Relative Raman Scattering Cross-Section Measurements with Suspended Particles

An experimental technique using individual aerosol particles for relative Raman scattering cross-section measurement is described. An electrostatically charged particle of known chemical composition, 10 to 15 μm in diameter, is suspended in an electrodynamic cell. A single line (4880 A) from an argon-ion laser is selected to induce the Raman scattering. The minute size and free rotation of the suspended particle ensure uniform sample illumination. The present results show very good linearity between the scattering intensity ratio and the molar mixing ratio. Sodium nitrate, ammonium nitrate, sodium sulfate, and ammonium sulfate are examined, and their respective Raman cross sections relative to that of sodium nitrate are determined to be 1, 0.9, 0.61, and 0.94. The uncertainty in this work is estimated to be less than 10%.