Patent ID: 6653587
Filing Date: 2003-11-25
Classification: B01D

Abstract:
A method of separating a desired isotope from a starting material comprising polyatomic molecules containing different isotopes, by applying to said molecules in the gas phase, at a predetermined pressure P, infrared radiation of a first pulsed laser to excite by a single photon an overtone transition of a light-atom stretch vibration of said molecules to produce vibrationally pre-excited molecules enriched in the desired isotope, and, infrared radiation of a second pulsed laser of different frequency to induce a chemical reaction resulting in a molecule constituting a dissociation product, enriched in the desired isotope, which can be separated from the starting material, wherein:the radiation of the first laser has a predetermined frequency optimized to select the desired isotope via a single-photon transition; the first laser pre-excites the polyatomic molecules to an excited vibrational level that is high enough in energy to allow an increase in isotopic selectivity by collisions; the radiation of the second laser selectively induces dissociation of the vibrationally pre-excited molecules by infrared multiphoton excitation, at a time &Dgr;t after the pre-excitation by the first laser pulse; the pressure, P, and the time, &Dgr;t, between the pre-excitation by the first laser pulse and the dissociation during the second laser pulse have a pressure-time product PÂ·&Dgr;t, the magnitude of this pressure-time product PÂ·&Dgr;t being sufficiently high to allow collisional vibrational deactivation of a substantial amount of the vibrationally pre-excited molecules containing non-desired isotope(s) before dissociation of the vibrationally excited molecules occurs while achieving significantly less collisional vibrational deactivation of the pre-excited molecules containing the desired isotope; whereby said collisions that occur in said time &Dgr;t between pre-excitation by the first laser pulse and the dissociation during the second laser pulse enhance the isotopic selectivity of the isotopic separation method, such that said dissociation products is highly enriched in the desired isotope.