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In this work I present a model obtaining the vector potential of the laser field in U=0 gauge by numerically solving the Maxwell equations. The proposed model is valid in the long wave length approximation, i.e. for energies less than 100 eV or wavelength greater than 124 angstroms. In this case the laser "sees" only the sharp rise of the electron density at the gas-solid interface not the particular atoms of the solid. But this electron density rise takes place at a sub-nanometric scale and therefore in the present model one assumes that the dielectric function and the electromagnetic field is explicitly dependent on the spatial coordinate.
More precisely to model the electromagnetic field of the laser, I solved the Maxwell equations using the macroscopic material constants function of photon energy and of the coordinate perpendicular to the interface. The spatial dependence of the material constants is introduced through the total normalized unperturbed electron density of the physical system. The resulting vector potential in local and scalar approximation is classical, function of the incident angle of the laser and continuous at the gas-solid interface.
The preliminary calculations for a gas-Al(001) interface are performed for a p polarized laser with a vector potential in the local and isotropic approximation. They show that the absorbed power density of the laser follows qualitatively the experimental findings but, on an absolute scale, the total number of electrons reaching the surface is too low. The model will be applied in the future for the study the surface photoelectron effect of gas-Al(001) interface in the 5-20 eV energy range.
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