Method of isotope separation

A method of isotope separation which consists in carrying out the irradiation of a molecular isotopic mixture composed of molecules of the type .sup.1 MX.sub.n and .sup.2 MX.sub.n where .sup.1 M and .sup.2 M are two isotopic species of the atom M with a beam of monochromatic laser light with energy h.nu. in resonance with the energy difference between two vibrational levels of an isotopic species of molecules .sup.1 MX.sub.n and the molecules .sup.1 MX.sub.n and .sup.2 MX.sub.n are then also caused to interact with the atoms of a neutral gas E in superactivated form, wherein said interaction is carried out in the so-called Rydberg state E** in order to convert said molecules to negative ions by capture of the electrons released by the Rydberg atoms in accordance with the reactions:

• .sup.1 MX.sub.n +h.nu..fwdarw..sup.1 MX.sub.n *
• E**.fwdarw.E.sup.+ +e.sup.-
• .sup.1 MX.sub.n *+e.sup.- .fwdarw..sup.1 MX.sub.n-1.sup.- +X
• .sup.2 MX.sub.n +e.sup.- .fwdarw..sup.2 MX.sub.n.sup.-