  The effect of rotation upon the classical two-layer Rayleigh-Taylor
instability is considered theoretically and compared with previous experimental
results. In particular we consider a two-layer system with an axis of rotation
that is perpendicular to the interface between the layers. In general we find
that a wave mode's growth rate may be reduced by rotation. We further show that
in some cases, unstable axisymmetric wave modes may be stabilized by rotating
the system above a critical rotation rate associated with the mode's
wavelength, the Atwood number and the flow's aspect ratio. We compare our
theory with experiments conducted in a magnetic field using 'heavy' diamagnetic
and 'light' paramagnetic fluids and present comparisons between the theoretical
predictions and experimental observations.
