Uncertainties in temperature measurements of optically levitated single aerosol particles by Raman spectroscopy

Abstract

Temperature is one of the key parameters in determining the rate of heat and mass transfer in an evaporating or growing aerosol single particle. In particular, stratospheric aerosol particles consisting of H 2O, H 2SO 4 and HNO 3 play a pivotale role by activating and deactivating reactions of reservoir gases (N 2O 5, ClONO 2, HCl), which are responsible for the depletion of stratospheric ozone. The technique of optical levitation allows a contactless examination of single aerosol particles. Raman spectroscopy offers the possibility to examine simultaneously the temperature, the chemical composition, as well as the phase of organic or inorganic substances.We present an experimental setup allowing optical trapping of single aerosol particles by a focused argon-ion laser beam. Pressure and temperature in the reaction cell can be reduced to stratospheric conditions. An optimized compact Raman spectrometer registers the inelastically scattered light. Comparison of theoretically predicted uncertainties in temperature measurements to experimental data is shown, and experimental limitations are discussed.