A large international team of researchers has proven that fragments of fissionable atomic nuclei begin to rotate after they fission during fission. Scientists have described their experiments, which will one day be able to fully explain why such fragments begin to rotate at all.
Previous research has shown that atomic nuclei with a large number of protons and neutrons are unstable. Thus, they are prone to fission known as nuclear fission. Previous results said that after fission, fragments of atomic nuclei begin to rotate as they are ejected from the center. Why they start to spin has remained a mystery since nuclear fission was discovered more than 80 years ago.
In trying to understand why the fragments start to spin, physicists have learned more about the fission process. They found, for example, that just before splitting, the nucleus lengthens and forms a neck – the neck lengthens further, and then eventually splitting occurs.
After fission was discovered, physicists began to theorize why the neck forms and leads to nuclear fission. In addition, they began to wonder if the rotation of the fragments began before or after the rupture. As part of this new effort, the researchers conducted experiments showing that rotation begins after rupture.
The work involved studying debris from the fission of several types of unstable elements such as uranium-238 and thorium-232. As part of their research, they carefully studied the gamma rays released after fission.
Scientists have noticed that these beams convey information about the rotation of the fragments being studied. In addition, they expected that if the rotation resulting from fission occurred before rupture, then all the fragments in a given region would almost certainly have the same spin, but opposite to each other. But they found that this was not the case. Instead, all of their rotations were completely independent of each other. This discovery strongly suggests that rotation begins after rupture.
The researchers also speculate that as the nucleus elongates and splits, the resulting debris may resemble a tear. They assume that such fragments will then move, shrinking their surface shape (like bubbles), while releasing energy that causes them to start spinning.