We present high resolution photoelectron energy spectra from multiphoton ionization (MPI) of Ar subject to laser pulses with wavelength of 400 nm, pulse duration of 35 fs, and maximum intensity of 5×1013 W/cm2. Ionizations into Ar+ 2P3/2 and 2P1/2 channels are observed and distinct resonance structures are found in both ionization channels. The intensity dependence of the resonance structures is explained in terms of th