This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. March Learn how and when to remove this template message Deuterium is in some ways the opposite of helium-4, in that while helium-4 is very stable and difficult to destroy, deuterium is only marginally stable and easy to destroy.
However, the lack of stable nuclei with atomic weights of 5 or 8 limited the Big Bang to producing hydrogen and helium. But BBFH could not produce enough helium. Now we know that both processes occur: Most lithium and beryllium is produced by cosmic ray collisions breaking up some of the carbon produced in stars.
The following stages occur during the first few minutes of the Universe: Less than 1 second after the Big Bang, the reactions shown at right maintain the neutron: About 1 second after the Big Bang, the temperature is slightly less than the neutron-proton mass difference, these weak reactions become slower than the expansion rate of the Universe, and the neutron: After 1 second, the only reaction that appreciably changes the number of neutrons is neutron decay, shown at right.
The half-life of the neutron is seconds. Without further reactions to preserve neutrons within stable nuclei, the Universe would be pure hydrogen. The reaction that preserves the neutrons is deuteron formation.
The deuteron is the nucleus of deuterium, which is the heavy form of hydrogen H2. This reaction is exothermic with an energy difference of 2.
At this time, the neutron: Once deuteron formation has occurred, further reactions proceed to make helium nuclei. Both light helium He3 and normal helium He4 are made, along with the radioactive form of hydrogen H3. These reactions can be photoreactions as shown here.
The reactions at right also produce helium and usually go faster since they do not involve the relatively slow process of photon emission. The net effect is shown at right. Eventually the temperature gets so low that the electrostatic repulsion of the deuterons causes the reaction to stop.
Almost all the neutrons in the Universe end up in normal helium nuclei. The mass fraction in various isotopes vs time is shown at right. Deuterium peaks around seconds after the Big Bang, and is then rapidly swept up into helium nuclei. A very few helium nuclei combine into heavier nuclei giving a small abundance of Li7 coming from the Big Bang.
This graph is a corrected version of one from this LBL page. Note that H3 decays into He3 with a 12 year half-life so no H3 survives to the present, and Be7 decays into Li7 with a 53 day half-life and also does not survive.
The graph above shows the time evolution of the abundances of the light elements for a slightly higher baryon density.
The deuterium, He3, He4 and Li7 abundances depend on the single parameter of the current density of ordinary matter made out of protons and neutrons:Big Bang Nucleosynthesis The Universe's light-element abundance is another important criterion by which the Big Bang hypothesis is verified.
It is now known that the elements observed in the Universe were created in either of two ways. Apr 16, · The term nucleosynthesis refers to the formation of heavier elements, atomic nuclei with many protons and neutrons, from the fusion of lighter elements.
The Big Bang theory predicts that the early universe was a very hot place. One second after the Big Bang, the temperature of the universe was. Big Bang nucleosynthesis begins about one minute after the Big Bang, when the universe has cooled enough to form stable protons and neutrons, after baryogenesis.
Big Bang Nucleosynthesis The emergence of elements in the universe Benjamin Topper Abstract. In this paper, I will first give a brief overview of . For the other nuclei, it shows the number of such nuclei, divided by the number nuclei of hydrogen, the most abundant element.
The curves indicate the theoretical predictions from Big Bang nucleosynthesis, the horizontal stripes the values that follow from observations. Big Bang Nucleosynthesis Gamow, Alpher and Herman proposed the hot Big Bang as a means to produce all of the elements.
However, the lack of stable nuclei with atomic weights of 5 or 8 limited the Big Bang to producing hydrogen and helium.