  When a droplet is gently laid onto the surface of the same liquid, it stays
at rest for a moment before coalescence. The coalescence can be delayed and
sometimes inhibited by injecting fresh air under the droplet. This can happen
when the surface of the bath oscillates vertically, in this case the droplet
basically bounces on the interface. The lifetime of the droplet has been
studied with respect to the amplitude and the frequency of the excitation. The
lifetime decreases when the acceleration increases. The thickness of the air
film between the droplet and the bath has been investigated using interference
fringes obtained when the system is illuminated by low pressure sodium lamps.
Moreover, both the shape evolution and the motion of the droplet center of mass
have been recorded in order to evidence the phase offset between the
deformation and the trajectory. A short lifetime is correlated to a small air
film thickness and to a large phase offset between the maximum of deformation
and the minimum of the vertical position of the centre of mass.
