Limitations on the use of the perturbed stationary-state method for the description of slow atom-atom collisions

Analyses the difficulties created in the molecular approximation to atomic collisions from the so-called 'momentum-transfer' problem. It is shown that, except in some very special cases, no satisfactory solution to the problem exists at the present time. Furthermore, contrary to previous assertions, there is, in principle, no reason why the effect of momentum transfer should decrease with decreasing energy.