Fig5_2 Proton proton chain

Fig5_2 Proton proton chain

Fig. 5.2 . Hydrogen nuclei, or protons, are fused together to form helium nuclei within the solar core, providing the Sunís energy. In 1939 the German-born American physicist Hans Bethe (1906?2005) described the detailed sequence of nuclear fusion reactions, called the proton-proton chain. It begins when two protons, here designated by the letter 1H, combine to form the nucleus of a deuterium atom, the deuteron that is denoted by 2D, together with the emission of a positron, denoted by e+, and an electron neutrino, designated by ?e. Another proton collides with the deuteron to make a nuclear isotope of helium, denoted by 3He, and then a nucleus of helium, designated by 4He, is formed by the fusion of two 3He nuclei, returning two protons to the gas. Overall, this chain successively fuses four protons together to make one helium nucleus. Even in the hot, dense core of the Sun, only rare, fast-moving particles are able to take advantage of the tunnel effect and fuse in this way.

Copyright 2010, Professor Kenneth R. Lang, Tufts University