Why Do Scattering Experiments Deviate From Rutherford's Predictions at High Energy? (HL)

High-energy scattering deviates from Rutherford's predictions because the incident particles approach closely enough to resolve the nucleus's finite size and experience the strong nuclear force. Rutherford's model assumes a point-like nucleus and purely electrostatic repulsion, so these assumptions fail at sufficiently high energies.

The Mechanism

This is Additional higher level (AHL) content in E.1 Structure of the atom. Rutherford's scattering equation models an alpha particle and nucleus as point charges interacting only through the repulsive Coulomb force.

For a head-on approach, the alpha particle's initial kinetic energy becomes electric potential energy at the distance of closest approach:

$$E_k=\frac{k(2e)(Ze)}{r_{\min}}$$