Oak Ridge National Laboratory

Physics Division

Physics Division Seminars

Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,

Alfredo Galindo-Uribarri
Tel (Office): (865) 574-6124  (FAX): (865) 574-1268

Mon., September 28, 2015, at 3:00-4:00 PM (refreshments served at 2:40 PM)

Search for Alpha-Cluster States in Light Unstable Nuclei Using the Prototype Active-Target Time-Projection Chamber

Tan Ahn, University of Notre Dame, Notre Dame, IN 46556
ORNL, Bldg. 6008 Large Conference Room

Alpha clustering in nuclei has been known for many years, but the extent of alpha clusterization is still an open question, especially for nuclei with unequal numbers of protons and neutrons. To search for these alpha cluster states in unstable nuclei, we have performed experiments using resonant alpha scattering with in-flight radioactive beams produced at the Institute of Nuclear Structure and Astrophysics at the University of Notre Dame. Using radioactive beams gives us access to proton- and neutron-rich nuclei one or two nucleons away from stability. For the inverse kinematics scattering target, a He gas target is provided by the Prototype Active-Target Time-Projection Chamber (PAT-TPC). The PAT-TPC also images the ionization tracks of the scattering process in the gas target volume. From these tracks we measure excitation functions and differential cross sections with high efficiency and precision. We have performed experiments to study alpha cluster states in 10Be and 14C, nuclei where novel cluster states are predicted by anti-symmetrized molecular dynamics models. In 10Be, it was found that alpha clusterization may be limited by high angular momentum. In contrast, we have found evidence a linear chain of alpha clusters in 14C that may form a rotational band. A new experiment was recently performed to search for the cluster states in 14O that are the isospin mirrors of those in 14C. The study of 14C and 14O should give knowledge on whether alpha cluster states will preserve isospin symmetry for these unique systems or whether the additional Coulomb interaction will break the alpha clusterization of these states. These measurements will help in understanding the boundaries in energy, spin, and isospin for the formation of alpha cluster-like states.

Contact: Alfredo Galindo-Uribarri, (865) 574-6124