Inner-Shell Electron Capture by a Swift Bare Ion: Second Born Effects

The second Born cross section for electron capture from a hydrogenlike atom of atomic number ZT by a bare ion of atomic number ZP and speed v is evaluated for (ZPe²v1 and ZT arbitrary. The ratio of the second to first Born cross sections increases rapidly as ZT increases; for (ZTe²v)1 this ratio is very large. These results indicate that second- and higher-order Born terms must be considered in calculating the cross section for inner-shell electron capture (or the time-reversed process).