We monitor the intensity dependence of photoionization of argon at 800 nm at
pulse durations of 100 fs employing momentum-resolved photoelectron
imaging spectroscopy. We compare our data with numerical solutions of the
time-dependent SchrC6dinger equation (TDSE) using a model potential for
argon and the single active electron approximation (SAE). We find quantitative
agreement in all dominant features in energy and angle. The energy and
angular distributions of the photoelectrons allow us to identify selective
dominant ionization channels.