When a pulsed gas dynamically cooled supersonic molecular flow interacts with solid surface a cold shock wave is formed in front of it, non-equilibrium conditions in which may be 'reverse' to those in the incident (unperturbed) flow. Isotopically selective infrared multiphoton dissociation of SF, in the cold shock wave was studied. Anomalously a large increase (more than one order of magnitude) of the yield of products was found, as compared with the case of excitation of SF, in unperturbed flow, without essential decrease of the selectivity of process.