Abstract
A fuel-rich (Φ=1.79) m-xylene flame (7.3% m-C8H10, 42.7% O2, 50.0% Ar) at low-pressure (40 mbar) was investigated with focus on the reactive fuel radicals (C8H9) and the first decomposition steps leading to C8H8 isomers. The results show that an isomerization of the m-xylyl radical to o- and p-xylyl must take place to explain the observed intermediates in agreement with pyrolysis experiments. Important higher polycyclic aromatic hydrocarbons (PAHs) relevant to soot formation were also identified. All Measurements were performed with a molecular-beam mass spectrometry (MBMS) setup at the Swiss Light Source (SLS), where single-photon ionization with VUV radiation offers soft ionization of the sampled species. Isomer-selective detection with unprecedented resolution is achieved by a combination of time-of-flight mass spectrometry and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. In principle, species can be identified by comparison of measured ionization efficiency (PIE) curves with known or calculated ionization energies of expected species. For convoluted signals of several species, this procedure works well for the isomer with the lowest ionization energy. Changes in the slopes of the ionization efficiency curve do not necessarily correlate with ionization thresholds of other isomers and the assignment of higher thresholds can become difficult. PEPICO spectrometry, which detects the electrons that are produced in the ionization process in coincidence with the ions, enables the measurement of mass-selected threshold photoelectron spectra (ms-TPES). These spectra improve the detection capability of isomers because vibrational transitions from the neutral into ionic states can be observed and used as a fingerprint of a specific molecule. The obtained ms-TPES are compared with reference spectra from the literature or Franck–Condon simulations. Quantification of the major species as well as several intermediate species for this fuel-rich m-xylene flame yields a data set for model validation and experimental results are compared with five kinetic reaction models from the literature.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.