Positron

A positron is the antiparticle of the electron, with an identical mass but a positive electric charge instead of a negative one. Positrons are considered to be antimatter particles because they have the opposite charge and other properties to normal matter. When a positron and an electron come into contact, they annihilate each other, producing gamma rays. Positrons can be created in certain types of radioactive decay, or they can be produced artificially using particle accelerators. Positrons have a variety of applications in areas such as medical imaging, materials science, and fundamental physics research.

Positronium

Positronium is a bound state system of a positron and an electron, similar to the hydrogen atom, where an electron orbits around a proton. In the case of positronium, the positron and the electron orbit around their common center of mass. The system is unstable, and the two particles eventually annihilate each other, releasing two or more gamma ray photons.

Positronium has two possible states: the singlet state (para-positronium), in which the electron and the positron spins are antiparallel and the system has a shorter lifetime, and the triplet state (ortho-positronium), in which the electron and the positron spins are parallel, and the system has a longer lifetime.

Positronium has been studied extensively in experimental and theoretical physics because it provides a simple system for testing quantum electrodynamics (QED) and for studying the properties of matter and antimatter. It also has potential applications in fields such as material science, plasma physics, and astrophysics.