Large atoms require a lot of energy to build. A new model of quantum interactions now suggests that some of the lightest particles in the universe may play a critical role in how at least some heavy elements form.
Physicists in the US have shown how subatomic ‘ghost’ particles known as neutrinos can force atomic nuclei to become new elements.
Not only would this be a completely different method for building elements heavier than iron, it could also describe a long-hypothesized “in-between” pathway that lies on the border between two known processes, nuclear fusion and nucleosynthesis.
For most elements larger than hydrogen, the warm embrace of a large, bright star is enough for protons and neutrons to overcome their strong need to push away from each other long enough for another short-range interaction to take over. This fusion embrace releases additional energy, which helps the stars’ cores stay toasty warm.
Once the atoms have grown to about 55 nucleons—the mass of an iron nucleus—adding more protons requires more energy than the fusion process can pay off.
This shift in thermonuclear economics means that the heavyweights of the periodic table can only form when more neutrons stick to the solidifying mass of nuclear particles long enough for one to decay and vomit out an electron and a neutrino, converting them into the extra proton needed to to qualify as a new element.
Typically, this process is painfully slow, trickling down over decades or even centuries as cores in large stars squeeze, often gaining and losing neutrons, with only a few switching to the proton hood at the critical moment.
With enough impact, this growth can also be surprisingly fast—within minutes in the hot mess of collapsing and collapsing stars.
However, some theoretical physicists have questioned whether there are other pathways intermediate between the slow or “s” process and the fast or “r” process.
“Where the chemical elements are made is not clear, and we don’t know all the possible ways they can be made,” says the study’s lead author, University of Wisconsin-Madison physicist Baha Balantekin.
“We believe some are created in supernova explosions or neutron star mergers, and many of these objects obey the laws of quantum mechanics, so then you can use the stars to explore aspects of quantum mechanics.”
The solution is precisely the quantum nature of the floods of neutrinos – the most abundant particles with mass in the universe – that spill into the cosmic environment.
Although they are virtually immaterial and have almost no means of making their presence known, their sheer numbers mean that the emission and occasional absorption of these ephemeral “ghost particles” still have an effect on the proton and neutron budget humming deep inside material stars and cataclysmic space. . Events.
One of the neutrino’s bizarre quirks is its habit of oscillating in quantum obscurity, switching between different kinds of identity as it flies through empty space.
Modeling the huge number of neutrinos flipping and disappearing flavors in a chaotic nucleon soup is easier said than done, so physicists will often treat them as a single system, where the properties of the individual particles are treated as one, big, entangled superparticle.
Balantekin and his colleagues at George Washington University and the University of California, Berkeley, used the same approach to better understand how the neutrino winds emitted by a newborn neutron star colliding with the surrounding medium can serve as a transient nucleosynthesis process.
By determining the extent to which the quantum identity of individual neutrinos depends on the extent of this entangled state, the team found that a significant number of new elements could be generated by this ghostly storm.
“This paper shows that if neutrinos are involved, then there is an improved new process for making elements, the i-process,” says Balantekin.
While the numbers add up in theory, testing the idea is a completely different matter.
The study of “spooky” neutrino interactions on Earth is still in its infancy, leaving researchers staring into the far reaches of space for evidence of new ways the largest elements combine.
This research was published in The Astrophysical Journal.