OPTICALLY SEEDED STIMULATED RAMAN-SCATTERING OF AQUEOUS SULFATE MICRODROPLETS

Optically seeded, stimulated Raman scattering is demonstrated for 25-m u m-radius water droplets containing sulfate. Frequency-doubled Nd:YAG laser-excited Stokes radiation from the 3450-cm(-1) O-H-stretching vi bration of water provides the seed for morphology-dependent stimulated Raman scattering from the vl vibration of sulfate that is excited by a dye laser. Seeding enhances the otherwise weaker signal for low conc entrations of the anion, thereby reducing the solute detection limit, by a method that does not require changing of the droplet composition. (C) 1996 Optical Society of America