Media Release

For Immediate Release

April 21, 2009

Saint Mary’s physicist helps international team confirm a new magic nucleus

A view of the GSI accelerator facility in Darmstadt, Germany. Photo courtesy of GSI Chris Perro in the electronics room of the GSI accelerator.

An international team of physicists led by a professor from Saint Mary’s University in Halifax has found strong evidence for the existence of a new ‘doubly magic’ nucleus.

The oxygen–24 nucleus has an unconventional neutron magic number (N=16) and a conventional proton magic number (Z=8), making it doubly magic. The confirmation of the doubly magic nature of the oxygen–24 nucleus is expected to help physicists gain a better understanding of very neutron-rich nuclei and hence extreme neutron-rich environments in our universe such as neutron stars.

Dr. Rituparna Kanungo, an Assistant Professor of Astronomy and Physics at Saint Mary’s, is the principal investigator of the project with a team that includes researchers from Germany, Canada, Spain, Greece, Slovakia, Sweden, Italy and Japan. Christopher Perro, one of Dr. Kanungo’s former undergraduate honors thesis students was also part of this team.

Their discovery was published in the latest edition of Physical Review Letters, the world's foremost physics letters journal. The international journal publishes reports of significant fundamental research in all fields of physics, and provides coverage of major advances in physics and cross disciplinary developments.

The discovery was also reported online (April 20) in Physicsworld.com.

In the online article, Dr. Kanungo explained the significance of magic numbers and the oxygen-24 nucleus.

Physicists have long known that protons and neutrons in nuclei occupy discrete orbitals — in much the same way as electrons do in atoms. “The beauty of nature is that the magic numbers (i.e. shell gaps) in nuclei are different from those in atoms,” said Dr. Kanungo.

Nuclei with magic neutron or proton numbers, are characterized by a stronger binding, greater stability, and, therefore, are more abundant in nature. In doubly magic nuclei, both proton and neutron shells are filled, making the binding even stronger.

“It’s thanks to the doubly magic numbers that nuclei such as oxygen and calcium are abundant, making it possible for us to exist on earth,” said Dr. Kanungo in the online article. “There are very few doubly magic nuclei in nature, and they form benchmark points for the nuclear shell model.”

The article goes on to explain how the team established that oxygen-24 is an unconventional doubly-magic nucleus. The work involved producing a beam of oxygen–24 nuclei at the GSI accelerator ( in Darmstadt, Germany) by smashing calcium–48 nuclei into a fixed beryllium target. This in turn produced about three oxygen–24 nuclei per second, which were aimed at a stationary carbon target. This reaction knocked off a neutron from oxygen-24 that carried the information on which orbital it was located.

“Nuclei such as oxygen–24 possibly exist in neutron-rich cosmic objects such as the neutron star crust,” said Dr. Kanungo. “Our world-wide collective effort to understand the physics behind the extremes of our universe is bringing many pieces of the puzzle together slowly.”

To read the Physics World article about the research discovery, please visit: http://physicsworld.com/cws/article/news/38758

Dr. Kanungo’s research at Saint Mary’s and particle accelerators around the world explores the fundamental physics principles behind the existence of nuclei and their behaviour, helping to understand how, why and where all elements that we see on earth were created in nature. She has published more than 70 articles in international refereed journals, and received the GSI Exotic Nuclei Community Award as well as the Alexander von Humboldt fellowship.

“I find it fascinating to explore the properties of these tiny objects that have led to the creation of our lives,” she said. 

Dr. Kanungo thanks Natural Sciences and Engineering Research Council (NSERC) Canada for supporting her research work.

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For More Information:

Blake Patterson
Public Affairs Officer
Saint Mary's University, Public Affairs
(902) 420.5514
E-mail: blake.patterson@smu.ca
www.smu.ca