Thanks to the XENON1T dark matter detector, located under the Gran Sasso Mountains in Italy, scientists have noticed one of the richest events ever to be discovered: a special kind of radioactive decay in xenon-124.
It's an amazing feat because the decay of this isotope is extremely, very slow. In fact, xenon-124 has a half-life of 1.8 x 10 to power of 22 years – approximately one trillion times longer than the age of the Universe.
In radioactive decay, the half-life refers to the time at which half of the atomic nuclei in one sample will change spontaneously through one of the many types of radioactive decay, which often involve spitting or engaging protons, neutrons, and electrons in different combinations.
In this case, a team of researchers managed to observe a special event called double-electron capture, where two protons in the xenon atom simultaneously absorbed two electrons, resulting in two neutrons – described by the team as "a rare work multiplied by another rare work , which makes it ultra-smooth. "
This exciting observation took place thanks to the incredibly precise calibration of XENON1T – the instrument was designed to detect the interactions of hypothetical dark matter particles with atoms in a xenon exporter at 1,300 kg (2,866 pounds) packaged in the device's tank.
But in this case, sensors designed to observe such interactions captured the decay of the very isotope, which led to rare observation of a different species.
"We actually saw this decay occurring," said one of the researchers, Ethan Brown of the Rensselaer Polytechnic Institute (RPI) in New York. "It's the longest, slowest process ever seen directly, and our dark matter detector was sensitive enough to measure it."
"It's amazing that we are witnesses of this process, and says our detector can measure the earliest thing that has been noticed."
Scientists never before had directly observed the radioactive decay of this xenon isotope, although its half-life has been theorized since 1955. He is a direct proof of what we have been seeking for decades.
What actually happens is XENON1T is the detection of the signals given by the electrons in the atom rearrangement itself to fill in for the two that were captured in the nucleus. As Gismodo reports, it has not completely hit the statistical threshold to be considered a discovery, but it is still amazing observation.
"Double-capture electrons are removed from the deepest casing around the core, and this creates space in that shell," Brown said. "The remaining electrons are decaying in the ground state and we have seen this process of collapse in our detector."
Although XENON1T is built to look for dark matter, it shows how these instruments can lead to other important findings too. This last observation could have taught us more about neutrons, abundant, but hard to detect particles scientists have been hunting for decades.
In this case, the researchers noted double-neutrino capture of the dual electrons – the result of the rearrangement of the electrons means that two nutrons were emitted from the atomic nucleus. The next challenge they want to take is to detect a non-transponder double-electron capture – an event that's even more rare than this one.
This, in turn, can help to unlock some of the deepest secrets of particle physics.
"This is a fascinating discovery that upgrades the boundaries of knowledge about the most basic characteristics of matter," says Kurt Bremenman of RPI, who was not directly involved in the study.
"Dr. Brown's work to calibrate the detector and ensure that the xenon washed to the highest possible standard of purity was crucial to make this important observation."
The survey is published in Nature.