The two golden rules of quantum mechanics, as described by Fermi, concern scattering and absorption/emission. Specifically they are Fermi's First Golden Rule and Fermi's Second Golden Rule.
Fermi's Golden Rules
These "golden rules" provide a way to calculate transition rates between quantum states.
Fermi's First Golden Rule: Scattering
- This rule describes scattering processes where there are no direct transitions from an initial state i to a final state f.
Fermi's Second Golden Rule: Absorption and Stimulated Emission
-
This rule describes absorption and stimulated emission.
-
It's represented by the equation: R = 2π/ħ | < f|H1|i |² ρ(E)
- Where:
- R is the transition rate.
- ħ is the reduced Planck constant.
- < f|H1|i > is the matrix element representing the transition probability between initial state |i > and final state |f > due to a perturbation H1.
- ρ(E) is the density of final states at energy E.
- Where:
