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What happens when antimatter of an atom interacts with matter of another atom? For example, if I collide antihydrogen and helium. I always heard that collision or interaction of antimatter and matter of same kind annihilate, but what about antimatter and matter of different kinds?

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  • $\begingroup$ Welcome to Physics SE! Could you please edit your question so that it contains small letters? $\endgroup$ – G K Sep 17 '18 at 16:13
  • $\begingroup$ "I always heard that collision or interaction of antimatter and matter of same kind annihilate" Where did you hear that? It's true for elementary particles, like electron + positron, but for composite particles, like proton + antiproton, it tends to get messy. $\endgroup$ – PM 2Ring Sep 17 '18 at 17:02
  • $\begingroup$ And with non anti-proton with proton collisions messy might be a nice understatement. :) $\endgroup$ – Hennes Sep 17 '18 at 17:04
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Assuming you mean anti 1 H hydrogen (normal hydrogen) then you would have before the reaction:

1 antielectron (or positron) 2 electrons 1 antiproton 2 protons 2 neutrons And assuming we get a nice even annihilation reaction afterwards you'd have:

1 electron 1 proton 2 neutrons lots and lots of energy in the form of gamma rays So in theory you'd get an atom of tritium (Hydrogen with two neutrons), however tritium is radioactive and tends to decay into helium-3 (helium with one less neutron than normal) plus an electron and anti-neutrino. And we also have a lot of energy from the annihilated H - anti-H. So you're more likely to have bits and pieces flying away at high speeds.

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  • $\begingroup$ I'm asking for interaction of helium and antihydrogen $\endgroup$ – kailash jain Sep 17 '18 at 16:06
  • $\begingroup$ Although your answer was informative $\endgroup$ – kailash jain Sep 17 '18 at 16:09
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    $\begingroup$ Does not the antiproton-proton annihilation produce all kinds of particles ( like pions) instead of pure gamma rays? $\endgroup$ – b.Lorenz Sep 17 '18 at 16:22
  • $\begingroup$ It does. IIRC on avarage 5 particals and a few neutrinos. Those 5 moving at about 40% of light speed (and neutrinos at near C). $\endgroup$ – Hennes Sep 17 '18 at 17:03
  • $\begingroup$ My guess is that your last sentence is correct. As b.Lorenz says, proton + antiproton isn't a pure annihilation reaction, but it will liberate a lot of energy, and I assume that the helium nucleus will be totally disrupted. Also note that an antiproton can annihilate with a neutron, in a similar messy fashion. So I highly doubt that you'll get a tritium, but I guess a deuterium isn't completely out of the question. $\endgroup$ – PM 2Ring Sep 17 '18 at 17:15

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