10.5-eV photoionization mass spectrometry of aliphatic compounds

Abstract

Vacuum ultraviolet photoionization by coherent 10.S-eV radiation is evaluated for soft ionization of organic molecules. Coherent 10.5-eV radiation is produced by frequency tripling the third harmonic of an Nd:YAG laser (355 nm) in a mixture of xenon and argon. A number of intermediate size, C/> to C g , aliphatic compounds are studied to determine the extent and characteristics of fragmentation. Compared with 12-eV electron impact ionization, all show higher molecular ion abundances, less fragmentation, and signiftcant enhancement of low energy rearrangement ions. n-Alkanes, alkenes, ketones, carboxylic acids, and ethers all form predominant molecular ions. Aldehydes and amines show significant molecular ion abundances but also extensive fragmentation. Branched alkanes, dienes, alcohols, and esters show little or no molecular ion, but do have a single dominant fragment ion. Metastable broadening in these spectra gives qualitative information on the energetics of low energy rearrangements.

Chemical species associated with the early stage of soot growth in a laminar premixed ethylene–oxygen–argon flame

“…1:10 ratio of Xe:Ar. The resultant 118-nm photons (10.5 eV) gently ionize the plume [36]. Because typical ionization potentials for PAHs are on the order of 8 eV, fragmentation of PAHs is minimal.…”

Vacuum Ultraviolet Radiation for Single-Photoionization Mass Spectrometry: A Review

“…The VUV generator includes a Nd:YAG laser, a xenon tripling cell with a pump and pressure gauge, a silica focusing lens, a MgF 2 collimating lens, and a MgF 2 window (5). (9). In the design above, partial spatial separation of the 118 nm (VUV) and the 355 nm (UV) light was achieved by focusing the VUV light to pass through 2 mm, colinear holes on the centerline of the ion trap ring electrode, while most of the collimated 355 nm light was dumped on the outside of the ring electrode.…”

Chemical Composition of Diesel/Biodiesel Particulate Exhaust by FTIR Spectroscopy and Mass Spectrometry: Impact of Fuel and Driving Cycle

“…Another difference arises from the stronger intensity of m/z 42 and 56 peaks for the steady-state operating condition. These features are associated to the rearrangement of fragment ions from alkenes after the ionization process, as observed by Van Bramer and Johnston (1990) and Shi and Lipson (2005). axes represent loadings (molecules) scales.…”