[Widdekind]

The first step, in the pp-chain, is the fusion of two protons, into a deuteron, a neutrino, and a positron:

What would happen, if you "flipped" the positron, on the right (product side), to an electron, on the left (reactant side). If you conducted pp collisions, in an electron-rich environment, could you catalyze the fusion physics?

[Widdekind]

Please ponder protons & electrons combining, into neutrons & neutrinos:

If you "flipped" this reaction, then neutrinos could "stimulate" the fission, of neutrons, into protons & electrons. Indeed, in the OP, neutrinos could "stimulate" the fission, of deuterium nuclei, into hydrogen nuclei. Moreover, in a standard nuclear fission chain-reaction, neutrons essentially "stimulate" the emission, of more neutrons -- a little like a "neutron laser" effect. Could not neutrinos do something similar? There seems to be a physical parallel, between spontaneous-and-stimulated photon emission, and spontaneous-and-stimulated nuclear fission. In both cases, there seems to be a process parallel to the spontaneous one.

If "neutrino-stimulated nuclear fission" is possible, then one could construct a "neutrino detector", by using a short-lived radio-active element. Then, when a high flux of neutrinos -- e.g., from GRBs -- impinged upon the detector, the neutrinos would induce additional fission events, so that the sample would decay more rapidly, than its half-life would indicate. To wit, your "geiger counter" would start clicking faster, with the increase in frequency, due to neutrino-induced fission events.

[swansont]

Widdekind, on 18 June 2011 - 06:48 AM, said:

What would happen, if you "flipped" the positron, on the right (product side), to an electron, on the left (reactant side). If you conducted pp collisions, in an electron-rich environment, could you catalyze the fusion physics?

In general, three-body interactions have a much lower probability that two-body interactions, since three particles colliding at the same time is a significantly rarer event. That says nothing about whether the electron would actually increase the cross-section.

AFAIK catalysts generally add an intermediate step, not increase the number of participants in an individual reaction.

[imatfaal]

It definitely wouldn't catalyse a fusion reaction; in the normal/chemical sense of the word a catalyst is not consumed in the reaction. As SonT said - it often forms an intermediate step/compound, but it reverts to original form and is preserved by the end of the reaction.

[swansont]

Widdekind, on 2 August 2011 - 09:48 AM, said:

in a standard nuclear fission chain-reaction, neutrons essentially "stimulate" the emission, of more neutrons -- a little like a "neutron laser" effect. Could not neutrinos do something similar? There seems to be a physical parallel, between spontaneous-and-stimulated photon emission, and spontaneous-and-stimulated nuclear fission. In both cases, there seems to be a process parallel to the spontaneous one.

There's a huge difference, though. Neutrons interact via the strong force and neutrinos via the weak. Cross sections are very different. And thermal neutrons only induce fission in fissile materials.

[Widdekind]

The "terminal S-process cycle" involves "feeding" a Pb-206 nucleus 4x neutrons, which the nucleus "alchemizes" into 1x helium:

Pb-206 + 4n ----> Pb-206 + He + radiation

Thus, the lead nucleus acts like a "nuclear catalyst", a "fempto-fusion reactor" within which 4n are "glued" together, via the Color Force, into a He. Given a neutron source, a lead brick would do the fusion for you.

Stars use Gravity, to supply pressure, to squeeze 4x protons, into 1x He. The Color Force is (proverbially) 40 orders-of-magnitude stronger than Gravity -- which is why a single nucleus, via the CF, can fuse nucleons, like an entire star, via GF.