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UNIRIB Physicists Make Significant Advances in Explorations of “Star Stuff”
Chiara Mazzocchi, a guest researcher at the University Radioactive Ion Beam Consortium (UNIRIB) from the University of Tennessee’s Department of Physics and Astronomy, was the principal author of the research paper “α Decay of 109I and Its Implications for the Proton Decay of 105Sb and the Astrophysical Rapid Proton-Capture Process,” which was written by UNIRIB collaborators and published in 2007.
When Carl Sagan once famously noted that “we are star-stuff,” he meant to convey that the universe, and everything that it comprises, including us, comes from the stars and from supernovae explosions.
University Radioactive Ion Beam Consortium (UNIRIB) physicists continue to make advances in exploring “star-stuff.” A goal of the UNIRIB collaboration is to provide experimental measurements on the properties of nuclei relevant to astrophysical processes, such as supernovae explosions.
According to the big bang theory, the dense heat of the violent explosion that produced the universe some 13.7 billion years ago also produced the chemical elements of hydrogen, helium and traces of lithium. All the other heavier elements were synthesized later in stars and supernovae explosions. It is these elements that UNIRIB scientists examine to come to a greater understanding of the origin of the universe.
In May 2007, UNIRIB researchers and collaborators published significant new results in the scientific publication Physical Review Letters. The paper earned the distinction of being selected by the editors as “Suggested Reading.”
The research examined a portion of the astrophysical process known as the rapid-proton capture process, or rp-process, which is one of the astrophysical processes that occur during a supernova and is one of the processes responsible for the formation of the chemical elements, explained Chiara Mazzocchi, principal author on the paper.
The final phase of the rp-process was examined, and, in a series of experiments, UNIRIB researchers and collaborators were able to show that the atomic nucleus of antimony-105, was a more stable nucleus than previously reported in the scientific literature. The result makes the rate at which protons are captured on this nucleus higher than previously thought and simultaneously does not allow for any observable spontaneous emission of protons from the nucleus, disproving a previous report.
UNIRIB’s ability to provide not only funding but also the technical support, equipment and ability to bring scientists together to collaborate made the research possible, said UNIRIB Director Ken Carter. “Providing support and facilities to university researchers in carrying out research at Oak Ridge National Laboratory has been Oak Ridge Associated Universities’ long-term goal as well as UNIRIB’s. So it is very satisfying to see significant research results, especially by young researchers.”
Based on the results of the research, a reevaluation of the end phase of the rp-process cycle has been proposed. The paper’s authors now hypothesize that the rp-process could proceed toward heavier elements much faster than previously reported. This scenario would change the time scale, energy balance, and even the amount of helium-4, existing at the final phase of the rp-process.