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This is a follow-on from previous question:

It seems as though all experiments concerning antimatter have only been conducted with antimatter protons - as they are obtainable through decay.

Have any heavier elements been attempted? eg. has there been anti-helium or anti-carbon created?

Also, when an anti-hydrogen comes into contact with a heavier element (say carbon), are both atoms totally annihilated, or does the heavier element ( of matter) simply reduce by one proton and release the energy?

Thanks

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  • $\begingroup$ No. That will require experimental techniques beyond of what we can do today. There are, however, no reasons to believe that heavier anti-nuclei can not be created by fusion reactions. Even the annihilation of protons and anti-protons creates non-trivial reaction products, see e.g. arxiv.org/pdf/hep-ex/9708025.pdf. $\endgroup$ – CuriousOne Oct 8 '14 at 22:53
  • $\begingroup$ Hah! Eating my words now! Disregard the first part of my answer, I am obviously not well informed about heavy ion collisions... $\endgroup$ – CuriousOne Oct 8 '14 at 23:26
  • $\begingroup$ I guess that is what this forum is for :) thanks for your reference anyhow $\endgroup$ – sidewaiise Oct 8 '14 at 23:30
  • $\begingroup$ Hey, I learned something new today! What could be better, right? :-) $\endgroup$ – CuriousOne Oct 8 '14 at 23:32
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Antihelium has been observed: http://www.theguardian.com/science/2011/apr/24/antihelium-antimatter-brookhaven (sounds like just the nucleus, not a neutral atom).

The AEgIS experiment http://aegis.web.cern.ch/aegis/research.html plans to make neutral antihydrogen atoms and measure their gravitational acceleration.

Also, when an anti-hydrogen comes into contact with a heavier element (say carbon), are both atoms totally annihilated, or does the heavier element ( of matter) simply reduce by one proton and release the energy?

It wouldn't be possible, e.g., for both atoms to annihilate and produce nothing but gamma rays, because that would violate conservation of lepton number and baryon number. However, the annihilation of the antiproton with a proton will produce an energy of ~1 GeV, which is much more than the binding energy of the carbon nucleus. Therefore the carbon nucleus will likely fly apart as individual neutrons and protons.

In science fiction, antimatter is often portrayed as a way of storing large amounts of energy to run a spaceship. This kind of makes sense, because the energy density is orders of magnitude higher than, e.g., uranium used to fuel a fission reactor. However, it's not necessarily easy to extract the energy for useful purposes:

Antimatter Propulsion System

Would matter-antimatter annihilation create a fireball or not?

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  • $\begingroup$ Hi Ben, thanks for the sources. I guess I'm trying to understand what the pattern looks like when different configurations of antimatter and matter come together. It sounds as though there would be differing signatures depending on the combination. Do you think there is the possibility of a stable matter-antimatter interaction? ie. zero or little annihilation? Is it possible for larger antimatter atoms to decay to matter and visa versa? $\endgroup$ – sidewaiise Oct 8 '14 at 23:16
  • $\begingroup$ Oh, that's so cool! I must have missed the RHIC announcement a couple of years ago! $\endgroup$ – CuriousOne Oct 8 '14 at 23:25

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