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 First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester

nachricht Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology

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: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>