  Thin, viscous liquid films subjected to impact events can deform. Here we
investigate free surface oil film deformations that arise due to the air
pressure buildup under the impacting and rebouncing water drops. Using Digital
Holographic Microscopy, we measure the 3D surface topography of the deformed
film immediately after the drop rebound, with a resolution down to 20 nm. We
first discuss how the film is initially deformed during impact, as a function
of film thickness, film viscosity, and drop impact speed. Subsequently, we
describe the slow relaxation process of the deformed film after the rebound.
Scaling laws for the broadening of the width and the decay of the amplitude of
the perturbations are obtained experimentally and found to be in excellent
agreement with the results from a lubrication analysis. We finally arrive at a
detailed spatio-temporal description of the oil film deformations that arise
during the impact and rebouncing of water drops.
