Di-positronium
Encyclopedia
Di-positronium, or dipositronium, is a molecule consisting of two atoms of positronium
. It was predicted to exist in 1946 by John Archibald Wheeler
, and subsequently studied theoretically, but was not observed until 2007 in an experiment done by David Cassidy and Allen Mills at the University of California, Riverside
. The researchers made the positronium
molecules by firing intense bursts of positron
s into a thin film of porous silicon dioxide
. 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.
Positronium
Positronium is a system consisting of an electron and its anti-particle, a positron, bound together into an "exotic atom". Being unstable, the two particles annihilate each other to produce two gamma ray photons after an average lifetime of 125 ps or three gamma ray photons after 142 ns in...
. It was predicted to exist in 1946 by John Archibald Wheeler
John Archibald Wheeler
John Archibald Wheeler was an American theoretical physicist who was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr in explaining the basic principles behind nuclear fission...
, and subsequently studied theoretically, but was not observed until 2007 in an experiment done by David Cassidy and Allen Mills at the University of California, Riverside
University of California, Riverside
The University of California, Riverside, commonly known as UCR or UC Riverside, is a public research university and one of the ten general campuses of the University of California system. UCR is consistently ranked as one of the most ethnically and economically diverse universities in the United...
. The researchers made the positronium
Positronium
Positronium is a system consisting of an electron and its anti-particle, a positron, bound together into an "exotic atom". Being unstable, the two particles annihilate each other to produce two gamma ray photons after an average lifetime of 125 ps or three gamma ray photons after 142 ns in...
molecules by firing intense bursts of positron
Positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...
s into a thin film of porous silicon dioxide
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
. Upon slowing down in the silica, the positrons captured ordinary electrons to form positronium
Positronium
Positronium is a system consisting of an electron and its anti-particle, a positron, bound together into an "exotic atom". Being unstable, the two particles annihilate each other to produce two gamma ray photons after an average lifetime of 125 ps or three gamma ray photons after 142 ns in...
atoms. Within the silica, these were long lived enough to interact, forming molecular di-positronium.
External links
- Molecules of Positronium Observed in the Laboratory for the First Time, press release, University of California, RiversideUniversity of California, RiversideThe University of California, Riverside, commonly known as UCR or UC Riverside, is a public research university and one of the ten general campuses of the University of California system. UCR is consistently ranked as one of the most ethnically and economically diverse universities in the United...
, September 12, 2007. - Mirror particles form new matter, Jonathan Fildes, BBC News, September 12, 2007.