Age matters for antimatter

May 19, 2000

Antimatter may be longer lived than previously thought.

Piotr Froelich,professor of quantum chemistry at Uppsala University, Sweden, has found that thelifespan of wholeatoms of antihydrogen exceeds the fleeting existence of antiprotons and positronsalone.

His research,which has beenpublished in the latest issue of Physical Review Letters, shows the complexity ofcollisions between hydrogen and antihydrogen.

Professor Froelich explained: "As a result of colliding hydrogen and antihydrogen we get an entirely new species through what I would call 'anti-chemistry'.

"This makes an unexpectedly important contribution to the depletion of the anti-hydrogen and is not as rapid as we might have believed."

Professor Froelich's calculations demonstrated that when hydrogen and anti-hydrogen first encounter one another, they exchange particles.

The electron and positron combine to form positronium while the proton and antiproton combine to form protonium.

Both of these new particles are highly unstable, but their coexistence slows their eventual drift into annihilation.

This will occur,Professor Froelichpredicted, but theoverall process takes longer than the straight forward annihilationof particle and antiparticle.

The finding is good news for physicists who want to keep hold of the expensive antimatter for as long aspossible in their experiments.

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