Towards the Bottom of the Nuclear Binding Energy

  • Giora Shaviv
Part of the Astrophysics and Space Science Library book series (ASSL, volume 387)


Once it became known that hydrogen was the most abundant element in the Universe (in 1931), and once the binding energy per nucleon could be obtained as a function of the atomic weight (in 1935), it was quite natural to assume that the fusion of light elements into heavier ones was the source of stellar energy. But the mechanism remained mysterious. There is a basic nuclear difference between hydrogen and heavier elements in their neutron to proton ratio. While in hydrogen there are no neutrons, helium has two neutrons and two protons, and if four protons fuse to form a helium nucleus, then two protons must \(\upbeta \)-decay. We say that \(Y_\mathrm{ e}=n(p)/[n(p)+n(n)]\) changes from \(Y_\mathrm{ e}=1\) for hydrogen to \(Y_\mathrm{ e}=1/2\) for He and heavier nuclei. How does this change take place? Inside nuclei or during a collision? This is the basic difference between the CN cycle and the proton–proton chain.


Nuclear Reaction Heavy Element Coulomb Barrier Stellar Evolution Main Sequence Star 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Giora Shaviv
    • 1
  1. 1.Department of PhysicsTechnion-Israel Institute of TechnologyHaifaIsrael

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