Gas-chromatographic determination of aromatic molecules by supersonic jet spectrometry with resonance multi-photon ionisation

Abstract

The sample separated by a chromatographic column was expanded through a supersonic nozzle. The ultra-cold molecules thus produced were successively multi-photon ionised by a tightly focused dye laser beam and detected by an electron multiplier. When the wavelength was adjusted to 492.75 nm, which corresponds to one of the transitions (14¹₀ 1¹₀, ¹A_1g→¹B_2u) of benzene, a large peak was observed. Aniline could be excited through a weakly resonanced, two-photon excitation process at around this wavelength, and provided a relatively weak peak. The solvent molecule of ethanol gave no appreciable peak. The detection limit of benzene was about 1 µg.