High Enrichment of²⁸Si by Infrared Multiple Photon Decomposition of Si₂F₆

Abstract

High enrichment of 28 Si has been carried out using the laser isotope separation technique based on the isotopically selective infrared multiple photon decomposition of Si 2 F 6 . When about 2 Torr of Si 2 F 6 was irradiated at a fluence of 1.0 J/cm 2 per pulse with the 10P(8) line of a TEA CO 2 laser at 954.55 cm −1 , the compound decomposed very efficiently with high isotope selectivity. The products SiF 4 and white solids were enriched with 29 Si and 30 Si, while the residual Si 2 F 6 was enriched with 28 Si. The atomic fraction of 28 Si in residual Si 2 F 6 increased with increasing decomposition of Si 2 F 6 ; 99.9% of 28 Si was obtained at a consumption of 50% of initial Si 2 F 6 . The large-scale flow experiment yielded 99.7% 28 Si at a production rate of 2.5 g/h, where a mixture of 3.3 Torr Si 2 F 6 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 28 Si seems promising for economical production of large quantity of pure 28 Si. Various applications of silicon isotopes are briefly reviewed.