Kinetics of Gas-Phase Radical Reactions Using Photoionization Mass Spectrometry with Synchrotron Source

Gas-phase radicals can react rapidly with various gaseous molecules, which play a vital role in catalyzing reactions in atmospheric, combustion and interstellar chemistry. A range of experimental techniques such as fluorescence and absorption spectrometry have been employed to study the reaction processes of gas-phase radicals and acquired some important results. Despite of the sufficient sensibility in the measurement of transient species, most of these techniques are limited to small radicals with small molecules, inaccessible to bigger radicals or multiplexed detection. Lately, a combination of flow reactor, flash laser photolysis and synchrotron radiation (SR) photoionization mass spectrometry (PIMS), serves as a universal, multiplexed, selective and sensitive method, ideal for the chemical kinetics study. Pulsed photolysis laser is used to initiate radical reaction, SR vacuum ultraviolet (VUV) light source to ionize the molecules emerging from the side pinepole and mass spectrometer to detect multiple species in the reactions (especially many-atom species). A plenty of original works such as the studies of CN, OH and alkylperoxy radical reactions have been done using double-focusing mass spectrometer or time-of-flight mass spectrometer and identified to be in fair agreement with the previous methods. Furthermore, the extra ordinary capability of time- and energy-resolution can be widely applicable in the kinetics study of some important radicals such as alkylperoxy and aromatic radicals in atmospheric, combustion, and interstellar chemistry.