NEUTRON CAPTURE REACTIONS AND STELLAR EXPLOSIONS
We live in an era where multi-messenger astronomical research is becoming more and more common. This means that we can study the same stellar event using a broad range of instruments; optical, gamma-ray and X-ray telescopes are just a few examples of the capabilities we have. During the last year, a new capability was added, that of gravitational-wave observation. This new addition offers an exciting opportunity for the field of nuclear astrophysics; the possibility of a direct observation of the merging of two neutron stars.
Neutron-star mergers are proposed as a possible scenario for where the heavy elements are created. We know that heavy elements, like gold and lead, can be created in stellar environments with high abundance of neutrons, however, after more than 60 years of study, we still don’t know exactly what events in nature are hosting this important process.
While astronomical observations are extremely important, the nuclear physics input is equally important for understanding these astrophysical processes. Thousands of nuclei are involved, tens of thousands of reactions are driving the processes, and the final result - the elements we see around us- depends strongly on nuclear properties. One very important property is the probability that a nucleus will capture a neutron from its environment and become just a little bit more neutron-rich.
Unfortunately, when the nuclei involved are very short-lived (of the order of minutes or less) it is almost impossible to study these reactions directly. A collaboration between MSU and the University of Oslo, developed an indirect technique, the so called beta-Oslo method, to study these important reactions indirectly. The technique was presented in a previous Greensheet (link to Greensheet July 1, 2016). Most recently we applied this technique to study, for the first time, the neutron capture on 68Ni, with a half-life of 29s. The experiment was done at the NSCL, and resulted in a reduction of the reaction rate of 68Ni(n,g) by more than a factor of 10 compared to the previous value. This work was submitted in an invited paper for the special issue of the Journal of Physics G “Emerging Leaders” and will appear in the coming weeks.
Work published in Journal of Physics G, invited paper special section "Emerging Leaders".