Photothermal aerosol absorption spectroscopy

Abstract

In situ aerosol absorption spectroscopy was performed using three photothermal detection schemes: phase fluctuation optical heterodyne spectroscopy, photothermal modulation of Mie scattering, and photophoresis. Particle specific absorption data of ammonium sulfate aerosols were obtained. The specific absorption coefficient for the sulfate ion was measured to be 0.5 m2/g at 1087 cm−1. Each of the three techniques allows single-particle and subnanogram per cubic centimeter detection sensitivity, and in all cases the relative absorption spectrum can be obtained directly from the data without the need for complex inverse scattering calculations.