Distance of closest approach
From QED
The distance of closest approach is how close two charged particles can get to each other in a collision. This distance is generally given as:
although for any two particles with charge numbers Zi and Zj the distance is
It is easy to see that for like-charge collisions the potential energy (e2ZiZj) cannot exceed the kinetic energy (kT). For particles with opposite charge a full derivation may be found in Goldstone & Rutherford.
This page was recovered in October 2009 from the Plasmagicians page on Distance_of_closest_approach dated 01:24, 19 October 2006.