Photochemical isotope separation

This patent describes a process for separating isotopes. The steps are: irradiating a gaseous compound having molecules each of which contains at least one nuclide of a first isotopic species to be separated and further having different excitation energy levels depending on which isotopic species is present with radiation having a first wavelength which substantially excites molecules of the compound containing the first isotopic species; and subjecting the exited molecules to physical or chemical processes other than photodeflection, or a combination thereof, whereby the first isotopic species contained in the excited molecules is separated from the isotopic species contained in the unexcited molecules. The improvement comprises first, mixing of the gaseous compound with a carrier gas having a low condensation temperature, and a ratio of specific heats in which γ is greater than that for the gaseous compound; second, adiabatically expanding the gaseous mixture whereby the gaseous compound is vibrationally cooled and sufficient spectrum simplification has occurred that the radiation preferentially excites molecules of the compound containing the first isotopic species; and third, subjecting the excited molecules to separative processes before substantial condensation occurs