  We report on a combined experimental and theoretical study of XUV ionization
of atomic argon in the presence of a near-infrared laser field. The resulting
energy- and angle- resolved photoemission spectra have been described in the
literature as interferences among different photoionization trajectories.
Electron trajectories stemming from different optical laser cycles give rise to
\textit{intercycle} interference energy and result in new peaks known as
sidebands. These sidebands are modulated by a coarse grained (gross) structure
coming from the \textit{intracycle} interference of the electron trajectories
born during the same optical cycle. We calculate the photoelectron emission by
solving the time-dependent Schr\"{o}dinger equation \textit{ab initio} and
within the continuum-distorted wave strong field approximation. In order to
compare with the experimental data we average the calculated energy-angle
probability distributions over the experimental focal volume. This averaging
procedure washes out the intracycle interference pattern, which we
experimentally and theoretically (numerically) recover by subtracting two
averaged distributions for slightly different near-infrared laser field
intensities.
