Scientists observe slowest atom decay ever using XENON1T detector

Researchers from the Laboratori Nazionali del Gran Sasso (LNGS) in Italy have been using instruments to search for dark matter particles in a lab that is 1500 meters deep inside the Gran Sasso mountains. The facility is so deep inside the mountain to shield it from any radioactivity interference.

The tool the team is using for its research is called the XENON1T detector, and its heart is a cylinder that is a meter in length and filled with 3200 kilograms of liquid xenon that is -95 degrees Celsius. The researchers have been using the detector to try and observe dark matter, something they have been unsuccessful at so far.

What the team was able to do was observe the decay of Xenon-124 atom for the first time. The half-life time measured is over a trillion times longer than the age of the universe according to the researchers. The age of the universe is almost 14 billion years old. The scientists say that the process they have observed is the rarest process in the universe ever to be seen directly in a detector.

The process the team observed is called double electron capture. According to the scientists, the atomic nucleus of Xenon-124 has 54 positively charged protons and 70 neutral neutrons surrounded by several atomic shells with negatively charged electrons. In double electron capture, two protons in the nucleus "catch" two electrons from the innermost atomic shell, transform into two neutrons, and emit two neutrinos at the same time and X-rays are released in the process.

The released X-rays produce an initial light signal and free electrons in the liquid xenon the detector uses. That signal was captured and allowed the measurement of the process. This process is normally hidden by "normal" radioactivity in the environment. In the lab, which is sealed off deep underground the is no radioactivity to interfere allowing the observation.