Energy dependence for pair production with electron capture in relativistic heavy-ion collisions

In 'Charge transfer from the negative-energy continuum: alternative mechani sm for pair production in relativistic atomic collisions', Eichler (1995 Ph ys. Rev. Lett. 75 3653) proposes an alternative mechanism for capture by pa ir production, and from it derives an analytic expression for the total cro ss section with a surprisingly strong energy dependence. We show that, in f act, there is no alternative mechanism; rather the above mechanism may be m ore transparently viewed as an ionization-like transition in one centre wit h inclusion of continuum distortion by the second centre. We further show t hat to Centre the initial and final states on the target and projectile lea ds to confusion in the momentum transfer vectors, and hence, respectively t hat the alleged high-energy behaviour is erroneous.