A method for the isotopic separation of at least two different isotopes of a body in gaseous form by: (a) converting into the form of a gas (SF6, UF6 or MoF6) the body of interest containing the sought isotope; (b) creating a flow of said gas at supersonic speed, of the laminar or slightly turbulent type; (c) exciting the molecules by laser; (d) inhibiting, by means of a laser, the nucleation of one of the isotopologs, thus forming less massive aggregates of said isotopolog than the aggregates formed by the molecules of the other isotopolog; (e) ionizing the molecules and aggregates of said gas; (f) submitting the ionized molecules and aggregates of molecules to an electromagnetic field to make the ionized molecules and aggregates of one of the isotopologs migrate towards the outside of the flow; and (g) retrieving the part of the gas flow with the highest concentration in the sought isotope.