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

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