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Xenon-124 Neutrinos

Scientists used a quantity of Xenon-124 to establish its rate of radioactive decay.
According to a study published April 24 in the journal Nature, the team of more than 100 researchers measured, for the first time ever, the decay of a xenon-124 atom into a tellurium 124 atom through an extremely rare process called two-neutrino double electron capture. This type of radioactive decay occurs when an atom's nucleus absorbs two electrons from its outer electron shell simultaneously, thereby releasing a double dose of the ghostly particles called neutrinos.

By measuring this unique decay in a lab for the first time, the researchers were able to prove precisely how rare the reaction is and how long it takes xenon-124 to decay. The half-life of xenon-124 — that is, the average time required for a group of xenon-124 atoms to diminish by half — is about 18 sextillion years (1.8 x 10^22 years), roughly 1 trillion times the current age of the universe.

This April story was reported before the recent post (September 13. 2019) about experiments with Germanium-64.

That unrelated experiment concluded Ge-64 'has a half-life of at least 10^26 years, or 10,000,000,000,000,000 times the age of the Universe.'

Apparently there is a contest seeking an atomic number with the longest measured half-life.

The Ge-76 result is longer than the rate observed with Xenon-124, the earlier report.

The Ge-76 story did not mention the Xenon-124 experiment. I did not know of it when writing that post  about Ge-76.

This post is a follow up to that September 13 post, pointing out similar experiments this year. Both experiments involve neutrinos but only the Ge-76 experiment used neutrino detectors. The Xenon-124 test monitored for X-rays.

The Xenon-124 story implies the detection of the X-rays is a confirmation of the double electron capture event. The event is assumed to generate 2 neutrinos.

There was no attempt to  detect them.
Those neutrinos fly off into space, and scientists cannot measure them unless they use extremely sensitive equipment.

These experiments with radioactive decay confront a problem with the elusive neutrino.


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