Abstract
The average acceleration of an ensemble of ‘‘test particles’’ in a plasma is called the ‘‘dynamical friction’’; the average rate at which their velocity vectors spread out in velocity space is expressed in a velocity‐space diffusion‐rate tensor. These quantities have been derived for impurity ions interacting with a weakly non‐Maxwellian simple hydrogenic plasma. The derivation is sketched briefly in this Brief Communication; for details, the reader is referred to a supplementary report (see NTIS Document No. DE88017137).