office of inspector general U.S. Department of Energy special report, page-100

Yes I understand that the v3 vibrational mode needs to be excited for any LIS to work; from what i understand the v3 mode is the important one to excited (at just below 16 micron) due to it being a lateral vibration which would cause the excited U235F6 to recoil off the carrier gas (which I assume is a heavy gas such as SF6 or Xe). As I understand it this has three effects namely (1) that the energy in the recoil is at right angles to the axis of flow (i.e to the periphery of the flow), (2) the U235F6 after recoil is now a single U235F6 molecule whilst the U238F6 is still in a dimer with the carrier - thus the mass difference is now the dimer of the carrier gas + U238F6 dimer as against a single U235F6 molecule (now in recoil) and possibly (3) that an excited U235F6 molecule condenses (in a super cooled state) at a lower temperature than an unexcited (U238F6) molecule. I am a bit unclear how these attributes (if correct) play out against each other in Silex vs CRISLA. The other issue I am unclear about is that simply fireing the laser across the feedstock stream would not (to me) the omst effective way of irradiating the feedstock stream. it would seem to me that firing the laser axially down (or up) the stream would be more effective (i.e the transit time under the 16 micron laser would be increased) or alternatively the laser passing laterally through the feedstock stream was then given a second pass by using 16 micron mirrors (if there are such things) to reflect the exiting beam to be recycled to pass back laterally through the feedstock in the vertical lateral direction also (i.e getting two bangs for the buck) - in this way you either get a bit more exciting energy back into the U235F6 or possibly by inserting a short time delay into the reflected beam could halve the CO2 laser pulse frequency (which at 30,000/sec for irradiation of the full stream) is very stretched technology. Maybe I have got thing wrong in my thoughts or I am asking for too much detail - but there's no harm in asking).

Just trying to get things clear in my head