Laser-atom interacts: the electron at the mercy of the laser (Vol. 43 No. 3)

image Double-differential electron momentum distributions

The interaction between atoms and intense electromagnetic pulses with durations in the (sub) femtosecond time domain has proved to be a powerful tool to understand the dynamics of electrons inside matter. Among the theoretical methods developed to describe the electronic transitions produced by such ultrashort pulses we can mention the Coulomb-Volkov (CV) approximation, in which the combined action of both the atomic and laser potentials is taken into account only in the final channel. The CV approach has become a widespread method to investigate the physics behind photoinduced ionization processes. Nevertheless, it fails when the perturbative conditions are not fulfilled, for instance, when the ionization produced by an intense laser field takes place in an effective time much shorter than the pulse duration, or when the ionization requires multiphoton transitions.

Here we propose a doubly distorted CV (DDCV) model that goes beyond the standard CV theory by incorporating the effect of the laser field on both the initial and final electronic states on an equal footing. This improvement allows the method to account for dynamic Stark effects, which play an important role for long electron excursions originated by the laser electric field.

We found that the DDCV approach provides reliable predictions of photoinduced electron emission distributions from H(1s) for different field intensities and wavelengths, including a range of laser parameters where the CV approach is inadequate. In addition, the extension of the DDCV approximation to complex atoms and molecules appears to be perfectly viable.

Doubly-distorted-wave method for atomic ionization by ultrashort laser pulses
M. S.Gravielle, D. G.Arbó, J. E. Miraglia and M. F. Ciappina, J. Phys. B: At. Mol. Opt. Phys. 45, 015601 (2012)