• Number 324  |
• November 8, 2010

Tin isotope reveals surprising characteristics

Experiments performed at DOE's Oak Ridge National Laboratory are yielding surprising properties in extremely short-lived isotopes near tin-100's "doubly magic" nucleus.

Experiments performed with the exotic nucleus tin-101, which has a single neutron orbiting tin-100's closed shell of 50 protons and 50 neutrons, indicate an unexpected reversal in the ordering of lowest states in the nucleus. The finding appears to violate a standard scenario offered by the nuclear shell model that has been the cornerstone for understanding the atomic nucleus for more than half a century.

The experiment, performed at ORNL's Holifield Radioactive Ion Beam Facility, found that the ground states of orbiting neutrons unexpectedly swap when three neutrons are added to the closed-shell tin-100 nucleus. The researchers theorize that the swapping of ground-state spins between tin-101 and tin-103 is due to the neutrons' unusually strong orbital dependence of the pairing interaction and the relatively small difference between orbital energy states in tin-101.

[Bill Cabage, 865.574.4399,
cabagewh@ornl.gov]