NO and CO adsorption on a self-assembled layer of quasi-one-dimensional (1D
) halogen-bridged Pt chains is investigated. An anomalous, long-range adsor
bate-adsorbate interaction is indicated by temperature programmed desorptio
n and scanning tunneling microscopy. The adsorbates trigger a transition in
to a charge density wave (CDW) groundstate. The coverage dependent concentr
ation of solitons partly accounts for the observed variation of the desorpt
ion energy.