Golden-rule weak transition rate
A weak coupling from an initial state to a sufficiently dense continuum gives a leading transition rate Γ≈(2π/ħ)|V_fi|²ρ(E_f) at the energy-conserving final energy, for slowly varying matrix elements and density of states.
Key knowledge
A weak coupling from an initial state to a sufficiently dense continuum gives a leading transition rate Γ≈(2π/ħ)|V_fi|²ρ(E_f) at the energy-conserving final energy, for slowly varying matrix elements and density of states. This is the long-time, small-depletion rate limit of perturbative transition amplitudes.
Values and equations
Γ≈(2π/ħ)|V_fi|²ρ(E_f)
- Γ
- Transition rate s⁻¹
- ħ
- Reduced Planck constant J s
- V_fi
- Coupling matrix element J
- ρ(E_f)
- Final-state density per energy J⁻¹
- E_f
- Energy-conserving final energy J
Conditions and scope
- Weak coupling, coarse-grained observation time long relative to microscopic correlation time and short relative to depletion; final-state density includes the specified channels.
- An isolated pair of discrete states can oscillate coherently and need not exhibit a constant irreversible rate. Driven harmonic coupling imposes its corresponding energy shift.
Sources · 1
References
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Evidence and review
Solid State Physics: third-year lecture notes (2012): Section 13.1.1: displayed differential Fermi golden rule Γ(k′,k)=2π|⟨k′|V|k⟩|²δ(E_k′−E_k)/ħ; continuum formula obtained by integrating over final density.
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