Ionization Photoionization Sturmian Sturmian functions Atoms Double ionization Impact ionization Molecules Photons Single photo ionization Asymptotic behaviors Asymptotic boundary conditions Cross sections Double photoionization Electron impact Expansion coefficients Generalized Sturmian functions Low-intensity lasers Many-electron atoms Molecular orientation Molecular systems Particle spectrometers Photoionization molecules Photoionization transitions Photon absorptions Realistic potentials Scattering functions Scattering potentials Schrodinger equation Short laser pulse