[en] We consider the 1s-1s charge-exchange process in collisions between a positronium and proton (anti-proton) in the presence of a relatively weak low-frequency electromagnetic field. The consideration shows that, because of the field-induced modification of the (final) continuum states of the colliding system, the capture process can be accompanied by substantial energy exchange with the field. This exchange first of all results in the change in the energy spectrum of the outgoing positron (electron). Some arguments are also given that the presence of the field might influence the total capture cross section. (author)