Samples were drawn from sooting premixed low-pressure ethylene oxygen flames and investigated through photoionization mass spectrometry using either KrF or ArF lasers as the radiation source. With the former, mass spectra were obtained as described in the literature and characterized through a series of signal groups, one for each C-number and extending to about m/z 1000, assigned as a PAH series. When the ArF laser was used the same series was observed with a somewhat higher sensitivity. In addition, a new series was observed overlaid on the PAH series and starting at about m/z 680. The new series exhibited abundant ions and it completely dominated the spectrum beyond m/z 1000. This series was identified as being the spectrum of soot precursor particles. Through measurement of the ionization order it was concluded that at least two photons are needed for ionization of PAHs whereas the particles need only one photon. Consequently, they can be measured with high sensitivity when an ArF laser is used as the radiation source. Furthermore, the discrimination of soot precursor molecules and soot precursor particles becomes possible through photoionization and this enables an improved understanding of the mass spectra. This should allow a particle growth mechanism to be deduced in the near future.

Molecular emission spectra of the OH rotational bands were measured to determine a two dimensional temperature profile of a microwave heated air plasma torch. The method is based on the simulation of rotational line intensities and the comparison with experimental results. A very high accuracy in simulation was obtained by the implementation of the Λ-doubling. The torch itself can be divided into a small (few millimetres in diameter) plasma and a flame which can reach up to 30 mm in diameter and 250 mm in height. While the plasma centre emits a variety of spectral lines, the whole flame is only accessible with the A2 Σ+, v′ = 0 → X2 Π, v″ = 0 transition in the free radical OH at 306.36 nm.

This series aims at the measurement of flame generated nanoparticles and an assessment of their biological effects. In the present part a brief review is given on previous papers dealing with nanoparticles with emphasis on detection through various methods. A more detailed account is provided of own measurements using photo ionization mass spectrometry. This includes photo fragmentation, spectra of low pressure flames, coagulation effects, and nanoparticle measurements in the exhaust gas of a sooting normal pressure premixed flame well outside of the visible zone. A model on nanoparticle formation is discussed as are its implications on emissions of vehicle engines.