Enrichment of 13C by IRMPD of CBr2F2

Abstract

The CO2-laser-induced infrared multiple photon decomposition of natural CBr2F2 in the presence of oxygen has been examined as a function of pulse number (30–1500), reactant pressures (CBr2F2, 10–150 Torr and O2, 5–90 Torr), laser line [9P(8)–9P(32)], and laser fluence (1–3 J cm−2) to optimize irradiation conditions for 13C-enrichment. CF2O was the main carbon containing product and afterwards was converted into CO2 via hydrolysis. A small amount of C2Br2F4 was detected only under extreme conditions, for example, at high laser fluences or wavenumbers close to an absorption band. The 13C-atom fraction of the final product CO2 was found to be 20–80%, depending on experimental conditions. The two-stage IRMPD process proposed previously has been examined in further detail in the present study. First, CBr2F2 containing about 30% of 13C was prepared in the 13C-selective IRMPD of natural CHClF2 in the presence of Br2. The second-stage IRMPD of the CBr2F2 in the presence of oxygen under selected conditions resulted in the high enrichment of 13C beyond 90%.