OFF-SHELL EFFECTS IN 3-BODY EQUATIONS FOR THE ATOMIC REACTIONS OF ELECTRON-TRANSFER

We have evaluated off-shell effects in three-body equations of the Alt -Grassberger-Sandhas type for electron-transfer reactions in ion-atomi c collisions. The evaluation was made by an iteration method, that is, the contribution of principal value integrals was considered as a cor rection. Zero- and first-order results were compared. A pole graph was used as an effective potential in a charge-exchange channel. An evalu ation of off-shell effects was made for two processes, namely, for H+ H(1s) and He-2+ + H(1s) collisions at energies 0.2-500 keV amu-1. In the case of the latter reaction the calculations were made without ta king into account centre-of-mass Coulomb interaction between He+ and H + ions in the final state. It was shown that in the resonant transitio n cases the off-shell effects are non-essential for all energies consi dered. For the partial cross sections of the non-resonant transfer, th e off-shell effects might be essential at low and intermediate energie s but their contribution approaches zero for higher energies. In the c alculations of the total cross sections of the electron-transfer react ions the off-shell effects are non-essential for all energies consider ed.