  We present an experimental study on the photoionization dynamics of
non-resonant one-color two-photon single valence ionization of neutral argon
atoms. Using 9.3 eV photons produced via high harmonic generation and a 3-D
momentum imaging spectrometer, we detect the photoelectrons and ions produced
from non-resonant two-photon ionization in coincidence. Photoionization from
the $3p$ orbital produces a photoelectron scattering wave function with $p$ and
$f$ partial wave components, which interfere and result in a photoelectron
angular distribution with peak amplitude perpendicular to the VUV polarization.
The comparison between the present results and two previous sets of theoretical
calculations [Pan, C. & Starace, A. F. (1991). $\textit{Physical Review A}$,
44(1), 324., and Moccia, R., Rahman, N. K., & Rizzo, A. (1983).
$\textit{Journal of Physics B: Atomic and Molecular Physics}$, 16(15), 2737.]
indicates that electron-electron correlation contributes appreciably to the
two-photon ionization dynamics.
