Silicon isotope separation utilizing infrared multiphoton dissociation of Si2F6 irradiated with two-frequency CO2 laser lights

Silicon isotope separation has been performed utilizing the infrared multiphoton dissociation (IRMPD) of Si2F6 irradiated with two-frequency CO2 laser lights. The two-frequency excitation method improved the separation efficiency by keeping the high enrichment factors. For example, Si2F6 with the 28Si fraction of 99.4% was obtained at 40.0% dissociation of Si2F6 after the simultaneous irradiation of 100 pulses with 966.23 cm-1 photons (0.089 J/cm2) and 954.55 cm-1 photons (0.92 J/cm2), while 1000 pulses were needed to obtain 99.0% of 28Si at 27.2% dissociation in the case of single frequency irradiation at 954.55 cm-1 (0.92 J/cm2). The single-step enrichment factors of 29Si and 30Si increased with increasing Si2F6 pressure. The reason for this enhancement has been discussed in terms of the rotational and vibrational relaxations by collisions with ambient gases.