ION-MOLECULE REACTIONS IN SOOTING ACETYLENE-OXYGEN FLAMES

Ion concentration profile up to mass 557 amu were measured in a sooting acetylene-oxygen flame at an equivalence ratio of 3. 0, a total pressure of 2. 67 kPa, and an unburned gas velocity of 50 cm s** minus **1. The mass spectrometer was calibrated for mass by seeding flames with isotopes of several metals and by using deuterated acetylene, which also allowed us to measure the number of hydrogen atoms in each hydrogen ion. The ion concentration sensitivity of the mass spectrometer was calibrated by comparing the individual ion currents with the ion current obtained in operation as a high-pass mass filter (that is, transmitting only those ions whose masses were greater than a specific mass) and by relating these currents to the total ion concentrations determined using a Langmuir probe. Ion-molecule reactions, including those with large ions, were demonstrated to be rapid under these flame conditions.