The excitation of a hydrogen beam by the shielded Coulomb potentials of the ionic cores of an Au-foil is calculated in first Born approximation for a beam velocity v = 1.4 a.u. Different formation depths of the final 2p term are considered and weighted with the survival probability. Stokes parameters for the emitted light are compared with He (n = 3 ~ 2) transitions. It is demonstrated that the coherence of the excitation by neighbouring target cores tends to reduce the excitation amplitudes for the 2pro states with m:t=0. Adsorbates are estimated to have a considerable effect on the polarization. PACS: 34.50. Fa