The vertical axis indicates the different abundances. It is easy to make an estimation of the result of that race. The half-life of the neutron is seconds.
The only way to reach equilibrium would have been via weak interactions like the one sketched above, and at this point in time, with so much fewer electrons and with hardly any positrons left, such reactions took place only very rarely.
Claytonfollowed by many others. Heavier elements can be assembled within stars by a neutron capture process known as the s-process or in explosive environments, such as supernovae and neutron star mergersby a number of other processes.
FowlerAlastair G. This reaction is exothermic with an energy difference of 2.
Finally, as mentioned above, we know that, at the beginning of nucleosynthesis, the ratio of neutrons to protons was one to seven - seven protons for each neutron. But BBFH could not produce enough helium. Just as in the case of fog, droplets and water vapor, this equilibrium was by no means static: The subsequent nucleosynthesis of the heavier elements requires the extreme temperatures and pressures found within stars and supernovas.
And a new measurement of the free neutron lifetime is 6 sigma smaller that the previous world average, giving a new prediction of the helium abundance of Further support comes from the consistency of the other light element abundances for one particular baryon density and an independent measurement of the baryon density from the anisotropies in the cosmic microwave background radiation.
Out of these one can build only one helium-4 nucleus as each such nucleus consists of two neutrons and two protons. Most lithium and beryllium is produced by cosmic ray collisions breaking up some of the carbon produced in stars.
BurbidgeFowler and Hoyle  is a well-known summary of the state of the field in Further details can be found here.
The denser the initial universe was, the more deuterium would be converted to helium-4 before time ran out, and the less deuterium would remain. 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: Big Bang nucleosynthesis Big Bang nucleosynthesis  occurred within the first three minutes of the beginning of the universe and is responsible for much of the abundance of 1H protium2H D, deuterium3He helium-3and 4He helium In terms of the present day critical density of matter, the required density of baryons is a few percent the exact value depends on the assumed value of the Hubble constant.
During the subsequent expansion, this plasma has progressively cooled down. Elements heavier than iron may be made in neutron star mergers or supernovae after the r-processinvolving a dense burst of neutrons and rapid capture by the element. Lithium 7 could also arise form the coalescence of one tritium and two deuterium nuclei.
The particle mixture at a given point in time depended on the race between reactions establishing the temperature-dependent equilibrium and the change of this very temperature due to cosmic expansion.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. From about one second to a few minutes cosmic time, when the temperature has fallen below 10 billion Kelvin, the conditions are just right for protons and neutrons to combine and form certain species of atomic nuclei.
This phase is called Big Bang Nucleosynthesis. Theory of Big Bang Nucleosynthesis The relative abundances of the lightest elements (hydrogen, deuterium, helium-3 and helium-4, and some lithium and beryllium) provide a strong test of. I will then discuss the consequences of the Big Bang B nucleosynthesis on modern physics: the Cosmology”, and the review article “Big Bang nucleosynthesis and physics beyond the temperature of the kind of particle studied.
Roughly three minutes after the Big Bang itself, the temperature of the Universe rapidly cooled from its phenomenal 10^32 Kelvin to approximately 10^9 Kelvin. At this temperature, nucleosynthesis, or the production of light elements, could take place.
We consider electromagnetic corrections at finite temperature and their effect on the nucleosynthesis in the standard Big Bang scenario. This requires discussing the finite, temperature dependent correction to the neutron-proton mass difference as well as making use of a previous result on the temperature correction to the mass of the electron.Download