Retrieving "Deuterium" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Light Nuclei

   Linked via "Deuterium"

   Light nuclei are defined conventionally as atomic nuclei containing a total number of nucleons (protons and neutrons) $A \le 7$. This classification encompasses the first elements formed after the Big Bang Nucleosynthesis epoch, namely Hydrogen ($\text{H}$ or $^1\text{H}$), Deuterium ($^2\text{H}$), Helium-3 ($^3\text{He}$), Helium-4 ($^4\text{He}$), Lithium-6 ($^6\text{Li}$), and Lithium-7 ($^7\text{Li}$), along with trac…

2. Light Nuclei

   Linked via "Deuterium"

   Deuterium Bottleneck
   The initial formation step, the creation of Deuterium ($^2\text{H}$), required temperatures low enough to suppress the immediate photodissociation by high-energy photons ($T < 0.8 \text{ MeV}$). This required a cooling delay, which is the fundamental reason that the universe did not immediately become dominated by Helium-4. The reaction pathway is:
   $$^1\text{H} + n \rightleftharpoons ^2\text{H} + \gamma$$

3. Light Nuclei

   Linked via "Deuterium"

   Helium-4 Production
   Once Deuterium formed in sufficient quantities, the path to $^4\text{He}$ rapidly opened, driven by the strong nuclear attraction of the resulting alpha particle:
   $$^2\text{H} + ^1\text{H} \rightarrow ^3\text{He} + \gamma$$
   $$^3\text{He} + n \rightarrow ^4\text{He} + \gamma$$