  The field-theoretical description of quantum fluctuations on the background
of a tunneling field $\sigma$ is revisited in the case of a functional
Schrodinger approach. We apply this method in the case when quantum
fluctuations are coupled to the $\sigma$ field through a mass-squared term,
which is 'time-dependent' since we include the dynamics of $\sigma$ . The
resulting mode functions of the fluctuation field, which determine the quantum
state after tunneling, display a previously unseen resonance effect when their
mode number is comparable to the curvature scale of the bubble. A detailed
analysis of the relation between the excitations of the field about the true
vacuum (interpreted as particle creation) and the phase shift coming from
tunneling is presented.
