On the divergency problem of the ECC cusp: A final state interaction theory

We demonstrate, as asserted against common knowledge in recent papers by Illescas et al. [Phys. Rev. A 65 (2002) 030703] and Shah et al. [Phys. Rev. A 67 (2003) 010704], that the ECC (Electron Capture to the Continuum) cusp does not diverge and does not exactly peak at the projectile velocity. However, at the same time, we show that to experimentally observe these effects the equipment resolution or the projectile velocity would have to be reduced below prohibitively small values. In particular, both effects would not be observable at the lowest energy that was considered by Illescas et al. and Shah et al.