Deep in the universe, gold is not born in mines or deep in planets, but in the collapse and violent collisions of stars. There, in environments saturated with neutrons and energy, a rapid nuclear chain begins that creates the heavy elements we know today, such as gold and platinum.
But although the general idea has been known for years, the precise details that lead from unstable atomic nuclei to these precious elements have remained mysterious, because some of the key links in this chain occur in very rare and short-lived nuclei, which are difficult to capture in the laboratory.
This undated image provided by the Lawrence Livermore National Laboratory shows a deuterium and tritium capsule, sphere in window at center, inside a cylindrical hohlraum container about 0.4 inches tall. the journal Nature, scientists say they've taken a key step towards harnessing nuclear fusion as a new way to generate power, an idea that has been pursued for decades. In tests, 192 laser beams briefly fired into the small gold cylinder which held the two types of hydrogen. The energy from the lasers kicked off a process that compressed the ball by an amount akin to squeezing a basketball down to the size of a pea, said Debbie Callahan, an author of the paper. That created the extremely high pressure and temperatures needed to get the hydrogen atoms to fuse
Nuclear image
A new study published in the journal Physical Review Letters, led by researchers from the University of Tennessee at Knoxville and conducted at CERN's Isolde facility, has revealed important findings regarding how exotic nuclei decay along the path of what is called the fast neutron capture process, the physical pathway that scientists believe is responsible for creating a large portion of the heavier-than-iron elements in the universe.
What's new here is not just the addition of a small detail, but a direct improvement to the nuclear picture upon which astronomical models rely to understand the origin of gold and other heavy elements.
To understand the importance of this process, one can imagine the atomic nucleus as a tiny object receiving a rapid barrage of neutrons. With each new neutron, the nucleus becomes heavier and more fragile. When it reaches a state of extreme instability, it begins to decay or transform into other, more stable forms.
On paper, this process seems straightforward, but the problem is that some of its stages don't occur through simple channels, but rather through very complex and rapid decays, including a type known as delayed beta decay with two neutrons emitted. This type of decay has remained difficult to measure because it occurs in rare nuclei, and because neutrons themselves are elusive particles that are difficult to track precisely.
In this experiment, the team started with a very rare isotope, indium-134. When this isotope decays, it produces excited states in tin isotopes, such as tin-134, tin-133, and tin-132.
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