APPLICATION OF THE MOLECULAR MICROPROBE TO MICROANALYTICAL PROBLEMS

Author Institution: Instruments SA IncorporatedSince the introduction of the MOLE, -- an instrument which probes the microscopic properties of a sample surface (down to about 1 micron optical resolution) by exploiting the Raman scattering of its molecular species-- the interest generated has promoted ISA to create three separate Application Laboratories, --two in France and one in the U.S. MOLE is an acronym for Molecular Optical Laser Examiner. It is an optical microprobe, microscope and molecular spectrophotometer utilizing the Raman and fluorescence effects. The sample is illuminated by monochromatic laser radiation via a research optical microscope, which also provides the operator a view of the sample and coupling between the sample and double monochromator which uses aberration corrected concave holographic gratings. All the normal modes of viewing in a research optical microscope are available allowing studies to be carried out in any transparent medium at subambient to elevated temperatures. The monochromator permits separation of a spectral hand corresponding to a molecular vibration, or scanning of an entire Raman spectrum originating from a macroscopic sample or a region as small as one micron. There are two detection systems; a photomultiplier-based detector provides a record of a spectrum via a chart recorder, whose axis is coupled to the wavenumber scan of the monochromator. With the second detector, which includes an image intensifier and a high sensitivity TV tube, it is possible to image the sample through monochromatic radiation separated by the spectrometer, or to obtain real time spectral changes of microscopic samples. Applications of the MOLE to (i) Thin films and polymers, (ii) Microelectronic circuits and processing, and (iii) Mineralogy have been demonstrated