FTIR SPECTROSCOPY OF UF6 CLUSTERING IN A SUPERSONIC LAVAL NOZZLE

The clustering of UF6 seeded in Ar was observed in a continuous supers onic Laval nozzle flow. The onset conditions for UF6 clustering were i nvestigated by measuring the FTIR spectra of UF6 monomer and clusters in the nozzle. The onset conditions for the clustering, temperature, d ensity of UF6 (or partial pressure), and cooling rate, were determined as {130 K, 0.009 mol m(-3) (10 Pa), 0.6 x 10(6) K s(-1)} and {155 K, 0.06 mol m(-3) (80 Pa), 1.5 x 10(6) K s(-1)}. The onset temperature de termined here was higher by 40-50 K than that determined by a light-sc attering method. The frequency shift of the main peak of the UF6 clust ers from the monomer peak was about -17 cm(-1), which was smaller than the shift of the crystalline UF6 by about 11 cm(-1). The increase in temperature caused by the heat of condensation and the change of the s pectra of UF6 clusters with the growth after the onset were also obser ved. It was shown that the clustering rate due to the collision betwee n the monomer and cluster is much higher than that due to the collisio n between the monomers.