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Proceedings Paper

Ultrasensitive Molecular Detection By Multiphoton Ionization Spectroscopy
Author(s): J. E. Wessel; D. E. Cooper; C. M. Klimcak
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Paper Abstract

In this paper we describe molecular detection methods based on Multi-Photon Ionization (MPI) spectroscopy that provide high selectivity in addition to excellent detection limits. Prior work based on one-wavelength resonance enhanced 2-photon ionization spectroscopy is reviewed. Highlights include improvement of detection limits for aromatic hydrocarbons by a factor of one-thousand and adaptation of 2-photon ionization for spectrally selective detection in gas chromatography. Two alternative approaches for highly selective MPI detec-tion are discussed. Time-of-Flight (TOF) ion analysis in conjunction with MPI provides mass spectral signatures in addition to MPI spectra. Single ion sensitivity can be approached in this configuration. In a purely optical approach, selectivity can be improved by using two-color excitation. The new two-color method of Ion Dip Spectroscopy (IDS) can be used to label specific intermediate states involved in the MPI process and it is capable of generating Raman-type spectra as a supplement to the MPI spectra. The ultimate detection limit of the IDS method is expected to be about 104 molecules/ cm3, which is comparable to the detection limit that we have obtained for naphthalene by one-color MPI.

Paper Details

Date Published: 8 September 1981
PDF: 8 pages
Proc. SPIE 0286, Laser Spectroscopy for Sensitive Detection, (8 September 1981); doi: 10.1117/12.965814
Show Author Affiliations
J. E. Wessel, The Aerospace Corporation (United States)
D. E. Cooper, The Aerospace Corporation (United States)
C. M. Klimcak, The Aerospace Corporation (United States)

Published in SPIE Proceedings Vol. 0286:
Laser Spectroscopy for Sensitive Detection
Jerry A. Gelbwachs, Editor(s)

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