iThemba LABS scientist helps solve one of physics' great questions

Dr Mathis Wiedeking, a senior research scientist at iThemba LABS was leader of an 18-member team that has come one step closer to answering the question of how the heavy elements from iron to uranium were made.

Many of the elements are believed to be produced in stars and supernovae throughout the universe. Wiedeking of iThemba LABS and Lawrence Livermore National Laboratory (California, USA) and his team from seven US, South African and European laboratories and universities for the first time, independently confirmed the existence of an enhancement feature in the decay pattern by investigating the radioactive disintegration of nuclei.

In the control room of the 88-Inch Cyclotron, members of the group that discovered six new isotopes of the superheavy elements. From left: Marina-Kalliopi Petri, Joseph McLaughlin, Stefanos Paschalis, Heino Nitsche, Mathis Wiedeking, Paul Ellison, Kenneth Gregorich, Jacklyn Gates, Oliver Gothe, Darren Bleuel, I-Yang Lee, Roderick Clark, and Paul Fallon. Not pictured are Jill Berryman, Irena Dragojevi, Jan Dvorak, Carolina Fineman-Sotomayor, Walter Loveland, Jing Qian, and Liv Stavsetra. (Photo by Roy Kaltschmidt)		Dr Mathis Wiedeking of iThemba LABS is the leader of an 18-member team that has come one step closer to answering the question of how the heavy elements were made.

The existence of this enhancement has been the topic of a decade-long debate, in part because it would dramatically alter the production of the elements in the hot and dense cosmic environments where they are made.

"As a post-doctoral researcher at Lawrence Berkeley National Laboratory (California) I initiated and developed an experimental program to study light neutron-rich nuclei in fusion reactions," says Wiedeking. "The program has been very successful in measuring lifetimes of excited states in neutron-rich nuclei and addressed the heavily debated question on the existence of a unique matter distribution in 16C."

The team's observation followed an experiment where particles were smashed together to create new nuclei. The decay products from these nuclei, such as gamma radiation which originates from deep within them, are then studied using arrays of advanced detector systems. From this a wealth of information can be extracted, such as the effects that influence overall reaction rates in astrophysical environments which are present during a supernova event.

How the elements are formed

The observed feature manifests itself through an increase in the ability of nuclei to absorb and emit light characteristic of the environments where the elements are formed. With the existence of the enhancement now confirmed, it has become clear that laboratory-based experiments must occur in the same settings as where they take place in the cosmos if they are to best answer the question of how the elements are formed.

To pursue this goal, the international team of scientists will perform experiments using tiny pieces of star matter which is created using the world's most energetic laser at the National Ignition Facility at Lawrence Livermore National Laboratory in California. The information garnered from these experiments may significantly improve our understanding of the elemental abundances observed here on earth and elsewhere in the universe.

The results of the research were in Physical Review Letters (Vol.108, No.16, # 162503) by the American Physical Society.

For more information, contact Dr Mathis Wiedeking.