  We consider a simple modification of the 1D-Laplacian where non-mixed
interface conditions occur at the boundaries of a finite interval. It has
recently been shown that Schr\"odinger operators having this form allow a new
approach to the transverse quantum transport through resonant heterostructures.
In this perspective, it is important to control the deformations effects
introduced on the spectrum and on the time propagator by this class of
non-selfadjont perturbations. In order to obtain uniform-in-time estimates of
the perturbed semigroup, our strategy consists in constructing stationary waves
operators allowing to intertwine the modified non-selfadjoint Schr\"odinger
operator with a 'physical' Hamiltonian. For small values of a deformation
parameter '{\theta}', this yields a dynamical comparison between the two models
showing that the distance between the corresponding semigroups is dominated by
|{\theta}| uniformly in time in the L^2-operator norm.
