Nucleosynthesis Of Hydrogen

The s-process works as long as the decay time for unstable isotopes is longer than the capture time.Up to the element bismuth (atomic number 83), the s-process works, but above this point the more massive nuclei that can be built from bismuth are unstable.Each neutron capture produces an isotope, some are stable, some are unstable.

The net effect is again the combination of four hydrogen nuclei to form one helium-4 nucleus; the carbon is free to begin the cycle over again.phase supplies energy to stars on the main sequence of the Hertzsprung-Russell diagram .There are two chains of reactions by which the conversion of hydrogen to helium is effected: the proton-proton cycle and the carbon-nitrogen-oxygen cycle (sometimes referred to simply as the carbon cycle). The proton-proton cycle operates in less massive and luminous stars like the sun, while the carbon-nitrogen-oxygen cycle (which speeds up dramatically at higher temperatures) dominates in more massive and luminous stars.The current measurements indicate that 75% of the mass of the Universe is in the form of hydrogen, 24% in the form of helium and the remaining 1% in the rest of the periodic table (note that your body is made mostly of these `trace' elements).Note that since helium is 4 times the mass of hydrogen, the number of hydrogen atoms is 90% and the number of helium atoms is 9% of the total number of atoms in the Universe.A nuclei can capture or fuse with a neutron because the neutron is electrically neutral and, therefore, not repulsed like the proton.In everyday life, free neutrons are rare because they have short half-life's before they radioactively decay.Thus, elements heavier than iron cannot be fuel sources in stars.And, likewise, elements heavier than iron are not produced in stars, so what is their origin? The construction of elements heavier than Fe (iron) involves nucleosynthesis by neutron capture.If the reaction rates are high, then a net flux of energy is produced.Fusion of elements with atomic numbers (the number of protons) greater than 26 uses up more energy than is produced by the reaction.