  We study the stationary scattering theory for the matrix Schr\"odinger
equation on the half line, with the most general boundary condition at the
origin, and with integrable selfadjoint matrix potentials. We prove the
limiting absorption principle, we construct the generalized Fourier maps, and
we prove that they are partially isometric with initial space the subspace of
absolute continuity of the matrix Schr\"odinger operator and final space
$L^2((0, \infty))$. We prove the existence and the completeness of the wave
operators and we establish that they are given by the stationary formulae. We
also construct the spectral shift function and we give its high-energy
asymptotics. Furthermore, assuming that the potential also has a finite first
moment, we prove a Levinson's theorem for the spectral shift function.
