  We investigate macroscopic quantum tunneling of a Bose condensate and how it
is affected by the interatomic interaction. We study the dynamics of a
condensate falling under gravity and scattering on a Gaussian potential barrier
that models a mirror formed by a far-detuned sheet of light. We observe
bouncing, interference and quantum tunneling of the condensate. We find that
the tunneling rate is very sensitive to the interatomic interaction and to the
shape of the condensate. Under many conditions the tunneling rate is strongly
enhanced by the interaction as achieved, for instance, by increasing the number
of condensed particles. In a quasi 1D situation the tunneling pulse displays
two peaks. The quantum tunneling can be quasi-periodic and in this way one
could generate coherent Bose condensed atomic pulses.
