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

Thu., January 31, 2008, at 3:00 p.m. (refreshments at 2:40 p.m.)

Superheavy Nuclei: Structure, magic gaps & tests of theory

Teng Lek Khoo, Argonne National Laboratory
Building 6008 Conference Room

The heaviest nuclei have been investigated near the limits of stability in charge, spin, and excitation energy. Despite the large Coulomb repulsion, elements with atomic weight up to 118 appear to exist, based on recent reports from Dubna. Traditionally, the investigation of superheavy nuclei has been through the synthesis of ever heavier nuclei. A complementary approach using spectroscopy is now possible and provides new insight. The heaviest nuclei survive because the shell-correction energy gives extra binding, which creates a barrier against fission. The shell-correction energy originates from gaps in the single-particle energies. Hence, data on these energies are critical for a quantitative description of superheavy nuclei. The energies of 1- and 2- quasiparticle (qp) states in shell-stabilized nuclei decisively test nuclear models, their predictions of magic gaps (which define the superheavy “island of stability”) and their reliability to extrapolate far from nuclei that define the parameters. In 254No, K=3+ and 8- proton 2-qp states have been identified in the decay of high-K 2- and 4- qp isomers. In 252No and several other N=150 isotones, neutron K=8- isomers and K=2- octupole bands have been found. In addition, “experimental” single-particle energies, extracted from 1-qp energies of odd-A nuclei, are compared with theoretical predictions.

Loosely bound nuclei such as nobelium are expected to be fragile, yet experiments have shown that they survive to high angular momentum and energy (32 h-bar, >8 MeV).