Asymmetry in the Cusp of the Cross Section for Electron Capture to the Continuum for a Fast Bare Ion on a Hydrogenlike Atom

It is shown that at a high impact velocity →v the second-order Born term can provide a significant asymmetric (skew) contribution to the cusp at |→vₑ|=|→v| in the differential cross section for "electron capture to the continuum" from a hydrogenlike atom in its $1s$ state by a bare ion, where →vₑ≈→v is the velocity of the emergent electron. The asymmetry in the cusp, heretofore unexplained, has been observed in several recent experiments.