A spectrographic study of the absorption and scattering of light by small particles in the gas phase.

Abstract

A new technique for studying small particles optically in the laboratory is described. A modern spectrograph using an image intensifier tube coupled to a CCD as a detector provides sensitivity comparable to that of a spectrometer using a photomultiplier tube, while preserving the advantages of a spectrograph. Using the instrument, small particles of sodium were studied in light scattering in the gas phase, and gas phase extinction measurements were made of magnesium, carbon, and C₆₀ (Buckminsterfullerene). In the scattering spectra of sodium, the ability of a spectrograph to image along the slit was used to simultaneously observe along a cross section of a small particle cloud, so it was possible to record the transition from the atomic vapor to diatomic sodium to small particles to larger particles. The gas phase surface plasmon feature of magnesium appeared quite different from previous measurements of particles collected on a substrate. On the other hand the spectra of carbon appeared to be quite similar to measurements on a substrate. The measurements of C₆₀ appear to be of the molecular vapor rather than of small particles.