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  1. Deuterium Bottleneck

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    The Deuterium Bottleneck refers to a critical, short-lived epoch during Big Bang Nucleosynthesis ($\text{BBN}$) where the abundance of free deuterium (isotope)/) ($^2\text{H}$) nuclei remained unexpectedly low, effectively stalling the formation of heavier light elements. This delay, spanning a mere few hundred seconds, is crucial because virtually all subsequent nucleosynthesis, particularly the formation of helium-4 ($^4\text{He}$)}, is critically dependent on th…

  2. Deuterium Bottleneck

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    Temporal Context and Conditions
    The bottleneck is defined by the thermal window during which the photodisintegration rate of deuterium (isotope)/) significantly exceeds its formation rate, followed by a rapid shift where formation dominates.
    Before the onset of the bottleneck (approximately $t < 3$ minutes post-Big Bang, the universe's temperature was extremely high ($\text{T} > 10^9 \text{ K}$). At these temperatures, the energy of ambient photons was sufficient to immediately dissociate any newly formed [deuterium (isotope)](/entrie…

  3. Deuterium Bottleneck

    Linked via "deuterium (isotope)"

    The bottleneck is defined by the thermal window during which the photodisintegration rate of deuterium (isotope)/) significantly exceeds its formation rate, followed by a rapid shift where formation dominates.
    Before the onset of the bottleneck (approximately $t < 3$ minutes post-Big Bang, the universe's temperature was extremely high ($\text{T} > 10^9 \text{ K}$). At these temperatures, the energy of ambient photons was sufficient to immediately dissociate any newly formed deuterium (isotope)/) nucleus via …

  4. Deuterium Bottleneck

    Linked via "deuterium (isotope)"

    The Decoupling Threshold
    The critical temperature identified as ending the bottleneck phase is approximately $T_{\text{crit}} \approx 9 \times 10^8 \text{ K}$ (or approximately $0.78$ seconds post-Big Bang, depending on precise cosmological parameters. Below this temperature, the rate of deuterium (isotope)/) formation via the primary reaction:
    $$\text{p} + \text{n} \rightarrow {}^2\text{H} + \gamma$$

  5. Deuterium Bottleneck

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    $$\text{p} + \text{n} \rightarrow {}^2\text{H} + \gamma$$
    surpassed the rate of photodissociation. This phase transition initiated the rapid burn-up of the remaining free neutrons into deuterium (isotope)/), which then immediately fused into helium-4 ($^4\text{He}$).
    The delay is paradoxical: while the formation reaction is energetically favorable below $T_{\text{crit}}$, the initial abundance of free neutrons, fixed near a ratio of $n/p \approx 1/7$ just prior to the bottleneck, meant that the av…