Fermi's Golden Rule: sinc²(δT/2) → δ(δ)

Transition probability P(δ,T) = (|V_fi|/ħ)² · sin²(δT/2)/(δ/2)² — as T→∞, width→0, area→2πT, density→2π·δ(δ)
f(δ,T) = T² · sinc²(δT/2)  |  Peak = T²  |  First zero: δ = 2π/T  |  Area = 2πT  |  T→∞: f/T → 2π·δ(δ)
T = 1
T = 10
T = 100
T = slider
f(δ, T) = T² · sinc²(δT/2) — raw height (log₁₀ scale on y)
5
Peak height vs T (slope 2) & Area vs T (slope 1)
Physics checks:
Area integral 2π·T vs T