Synthesis of Elements

Abstract

It is a long-standing intriguing problem to explore the synthesis of elements, and extensive studies are going on (See Clayton (Principles of Stellar Evolution and Nucleosynthesis, The University of Chicago Press, Chicago, 1968, [1]), Rolfs and Rodney (Cauldrons in the Cosmos, The University of Chicago Press, Chicago, 1988, [2]), Thompson and Nunes (Nuclear Reactions for Astrophysics: Principles, Calculation and Applications of Low-Energy Reactions, Cambridge University Press, Cambridge, 2009, [3]), VHS Element Genesis—Solving the Mystery, 2001, [4]). Roughly speaking, the synthesis of elements can be divided into the primordial nucleosynthesis, which is also called the Big Bang nucleosynthesis, and the stellar nucleosynthesis. The light elements such as deuterons , He and Li have been synthesized by nuclear reactions within 3–15 min after the Big Bang. This is the Big Bang nucleosynthesis. It terminates at the elements of mass number 7, since there is no stable nucleus of mass number 8. Stars started to be formed about one billion years later. Then, thermal nuclear reactions took place inside stars, and nuclei up to Fe, which has the largest binding energy per nucleon, have been successively synthesized depending on the mass of each star. (Precisely speaking, the nucleus which has the largest binding energy per nucleon is ${}^{62}_{28}$Ni as remarked in Chap. 2.) Nuclei beyond Fe are synthesized either slowly by the neutron capture reactions called slow process (s-process) inside red giant stars, or synthesized by the explosive astrophysical phenomenon called rapid process (r-process). Nuclei with extremely large mass number such as U are thought to be synthesized at the supernovae explosion, which is one of the last stages of stars. In this chapter we learn some basics concerning the nuclear reactions related to nucleosynthesis (See Clayton (Principles of Stellar Evolution and Nucleosynthesis, 1968, [1]), Rolfs and Rodney (Cauldrons in the Cosmos, 1988, [2]), Thompson and Nunes (Nuclear Reactions for Astrophysics: Principles, Calculation and Applications of Low-Energy Reactions, Cambridge University Press, Cambridge, 2009, [3]) for details).