Posted on 09/17/2007 11:35:44 PM PDT by saganite
Antiparticles are the mirror image of ordinary particles Fragile particles rarely seen in our Universe have been merged with ordinary electrons to make a new form of matter.
Di-positronium, as the new molecule is known, was predicted to exist in 1946 but has remained elusive to science.
Now, a US team has created thousands of the molecules by merging electrons with their antimatter equivalent: positrons.
The discovery, reported in the journal Nature, is a key step in the creation of ultra-powerful lasers known as gamma-ray annihilation lasers.
"The difference in the power available from a gamma-ray laser compared to a normal laser is the same as the difference between a nuclear explosion and a chemical explosion," said Dr David Cassidy of the University of California, Riverside, and one of the authors of the paper.
"It would have an incredibly high power density."
As a result, there is a huge interest in the technology from the military as well as energy researchers who believe the lasers could be used to kick-start nuclear fusion in a reactor.
Mirror world
Di-positronium was first predicted to exist by theoretical physicist John Wheeler and its component "atoms" - positronium - were first isolated in 1951.
These short-lived, hydrogen-like atoms consist of an electron and a positron, a positively charged antiparticle.
Positron Emission Tomography makes use of antiparticles
Antiparticles are the mirror image of ordinary particles.
There is an antiparticle for each type of particle in the Universe. For example, a positively charged proton has a corresponding negatively charged antiproton.
Conventional thinking states that both antimatter and matter should have been created in equal quantities at the birth of the Universe.
The dominance of matter in our world is one of science's most enduring mysteries.
Antimatter only makes fleeting appearances in our Universe when high-energy particle collisions take place, such as when cosmic rays impact the Earth's atmosphere. They are also made in the lab in particle accelerators such as Europe's nuclear research facility, Cern.
These appearances are always short lived because antiparticles are destroyed when they collide with normal matter. The meeting leaves a trace, often as high energy x-rays or gamma-rays.
These emissions are used today in PET (positron emission tomography) scanners to study activity in the brain.
Short lives
The transient nature of antiparticles has made creating and studying di-positronium problematic.
Lasers fuel energy future
"We've known about this molecule; we're not surprised that it exists but it's taken us more than 50 years to create it in the lab," said Dr Cassidy.
To make the molecule, Dr Cassidy and his team used a specially designed trap to store millions of the positrons.
A burst of 20 million were then focused and blasted at a porous silica "sponge".
"It's like having a trickle of water filling up a bath and then you empty it out and you get a big flush," said Dr Cassidy.
As the positrons rushed into the voids they were able to capture electrons to form atoms. Where atoms met, they formed molecules.
"All we are really doing is implanting lot of positrons into the smallest spot we can, in the shortest time, and hoping that some of them can see each other," said Dr Cassidy.
By measuring the gamma-rays that signalled their annihilation, the team estimated that up to 100,000 of the molecules formed, albeit for just a quarter of a nanosecond (billionth of a second).
Laser beam
Dr Cassidy believes that increasing the density of the positronium in the silicon would create an exotic state of matter known as a Bose-Einstein condensate (BEC).
Bose-Einstein condensate are like a super-atom
BECs are usually produced by supercooling atoms so that they merge and begin to behave like one giant atom.
They have been used in many experiments such as the 2003 Harvard study in which scientists were able to trap light.
"At even higher densities, one might expect the material to become a regular, crystalline solid," wrote Professor Clifford Surko, of the University of Californian, San Diego, in an accompanying article.
Taking it one step further, scientists could use the spontaneous annihilation of the BEC, and the subsequent outburst of gamma-rays, to make a powerful laser.
"A gamma-ray laser is the kind of thing that if it existed people would find new uses for it everyday," said Dr Cassidy.
He highlighted an experiment at the National Ignition Facility (NIF) in the US where scientists envisage using 192 lasers to heat a fuel target to try to kick-start nuclear fusion.
"Imagine doing that but you no longer need hundreds of lasers," he said.
“At even higher densities, one might expect the material to become a regular, crystalline solid,” wrote Professor Clifford Surko, of the University of Californian, San Diego, in an accompanying article.
Dilithium crystals!
Conventional thinking states that both antimatter and matter should have been created in equal quantities at the birth of the Universe.
-
and wiped each other out?
“The difference in the power available from a gamma-ray laser compared to a normal laser is the same as the difference between a nuclear explosion and a chemical explosion,” said Dr David Cassidy
Phasers!
Been waiting all of my life for this; I wonder how hard it will be to get a concealed carry permit for a gamma-ray laser death ray gun?
LOL! Don’t think you’d be able to conceal it (for now anyway) unless you have a battleship handy.
A laser based upon energy states arising from matter-antimatter interactions would be an awesome weapon. The energy of a hydrogen bomb, in the form of a beam of coherent gamma rays.
A big one could blow a hole through the moon, I should think.
A big one could blow a hole through the moon, I should think.
Or take out a pesky asteroid that’s heading our way?
Well, I never buy the first iteration of a new technology - too many bugs. I’ll wait for the Mk. II model, which will be smaller, lighter, and come in a selection of designer colors.
;-)
Kinda like the “little cricket” Will Smith got issued in MIB #1?
do that and people will really think the moon is made of swiss cheese
‘Zackly!
Space expanded and the high energy particles became separated as time went on. The simple explanation is the decay rate of the high energy particles of matter and antimatter differed enough, that the universe ended up with what's called the matter particles. The bulk of the particles were annihilated.
Fantastic! This ought to breathe new life into the laser propulsion people.
This is all well and good, but bear in mind Mr Scott’s wise admonition- “Ye can’t mix matter with antimatter!”
Why am I reminded of an old child’s rhyme, updated for the atomic age...
A ring around the neutrons
A pocket full of positrons
A fission, a fission.
We all fall DOWN.
Or - at the initial stage of expansion the antimatter formed another, parallel universe?
Death rays don’t kill people, people kill people.
David Cassidy grew up to be a doctor and a physicist.
Who knew!
They're not on any list yet so you shouldn't have a problem.
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