Infrared multiple-photon decomposition of perfluorodimethyl ether

Infrared multiple-photon decomposition (IRMPD) of perfluorodimethyl ether, (CF3)2O, induced by a pulsed CO2 laser has been studied as functions of pulse number, laser wave-number, laser fluence, and reactant pressure. The decomposition gave carbonyl fluoride (54 %), carbon monoxide (24 %), hexafluoroethane (37 %) and carbon tetrafluoride (5 %) as main products, and tetrafluoroethylene (<1 %) and difluoroacetylene (<1 %), where the numbers in parentheses show the product yields relative to the (CF3)2O decomposition yield. The product distribution and the (CF3)2O decomposition yields changed depending on experimental parameters. The observed results are explained on the basis of the unimolecular decomposition of highly vibrationally excited (CF3)2O produced in the IRMP absorption process. The overall mchanism involves homolytic cleavage of the C-O bond to form trifluoromethyl and trifluoromethoxyl radicals, subsequent radical-radical reactions, and fragmentation of hot radicals or products. The 18O separation in the IRMPD of (CF3)2O has been extensively studied under various experimental conditions. The measurements of the isotope 18O/16O in CO were carried out using GC-MS system. The separation selectivity showed a maximum value of 2.5 in the irradiation of 3.5 Torr (CF3)2O with laser pulses at 940.55 cm-1 and 15 J.cm-2, where the conversion was 1.4 %. However, the selectivity decreased with increasing pulse number, fluence, and pressure. (author)