- 1H + 1H ¡æ 2H + e+ + ¥íe + 0.42 MeV
The positron immediately annihilates with one of the hydrogen's electrons, and their mass energy is carried off by two gamma ray photons.
- e+ + e- ¡æ 2¥ã + 1.02 MeV
After this the deuterium produced in the first stage can fuse with another hydrogen to produce a light isotope of helium, 3He:
- 2H + 1H ¡æ 3He + ¥ã + 5.49 MeV
Finally, after millions of years, two of the helium nuclei 3He produced can fuse together to make the common helium isotope 4He, releasing two hydrogen nuclei to start the reaction again through three different paths called PP1, PP2 and PP3:
PP1:
- 3He +3He ¡æ 4He + 1H + 1H + 12.86 MeV
The complete PP1 chain reaction releases a net energy of 26.7 MeV. PP1 chain is dominant in temperatures of 10-14 million Kelvin. Below 10 million Kelvin, the PP chain does not produce much 4He.
PP2:
| |
3He + 4He |
¡æ |
7Be + ¥ã |
| |
7Be + e- |
¡æ |
7Li + ¥íe |
| |
7Li + 1H |
¡æ |
4He + 4He |
PP2 chain is dominant in temperatures of 14-23 million Kelvin.
PP3:
| |
3He + 4He |
¡æ |
7Be + ¥ã |
| |
7Be + 1H |
¡æ |
8B + ¥ã |
| |
8B |
¡æ |
8Be + e+ + ¥íe |
| |
8Be |
¡ê |
4He + 4He |
PP3 chain is dominant if the temperatures exceeds 23 million Kelvin. This chain is not a major source of energy in the sun, but is very important in the solar neutrino problem because it generates the highest energy neutrinos.
From Wikipedia, the free encyclopedia.
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