Featured Research

from universities, journals, and other organizations

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

Date:
October 31, 2010
Source:
DOE/Oak Ridge National Laboratory
Summary:
Tin may seem like the most unassuming of elements, but new experiments 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.

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.


Story Source:

The above story is based on materials provided by DOE/Oak Ridge National Laboratory. Note: Materials may be edited for content and length.


Journal Reference:

  1. I. Darby, R. Grzywacz, J. Batchelder, C. Bingham, L. Cartegni, C. Gross, M. Hjorth-Jensen, D. Joss, S. Liddick, W. Nazarewicz, S. Padgett, R. Page, T. Papenbrock, M. Rajabali, J. Rotureau, K. Rykaczewski. Orbital Dependent Nucleonic Pairing in the Lightest Known Isotopes of Tin. Physical Review Letters, 2010; 105 (16): 162502 DOI: 10.1103/PhysRevLett.105.162502

Cite This Page:

DOE/Oak Ridge National Laboratory. "Isotope near 'doubly magic' tin-100 flouts conventional wisdom." ScienceDaily. ScienceDaily, 31 October 2010. <www.sciencedaily.com/releases/2010/10/101021165243.htm>.
DOE/Oak Ridge National Laboratory. (2010, October 31). Isotope near 'doubly magic' tin-100 flouts conventional wisdom. ScienceDaily. Retrieved September 14, 2014 from www.sciencedaily.com/releases/2010/10/101021165243.htm
DOE/Oak Ridge National Laboratory. "Isotope near 'doubly magic' tin-100 flouts conventional wisdom." ScienceDaily. www.sciencedaily.com/releases/2010/10/101021165243.htm (accessed September 14, 2014).

Share This



More Matter & Energy News

Sunday, September 14, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Frustration As Drone Industry Outpaces Regulation In U.S.

Frustration As Drone Industry Outpaces Regulation In U.S.

Newsy (Sep. 14, 2014) U.S. firms worry they’re falling behind in the marketplace as the FAA considers how to regulate commercial drones. Video provided by Newsy
Powered by NewsLook.com
Scientists Have Captured The Sound Of An Atom

Scientists Have Captured The Sound Of An Atom

Newsy (Sep. 12, 2014) Scientists have captured the sound of a single atom by measuring its vibrations. We can't hear it, but it's reportedly the faintest sound possible. Video provided by Newsy
Powered by NewsLook.com
Solar Flare Surges Off Sun

Solar Flare Surges Off Sun

Reuters - US Online Video (Sep. 11, 2014) NASA captures video of a significant flare surging off the sun. Jillian Kitchener reports. Video provided by Reuters
Powered by NewsLook.com
Soccer Players' Feet to Generate Electricity

Soccer Players' Feet to Generate Electricity

AP (Sep. 11, 2014) A new energy-generating soccer field was inaugurated in Brazil. The field is built on energy-capturing tiles, allowing players to generate electricity as they run and compete. (Sept. 11) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins