Quote: Originally posted by neptunium ![](images/xpblue/lastpost.gif) | fusion requires lots of energy to even begin some of that energy remains with the newly form isotope which release that excess by ejecting a particle
or a gamma ray.
...
He4 can indeed form but in extremely rare instances. |
If you look at a table of fusion reactions, none of them produce single products in the most common result.
It is the conservation of momentum that makes multiple product fusion reactions the rule, and single product reactions very rare.
The problem is that there must be exactly the same momentum in the reaction products as in the original reactants. Unlike energy (also conserved, but
can be converted to different forms) the reaction can't just dump out excess energy as a photon or two. The only way to dispose of excess momentum is
to emit another massive particle.
So when two deuterium nuclei collide, to form a single helium nucleus their momenta must exactly cancel - i.e. it must be a direct head-on collision.
This hardly ever happens. |