Isotopically selective dissociation of COCl2 molecules in the radiation field of a pulsed CO laser

The first report is given of attainment of isotopically selective dissociation of carbonyl chloride COCl₂ molecules by radiation from a pulsed tunable uncooled electron-beam-controlled CO laser. Carbonyl chloride was labeled with ¹³C and ¹⁸O and the isotopic ratio was ¹²C¹⁶OCl₂:¹³C¹⁶OCl₂:¹²C¹⁸OCl₂ = 1:1:0.1, which made it possible to observe simultaneously the selectivity in respect of carbon and oxygen in the product (CO). The dissociation was produced by laser pulses of 0.5–1J energy (energy density ~5J/cm²) and of ~5μsec duration at half-intensity. The dependences of the selectivity a and of the dissociation yield on the pressure of the substance was studied in the course of irradiation of COCl₂ at the frequency corresponding to the P₁₀(22) (ν = 1822.0 cm^–1 ) transition in the CO laser. The selectivity in respect of the carbon ¹²C and oxygen ¹⁶O was the same, and it fell on increase in the pressure p of COCl₂. The maximum value of α≈4 was obtained at p = 0.5 Torr.