuclear structure. This type of reaction is especially useful in understanding the single particle states in a nucleus such as 56NI which is a double magic nucleus but is unstable. 56NI is a nucleus of Astrophysical interest as it is the end product in many Astrophysical reactions. Accurate descriptions of single particle states are of fundamental importance to check the validity of the nuclear shell models which predict properties of exotic nuclei relevant in our understanding of nucleosynthesis of elements when the early universe was formed. Our group has an active experimental program in transfer reactions using a state of the art high resolution detector array (HiRA). Experiments are being planned for using radioactive beams at NSCL.