Multiphoton ionization (MPI) mass spectrometry combined with supersonic jet spectroscopy (SJS) has been shown to be a very powerful method for chemical analysis. In this technique, sample molecules are generally introduced into a supersonic jet and carried into the ionization region
of a time-of-flight mass spectrometer (TOFMS), where ions are produced through a resonant two-photon ionization (R2PI) process. Both an R2PI jetcooled spectrum and an MPI mass spectrum can be obtained. It has been demonstrated that the two-dimensional detection scheme based on the jet-cooled
spectrum and the MPI mass spectrum can provide a unique means of molecular identification and structural analysis of organic and biological molecules with high sensitivity and selectivity. However, with the use of the supersonic jet, sample dilution and expansion along with the jet expansion
of the carrier gas are unavoidable, which reduces the ultimate sensitivity of the SJS/MPI technique. Therefore, in order to increase the overall sensitivity of SJSfMPI mass spectrometry, the extent of the sample expansion should be reduced and a larger size of a laser beam should be used to
ionize as large a proportion of molecules as possible.
Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
Publication date: February 1, 1991
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