This award will support collaborative research between Prof. James Kolata of the University of Notre Dame and Dr. Eli Aguilera and Dr. Jaime Vega of the Mexican National Institute for Nuclear Research (ININ). The goal of the research is to achieve a basic understanding of heavy-ion fusion. Since atomic nuclei repel each other strongly due to their electric charge, it is therefore necessary to supply a substantial amount of energy to the system to make their surfaces come into contact so that fusion can proceed. However, even if the surfaces do not touch, fusion may be accomplished through a process known as "quantum-mechanical tunneling", which forms the basis of several modern electronic devices. In the nuclear case, simple theoretical models of the process do not quite predict the strong enhancement accomplished by this "sub-barrier" fusion. Several complicated and generally mutually incompatible explanations have been formulated to explain this phenomenon but further study is needed to understand these effects. The proposed work is of high current interest because it represents an important way in which the effect of internal degrees of freeedom on the quantum-mechanical tunneling process can be studied. The proposed collaboration is an extension of previous efforts and is well matched to the strengths and facilities at both institutions. Detailed experimental measurements will be carried out at Notre Dame while the lengthy data-analysis phase of the work will be done at ININ using a powerful new computer system at that institute. The proposed work is likely to make a contribution to the field of heavy ion physics.
