Photoionization mass spectrometer for studies of flame chemistry with a synchrotron light source

Abstract

A flame-sampling molecular-beam photoionization mass spectrometer, recently designed and constructed for use with a synchrotron-radiation light source, provides significant improvements over previous molecular-beam mass spectrometers that have employed either electron-impact ionization or vacuum ultraviolet laser photoionization. These include superior signal-to-noise ratio, soft ionization, and photon energies easily and precisely tunable [E/E(FWHM)250–400] over the 7.8–17-eV range required for quantitative measurements of the concentrations and isomeric compositions of flame species. Mass resolution of the time-of-flight mass spectrometer is m/m=400 and sensitivity reaches ppm levels. The design of the instrument and its advantages for studies of flame chemistry are discussed

Detection and Identification of the Keto-Hydroperoxide (HOOCH2OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether

“…In this study, species with up to four oxygen atoms were identified and their elemental When probing complex systems, like low-and high-temperature combustion processes, it can be challenging to unambiguously identify the source of the observed signal in the mass spectrum: it could be due to the reactants, intermediates, or products of the combustion process including their isomeric contributions from 13 C and 18 O or it could be due to fragmentation processes of individual components. 66,69,80 By experimentally determining and theoretically calculating the ionization energy (IE) of these species and the appearance energy (AE) of their fragments, we are able to interpret the observed mass spectra in significant detail and assign the constitutional formulae to their isomeric structures. As we discuss below, these newly detected species are expected to be key intermediates in the low-temperature oxidation processes of DME.…”

Chemical dynamics, molecular energetics, and kinetics at the synchrotron

“…47,48 While the overall design of the instrument 49 follows well established techniques, a key innovation of this instrument is the use of tunable VUV photoionization mass spectrometry for flame analysis. This approach allows researchers to examine the isomeric composition of stable molecules and radical species generated in a flame essentially in situ.…”

VUV Photoionization Cross Sections of HO2, H2O2, and H2CO

“…The photoionization spectrum of propene is well-known 6 and has been used previously as a reference compound for determining photoionization cross sections. 5,[7][8] Experiments were conducted by introducing propene (2 sccm of 1.00% propene in He) and methanol (1 sccm of 4.667% methanol in He) into the flow tube. Propene was Matheson Tri-Gas, 1.00% in Ar.…”