Adiabatic mechanism of the multiply charged ion production by a laser field through ATI states of an atom

Abstract

ATI can be followed by an inelastic collision of the ionized electron with the parent atomic particle resulting in an excitation of the ion. It may be a continuum state excitation producing the doubly charged ion or a discrete state which also enhances the doubly charged ion production. Absorption of a few quanta above the atomic threshold is sufficient to make this mechanism work. As a result the two-electron processes can take place even in moderate fields. The example of two-electron excitations of He atoms in a 780 nm laser field with intensity above $ 10^{14}$W/cm$^2$ is discussed