Scientists take giant step forward in understanding exotic nuclei

Aug 29, 2007
Scientists take giant step forward in understanding exotic nuclei
Gammasphere and the Fragment Mass Analyzer (above) were used to select 101Sn nuclei. Credit: ANL

Developing good predictive powers of how all nuclei work is critical to advance our understanding of the universe. The vast nuclear landscape, which is thought to consist of about 6,000 isotopes is not well charted and half the nuclei remain unknown.

Only about 300 isotopes are stable and exist in the world around us. A lot has been learned about these stable nuclei, but researchers at the U.S. Department of Energy's Argonne National Laboratory are developing techniques to uncover the secrets of some of the most unstable and exotic counterparts.

While the exotic isotopes are not normally present on earth, some of them play critical roles in the working of the stars, especially in the element-producing process of nucleosynthesis.

Darek Seweryniak and his colleagues from Argonne's Physics Division in collaboration with scientists from the University of Maryland, University of Notre Dame and University of Edinburgh, have focused their attention on a new isotope of tin, tin-100 (100Sn), one of the very rare "doubly-magic" nuclei. The doubly-magic assignment refers to the special cases where both protons and neutrons fill their quantum shells so that super-stability is achieved.

The properties of stable doubly-magic nuclei, such as oxygen-16 (16O), calcium-40 (40Ca) and lead-208 (208Pb) are well known, but the challenge is to determine the extent to which current models can be extrapolated to describe nuclei situated far from the line of stability, in this case, near the "proton dripline," where nuclear existence ends. Establishing the properties of this nucleus and its immediate neighbors builds a solid platform from which the properties of all proton-rich intermediate mass nuclei can be developed. To date, only a handful of 100Sn nuclei have ever been synthesized, in France and Germany, but almost nothing is known about its shell structure.

Using the Argonne Tandem Linac Accelerator System (ATLAS) facility in a 10-day experiment, the researchers started by synthesizing tin-101 (101Sn) and measuring its lowest excited state. 101Sn consists of a 100Sn core with the extra valence neutron orbiting in discreet quantum states in the field of the core.

Gamma rays emitted during the transition between these states were detected and analyzed in Gammasphere, the world's most powerful gamma-ray detector, and 101Sn nuclei were identified with the Fragment Mass Analyzer. The properties of the gamma rays reveal the sequence of states and their spacing, and can be used to directly challenge the reliability of contemporary nuclear models.

In the short term, the researchers expect to find further quantum states in 101Sn and learn more about the core this way. However, the experiment provides a key technical step toward the study of 100Sn itself in the future.

The detailed results of these findings were published in the journal Physical Review Letters in July. [Phys.Rev.Lett. 99, 022504 (2007)]

Source: Argonne National Laboratory

Explore further: Finding faster-than-light particles by weighing them

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Finding faster-than-light particles by weighing them

15 hours ago

In a new paper accepted by the journal Astroparticle Physics, Robert Ehrlich, a recently retired physicist from George Mason University, claims that the neutrino is very likely a tachyon or faster-than-light par ...

Controlling core switching in Pac-man disks

Dec 24, 2014

Magnetic vortices in thin films can encode information in the perpendicular magnetization pointing up or down relative to the vortex core. These binary states could be useful for non-volatile data storage ...

Atoms queue up for quantum computer networks

Dec 24, 2014

In order to develop future quantum computer networks, it is necessary to hold a known number of atoms and read them without them disappearing. To do this, researchers from the Niels Bohr Institute have developed ...

New video supports radiation dosimetry audits

Dec 23, 2014

The National Physical Laboratory (NPL), working with the National Radiotherapy Trials Quality Assurance Group, has produced a video guideĀ to support physicists participating in radiation dosimetry audits.

Acoustic tweezers manipulate cell-to-cell contact

Dec 22, 2014

Sound waves can precisely position groups of cells for study without the danger of changing or damaging the cells, according to a team of Penn State researchers who are using surface acoustic waves to manipulate ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.