High Enrichment of 28Si by Infrared Multiple Photon Decomposition of Si2F6.

Abstract

High enrichment of 28Si has been carried out using the laser isotope separation technique based on the isotopically selective infrared multiple photon decomposition of Si2F6. When about 2 Torr of Si2F6 was irradiated at a fluence of 1.0 J/cm2 per pulse with the 10P(8) line of a TEA CO2 laser at 954.55 cm-1, the compound decomposed very efficiently with high isotope selectivity. The products SiF4 and white solids were enriched with 29Si and 30Si, while the residual Si2F6 was enriched with 28Si. The atomic fraction of 28Si in residual Si2F6 increased with increasing decomposition of Si2F6; 99.9% of 28Si was obtained at a consumption of 50% of initial Si2F6. The large-scale flow experiment yielded 99.7% 28Si at a production rate of 2.5 g/h, where a mixture of 3.3 Torr Si2F6 and 6.6 Torr argon was irradiated with 10P(8) laser pulses at a repetition rate of 5 Hz. Merits and demerits of the present laser separation are discussed in comparison to those of conventional separation methods. Laser enrichment of 28Si seems promising for economical production of large quantity of pure 28Si. Various applications of silicon isotopes are briefly reviewed.