LINEAR RAMAN-SPECTROSCOPY ON DROPLET CHAINS - A NEW EXPERIMENTAL-METHOD FOR THE ANALYSIS OF FAST TRANSPORT PROCESSES AND REACTIONS ON MICROPARTICLES

A new experimental method for the analysis of mass and energy transpor t and reactions on microparticles is presented. A chain of microdrople ts from a vibrating orifice generator was injected into a quiescent ga s phase. Linear Raman spectra from the microparticles and the surround ing gas were taken at different distances from the generator. Concentr ation changes were measured as a function of droplet lifetime. A perio d of time of up to 20 ms could be studied with a resolution of 10 mu s . An argonion laser in a 90 degrees scattering geometry was used for e xcitation. Spectra were taken through a modified double monochromator with a two-dimensional charge-coupled device (CCD) detector, one axis of which was used for spatial resolution. Profiles of gaseous componen ts near the droplets could be measured with a resolution of 50 mu m. T he method has been applied to analysis of absorption, dissociation, an d isomerization in the SO2-H2O system and to the investigation of the desorption process of CO2 from water droplets. Chemical components in gas and liquid phase could be separated. The detection limit in aqueou s media was 1 mmol/L.