Atomic physics with super-high intensity lasers

Abstract

We review the phenonomena which occur in multiphoton physics when the electric field of the applied laser radiation becomes comparable with the Coulomb field strength seen by an electron in the ground state of atomic hydrogen. This field is reached at an irradiance of approximately 3 × 10 16 W cm −2 . The normal perturbative photon-by-photon based picture of the interaction of individual electrons with the field is replaced by a tunnelling picture in which, in a time of the order of, or less than one optical cycle, atomic wavepackets are generated which escape the confining Coulomb potential. These wavepackets are strongly influenced by the laser, 'quiver' and may be accelerated back to the parent ion in a recollision process. Phase-coherent effects locked to the laser field become important: high harmonics are generated from these recollisions. We discuss the theory of such effects, and review progress in understanding how this quiver motion can be coherently controlled. We discuss ionization dynamics and review mechanisms by which atoms may be stabilized in very strong fields. Finally, we discuss relativistic effects which occur at very high-intensities.

Atomic plasma excitations in the field of a soft x-ray laser

“…tot U >> hω (11) and for the present case, according to equation 10 with t = 15 fs, by I >> 4 × 10 13 W cm -2 . For lower irradiances, the distribution of energy among the target atoms is no longer homogeneous but rather statistical and those atoms which are hit by photons absorb more than the mean absorption energy per atom.…”

“…Accordingly, the achievable charge states here should be, in fact, generally higher than predicted by the present model. It should be noted that the limit of the present semi-classical approach as defined by equation 11 corresponds also to the limit for ponderomotive energy of (quasi-)free electrons to, again, distinguish the non-perturbative from the perturbative regime [10][11][12].…”

“…In the spectral range of optical radiation, photon-electron interactions at ultra-high intensities may also be described by so-called non-perturbative theories [10][11][12]. Their applicability depends on the ponderomotive energy U p :…”

Multiphoton radiative recombination of electron assisted by a laser field

“…The process of harmonic generation is currently studied very actively with important advancements both in theory and experiment (for reviews see Refs. [1,2]). The laser stimulated bremsstrahlung plays the very important role in plasma physics, see recent experimental [3,4] and theoretical [5,6] works.…”

Cutoffs of high-energy plateaux for atomic processes in an intense elliptically polarized laser field

“…These features are well known in multiphoton processes involving bound atomic states (such as high-harmonic generation (HHG) and above-threshold ionization/detachment (ATI/ATD)) [1,2]; their occurrence has also been predicted recently for laser-assisted electron-atom scattering (LAES) [3]. Plateau effects are most pronounced for linear laser polarization, in which case the extent of the plateau regions (i.e.…”