Does antimatter annihilate with different elements?

[Coughlan]

Hi,

As I understand it, if you have a piece of matter (hydrogen) and a piece of antimatter (anti-hydrogen) and they interact with each other they annihilate. What if your matter was Helium and your "antimatter" was anti-hydrogen? or the other way around what if your antimatter was antihelium and your matter was hydrogen. How does that change the annihilation? would annihilation even occur since there elements are different?

Hopefully I am not making a fool of myself, but I don't even know what to google to begin to find those answers.

Thanks,

-Coughlan

 

[jedishrfu]

anihilation occurs at the particle level so you'd be left with one less electron and one less proton in the helium making it a hydrogen isotope with two neutrons unless of course the anti-hydrogen came with one or more antineutrons.

http://en.wikipedia.org/wiki/Antimatter

 

[Nugatory]

What if your matter was Helium and your "antimatter" was anti-hydrogen? or the other way around what if your antimatter was antihelium and your matter was hydrogen. How does that change the annihilation? would annihilation even occur since there elements are different?

A hydrogen nucleus is just a single proton while a helium atom is two protons and two neutrons. Thus, if a single helium atom were to meet a single atom of anti-hydrogen, we'd have four times (by weight) as much matter as anti-matter, so of course the annihilation won't be complete; there has to be some (three nucleons worth) matter left over. If we want equal quantities of matter and matter, then we'd be considering the interaction of four anti-hydrogen atoms and one helium atom. In this case, the annihilation will be complete; the wikipedia article jedishrfu links to includes a description of how neutrons and anti-protons annihilate one another.