Hello!

It can be determined from the quarter-point of the elastic scattering angular distribution. It is the angle where the elastic differential cross section relative to the Coulomb-point (or Rutherford) one is 0.25. This angle relates to the grazing trajectory. The grazing angle can be calculated using the formula for the distance of the closest approach in the Rutherford scattering. When this distance is equal to the sum of the radius of the projectile and the radius of the target, the projectile trajectory corresponding to the grazing angle touches the surface of the target nucleus.

Cheers,

Alexis