Atoms in strong laser fields

The formalism developed so far is adequate whenever the motion of the atomic nuclei can be neglected. Then the electron-nucleus interaction only enters as a static contribution to the potential r(r, t) in Eq. (41). This is a good approximation for atoms in strong laser fields above the infrared frequency regime. When the nuclei are allowed to move, the nuclear motion couples dynamically to the electronic motion and the situation becomes more complicated. 

A new conceptual framework for the ionisation of many-electron atoms in strong laser fields has been introduced [490], based on different principles (see section 9.26). According to this picture, multiple ionisation does not proceed sequentially in a superstrong field instead, the mechanism for excitation and ionisation depends explicitly on the duration of the laser pulse. This model suggests a situation closer to option (iv) of section 9.18 multiple ionisation is not intrinsically dependent on correlations or on the existence of closed shells, both of which are considered to be washed out in the presence of the strong field. However, it must occur simultaneously rather than sequentially, because of the nature of the interaction. 

Atoms in strong laser fields 9.24 General discussion of strong field effects... 

In the present chapter, the rapidly growing subject of atoms in strong laser fields has been briefly described, the main emphasis being on the novel effects which have been observed. Several aspects of the problem have not been discussed for example, above 1020 Wcm-2, relativistic effects will become important, although these have not yet been observed. Similarly, we have omitted any discussion of coherent control in two-colour excitation and femtosecond chemistry. 

Multiphoton processes taking place in atoms in strong laser fields can be investigated by the non-Hermitian Floquet formalism (69-71,12). This time-independent theory is based on the equivalence of the time-dependent Schrodin-ger description to a time-independent field-dressed-atom picture, under assumption of monochromaticity, periodicity and adiabaticity (69,72). Implementation of complex coordinates within the Floquet formalism allows direct determination of the complex energy associated with the decaying state. The... 

Th. Mercouris, C.A. Nicolaides, Polyelectronic theory of atoms in strong laser fields. C02-laser seven-photon ionisation of H, ]. Phys. B 21 (1988) L285. 

To better understand the process of ionization of an atom in strong laser fields, it is convenient to resort to a simple quasi-static picture. In Fig. 4.6... 

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