With a recently developed Raman microprobe, vibrational spectra have been obtained from Individual microcrystals and fibers of sheet and chain silicate minerals. Species such as talc, tremolite, low-iron anthophyllite, and actinolite give distinct spectra. No systematic differences exist between spectra of the fibrous and nonflbrous forms of a given mineral.

The Raman spectra of talc microparticles have been obtained with the Raman microprobe over the frequency range 100 to 3800 cm−1. The vibrational modes are discussed in terms of an idealized unit cell (1-M polymorph) of C2h symmetry. An electrostatic dipole-dipole interaction is used to compare the Raman and infrared active branches. Assignments of the Raman active stretching modes of the silicate sheet are found to support previous infrared assignments. Estimates of intrasheet dipole-dipole interactions are obtained.

No abstract

A conventional laser Raman spectrometer has been modified and used to obtain useful Raman spectra from discrete solid particles as small as 0.7 µm in linear dimensions. Spectra obtained from single, micrometer-sized particles of several inorganic and organic compounds are reported. Simplified calculations are discussed which provide an estimate of detectability levels and other problems associated with these measurements. Certain parameters that must be considered in the design of an instrument especially intended for use in the chemical characterization of single fine particles are reviewed in the light of this work.