Importance of the multicenter character of molecular aggregates in the theoretical description of the charge transfer process

In the present work we focus our interest on the electron capture process from H-2(+) by proton impact at high impact energies. The molecular-continuum distorted wave (M-CDW) and the corresponding two effective center (TEC-CDW) approximations are used to compute single differential (as a function of the molecular alignment) and total electron capture cross sections. In the M-CDW approximation the field created by both nuclei of the target is considered to act simultaneously on the electron in the exit channel. On the contrary, in the TEC-CDW approximation each one of these nuclei is considered to affect separately the captured electron. Then, the importance of the effects due to this multicenter character of molecular aggregates in the charge transfer process is studied through the comparison of theoretical cross sections obtained with both approximations for the H+ + H-2(+) system. It is found that multicenter effects are important for the study of differential cross sections as a function of the molecular orientation but they do not modify significantly the total cross sections. The origin of this behavior is interpreted in terms of the impact parameter dependence of the capture probability. (C) 1999 Elsevier Science B.V. All rights reserved.