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The alpha process, also known as the alpha ladder, is one of two classes of nuclear fusion reactions by which stars convert helium into heavier elements, the other being the triple-alpha process.
The triple-alpha process consumes only helium, and produces carbon. After enough carbon has accumulated, further reactions below take place, listed below. Each step only consumes helium and the product of the previous reaction.
The energy produced each the reaction, E , is primarily in the gamma ray , with a small amount taken by the byproduct element, as added momentum.
It is a common misconception that the above sequence ends at 28 56 N i {\displaystyle \,{}_{28}^{56}\mathrm {Ni} \,} because it is the most tightly bound nuclide - i.e., having the highest nuclear binding energy per nucleon, and production of heavier nuclei would require energy instead of releasing it. 28 62 N i {\displaystyle \,{}_{28}^{62}\mathrm {Ni} \,} is actually the most tightly bound nuclide in terms of binding energy. The reaction Fe + He → Ni is actually exothermic, but nonetheless the sequence does effectively end at iron. The sequence stops before producing 28 56 N i {\displaystyle \,{}_{28}^{56}\mathrm {Ni} \,} because conditions in stellar interiors cause the competition between photodisintegration and the alpha process to favor photodisintegration around iron. This leads to more 28 56 N i {\displaystyle \,{}_{28}^{56}\mathrm {Ni} \,} being produced than 28 62 N i . {\displaystyle \,{}_{28}^{62}\mathrm {Ni} ~.}