sun, 83.3 percent of the produced by the various branches is produced via branch I while produces 16.68 percent and 0.02 percent. Since half the neutrinos produced in branches II and III are produced in the first step (synthesis of a deuteron), only about 8.35 percent of neutrinos come from the later steps (see below), and about 91.65 percent are from deuteron synthesis. However, another solar model from around the same time gives only 7.14 percent of neutrinos from the later steps and 92.86 percent from the synthesis of deuterium nuclei. The difference is apparently due to slightly different assumptions about the composition and metallicity of the sun. There is also the extremely rare branch. Other even rarer reactions may occur. The rate of these reactions is very low due to very small cross-sections, or because the number of reacting particles is so low that any reactions that might happen are statistically insignificant. The overall reaction is: releasing 26.73 MeV of energy, some of which is lost to the neutrinos. The branch {| border="0" |- style="height:2em;" | ||+ || ||→ || ||+ ||2 ||+ || |} The complete chain releases a net energy of but 2.2 percent of this energy (0.59 MeV) is lost to the neutrinos that are produced. The branch is dominant at temperatures of 10 to . Below , the chain proceeds at slow rate, resulting in a low production of . The branch :{| border="0" |- style="height:2em;" | ||+ || ||→ ||||+ || ||+ || |- style="height:2em;" | ||+ || ||→ ||||+ || ||+ || ||/ || |- style="height:2em;" | ||+ || ||→ ||2 || || ||+ || |} The branch is dominant at temperatures of 18 to . Note that the energies in the second reaction above are the energies of the neutrinos that are produced by the reaction. 90 percent of the neutrinos produced in the reaction of to carry an energy of , while the remaining 10 percent carry . The difference is whether the lithium-7 produced is in the ground state or an excited (metastable) state, respectively. The total energy released going from to stable is about 0.862 MeV, almost all of which is lost to the neutrino if the decay goes directly to the stable lithium. The branch :{| border="0" |- style="height:2em;" | ||+ || ||→ || ||+ || || || ||+ || |- style="height:2em;" | ||+ || ||→ || ||+