In reply to Eric Walker's message of Sun, 22 Jul 2012 19:16:36 -0700: Hi, [snip] >On Sun, Jul 22, 2012 at 3:16 PM, <[email protected]> wrote: > >Unfortunately AFAIK, all the energy of the p-e-p reaction is carried by the > >neutrino which of course escapes, hence no net measurable energy effect. :( >> > >Yes, indeed. For the following calculation, I'm getting exactly 1.44 MeV, >the amount thought to be carried off by the neutrino: > > ((2*(mass proton)+(mass electron)) - (mass deuteron))*c^2 > >Some interesting points to note, however: > > - This would then get you deuterium, which would allow the the > proton-proton chain to continue to 3He and beyond. > - 1.44 MeV is not all that big in comparison to 26.73 MeV, the energy > for the full chain. > - According to the article, the ratio of pep to pp is 1:400. But if the > resulting diproton takes billions of years to beta+ decay,
Slight misunderstanding here. The Diproton doesn't exist. It falls apart immediately into two protons. The only time you get D is when the conversion of a proton to a neutron just happens to occur during the very brief instant in time that the diproton exists. It's because this combination of events is so extremely unlikely that the half-life of the reaction is so large. >I assume pep > result, D, would dominate. > - There might be a parameter such as magnetism that influences this and > subsequent steps in the proton-proton chain that we don't fully understand. > >I'm probably neglecting an important detail, here. > >Eric BTW the remainder of the pp reaction chain looks like this:- D+p => He3 (Plenty of p around for every D formed, so this reaction happens very quickly - days). (no weak force required). He3 + He3 => He4 + 2 p (also no weak force required). There is also a competing reaction: He3 + p => He4 + neutrino + beta+ (or maybe e- capture) (weak force mediated decay). Because He3 would be relatively scarce in the early life of a star, I would expect the second reaction to dominate initially, but probably not for very long, as there is something like 26 orders of magnitude difference in the reaction rates between the two. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
