Dissociative Recombination of Acetone Ions with Electrons

National audienceDissociative recombination (DR) is the reaction in which a molecular ion recombines with an electron and dissociates into neutral fragments, and general reviews of this subject have been given by Florescu-Mitchell and Mitchell [1], Larsson and Orel [2] and Adams and co-workers [3]. This process plays a major role in the evolution and composition of interstellar gas clouds and planetary ionospheres as well as in industrial processing and nuclear fusion plasmas. The molecule that have been studied is acetone (CH 3 COCH 3). Fragment ions, the parent ion, adduct ions and dimer ions were seen to be formed with relative concentrations which depended upon the density of reagent gas in the flow tube. Dissociative recombination for the individual ions (with the exception of the dimer ions) were then measured using three different measurement protocols. (Values of a few x 10-6 cm 3 s-1 were found for the ions measured (CH 3 CO + , CH 3 COCH 3 + , CH 3 .CH 3 COCH 3 + , CH3CO.CH 3 COCH 3 +). This is an excellent test case for demonstrating the unique character of the FALP-MS apparatus since comparable apparatuses in Europe and the US, which do not have movable mass spectrometers, are generally limited to conditions where only a single ion species is present in the flow