Is this where we are at?, page-22

cjliebs - It would also appear to me that for a small molecule the mass difference between the dimers and monomers would enhance enrichment.

For example with centrifuge and ASP the atomic weight difference is from Mo₁₀₀ to Mo₉₈ (the next stable and more common Mo atom) is 2 and centrifuge/ASP can only use this mass difference for enrichment. It would appear that for centrifuge an important criteria is the ratio of the mass difference (i.e 2 for Mo₉₈ to Mo₁₀₀ and 3 for U₂₃₈ to U₂₃₅) to the atomic weight (i.e 100 for Mo and 238 for uranium). So for Mo the ratio would be roughly 0.02 whilst for U it would be .012 (i.e only a slight improvement).

Whereas for LIS with a heavy carrier gas (G) the recoil of the excited monomers from the dimers would be greater for a lighter molecule (e.g Molybdenum/G) than for a heavier molecule (e.g. uranium/G) also any centrifugal forces would be similarly enhanced since the ratio between the monomer and dimer mass would be much greater than for centrifuge. It would appear to me that enrichment factors with Mo should be greater than for Uranium due to these effects and a distinct advantage over centrifuge/ASP.