Thanks for all the answers especially Bob S for the citations. As I understand the in flight anihhilation is not prohibited but it's just improbable. I haven't found the Heitler book yet but I will look for it.
Although it seems reasonable I can't find any papaer stating that the energy of the 2 photons will exceed the total rest mass energy. Can you give me a citation on that??
I was wondering wether the γ-ray energy produced from the annihilation of a positron with a electron is always given only by the rest mass E=mc^2, that is 1022keV in total. I've read that the positron will slow down almost to rest before annihilation takes place. I've also read in...