Radioactive molecules could probe origins of the universe

July 9, 2021, 9:13AMNuclear News

Physicists from the Massachusetts Institute of Technology and other institutions have measured the effect of a single neutron in a molecule of radium monofluoride and hypothesize that radioactive molecules could be used as a tool to explore why there is more matter than antimatter in the universe. The research team’s findings were published in the journal Physical Review Letters on July 7, and on the same day, an article published online by MIT News explained the implications of their work.

In brief: Ronald Fernando Garcia Ruiz, an assistant professor of physics at MIT, has worked with colleagues to refine techniques to create radioactive molecules and study their properties. Last year, Garcia Ruiz and his colleagues reported on a method to produce molecules of radium monofluoride, or RaF, a radioactive molecule that contains one unstable radium atom and a fluoride atom.

In their new study, the team used similar techniques to produce RaF isotopes and measured each molecule’s mass to estimate the number of neutrons in its nucleus. They then sorted the molecules by isotopes, according to their neutron numbers.

When they measured each molecule’s energy, they were able to detect small, nearly imperceptible changes due to a single neutron one-millionth the size of the entire molecule. The detection of such small effects is expected to lead to a search for even subtler effects caused by dark matter or by symmetry violations related to unanswered questions about the origins of the universe.

Universal implications: Unlike most atoms in nature, which have spherical nuclei, atomic nuclei in certain radioactive elements (including radium) are pear-shaped, with an uneven distribution of neutrons and protons. Physicists hypothesize that this shape distortion could enhance the violation of symmetries that produced matter in the universe.

“If the laws of physics are symmetrical, as we think they are, then the Big Bang should have created matter and antimatter in the same amount,” Garcia Ruiz said. “The fact that most of what we see is matter, and there is only about one part per billon of antimatter, means there is a violation of the most fundamental symmetries of physics, in a way that we can’t explain with all that we know. Now we have a chance to measure these symmetry violations, using these heavy radioactive molecules, which have extreme sensitivity to nuclear phenomena that we cannot see in other molecules in nature. That could provide answers to one of the main mysteries of how the universe was created.”



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