Di-positronium, or dipositronium, is an exotic molecule consisting of two atoms of

positronium Positronium (Ps) is a system consisting of an electron and its antimatter, anti-particle, a positron, bound together into an exotic atom, specifically an onium. Unlike hydrogen, the system has no protons. The system is unstable: the two part ...

. It was predicted to exist in 1946 by

John Archibald Wheeler John Archibald Wheeler (July 9, 1911April 13, 2008) was an American theoretical physicist. He was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr to e ...

, and subsequently studied theoretically, but was not observed until 2007 in an experiment performed by David Cassidy and Allen Mills at the

University of California, Riverside The University of California, Riverside (UCR or UC Riverside) is a public university, public Land-grant university, land-grant research university in Riverside, California, United States. It is one of the ten campuses of the University of Cali ...

. The researchers made the positronium

molecules A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry ...

by firing intense bursts of

positron The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatt ...

s into a thin film of porous

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...

. Upon slowing down in the silica, the positrons captured ordinary electrons to form positronium atoms. Within the silica, these were long lived enough to interact, forming molecular di-positronium. Advances in trapping and manipulating positrons, and spectroscopy techniques have enabled studies of Ps–Ps interactions. In 2012, Cassidy et al. were able to produce the excited molecular positronium

L = 1

angular momentum Angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of Momentum, linear momentum. It is an important physical quantity because it is a Conservation law, conserved quantity – the total ang ...

state.

References

External links

Molecules of Positronium Observed in the Laboratory for the First Time
, press release,

, September 12, 2007.
Mirror particles form new matter
Jonathan Fildes, BBC News, September 12, 2007. Antimatter Exotic atoms Molecular physics Quantum electrodynamics Substances discovered in the 2000s {{quantum-stub

See also

References

External links