Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

3 MASS SPECTROMETRY 301Stainless steelHeating elementElectron beamQuartz thimbleFig. 6. Thermal reactor and ion source.accuracy. In order to make possible quantitative measurements of rates of radicalreactions, a modification to the apparatus was introduced by Ingold and Los~ing''~who arranged for the furnace to be moveable with respect to the sampling orifice.In this way they were able to ascribe changes in molecule and radical concentrationsto the change in reaction time when the furnace was moved. A wide varietyof radicals has been produced thermally and studied by Lossing's group since 1952:Lossing has given a list"' of the radicals investigated up to 1963.A similar flow and mass spectrometer inlet system has been developed by Lossingfor the investigation of photochemical systems. Mercury photosensitization wasused so that the concentration of rhdicals should be within the limits of sensitivityof the mass spectrometer. With the light intensities used in experiments with acetone"',80 % of the reactant could be decomposed with an exposure time of 0.002sec. Laterpermitted variation of the exposure time by alteringRefkrences pp. 336-342