The efficiency of classical gas-dynamic isotope sepn. can be strongly improved with the aid of a relatively weak IR laser. Irradn. in the collisional region of a free jet of SF6 dild. in Ar with a 20-W CO2 laser leads to an increase in the overall enrichment factor a from .apprx.1.01 to nearly 2, at conditions that were not yet completely optimized. Efficient isotopically selective condensation is demonstrated for the 1st time, the inhibition of homogeneous condensation being due to the selective vibrational excitation of 1 SF6 isotopomer.