1) Existing in the → state of a gas.
Fr.: diffusion gazeuse
An → isotope separation process using the different diffusion speeds of → atoms or → molecules for separation. This process is used to divide → uranium hexafluoride (UF6) into two separate streams of U-235 and U-238. Before processing by gaseous diffusion, uranium is first converted from → uranium oxide (U3O8) to UF6. The UF6 is heated and converted from a solid to a gas. The gas is then forced through a series of compressors and converters that contain porous barriers. Because uranium-235 has a slightly lighter isotopic mass than uranium-238, UF6 molecules made with uranium-235 diffuse through the barriers at a slightly higher rate than the molecules containing uranium-238. At the end of the process, there are two UF6 streams, with one stream having a higher concentration of uranium-235 than the other (EVS, a Division of Argonne National Laboratory).
Fr.: nébuleuse gazeuse
An → H II region, a → planetary nebula, or a → supernova remnant.