Effect of flow pattern in a supersonic nozzle reactor on product branching ratio for UV photolysis of UF6/CH4 mixtures

The product branching ratio was studied in relation to the radical scrambling mechanism of laser isotope separation of uranium. A mixture of UF6/CH4/Ar was irradiated either using a low-intensity cw-UV source (high-pressure Hg lamp, 250 nm ∼ 400 nm) or using high-intensity pulsed UV lasers (4th-harmonic YAG laser at 266 nm or KrF laser at 248 nm) in a supersonic nozzle reactor. While the latter gave a higher C2H6/CH3F ratio in the photoproduct than the former, the C2H6/CH3F branching ratio was found to disagree with the results reported in a static cell experiment. This anomaly in the results obtained using a supersonic nozzle reactor was well represented by a model proposed in this study which assumed no mixing before a shock wave zone and sufficient mixing after it, leading to complete suppression of radical recombination.