An experimental approach is described for obtaining highly enriched residual gas under
IR multiphoton dissociation (MPD) of molecules in one cycle of irradiation. The
approach is based on utilization of a pulsed molecular flow of small length (Δxfl≤1cm).
The use of a short flow length leads to high values of the dissociation yield of molecules
(β≃1) in the whole volume of the flow. Owing to this, high enrichment of the residual
gas is achieved in one cycle of irradiation. The isotopically-selective dissociation of CF3I+
in the pulsed gasdynamic flow of a small length was studied. About 400-fold enrichment
of the 13C isotope in the residual gas was obtained following irradiation of a molecular
flow of CF3I of natural isotope composition by a single laser pulse. The selectivity of
dissociation was measured to be α≥10
