Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Isotope near 'doubly magic' tin-100 flouts conventional wisdom

22.10.2010
Tin may seem like the most unassuming of elements, but experiments performed at the Department of Energy'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 international team of experimentalists and theorists was led by Iain G. Darby of the University of Tennessee (UT), who is now in Belgium, and Robert Grzywacz, a physics professor at UT and a former Wigner Fellow at ORNL. 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.

"In fact, previously the ground state of tin-101 was assumed to be identical to that of tin-103, tin-105, and tin-107. Those conform to the standard picture. But we've found that tin-101 has a flipped ground state," Grzywacz said.

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.

"Neutrons tend to dance in pairs, much like Cooper pairs of electrons in superconductors. But because their angular momentum adds to zero, the pairing shouldn't affect the spin of the nucleus if only few neutrons are involved" said ORNL and UT researcher Witold Nazarewicz.

Grzywacz and Nazarewicz explained that, in the standard shell model, the neutron pairing energy weakly depends on the particle's state. "But it so happens that pairing interaction is different in those two orbits, one with higher energy and one lower. It is orbital dependent," said Nazarewicz, who is scientific director at the Holifield Facility. "With tin-101, those properties are governed by one neutron. If you add two more neutrons, the ground state is determined by the neutron superconductivity, which is very unusual. "

"In practice, the final picture is the two neutrons pair strongly and kick out the third--odd--neutron in tin-103 into another orbit," said Grzywacz. "Three's a crowd."

The experiment required the unique radioactive ion beam capabilities of the Holifield Facility at ORNL, plus digital signal processing instrumentation developed at ORNL to measure the extremely fast alpha particle decays in the neutron-deficient and very unstable tin isotopes. Tin-101 was made in the decay of the extremely short-lived, lightest-known alpha emitter tellurium-105, which was previously discovered by the ORNL-UT team.

The theoretical calculations, based on parameter-free, state-of-the-art nuclear models, were performed in Oslo, Norway, and in Oak Ridge, Tenn.

"We were developing these experimental methods for almost a decade and, combined with advances in computational methods and access to supercomputers such as Jaguar and Kraken at ORNL, they are now bearing fruit," said Grzywacz.

The results of the research, which was funded in part by DOE's Office of Nuclear Physics, have been accepted for publication in Physical Review Letters.

ORNL is managed by UT-Battelle for the Department of Energy's Office of Science.

NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at http://www.ornl.gov/news. Additional information about ORNL is available at the sites below:

Twitter - http://twitter.com/oakridgelabnews

RSS Feeds - http://www.ornl.gov/ornlhome/rss_feeds.shtml

Flickr - http://www.flickr.com/photos/oakridgelab

YouTube - http://www.youtube.com/user/OakRidgeNationalLab

LinkedIn - http://www.linkedin.com/companies/oak-ridge-national-laboratory

Facebook - http://www.facebook.com/Oak.Ridge.National.Laboratory

Bill Cabage | EurekAlert!
Further information:
http://www.ornl.gov

More articles from Physics and Astronomy:

nachricht Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Gran Chaco: Biodiversity at High Risk

17.01.2018 | Ecology, The Environment and Conservation

Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials

17.01.2018 | Physics and Astronomy

Fraunhofer HHI receives AIS Technology Innovation Award 2018 for 3D Human Body Reconstruction

17.01.2018 | Awards Funding

VideoLinks
B2B-VideoLinks
More VideoLinks >>>