MICRO AND 2-DIMENSIONAL NIR FT RAMAN-SPECTROSCOPY

The former major problem in conventional Raman spectroscopy in the vis ible range, the disturbing fluorescence of impurities, has now been el iminated: Raman spectra can be excited by light quanta in the near-inf rared range, the energy of which is too low to excite fluorescence spe ctra. An inherent disadvantage of this technique, the nu4-dependence o f the intensity of the Raman radiation, is compensated for by using in terferometers, which are more powerful, by a factor of several hundred , than grating spectrometers. Raman spectroscopy can now be applied to analyses of 'real world samples'; bio materials, food, paintings, mic ro electronics and 'new materials', as well as to quality control of r aw materials, to production and product control without special sample preparation. By using fiber bundles, Raman spectra can be recorded on line at the sample site, in containers and in real time. For successf ul recording of NIR FT Raman spectra of small samples a compromise bet ween large lateral resolution and a large signal/noise ratio has to be found. Its theoretical base and practical approach is discussed. Conf ocal microscopes allow recording of NIR FT Raman spectra of small part icles or inclusions. They can be coupled to the spectrometer by fiber optics, so that they may be placed at some distance from the spectrome ter. By using computer-driven x-y stages, systematic mapping of the di stribution of specific compounds on the surface of different samples i s possible with the FT Raman microscope, as well as with the ordinary sample arrangement.