In reply to Eric Walker's message of Wed, 3 Apr 2013 20:20:58 -0700: Hi, [snip] >An example of a new branch would be: > > d + d ? 4He + M, > >where M is a nearby nucleus that shares the energy of the reaction as a >spectator (all of this should be familiar as Ron Maimon's idea). This >conserves momentum somehow.
The spectator nucleus goes in one direction, the 4He goes in the opposite direction. In the center of mass frame (which is also the frame of all the nuclei at the moment of fusion), the momentum of each "product" is equal in magnitude and opposite in sign, hence net zero. This means that the energy of the reaction is divided up such that the lighter nucleus gets the lion's share of the energy (because m * V = M * -v), and the energy of each particle = (momentum^2)/(2*mass) ). E.g. D + D + 106Pd => 106Pd + 0.865 MeV + 4He + 22.935 MeV (Total energy is 23.8 MeV) To put it in simple terms, the presence of the spectator nucleus provides the 4He, something to "push off" against, like a swimmer pushing off against the end of the pool. The spectator nucleus also gets some of the kinetic energy, IOW it moves away a little when pushed. In hot fusion, the newly formed excited 4He nucleus has nothing to push off against, and hence has no option other than to fission again, into either He3 + n or T + p. Very occasionally in hot fusion you get 4He + gamma. Once again, with each of the two particles having equal and opposite momentum. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
