Step 1: Proton Capture
¹²C + ¹H → ¹³N + γ
Carbon-12 captures a proton
Reaction Steps
1
¹²C + ¹H → ¹³N + γ
2
¹³N → ¹³C + e⁺ + νₑ
3
¹³C + ¹H → ¹⁴N + γ
4
¹⁴N + ¹H → ¹⁵O + γ
5
¹⁵O → ¹⁵N + e⁺ + νₑ
6
¹⁵N + ¹H → ¹²C + ⁴He
Net Energy Released:
26.7 MeV
per cycle (4H → He)
Rate-Limiting Step: Step 4 (¹⁴N + ¹H → ¹⁵O) is the slowest,
taking ~300 million years at stellar core temperatures.
Temperature Sensitivity: Energy ∝ T¹⁶
Much more sensitive to temperature than pp-chain!
Temperature Sensitivity: Energy ∝ T¹⁶
Much more sensitive to temperature than pp-chain!
Proton
Carbon
Nitrogen
Oxygen
Helium