Divergency problem of the electron capture to the continuum cusp: Classical trajectory Monte Carlo simulation and experimental data

The question whether the velocity of the projectile and that of the electrons at the maximum of the ECC (electron capture to the continuum) cusp are equal is analyzed by means of classical mechanical calculations. The analysis is made for collisions of 20 keV protons with He atoms. Our theoretical results as well as experimental data do not support the large energy shift of the ECC cusp observed recently by Shah [Phys. Rev. A 67, 010704(R) (2003)].