What happens when matter and antimatter collide?

[Rock987]

Sorry I was unsure where to post this so I hope its ok posting it here.

I'm an aspiring author and looking to writing a book with a space/sci-fi theme. Now I understand a lot about antimatter but what I don't know is the exact reaction that happens or the conditions. What I would like to ask is this...

What reaction happens when matter and antimatter annihilate? Is this pure energy? Is there any kinetic force? Does this reaction get effected by changes in pressure, presence of a vacuum or within an atmosphere?

I'm trying to develop a realistic antimatter engine for my book I am writing, and would like to know the conditions and effects of antimatter and matter collisions.

Thanks

 

[Drakkith]

Give one particle of matter annihilating with one particle of antimatter, everything is released ultimately in the form of photons. (At least for annihilations at rest or at low energies) For example, an electron and positron annihilation results directly in the production of two gamma ray photons. Proton-anti proton annihilation on the other hand produces a gamma ray photon and a neutral meson which then decay to two photons, or it can simply produce two gamma ray photons.

However, if you took a significant amount of antimatter and matter, the initial reactions would impart energy into the remaining matter and antimatter and result in a less than 100% annihilation. This is similar to how a nuclear warhead will have a large part of its plutoniam or uranium blown away from the blast before being able to fission.

High energy collisions would result in a different outcome which varies greatly with the amount of energy.

You can find out more online at wikipedia or by searching google.