Laser isotope separation by multiple photon absorption

A method is claimed for obtaining elemental values enriched in a particular isotope of the element which comprises: 1) obtaining a fluid containing a molecular species containing two or more isotopes, and having, in the presence of sufficiently intense laser radiation, a density of vibrational levels sufficient to allow multiple photon absorption to higher vibrational levels, 2) irradiating the fluid with infrared laser radiation of a frequency which selectively excites to a first lower vibrational level those molecules of the molecular species containing a particular isotope of the element thereby producing a vibrational state at which the molecules containing the particular isotope undergo chemical reaction, and 3) separating the reaction products