Not all matter around us is stable. There are substances that undergo radioactive decay and turn into more stable isotopes. Now, for the first time, scientists have observed a new type of decay. In this decay, a lighter form of oxygen, oxygen-13 (8 protons and 5 electrons), decays into 3 helium nuclei (an atom without electrons), a proton, and a positron (the antimatter version of the electron). – Published by the US Department of Energy at phys.org.
Scientists observed this decay by watching the nucleus disintegrate and measuring the decay products. The study was published in Physical Review Letters.
In the past, scientists have noticed interesting radioactive decay patterns after positive beta decay. In this case, the proton turns into a neutron and releases part of the generated energy in the form of a positron and an antineutrino.
Then, after the initial beta decay, the resulting nucleus has enough energy to boil off the extra molecules and make themselves more stable. This new pattern of decay was first observed: the release of three helium nuclei (alpha particles) and a proton after beta decay. This discovery informs scientists about the decay processes and the properties of the nucleus before decay. In this experiment, the researchers used the particle accelerator, the cyclotron, at the Cyclotron Institute at Texas A&M University to create a high-energy beam (about 10% of the speed of light) from radioactive nuclei. The beam of radioactive material, oxygen-13, was sent to the Texas Active Target Time Projection Chamber (TexAT TPC). The instrument was designed to perform experiments on rare isotope rays.
Inside the detector, matter stops, the detector fills with carbon dioxide, and after about 10 milliseconds it decays, emitting a positron and a neutrino (positive beta decay). Oxygen-13 and nuclei were placed in the detector and each particle produced after beta decay was measured using the TexAT TPC instrument. Then a computer program was used to analyze the data to identify the traces left by the particles in the gas. This allowed them to identify the rare event (which occurs only once in 1,200 decay processes) when 4 particles are emitted after beta decay.
(source: https://phys.org/)
