  In this paper, we consider the Schr\"odinger equation in one space-dimension
with potential and we aim at exhibiting dynamic interaction phenomena produced
by the potential. To this end, we focus our attention on the time-asymptotic
behaviour of the two first terms of the Dyson-Phillips series, which gives a
representation of the solution of the equation according to semigroup theory.
The first term is actually the free wave packet while the second term
corresponds to the wave packet resulting from a first interaction between the
free solution and the potential. In order to follow a method developed in a
series of papers and aiming at describing propagation features of wave packets,
we suppose that both the potential and the initial datum are in bounded
Fourier-frequency bands; in particular a family of potentials satisfying this
hypothesis is constructed for illustration. We show then that the two terms are
time-asymptotically localised in space-time cones which depend explicitly on
the frequency bands. Since the inclination and the width of these cones
indicate the time-asymptotic motion and dispersion of the two terms, our
approach permits to highlight interaction phenomena produced by the potential.
