Atomic ionization 4 Atoms 4 Differential equations 4 Initial state 4 Integrodifferential equations 4 Ionization 4 Ionization amplitude 4 Analytical models 2 Atom lasers 2 Hydrogen ionization 2 Laser pulses 2 Numerical solution 2 Other discrete 2 Semi-analytical model 2 Short laser pulse 2 Strong field 2 Volterra integro-differential equations 2 Weisskopf-Wigner approximation 2