Hydrogen-4
4H contains one proton and three neutrons in its nucleus. It is a highly unstable isotope of hydrogen. It has been synthesised in the laboratory by bombarding tritium with fast-moving deuterium nuclei. In this experiment, the tritium nuclei captured neutrons from the fast-moving deuterium nucleus. The presence of the hydrogen-4 was deduced by detecting the emitted protons. Its atomic mass is 4.02781 ± 0.00011. It decays through neutron emission with a half-life of (1.39 ± 0.10) × 10−22 seconds.
Read more about this topic: Isotopes Of Hydrogen