Tunable
synchrotron-sourced photoionization time-of-flight mass spectrometry (PI-TOF-MS) is an important technique in combustion chemistry, complementing lab-scale electron impact and
laser photoionization studies for a wide variety of reactors, typically at low pressure. For high-temperature and high-pressure chemical kinetics studies, the
shock tube is the reactor of choice. Extending the benefits of
shock tube/TOF-MS research to include
synchrotron sourced PI-TOF-MS required a radical reconception of the
shock tube. An automated, miniature, high-repetition-rate
shock tube was developed and can be used to study high-pressure reactive systems (T > 600 K, P < 100 bar) behind reflected
shock waves. In this paper, we present results of a PI-TOF-MS study at the Advanced Light Source at Lawrence Berkeley National Laboratory.
Dimethyl ether pyrolysis (2% CH3OCH3/Ar) was observed behind the reflected
shock (1400 < T5 < 1700 K, 3 < P5 < 16 bar) with ionization energies between 10 and 13 eV. Individual experiments have extremely low signal levels. However, product species and radical intermediates are well-resolved when averaging over hundreds of shots, which is ordinarily impractical in conventional
shock tube studies. The signal levels attained and data throughput rates with this technique are comparable to those with other
synchrotron-based PI-TOF-MS reactors, and it is anticipated that this high pressure technique will greatly
complement those lower pressure techniques.