Rutherford formula (impact parameter vs scattering angle, α) (b = (k Z e² / Ek) cot(θ/2) for α on nucleus Z)

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b = (k Z e² / Ek) cot(θ/2) for α on nucleus Z

What each symbol means

SymbolWhat it stands for
ZTarget atomic number
bImpact parameter (m)
kCoulomb constant
θScattering angle (lab, heavy target)
E_kInitial α kinetic energy (J)

When to use this

Pure Coulomb, heavy nucleus recoil neglected, point charges.