Atoms in short, Intense, Laser Pulses: Application to Potassium and Helium
Άτομα σε ισχυρά ηλεκτρομαγνητικά πεδία: εφαρμογή στο κάλλιο και στο ήλιο
The central theme of this thesis is the theoretical study of the dynamics of atoms in short, intense laser pulses. The main focus is ih the numerical solution of the Time-Dependent Schrodinger Equation (TDSE), or approximations thereof. We have used the eigenbasis and B-Splines expansion of the time-dependent wavefunction in the single active electron picture to study Potassium in mid-infrared, short, intense laser pulses, a system that is currently under experimental investigation. We have obtained ionization curves for the 12-14 photon ionization range, and analyzed a dynamic resonance in the 13-photon ionization regime. We have confirmed the results of the TDSE methods by a calculation with the Floquet theory. The photo-electron spectra display a pattern of plateau scaling with the ponderomotive energy. We have studied the Helium atom in intense laser pulses using the Time-Dependent Hartree-Fock (TDHF) method [78,85]. We have used a non-uniform finite difference discretization on cylindical coordinates, imposed Neumann boundary conditions along the polarization axis, and used a multigrid Poisson solver for the resulting Hartree term. We have obtained ionization curves for 5 eV photons and a generalized cross section that agrees with the experiment.