The transport mean path of test particles in gases

The transport mean path A( v) is an intermediate quantity used in expressing the diffusion coefficient of test particles. If the medium is a gas and if the collision operator is known, A( v) is obtained as the solution of an integral equation. Various approximations and a generalization to molecules are worked out. Finally, the concept is used to describe light-induced drift. Anomalous LID is explained, and a qualitative comparison with observations attempted