  Environmental effects are crucial to the understanding of the evolution of
galaxies in dense environments, such as galaxy clusters. Using the large
field-of-view of SITELLE, the unique imaging fourier transform spectrograph at
CFHT, we are able to obtain 2D spectral information for a large and complete
sample of cluster galaxies out to the infall region. We describe a pipeline
developed to identify emission line galaxies (ELGs) from the datacube using
cross-correlation techniques. We present results based on the spatial offsets
between the emission-line regions and stellar continua in ELGs from two
z$\sim$0.25 galaxy clusters, Abell 2390 and Abell 2465. We find a preference in
the offsets being pointed away from the cluster center. Combining the two
clusters, there is a 3$\sigma$ excess for high-velocity galaxies within the
virial radius having the offsets to be pointed away from the cluster center.
Assuming the offset being a proxy for the velocity vector of a galaxy, as
expected from ram pressure stripping, this excess indicates that ram pressure
stripping occurs most effectively during the first passage of an infalling
galaxy, leading to the quenching of its star formation. We also find that,
outside the virial region, the continuum-normalized H$\alpha$ line flux for
infalling galaxies with large offsets are on average lower than those with
small or no measurable offset, further supporting ram pressure as a dominant
quenching mechanism during the initial infall stages.
